initial commit of ebook 2355HEADmain

30 files changed, 20113 insertions, 0 deletions

diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..6833f05
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,3 @@
+* text=auto
+*.txt text
+*.md text
diff --git a/2355-0.txt b/2355-0.txt
new file mode 100644
index 0000000..a3a2218
--- /dev/null
+++ b/2355-0.txt
@@ -0,0 +1,6083 @@
+The Project Gutenberg eBook of The Formation of Vegetable Mould, by Charles Darwin
+
+This eBook is for the use of anyone anywhere in the United States and
+most other parts of the world at no cost and with almost no restrictions
+whatsoever. You may copy it, give it away or re-use it under the terms
+of the Project Gutenberg License included with this eBook or online at
+www.gutenberg.org. If you are not located in the United States, you
+will have to check the laws of the country where you are located before
+using this eBook.
+
+Title: The Formation of Vegetable Mould
+       through the action of worms with observations on their habits
+
+Author: Charles Darwin
+
+Release Date: December 1, 1999 [eBook #2355]
+[Most recently updated: February 20, 2021]
+
+Language: English
+
+Character set encoding: UTF-8
+
+Produced by: David Price
+
+*** START OF THE PROJECT GUTENBERG EBOOK THE FORMATION OF VEGETABLE MOULD ***
+
+                          [Picture: Book cover]
+
+
+
+
+
+                             THE FORMATION OF
+                             VEGETABLE MOULD
+                       THROUGH THE ACTION OF WORMS
+                    WITH OBSERVATIONS ON THEIR HABITS.
+
+
+                     BY CHARLES DARWIN, LL.D., F.R.S.
+
+                           THIRTEENTH THOUSAND
+                            WITH ILLUSTRATIONS
+
+                                * * * * *
+
+                                  LONDON
+                      JOHN MURRAY, ALBEMARLE STREET
+                                   1904
+
+                                * * * * *
+
+                                PRINTED BY
+                    WILLIAM CLOWES AND SONS, LIMITED,
+                           LONDON AND BECCLES.
+
+                                * * * * *
+
+
+
+
+CONTENTS.
+
+INTRODUCTION                                                  Page 1–6
+                              CHAPTER I.
+                           HABITS OF WORMS.
+Nature of the sites inhabited—Can live long under                 7–15
+water—Nocturnal—Wander about at night—Often lie close
+to the mouths of their burrows, and are thus destroyed
+in large numbers by birds—Structure—Do not possess
+eyes, but can distinguish between light and
+darkness—Retreat rapidly when brightly illuminated, not
+by a reflex action—Power of attention—Sensitive to heat
+and cold—Completely deaf—Sensitive to vibrations and to
+touch—Feeble power of smell—Taste—Mental
+qualities—Nature of food—Omnivorous—Digestion—Leaves
+before being swallowed, moistened with a fluid of the
+nature of the pancreatic secretion—Extra-stomachal
+digestion—Calciferous glands, structure of—Calcareous
+concretions formed in the anterior pair of glands—The
+calcareous matter primarily an excretion, but
+secondarily serves to neutralise the acids generated
+during the digestive process.
+                             CHAPTER II.
+                     HABITS OF WORMS—_continued_.
+Manner in which worms seize objects—Their power of              52–120
+suction—The instinct of plugging up the mouths of their
+burrows—Stones piled over the burrows—The advantages
+thus gained—Intelligence shown by worms in their manner
+of plugging up their burrows—Various kinds of leaves
+and other objects thus used—Triangles of paper—Summary
+of reasons for believing that worms exhibit some
+intelligence—Means by which they excavate their
+burrows, by pushing away the earth and swallowing
+it—Earth also swallowed for the nutritious matter which
+it contains—Depth to which worms burrow, and the
+construction of their burrows—Burrows lined with
+castings, and in the upper part with leaves—The lowest
+part paved with little stones or seeds—Manner in which
+the castings are ejected—The collapse of old
+burrows—Distribution of worms—Tower-like castings in
+Bengal—Gigantic castings on the Nilgiri
+Mountains—Castings ejected in all countries.
+                             CHAPTER III.
+     THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE SURFACE.
+Rate at which various objects strewed on the surface of        121–163
+grass-fields are covered up by the castings of
+worms—The burial of a paved path—The slow subsidence of
+great stones left on the surface—The number of worms
+which live within a given space—The weight of earth
+ejected from a burrow, and from all the burrows within
+a given space—The thickness of the layer of mould which
+the castings on a given space would form within a given
+time if uniformly spread out—The slow rate at which
+mould can increase to a great thickness—Conclusion.
+                             CHAPTER IV.
+ THE PART WHICH WORMS HAVE PLAYED IN THE BURIAL OF ANCIENT BUILDINGS.
+The accumulation of rubbish on the sites of great              164–208
+cities independent of the action of worms—The burial of
+a Roman villa at Abinger—The floors and walls
+penetrated by worms—Subsidence of a modern pavement—The
+buried pavement at Beaulieu Abbey—Roman villas at
+Chedworth and Brading—The remains of the Roman town at
+Silchester—The nature of the débris by which the
+remains are covered—The penetration of the tesselated
+floors and walls by worms—Subsidence of the
+floors—Thickness of the mould—The old Roman city of
+Wroxeter—Thickness of the mould—Depth of the
+foundations of some of the Buildings—Conclusion.
+                              CHAPTER V.
+          THE ACTION OF WORMS IN THE DENUDATION OF THE LAND.
+Evidence of the amount of denudation which the land has        209–236
+undergone—Sub-aerial denudation—The deposition of
+dust—Vegetable mould, its dark colour and fine texture
+largely due to the action of worms—The disintegration
+of rocks by the humus-acids—Similar acids apparently
+generated within the bodies of worms—The action of
+these acids facilitated by the continued movement of
+the particles of earth—A thick bed of mould checks the
+disintegration of the underlying soil and rocks.
+Particles of stone worn or triturated in the gizzards
+of worms—Swallowed stones serve as mill-stones—The
+levigated state of the castings—Fragments of brick in
+the castings over ancient buildings well rounded.  The
+triturating power of worms not quite insignificant
+under a geological point of view.
+                             CHAPTER VI.
+               THE DENUDATION OF THE LAND—_continued_.
+Denudation aided by recently ejected castings flowing          237–279
+down inclined grass-covered surfaces—The amount of
+earth which annually flows downwards—The effect of
+tropical rain on worm castings—The finest particles of
+earth washed completely away from castings—The
+disintegration of dried castings into pellets, and
+their rolling down inclined surfaces—The formation of
+little ledges on hill-sides, in part due to the
+accumulation of disintegrated castings—Castings blown
+to leeward over level land—An attempt to estimate the
+amount thus blown—The degradation of ancient
+encampments and tumuli—The preservation of the crowns
+and furrows on land anciently ploughed—The formation
+and amount of mould over the Chalk formation.
+                             CHAPTER VII.
+                             CONCLUSION.
+Summary of the part which worms have played in the             280–288
+history of the world—Their aid in the disintegration of
+rocks—In the denudation of the land—In the preservation
+of ancient remains—In the preparation of the soil for
+the growth of plants—Mental powers of worms—Conclusion.
+
+
+
+
+INTRODUCTION.
+
+
+THE share which worms have taken in the formation of the layer of
+vegetable mould, which covers the whole surface of the land in every
+moderately humid country, is the subject of the present volume.  This
+mould is generally of a blackish colour and a few inches in thickness.
+In different districts it differs but little in appearance, although it
+may rest on various subsoils.  The uniform fineness of the particles of
+which it is composed is one of its chief characteristic features; and
+this may be well observed in any gravelly country, where a
+recently-ploughed field immediately adjoins one which has long remained
+undisturbed for pasture, and where the vegetable mould is exposed on the
+sides of a ditch or hole.  The subject may appear an insignificant one,
+but we shall see that it possesses some interest; and the maxim “de
+minimis non curat lex,” does not apply to science.  Even Élie de
+Beaumont, who generally undervalues small agencies and their accumulated
+effects, remarks: {2} “La couche très-mince de la terre végétale est un
+monument d’une haute antiquité, et, par le fait de sa permanence, un
+objet digne d’occuper le géologue, et capable de lui fournir des
+remarques intéressantes.”  Although the superficial layer of vegetable
+mould as a whole no doubt is of the highest antiquity, yet in regard to
+its permanence, we shall hereafter see reason to believe that its
+component particles are in most cases removed at not a very slow rate,
+and are replaced by others due to the disintegration of the underlying
+materials.
+
+As I was led to keep in my study during many months worms in pots filled
+with earth, I became interested in them, and wished to learn how far they
+acted consciously, and how much mental power they displayed.  I was the
+more desirous to learn something on this head, as few observations of
+this kind have been made, as far as I know, on animals so low in the
+scale of organization and so poorly provided with sense-organs, as are
+earth-worms.
+
+In the year 1837, a short paper was read by me before the Geological
+Society of London, {3} “On the Formation of Mould,” in which it was shown
+that small fragments of burnt marl, cinders, &c., which had been thickly
+strewed over the surface of several meadows, were found after a few years
+lying at the depth of some inches beneath the turf, but still forming a
+layer.  This apparent sinking of superficial bodies is due, as was first
+suggested to me by Mr. Wedgwood of Maer Hall in Staffordshire, to the
+large quantity of fine earth continually brought up to the surface by
+worms in the form of castings.  These castings are sooner or later spread
+out and cover up any object left on the surface.  I was thus led to
+conclude that all the vegetable mould over the whole country has passed
+many times through, and will again pass many times through, the
+intestinal canals of worms.  Hence the term “animal mould” would be in
+some respects more appropriate than that commonly used of “vegetable
+mould.”
+
+Ten years after the publication of my paper, M. D’Archiac, evidently
+influenced by the doctrines of Élie de Beaumont, wrote about my
+“singulière théorie,” and objected that it could apply only to “les
+prairies basses et humides;” and that “les terres labourées, les bois,
+les prairies élevées, n’apportent aucune preuve à l’appui de cette
+manière de voir.” {4a}  But M. D’Archiac must have thus argued from inner
+consciousness and not from observation, for worms abound to an
+extraordinary degree in kitchen gardens where the soil is continually
+worked, though in such loose soil they generally deposit their castings
+in any open cavities or within their old burrows instead of on the
+surface.  Hensen estimates that there are about twice as many worms in
+gardens as in corn-fields. {4b}  With respect to “prairies élevées,” I do
+not know how it may be in France, but nowhere in England have I seen the
+ground so thickly covered with castings as on commons, at a height of
+several hundred feet above the sea.  In woods again, if the loose leaves
+in autumn are removed, the whole surface will be found strewed with
+castings.  Dr. King, the superintendent of the Botanic Garden in
+Calcutta, to whose kindness I am indebted for many observations on
+earth-worms, informs me that he found, near Nancy in France, the bottom
+of the State forests covered over many acres with a spongy layer,
+composed of dead leaves and innumerable worm-castings.  He there heard
+the Professor of “Aménagement des Forêts” lecturing to his pupils, and
+pointing out this case as a “beautiful example of the natural cultivation
+of the soil; for year after year the thrown-up castings cover the dead
+leaves; the result being a rich humus of great thickness.”
+
+In the year 1869, Mr. Fish {5} rejected my conclusions with respect to
+the part which worms have played in the formation of vegetable mould,
+merely on account of their assumed incapacity to do so much work.  He
+remarks that “considering their weakness and their size, the work they
+are represented to have accomplished is stupendous.”  Here we have an
+instance of that inability to sum up the effects of a continually
+recurrent cause, which has often retarded the progress of science, as
+formerly in the case of geology, and more recently in that of the
+principle of evolution.
+
+Although these several objections seemed to me to have no weight, yet I
+resolved to make more observations of the same kind as those published,
+and to attack the problem on another side; namely, to weigh all the
+castings thrown up within a given time in a measured space, instead of
+ascertaining the rate at which objects left on the surface were buried by
+worms.  But some of my observations have been rendered almost superfluous
+by an admirable paper by Hensen, already alluded to, which appeared in
+1877. {6}  Before entering on details with respect to the castings, it
+will be advisable to give some account of the habits of worms from my own
+observations and from those of other naturalists.
+
+[FIRST EDITION,
+            _October_ 10_th_, 1881.]
+
+
+
+
+CHAPTER I.
+HABITS OF WORMS.
+
+
+Nature of the sites inhabited—Can live long under water—Nocturnal—Wander
+about at night—Often lie close to the mouths of their burrows, and are
+thus destroyed in large numbers by birds—Structure—Do not possess eyes,
+but can distinguish between light and darkness—Retreat rapidly when
+brightly illuminated, not by a reflex action—Power of attention—Sensitive
+to heat and cold—Completely deaf—Sensitive to vibrations and to
+touch—Feeble power of smell—Taste—Mental qualities—Nature of
+food—Omnivorous—Digestion—Leaves before being swallowed, moistened with a
+fluid of the nature of the pancreatic secretion—Extra-stomachal
+digestion—Calciferous glands, structure of—Calcareous concretions formed
+in the anterior pair of glands—The calcareous matter primarily an
+excretion, but secondarily serves to neutralise the acids generated
+during the digestive process.
+
+EARTH-WORMS are distributed throughout the world under the form of a few
+genera, which externally are closely similar to one another.  The British
+species of Lumbricus have never been carefully monographed; but we may
+judge of their probable number from those inhabiting neighbouring
+countries.  In Scandinavia there are eight species, according to Eisen;
+{8a} but two of these rarely burrow in the ground, and one inhabits very
+wet places or even lives under the water.  We are here concerned only
+with the kinds which bring up earth to the surface in the form of
+castings.  Hoffmeister says that the species in Germany are not well
+known, but gives the same number as Eisen, together with some strongly
+marked varieties. {8b}
+
+Earth-worms abound in England in many different stations.  Their castings
+may be seen in extraordinary numbers on commons and chalk-downs, so as
+almost to cover the whole surface, where the soil is poor and the grass
+short and thin.  But they are almost or quite as numerous in some of the
+London parks, where the grass grows well and the soil appears rich.  Even
+on the same field worms are much more frequent in some places than in
+others, without any visible difference in the nature of the soil.  They
+abound in paved court-yards close to houses; and an instance will be
+given in which they had burrowed through the floor of a very damp cellar.
+I have seen worms in black peat in a boggy field; but they are extremely
+rare, or quite absent in the drier, brown, fibrous peat, which is so much
+valued by gardeners.  On dry, sandy or gravelly tracks, where heath with
+some gorse, ferns, coarse grass, moss and lichens alone grow, hardly any
+worms can be found.  But in many parts of England, wherever a path
+crosses a heath, its surface becomes covered with a fine short sward.
+Whether this change of vegetation is due to the taller plants being
+killed by the occasional trampling of man and animals, or to the soil
+being occasionally manured by the droppings from animals, I do not know.
+{9b}  On such grassy paths worm-castings may often be seen.  On a heath
+in Surrey, which was carefully examined, there were only a few castings
+on these paths, where they were much inclined; but on the more level
+parts, where a bed of fine earth had been washed down from the steeper
+parts and had accumulated to a thickness of a few inches, worm-castings
+abounded.  These spots seemed to be overstocked with worms, so that they
+had been compelled to spread to a distance of a few feet from the grassy
+paths, and here their castings had been thrown up among the heath; but
+beyond this limit, not a single casting could be found.  A layer, though
+a thin one, of fine earth, which probably long retains some moisture, is
+in all cases, as I believe, necessary for their existence; and the mere
+compression of the soil appears to be in some degree favourable to them,
+for they often abound in old gravel walks, and in foot-paths across
+fields.
+
+Beneath large trees few castings can be found during certain seasons of
+the year, and this is apparently due to the moisture having been sucked
+out of the ground by the innumerable roots of the trees; for such places
+may be seen covered with castings after the heavy autumnal rains.
+Although most coppices and woods support many worms, yet in a forest of
+tall and ancient beech-trees in Knole Park, where the ground beneath was
+bare of all vegetation, not a single casting could be found over wide
+spaces, even during the autumn.  Nevertheless, castings were abundant on
+some grass-covered glades and indentations which penetrated this forest.
+On the mountains of North Wales and on the Alps, worms, as I have been
+informed, are in most places rare; and this may perhaps be due to the
+close proximity of the subjacent rocks, into which worms cannot burrow
+during the winter so as to escape being frozen.  Dr. McIntosh, however,
+found worm-castings at a height of 1500 feet on Schiehallion in Scotland.
+They are numerous on some hills near Turin at from 2000 to 3000 feet
+above the sea, and at a great altitude on the Nilgiri Mountains in South
+India and on the Himalaya.
+
+Earth-worms must be considered as terrestrial animals, though they are
+still in one sense semi-aquatic, like the other members of the great
+class of annelids to which they belong.  M. Perrier found that their
+exposure to the dry air of a room for only a single night was fatal to
+them.  On the other hand he kept several large worms alive for nearly
+four months, completely submerged in water. {11}  During the summer when
+the ground is dry, they penetrate to a considerable depth and cease to
+work, as they do during the winter when the ground is frozen.  Worms are
+nocturnal in their habits, and at night may be seen crawling about in
+large numbers, but usually with their tails still inserted in their
+burrows.  By the expansion of this part of their bodies, and with the
+help of the short, slightly reflexed bristles, with which their bodies
+are armed, they hold so fast that they can seldom be dragged out of the
+ground without being torn into pieces. {12}  During the day they remain
+in their burrows, except at the pairing season, when those which inhabit
+adjoining burrows expose the greater part of their bodies for an hour or
+two in the early morning.  Sick individuals, which are generally affected
+by the parasitic larvæ of a fly, must also be excepted, as they wander
+about during the day and die on the surface.  After heavy rain succeeding
+dry weather, an astonishing number of dead worms may sometimes be seen
+lying on the ground.  Mr. Galton informs me that on one such occasion
+(March, 1881), the dead worms averaged one for every two and a half paces
+in length on a walk in Hyde Park, four paces in width.  He counted no
+less than 45 dead worms in one place in a length of sixteen paces.  From
+the facts above given, it is not probable that these worms could have
+been drowned, and if they had been drowned they would have perished in
+their burrows.  I believe that they were already sick, and that their
+deaths were merely hastened by the ground being flooded.
+
+It has often been said that under ordinary circumstances healthy worms
+never, or very rarely, completely leave their burrows at night; but this
+is an error, as White of Selborne long ago knew.  In the morning, after
+there has been heavy rain, the film of mud or of very fine sand over
+gravel-walks is often plainly marked with their tracks.  I have noticed
+this from August to May, both months included, and it probably occurs
+during the two remaining months of the year when they are wet.  On these
+occasions, very few dead worms could anywhere be seen.  On January 31,
+1881, after a long-continued and unusually severe frost with much snow,
+as soon as a thaw set in, the walks were marked with innumerable tracks.
+On one occasion, five tracks were counted crossing a space of only an
+inch square.  They could sometimes be traced either to or from the mouths
+of the burrows in the gravel-walks, for distances between 2 or 3 up to 15
+yards.  I have never seen two tracks leading to the same burrow; nor is
+it likely, from what we shall presently see of their sense-organs, that a
+worm could find its way back to its burrow after having once left it.
+They apparently leave their burrows on a voyage of discovery, and thus
+they find new sites to inhabit.
+
+Morren states {14} that worms often lie for hours almost motionless close
+beneath the mouths of their burrows.  I have occasionally noticed the
+same fact with worms kept in pots in the house; so that by looking down
+into their burrows, their heads could just be seen.  If the ejected earth
+or rubbish over the burrows be suddenly removed, the end of the worm’s
+body may very often be seen rapidly retreating.  This habit of lying near
+the surface leads to their destruction to an immense extent.  Every
+morning during certain seasons of the year, the thrushes and blackbirds
+on all the lawns throughout the country draw out of their holes an
+astonishing number of worms, and this they could not do, unless they lay
+close to the surface.  It is not probable that worms behave in this
+manner for the sake of breathing fresh air, for we have seen that they
+can live for a long time under water.  I believe that they lie near the
+surface for the sake of warmth, especially in the morning; and we shall
+hereafter find that they often coat the mouths of their burrows with
+leaves, apparently to prevent their bodies from coming into close contact
+with the cold damp earth.  It is said that they completely close their
+burrows during the winter.
+
+_Structure_.—A few remarks must be made on this subject.  The body of a
+large worm consists of from 100 to 200 almost cylindrical rings or
+segments, each furnished with minute bristles.  The muscular system is
+well developed.  Worms can crawl backwards as well as forwards, and by
+the aid of their affixed tails can retreat with extraordinary rapidity
+into their burrows.  The mouth is situated at the anterior end of the
+body, and is provided with a little projection (lobe or lip, as it has
+been variously called) which is used for prehension.  Internally, behind
+the mouth, there is a strong pharynx, shown in the accompanying diagram
+(Fig. 1) which is pushed forwards when the animal eats, and this part
+corresponds, according to Perrier, with the protrudable trunk or
+proboscis of other annelids.  The pharynx leads into the œsophagus, on
+each side of which in the lower part there are three pairs of large
+glands, which secrete a surprising amount of carbonate of lime.  These
+calciferous glands are highly remarkable, for nothing like them is known
+in any other animal.  Their use will be discussed when we treat of the
+digestive process.  In most of the species, the œsophagus is enlarged
+into a crop in front of the gizzard.  This latter organ is lined with a
+smooth thick chitinous membrane, and is surrounded by weak longitudinal,
+but powerful transverse muscles.  Perrier saw these muscles in energetic
+action; and, as he remarks, the trituration of the food must be chiefly
+effected by this organ, for worms possess no jaws or teeth of any kind.
+Grains of sand and small stones, from the 1/20 to a little more than the
+1/10 inch in diameter, may generally be found in their gizzards and
+intestines.  As it is certain that worms swallow many little stones,
+independently of those swallowed while excavating their burrows, it is
+probable that they serve, like mill-stones, to triturate their food.  The
+gizzard opens into the intestine, which runs in a straight course to the
+vent at the posterior end of the body.  The intestine presents a
+remarkable structure, the typhlosolis, or, as the old anatomists called
+it, an intestine within an intestine; and Claparède {17} has shown that
+this consists of a deep longitudinal involution of the walls of the
+intestine, by which means an extensive absorbent surface is gained.
+
+[Picture: Fig. 1: Diagram of the alimentary canal of an earth-worm.  Fig.
+                  2: Tower-like casting from near Nice]
+
+The circulatory system is well developed.  Worms breathe by their skin,
+as they do not possess any special respiratory organs.  The two sexes are
+united in the same individual, but two individuals pair together.  The
+nervous system is fairly well developed; and the two almost confluent
+cerebral ganglia are situated very near to the anterior end of the body.
+
+_Senses_.—Worms are destitute of eyes, and at first I thought that they
+were quite insensible to light; for those kept in confinement were
+repeatedly observed by the aid of a candle, and others out of doors by
+the aid of a lantern, yet they were rarely alarmed, although extremely
+timid animals.  Other persons have found no difficulty in observing worms
+at night by the same means. {18a}
+
+Hoffmeister, however, states {18b} that worms, with the exception of a
+few individuals, are extremely sensitive to light; but he admits that in
+most cases a certain time is requisite for its action.  These statements
+led me to watch on many successive nights worms kept in pots, which were
+protected from currents of air by means of glass plates.  The pots were
+approached very gently, in order that no vibration of the floor should be
+caused.  When under these circumstances worms were illuminated by a
+bull’s-eye lantern having slides of dark red and blue glass, which
+intercepted so much light that they could be seen only with some
+difficulty, they were not at all affected by this amount of light,
+however long they were exposed to it.  The light, as far as I could
+judge, was brighter than that from the full moon.  Its colour apparently
+made no difference in the result.  When they were illuminated by a
+candle, or even by a bright paraffin lamp, they were not usually affected
+at first.  Nor were they when the light was alternately admitted and shut
+off.  Sometimes, however, they behaved very differently, for as soon as
+the light fell on them, they withdrew into their burrows with almost
+instantaneous rapidity.  This occurred perhaps once out of a dozen times.
+When they did not withdraw instantly, they often raised the anterior
+tapering ends of their bodies from the ground, as if their attention was
+aroused or as if surprise was felt; or they moved their bodies from side
+to side as if feeling for some object.  They appeared distressed by the
+light; but I doubt whether this was really the case, for on two occasions
+after withdrawing slowly, they remained for a long time with their
+anterior extremities protruding a little from the mouths of their
+burrows, in which position they were ready for instant and complete
+withdrawal.
+
+When the light from a candle was concentrated by means of a large lens on
+the anterior extremity, they generally withdrew instantly; but this
+concentrated light failed to act perhaps once out of half a dozen trials.
+The light was on one occasion concentrated on a worm lying beneath water
+in a saucer, and it instantly withdrew into its burrow.  In all cases the
+duration of the light, unless extremely feeble, made a great difference
+in the result; for worms left exposed before a paraffin lamp or a candle
+invariably retreated into their burrows within from five to fifteen
+minutes; and if in the evening the pots were illuminated before the worms
+had come out of their burrows, they failed to appear.
+
+From the foregoing facts it is evident that light affects worms by its
+intensity and by its duration.  It is only the anterior extremity of the
+body, where the cerebral ganglia lie, which is affected by light, as
+Hoffmeister asserts, and as I observed on many occasions.  If this part
+is shaded, other parts of the body may be fully illuminated, and no
+effect will be produced.  As these animals have no eyes, we must suppose
+that the light passes through their skins, and in some manner excites
+their cerebral ganglia.  It appeared at first probable that the different
+manner in which they were affected on different occasions might be
+explained, either by the degree of extension of their skin and its
+consequent transparency, or by some particular incident of the light; but
+I could discover no such relation.  One thing was manifest, namely, that
+when worms were employed in dragging leaves into their burrows or in
+eating them, and even during the short intervals whilst they rested from
+their work, they either did not perceive the light or were regardless of
+it; and this occurred even when the light was concentrated on them
+through a large lens.  So, again, whilst they are paired, they will
+remain for an hour or two out of their burrows, fully exposed to the
+morning light; but it appears from what Hoffmeister says that a light
+will occasionally cause paired individuals to separate.
+
+When a worm is suddenly illuminated and dashes like a rabbit into its
+burrow—to use the expression employed by a friend—we are at first led to
+look at the action as a reflex one.  The irritation of the cerebral
+ganglia appears to cause certain muscles to contract in an inevitable
+manner, independently of the will or consciousness of the animal, as if
+it were an automaton.  But the different effect which a light produced on
+different occasions, and especially the fact that a worm when in any way
+employed and in the intervals of such employment, whatever set of muscles
+and ganglia may then have been brought into play, is often regardless of
+light, are opposed to the view of the sudden withdrawal being a simple
+reflex action.  With the higher animals, when close attention to some
+object leads to the disregard of the impressions which other objects must
+be producing on them, we attribute this to their attention being then
+absorbed; and attention implies the presence of a mind.  Every sportsman
+knows that he can approach animals whilst they are grazing, fighting or
+courting, much more easily than at other times.  The state, also, of the
+nervous system of the higher animals differs much at different times, for
+instance, a horse is much more readily startled at one time than at
+another.  The comparison here implied between the actions of one of the
+higher animals and of one so low in the scale as an earth-worm, may
+appear far-fetched; for we thus attribute to the worm attention and some
+mental power, nevertheless I can see no reason to doubt the justice of
+the comparison.
+
+Although worms cannot be said to possess the power of vision, their
+sensitiveness to light enables them to distinguish between day and night;
+and they thus escape extreme danger from the many diurnal animals which
+prey on them.  Their withdrawal into their burrows during the day
+appears, however, to have become an habitual action; for worms kept in
+pots covered by glass plates, over which sheets of black paper were
+spread, and placed before a north-east window, remained during the
+day-time in their burrows and came out every night; and they continued
+thus to act for a week.  No doubt a little light may have entered between
+the sheets of glass and the blackened paper; but we know from the trials
+with coloured glass, that worms are indifferent to a small amount of
+light.
+
+Worms appear to be less sensitive to moderate radiant heat than to a
+bright light.  I judge of this from having held at different times a
+poker heated to dull redness near some worms, at a distance which caused
+a very sensible degree of warmth in my hand.  One of them took no notice;
+a second withdrew into its burrow, but not quickly; the third and fourth
+much more quickly, and the fifth as quickly as possible.  The light from
+a candle, concentrated by a lens and passing through a sheet of glass
+which would intercept most of the heat-rays, generally caused a much more
+rapid retreat than did the heated poker.  Worms are sensitive to a low
+temperature, as may be inferred from their not coming out of their
+burrows during a frost.
+
+Worms do not possess any sense of hearing.  They took not the least
+notice of the shrill notes from a metal whistle, which was repeatedly
+sounded near them; nor did they of the deepest and loudest tones of a
+bassoon.  They were indifferent to shouts, if care was taken that the
+breath did not strike them.  When placed on a table close to the keys of
+a piano, which was played as loudly as possible, they remained perfectly
+quiet.
+
+Although they are indifferent to undulations in the air audible by us,
+they are extremely sensitive to vibrations in any solid object.  When the
+pots containing two worms which had remained quite indifferent to the
+sound of the piano, were placed on this instrument, and the note C in the
+bass clef was struck, both instantly retreated into their burrows.  After
+a time they emerged, and when G above the line in the treble clef was
+struck they again retreated.  Under similar circumstances on another
+night one worm dashed into its burrow on a very high note being struck
+only once, and the other worm when C in the treble clef was struck.  On
+these occasions the worms were not touching the sides of the pots, which
+stood in saucers; so that the vibrations, before reaching their bodies,
+had to pass from the sounding board of the piano, through the saucer, the
+bottom of the pot and the damp, not very compact earth on which they lay
+with their tails in their burrows.  They often showed their sensitiveness
+when the pot in which they lived, or the table on which the pot stood,
+was accidentally and lightly struck; but they appeared less sensitive to
+such jars than to the vibrations of the piano; and their sensitiveness to
+jars varied much at different times.
+
+It has often been said that if the ground is beaten or otherwise made to
+tremble, worms believe that they are pursued by a mole and leave their
+burrows.  From one account that I have received, I have no doubt that
+this is often the case; but a gentleman informs me that he lately saw
+eight or ten worms leave their burrows and crawl about the grass on some
+boggy land on which two men had just trampled while setting a trap; and
+this occurred in a part of Ireland where there were no moles.  I have
+been assured by a Volunteer that he has often seen many large earth-worms
+crawling quickly about the grass, a few minutes after his company had
+fired a volley with blank cartridges.  The Peewit (_Tringa vanellus_,
+Linn.) seems to know instinctively that worms will emerge if the ground
+is made to tremble; for Bishop Stanley states (as I hear from Mr.
+Moorhouse) that a young peewit kept in confinement used to stand on one
+leg and beat the turf with the other leg until the worms crawled out of
+their burrows, when they were instantly devoured.  Nevertheless, worms do
+not invariably leave their burrows when the ground is made to tremble, as
+I know by having beaten it with a spade, but perhaps it was beaten too
+violently.
+
+The whole body of a worm is sensitive to contact.  A slight puff of air
+from the mouth causes an instant retreat.  The glass plates placed over
+the pots did not fit closely, and blowing through the very narrow chinks
+thus left, often sufficed to cause a rapid retreat.  They sometimes
+perceived the eddies in the air caused by quickly removing the glass
+plates.  When a worm first comes out of its burrow, it generally moves
+the much extended anterior extremity of its body from side to side in all
+directions, apparently as an organ of touch; and there is some reason to
+believe, as we shall see in the next chapter, that they are thus enabled
+to gain a general notion of the form of an object.  Of all their senses
+that of touch, including in this term the perception of a vibration,
+seems much the most highly developed.
+
+In worms the sense of smell apparently is confined to the perception of
+certain odours, and is feeble.  They were quite indifferent to my breath,
+as long as I breathed on them very gently.  This was tried, because it
+appeared possible that they might thus be warned of the approach of an
+enemy.  They exhibited the same indifference to my breath whilst I chewed
+some tobacco, and while a pellet of cotton-wool with a few drops of
+millefleurs perfume or of acetic acid was kept in my mouth.  Pellets of
+cotton-wool soaked in tobacco juice, in millefleurs perfume, and in
+paraffin, were held with pincers and were waved about within two or three
+inches of several worms, but they took no notice.  On one or two
+occasions, however, when acetic acid had been placed on the pellets, the
+worms appeared a little uneasy, and this was probably due to the
+irritation of their skins.  The perception of such unnatural odours would
+be of no service to worms; and as such timid creatures would almost
+certainly exhibit some signs of any new impression, we may conclude that
+they did not perceive these odours.
+
+The result was different when cabbage-leaves and pieces of onion were
+employed, both of which are devoured with much relish by worms.  Small
+square pieces of fresh and half-decayed cabbage-leaves and of onion bulbs
+were on nine occasions buried in my pots, beneath about ¼ of an inch of
+common garden soil; and they were always discovered by the worms.  One
+bit of cabbage was discovered and removed in the course of two hours;
+three were removed by the next morning, that is, after a single night;
+two others after two nights; and the seventh bit after three nights.  Two
+pieces of onion were discovered and removed after three nights.  Bits of
+fresh raw meat, of which worms are very fond, were buried, and were not
+discovered within forty-eight hours, during which time they had not
+become putrid.  The earth above the various buried objects was generally
+pressed down only slightly, so as not to prevent the emission of any
+odour.  On two occasions, however, the surface was well watered, and was
+thus rendered somewhat compact.  After the bits of cabbage and onion had
+been removed, I looked beneath them to see whether the worms had
+accidentally come up from below, but there was no sign of a burrow; and
+twice the buried objects were laid on pieces of tin-foil which were not
+in the least displaced.  It is of course possible that the worms whilst
+moving about on the surface of the ground, with their tails affixed
+within their burrows, may have poked their heads into the places where
+the above objects were buried; but I have never seen worms acting in this
+manner.  Some pieces of cabbage-leaf and of onion were twice buried
+beneath very fine ferruginous sand, which was slightly pressed down and
+well watered, so as to be rendered very compact, and these pieces were
+never discovered.  On a third occasion the same kind of sand was neither
+pressed down nor watered, and the pieces of cabbage were discovered and
+removed after the second night.  These several facts indicate that worms
+possess some power of smell; and that they discover by this means
+odoriferous and much-coveted kinds of food.
+
+It may be presumed that all animals which feed on various substances
+possess the sense of taste, and this is certainly the case with worms.
+Cabbage-leaves are much liked by worms; and it appears that they can
+distinguish between different varieties; but this may perhaps be owing to
+differences in their texture.  On eleven occasions pieces of the fresh
+leaves of a common green variety and of the red variety used for pickling
+were given them, and they preferred the green, the red being either
+wholly neglected or much less gnawed.  On two other occasions, however,
+they seemed to prefer the red.  Half-decayed leaves of the red variety
+and fresh leaves of the green were attacked about equally.  When leaves
+of the cabbage, horse-radish (a favourite food) and of the onion were
+given together, the latter were always, and manifestly preferred.  Leaves
+of the cabbage, lime-tree, Ampelopsis, parsnip (Pastinaca), and celery
+(Apium) were likewise given together; and those of the celery were first
+eaten.  But when leaves of cabbage, turnip, beet, celery, wild cherry and
+carrots were given together, the two latter kinds, especially those of
+the carrot, were preferred to all the others, including those of celery.
+It was also manifest after many trials that wild cherry leaves were
+greatly preferred to those of the lime-tree and hazel (Corylus).
+According to Mr. Bridgman the half-decayed leaves of _Phlox verna_ are
+particularly liked by worms. {31}
+
+Pieces of the leaves of cabbage, turnip, horse-radish and onion were left
+on the pots during 22 days, and were all attacked and had to be renewed;
+but during the whole of this time leaves of an Artemisia and of the
+culinary sage, thyme and mint, mingled with the above leaves, were quite
+neglected excepting those of the mint, which were occasionally and very
+slightly nibbled.  These latter four kinds of leaves do not differ in
+texture in a manner which could make them disagreeable to worms; they all
+have a strong taste, but so have the four first mentioned kinds of
+leaves; and the wide difference in the result must be attributed to a
+preference by the worms for one taste over another.
+
+_Mental Qualities_.—There is little to be said on this head.  We have
+seen that worms are timid.  It may be doubted whether they suffer as much
+pain when injured, as they seem to express by their contortions.  Judging
+by their eagerness for certain kinds of food, they must enjoy the
+pleasure of eating.  Their sexual passion is strong enough to overcome
+for a time their dread of light.  They perhaps have a trace of social
+feeling, for they are not disturbed by crawling over each other’s bodies,
+and they sometimes lie in contact.  According to Hoffmeister they pass
+the winter either singly or rolled up with others into a ball at the
+bottom of their burrows. {32}  Although worms are so remarkably deficient
+in the several sense-organs, this does not necessarily preclude
+intelligence, as we know from such cases as those of Laura Bridgman; and
+we have seen that when their attention is engaged, they neglect
+impressions to which they would otherwise have attended; and attention
+indicates the presence of a mind of some kind.  They are also much more
+easily excited at certain times than at others.  They perform a few
+actions instinctively, that is, all the individuals, including the young,
+perform such actions in nearly the same fashion.  This is shown by the
+manner in which the species of Perichæta eject their castings, so as to
+construct towers; also by the manner in which the burrows of the common
+earth-worm are smoothly lined with fine earth and often with little
+stones, and the mouths of their burrows with leaves.  One of their
+strongest instincts is the plugging up the mouths of their burrows with
+various objects; and very young worms act in this manner.  But some
+degree of intelligence appears, as we shall see in the next chapter, to
+be exhibited in this work,—a result which has surprised me more than
+anything else in regard to worms.
+
+_Food and Digestion_.—Worms are omnivorous.  They swallow an enormous
+quantity of earth, out of which they extract any digestible matter which
+it may contain; but to this subject I must recur.  They also consume a
+large number of half-decayed leaves of all kinds, excepting a few which
+have an unpleasant taste or are too tough for them; likewise petioles,
+peduncles, and decayed flowers.  But they will also consume fresh leaves,
+as I have found by repeated trials.  According to Morren {33} they will
+eat particles of sugar and liquorice; and the worms which I kept drew
+many bits of dry starch into their burrows, and a large bit had its
+angles well rounded by the fluid poured out of their mouths.  But as they
+often drag particles of soft stone, such as of chalk, into their burrows,
+I feel some doubt whether the starch was used as food.  Pieces of raw and
+roasted meat were fixed several times by long pins to the surface of the
+soil in my pots, and night after night the worms could be seen tugging at
+them, with the edges of the pieces engulfed in their mouths, so that much
+was consumed.  Raw fat seems to be preferred even to raw meat or to any
+other substance which was given them, and much was consumed.  They are
+cannibals, for the two halves of a dead worm placed in two of the pots
+were dragged into the burrows and gnawed; but as far as I could judge,
+they prefer fresh to putrid meat, and in so far I differ from
+Hoffmeister.
+
+Léon Fredericq states {34} that the digestive fluid of worms is of the
+same nature as the pancreatic secretion of the higher animals; and this
+conclusion agrees perfectly with the kinds of food which worms consume.
+Pancreatic juice emulsifies fat, and we have just seen how greedily worms
+devour fat; it dissolves fibrin, and worms eat raw meat; it converts
+starch into grape-sugar with wonderful rapidity, and we shall presently
+show that the digestive fluid of worms acts on starch. {35a}  But they
+live chiefly on half-decayed leaves; and these would be useless to them
+unless they could digest the cellulose forming the cell-walls; for it is
+well known that all other nutritious substances are almost completely
+withdrawn from leaves, shortly before they fall off.  It has, however,
+now been ascertained that some forms of cellulose, though very little or
+not at all attacked by the gastric secretion of the higher animals, are
+acted on by that from the pancreas. {35b}
+
+The half-decayed or fresh leaves which worms intend to devour, are
+dragged into the mouths of their burrows to a depth of from one to three
+inches, and are then moistened with a secreted fluid.  It has been
+assumed that this fluid serves to hasten their decay; but a large number
+of leaves were twice pulled out of the burrows of worms and kept for many
+weeks in a very moist atmosphere under a bell-glass in my study; and the
+parts which had been moistened by the worms did not decay more quickly in
+any plain manner than the other parts.  When fresh leaves were given in
+the evening to worms kept in confinement and examined early on the next
+morning, therefore not many hours after they had been dragged into the
+burrows, the fluid with which they were moistened, when tested with
+neutral litmus paper, showed an alkaline reaction.  This was repeatedly
+found to be the case with celery, cabbage and turnip leaves.  Parts of
+the same leaves which had not been moistened by the worms, were pounded
+with a few drops of distilled water, and the juice thus extracted was not
+alkaline.  Some leaves, however, which had been drawn into burrows out of
+doors, at an unknown antecedent period, were tried, and though still
+moist, they rarely exhibited even a trace of alkaline reaction.
+
+The fluid, with which the leaves are bathed, acts on them whilst they are
+fresh or nearly fresh, in a remarkable manner; for it quickly kills and
+discolours them.  Thus the ends of a fresh carrot-leaf, which had been
+dragged into a burrow, were found after twelve hours of a dark brown
+tint.  Leaves of celery, turnip, maple, elm, lime, thin leaves of ivy,
+and, occasionally those of the cabbage were similarly acted on.  The end
+of a leaf of _Triticum repens_, still attached to a growing plant, had
+been drawn into a burrow, and this part was dark brown and dead, whilst
+the rest of the leaf was fresh and green.  Several leaves of lime and elm
+removed from burrows out of doors were found affected in different
+degrees.  The first change appears to be that the veins become of a dull
+reddish-orange.  The cells with chlorophyll next lose more or less
+completely their green colour, and their contents finally become brown.
+The parts thus affected often appeared almost black by reflected light;
+but when viewed as a transparent object under the microscope, minute
+specks of light were transmitted, and this was not the case with the
+unaffected parts of the same leaves.  These effects, however, merely show
+that the secreted fluid is highly injurious or poisonous to leaves; for
+nearly the same effects were produced in from one to two days on various
+kinds of young leaves, not only by artificial pancreatic fluid, prepared
+with or without thymol, but quickly by a solution of thymol by itself.
+On one occasion leaves of Corylus were much discoloured by being kept for
+eighteen hours in pancreatic fluid, without any thymol.  With young and
+tender leaves immersion in human saliva during rather warm weather, acted
+in the same manner as the pancreatic fluid, but not so quickly.  The
+leaves in all these cases often became infiltrated with the fluid.
+
+Large leaves from an ivy plant growing on a wall were so tough that they
+could not be gnawed by worms, but after four days they were affected in a
+peculiar manner by the secretion poured out of their mouths.  The upper
+surfaces of the leaves, over which the worms had crawled, as was shown by
+the dirt left on them, were marked in sinuous lines, by either a
+continuous or broken chain of whitish and often star-shaped dots, about 2
+mm. in diameter.  The appearance thus presented was curiously like that
+of a leaf, into which the larva of some minute insect had burrowed.  But
+my son Francis, after making and examining sections, could nowhere find
+that the cell-walls had been broken down or that the epidermis had been
+penetrated.  When the section passed through the whitish dots, the grains
+of chlorophyll were seen to be more or less discoloured, and some of the
+palisade and mesophyll cells contained nothing but broken down granular
+matter.  These effects must be attributed to the transudation of the
+secretion through the epidermis into the cells.
+
+The secretion with which worms moisten leaves likewise acts on the
+starch-granules within the cells.  My son examined some leaves of the ash
+and many of the lime, which had fallen off the trees and had been partly
+dragged into worm-burrows.  It is known that with fallen leaves the
+starch-grains are preserved in the guard-cells of the stomata.  Now in
+several cases the starch had partially or wholly disappeared from these
+cells, in the parts which had been moistened by the secretion; while it
+was still well preserved in the other parts of the same leaves.
+Sometimes the starch was dissolved out of only one of the two
+guard-cells.  The nucleus in one case had disappeared, together with the
+starch-granules.  The mere burying of lime-leaves in damp earth for nine
+days did not cause the destruction of the starch-granules.  On the other
+hand, the immersion of fresh lime and cherry leaves for eighteen hours in
+artificial pancreatic fluid, led to the dissolution of the
+starch-granules in the guard-cells as well as in the other cells.
+
+From the secretion with which the leaves are moistened being alkaline,
+and from its acting both on the starch-granules and on the protoplasmic
+contents of the cells, we may infer that it resembles in nature not
+saliva, {40} but pancreatic secretion; and we know from Fredericq that a
+secretion of this kind is found in the intestines of worms.  As the
+leaves which are dragged into the burrows are often dry and shrivelled,
+it is indispensable for their disintegration by the unarmed mouths of
+worms that they should first be moistened and softened; and fresh leaves,
+however soft and tender they may be, are similarly treated, probably from
+habit.  The result is that they are partially digested before they are
+taken into the alimentary canal.  I am not aware of any other case of
+extra-stomachal digestion having been recorded.  The boa-constrictor is
+said to bathe its prey with saliva, but this is doubtful; and it is done
+solely for the sake of lubricating its prey.  Perhaps the nearest analogy
+may be found in such plants as Drosera and Dionæa; for here animal matter
+is digested and converted into peptone not within a stomach, but on the
+surfaces of the leaves.
+
+_Calciferous Glands_.—These glands (see Fig. 1), judging from their size
+and from their rich supply of blood-vessels, must be of much importance
+to the animal.  But almost as many theories have been advanced on their
+use as there have been observers.  They consist of three pairs, which in
+the common earth-worm debouch into the alimentary canal in advance of the
+gizzard, but posteriorly to it in Urochæta and some other genera. {41a}
+The two posterior pairs are formed by lamellæ, which, according to
+Claparède, are diverticula from the œsophagus. {41b}  These lamellæ are
+coated with a pulpy cellular layer, with the outer cells lying free in
+infinite numbers.  If one of these glands is punctured and squeezed, a
+quantity of white pulpy matter exudes, consisting of these free cells.
+They are minute, and vary in diameter from 2 to 6 _μ_.  They contain in
+their centres a little excessively fine granular matter; but they look so
+like oil globules that Claparède and others at first treated them with
+ether.  This produces no effect; but they are quickly dissolved with
+effervescence in acetic acid, and when oxalate of ammonia is added to the
+solution a white precipitate is thrown down.  We may therefore conclude
+that they contain carbonate of lime.  If the cells are immersed in a very
+little acid, they become more transparent, look like ghosts, and are soon
+lost to view; but if much acid is added, they disappear instantly.  After
+a very large number have been dissolved, a flocculent residue is left,
+which apparently consists of the delicate ruptured cell-walls.  In the
+two posterior pairs of glands the carbonate of lime contained in the
+cells occasionally aggregates into small rhombic crystals or into
+concretions, which lie between the lamellæ; but I have seen only one
+case, and Claparède only a very few such cases.
+
+The two anterior glands differ a little in shape from the four posterior
+ones, by being more oval.  They differ also conspicuously in generally
+containing several small, or two or three larger, or a single very large
+concretion of carbonate of lime, as much as 1½ mm. in diameter.  When a
+gland includes only a few very small concretions, or, as sometimes
+happens, none at all, it is easily overlooked.  The large concretions are
+round or oval, and exteriorly almost smooth.  One was found which filled
+up not only the whole gland, as is often the case, but its neck; so that
+it resembled an olive-oil flask in shape.  These concretions when broken
+are seen to be more or less crystalline in structure.  How they escape
+from the gland is a marvel; but that they do escape is certain, for they
+are often found in the gizzard, intestines, and in the castings of worms,
+both with those kept in confinement and those in a state of nature.
+
+Claparède says very little about the structure of the two anterior
+glands, and he supposes that the calcareous matter of which the
+concretions are formed is derived from the four posterior glands.  But if
+an anterior gland which contains only small concretions is placed in
+acetic acid and afterwards dissected, or if sections are made of such a
+gland without being treated with acid, lamellæ like those in the
+posterior glands and coated with cellular matter could be plainly seen,
+together with a multitude of free calciferous cells readily soluble in
+acetic acid.  When a gland is completely filled with a single large
+concretion, there are no free cells, as these have been all consumed in
+forming the concretion.  But if such a concretion, or one of only
+moderately large size, is dissolved in acid, much membranous matter is
+left, which appears to consist of the remains of the formerly active
+lamellæ.  After the formation and expulsion of a large concretion, new
+lamellæ must be developed in some manner.  In one section made by my son,
+the process had apparently commenced, although the gland contained two
+rather large concretions, for near the walls several cylindrical and oval
+pipes were intersected, which were lined with cellular matter and were
+quite filled with free calciferous cells.  A great enlargement in one
+direction of several oval pipes would give rise to the lamellæ.
+
+Besides the free calciferous cells in which no nucleus was visible, other
+and rather larger free cells were seen on three occasions; and these
+contained a distinct nucleus and nucleolus.  They were only so far acted
+on by acetic acid that the nucleus was thus rendered more distinct.  A
+very small concretion was removed from between two of the lamellæ within
+an anterior gland.  It was imbedded in pulpy cellular matter, with many
+free calciferous cells, together with a multitude of the larger, free,
+nucleated cells, and these latter cells were not acted on by acetic acid,
+while the former were dissolved.  From this and other such cases I am led
+to suspect that the calciferous cells are developed from the larger
+nucleated ones; but how this was effected was not ascertained.
+
+When an anterior gland contains several minute concretions, some of these
+are generally angular or crystalline in outline, while the greater number
+are rounded with an irregular mulberry-like surface.  Calciferous cells
+adhered to many parts of these mulberry-like masses, and their gradual
+disappearance could be traced while they still remained attached.  It was
+thus evident that the concretions are formed from the lime contained
+within the free calciferous cells.  As the smaller concretions increase
+in size, they come into contact and unite, thus enclosing the now
+functionless lamellæ; and by such steps the formation of the largest
+concretions could be followed.  Why the process regularly takes place in
+the two anterior glands, and only rarely in the four posterior glands, is
+quite unknown.  Morren says that these glands disappear during the
+winter; and I have seen some instances of this fact, and others in which
+either the anterior or posterior glands were at this season so shrunk and
+empty, that they could be distinguished only with much difficulty.
+
+With respect to the function of the calciferous glands, it is probable
+that they primarily serve as organs of excretion, and secondarily as an
+aid to digestion.  Worms consume many fallen leaves; and it is known that
+lime goes on accumulating in leaves until they drop off the parent-plant,
+instead of being re-absorbed into the stem or roots, like various other
+organic and inorganic substances. {46}  The ashes of a leaf of an acacia
+have been known to contain as much as 72 per cent. of lime.  Worms
+therefore would be liable to become charged with this earth, unless there
+were some special means for its excretion; and the calciferous glands are
+well adapted for this purpose.  The worms which live in mould close over
+the chalk, often have their intestines filled with this substance, and
+their castings are almost white.  Here it is evident that the supply of
+calcareous matter must be super-abundant.  Nevertheless with several
+worms collected on such a site, the calciferous glands contained as many
+free calciferous cells, and fully as many and large concretions, as did
+the glands of worms which lived where there was little or no lime; and
+this indicates that the lime is an excretion, and not a secretion poured
+into the alimentary canal for some special purpose.
+
+On the other hand, the following considerations render it highly probable
+that the carbonate of lime, which is excreted by the glands, aids the
+digestive process under ordinary circumstances.  Leaves during their
+decay generate an abundance of various kinds of acids, which have been
+grouped together under the term of humus acids.  We shall have to recur
+to this subject in our fifth chapter, and I need here only say that these
+acids act strongly on carbonate of lime.  The half-decayed leaves which
+are swallowed in such large quantities by worms would, therefore, after
+they have been moistened and triturated in the alimentary canal, be apt
+to produce such acids.  And in the case of several worms, the contents of
+the alimentary canal were found to be plainly acid, as shown by litmus
+paper.  This acidity cannot be attributed to the nature of the digestive
+fluid, for pancreatic fluid is alkaline; and we have seen that the
+secretion which is poured out of the mouths of worms for the sake of
+preparing the leaves for consumption, is likewise alkaline.  The acidity
+can hardly be due to uric acid, as the contents of the upper part of the
+intestine were often acid.  In one case the contents of the gizzard were
+slightly acid, those of the upper intestines being more plainly acid.  In
+another case the contents of the pharynx were not acid, those of the
+gizzard doubtfully so, while those of the intestine were distinctly acid
+at a distance of 5 cm. below the gizzard.  Even with the higher
+herbivorous and omnivorous animals, the contents of the large intestine
+are acid.  “This, however, is not caused by any acid secretion from the
+mucous membrane; the reaction of the intestinal walls in the larger as in
+the small intestine is alkaline.  It must therefore arise from acid
+fermentations going on in the contents themselves . . .  In Carnivora the
+contents of the coecum are said to be alkaline, and naturally the amount
+of fermentation will depend largely on the nature of the food.” {49}
+
+With worms not only the contents of the intestines, but their ejected
+matter or the castings, are generally acid.  Thirty castings from
+different places were tested, and with three or four exceptions were
+found to be acid; and the exceptions may have been due to such castings
+not having been recently ejected; for some which were at first acid, were
+on the following morning, after being dried and again moistened, no
+longer acid; and this probably resulted from the humus acids being, as is
+known to be the case, easily decomposed.  Five fresh castings from worms
+which lived in mould close over the chalk, were of a whitish colour and
+abounded with calcareous matter; and these were not in the least acid.
+This shows how effectually carbonate of lime neutralises the intestinal
+acids.  When worms were kept in pots filled with fine ferruginous sand,
+it was manifest that the oxide of iron, with which the grains of silex
+were coated, had been dissolved and removed from them in the castings.
+
+The digestive fluid of worms resembles in its action, as already stated,
+the pancreatic secretion of the higher animals; and in these latter,
+“pancreatic digestion is essentially alkaline; the action will not take
+place unless some alkali be present; and the activity of an alkaline
+juice is arrested by acidification, and hindered by neutralization.” {50}
+Therefore it seems highly probable that the innumerable calciferous
+cells, which are poured from the four posterior glands into the
+alimentary canal of worms, serve to neutralise more or less completely
+the acids there generated by the half-decayed leaves.  We have seen that
+these cells are instantly dissolved by a small quantity of acetic acid,
+and as they do not always suffice to neutralise the contents of even the
+upper part of the alimentary canal, the lime is perhaps aggregated into
+concretions in the anterior pair of glands, in order that some may be
+carried down to the posterior parts of the intestine, where these
+concretions would be rolled about amongst the acid contents.  The
+concretions found in the intestines and in the castings often have a worn
+appearance, but whether this is due to some amount of attrition or of
+chemical corrosion could not be told.  Claparède believes that they are
+formed for the sake of acting as mill-stones, and of thus aiding in the
+trituration of the food.  They may give some aid in this way; but I fully
+agree with Perrier that this must be of quite subordinate importance,
+seeing that the object is already attained by stones being generally
+present in the gizzards and intestines of worms.
+
+
+
+
+CHAPTER II.
+HABITS OF WORMS—_continued_.
+
+
+Manner in which worms seize objects—Their power of suction—The instinct
+of plugging up the mouths of their burrows—Stones piled over the
+burrows—The advantages thus gained—Intelligence shown by worms in their
+manner of plugging up their burrows—Various kinds of leaves and other
+objects thus used—Triangles of paper—Summary of reasons for believing
+that worms exhibit some intelligence—Means by which they excavate their
+burrows, by pushing away the earth and swallowing it—Earth also swallowed
+for the nutritious matter which it contains—Depth to which worms burrow,
+and the construction of their burrows—Burrows lined with castings, and in
+the upper part with leaves—The lowest part paved with little stones or
+seeds—Manner in which the castings are ejected—The collapse of old
+burrows—Distribution of worms—Tower-like castings in Bengal—Gigantic
+castings on the Nilgiri Mountains—Castings ejected in all countries.
+
+IN the pots in which worms were kept, leaves were pinned down to the
+soil, and at night the manner in which they were seized could be
+observed.  The worms always endeavoured to drag the leaves towards their
+burrows; and they tore or sucked off small fragments, whenever the leaves
+were sufficiently tender.  They generally seized the thin edge of a leaf
+with their mouths, between the projecting upper and lower lip; the thick
+and strong pharynx being at the same time, as Perrier remarks, pushed
+forward within their bodies, so as to afford a point of resistance for
+the upper lip.  In the case of broad flat objects they acted in a wholly
+different manner.  The pointed anterior extremity of the body, after
+being brought into contact with an object of this kind, was drawn within
+the adjoining rings, so that it appeared truncated and became as thick as
+the rest of the body.  This part could then be seen to swell a little;
+and this, I believe, is due to the pharynx being pushed a little
+forwards.  Then by a slight withdrawal of the pharynx or by its
+expansion, a vacuum was produced beneath the truncated slimy end of the
+body whilst in contact with the object; and by this means the two adhered
+firmly together. {53}  That under these circumstances a vacuum was
+produced was plainly seen on one occasion, when a large worm lying
+beneath a flaccid cabbage leaf tried to drag it away; for the surface of
+the leaf directly over the end of the worm’s body became deeply pitted.
+On another occasion a worm suddenly lost its hold on a flat leaf; and the
+anterior end of the body was momentarily seen to be cup-formed.  Worms
+can attach themselves to an object beneath water in the same manner; and
+I saw one thus dragging away a submerged slice of an onion-bulb.
+
+The edges of fresh or nearly fresh leaves affixed to the ground were
+often nibbled by the worms; and sometimes the epidermis and all the
+parenchyma on one side was gnawed completely away over a considerable
+space; the epidermis alone on the opposite side being left quite clean.
+The veins were never touched, and leaves were thus sometimes partly
+converted into skeletons.  As worms have no teeth and as their mouths
+consist of very soft tissue, it may be presumed that they consume by
+means of suction the edges and the parenchyma of fresh leaves, after they
+have been softened by the digestive fluid.  They cannot attack such
+strong leaves as those of sea-kale or large and thick leaves of ivy;
+though one of the latter after it had become rotten was reduced in parts
+to the state of a skeleton.
+
+Worms seize leaves and other objects, not only to serve as food, but for
+plugging up the mouths of their burrows; and this is one of their
+strongest instincts.  They sometimes work so energetically that Mr. D. F.
+Simpson, who has a small walled garden where worms abound in Bayswater,
+informs me that on a calm damp evening he there heard so extraordinary a
+rustling noise from under a tree from which many leaves had fallen, that
+he went out with a light and discovered that the noise was caused by many
+worms dragging the dry leaves and squeezing them into the burrows.  Not
+only leaves, but petioles of many kinds, some flower-peduncles, often
+decayed twigs of trees, bits of paper, feathers, tufts of wool and
+horse-hairs are dragged into their burrows for this purpose.  I have seen
+as many as seventeen petioles of a Clematis projecting from the mouth of
+one burrow, and ten from the mouth of another.  Some of these objects,
+such as the petioles just named, feathers, &c., are never gnawed by
+worms.  In a gravel-walk in my garden I found many hundred leaves of a
+pine-tree (_P. austriaca_ or _nigricans_) drawn by their bases into
+burrows.  The surfaces by which these leaves are articulated to the
+branches are shaped in as peculiar a manner as is the joint between the
+leg-bones of a quadruped; and if these surfaces had been in the least
+gnawed, the fact would have been immediately visible, but there was no
+trace of gnawing.  Of ordinary dicotyledonous leaves, all those which are
+dragged into burrows are not gnawed.  I have seen as many as nine leaves
+of the lime-tree drawn into the same burrow, and not nearly all of them
+had been gnawed; but such leaves may serve as a store for future
+consumption.  Where fallen leaves are abundant, many more are sometimes
+collected over the mouth of a burrow than can be used, so that a small
+pile of unused leaves is left like a roof over those which have been
+partly dragged in.
+
+A leaf in being dragged a little way into a cylindrical burrow is
+necessarily much folded or crumpled.  When another leaf is drawn in, this
+is done exteriorly to the first one, and so on with the succeeding
+leaves; and finally all become closely folded and pressed together.
+Sometimes the worm enlarges the mouth of its burrow, or makes a fresh one
+close by, so as to draw in a still larger number of leaves.  They often
+or generally fill up the interstices between the drawn-in leaves with
+moist viscid earth ejected from their bodies; and thus the mouths of the
+burrows are securely plugged.  Hundreds of such plugged burrows may be
+seen in many places, especially during the autumnal and early winter
+months.  But, as will hereafter be shown, leaves are dragged into the
+burrows not only for plugging them up and for food, but for the sake of
+lining the upper part or mouth.
+
+When worms cannot obtain leaves, petioles, sticks, &c., with which to
+plug up the mouths of their burrows, they often protect them by little
+heaps of stones; and such heaps of smooth rounded pebbles may frequently
+be seen on gravel-walks.  Here there can be no question about food.  A
+lady, who was interested in the habits of worms, removed the little heaps
+of stones from the mouths of several burrows and cleared the surface of
+the ground for some inches all round.  She went out on the following
+night with a lantern, and saw the worms with their tails fixed in their
+burrows, dragging the stones inwards by the aid of their mouths, no doubt
+by suction.  “After two nights some of the holes had 8 or 9 small stones
+over them; after four nights one had about 30, and another 34 stones.”
+{58}  One stone—which had been dragged over the gravel-walk to the mouth
+of a burrow weighed two ounces; and this proves how strong worms are.
+But they show greater strength in sometimes displacing stones in a
+well-trodden gravel-walk; that they do so, may be inferred from the
+cavities left by the displaced stones being exactly filled by those lying
+over the mouths of adjoining burrows, as I have myself observed.
+
+Work of this kind is usually performed during the night; but I have
+occasionally known objects to be drawn into the burrows during the day.
+What advantage the worms derive from plugging up the mouths of their
+burrows with leaves, &c., or from piling stones over them, is doubtful.
+They do not act in this manner at the times when they eject much earth
+from their burrows; for their castings then serve to cover the mouths.
+When gardeners wish to kill worms on a lawn, it is necessary first to
+brush or rake away the castings from the surface, in order that the
+lime-water may enter the burrows. {59a}  It might be inferred from this
+fact that the mouths are plugged up with leaves, &c., to prevent the
+entrance of water during heavy rain; but it may be urged against this
+view that a few, loose, well-rounded stones are ill-adapted to keep out
+water.  I have moreover seen many burrows in the perpendicularly cut
+turf-edgings to gravel-walks, into which water could hardly flow, as well
+plugged as burrows on a level surface.  It is not probable that the plugs
+or piles of stones serve to conceal the burrows from scolopendras, which,
+according to Hoffmeister, {59b} are the bitterest enemies of worms, or
+from the larger species of Carabus and Staphylinus which attack them
+ferociously, for these animals are nocturnal, and the burrows are opened
+at night.  May not worms when the mouth of the burrow is protected be
+able to remain with safety with their heads close to it, which we know
+that they like to do, but which costs so many of them their lives?  Or
+may not the plugs check the free ingress of the lowest stratum of air,
+when chilled by radiation at night, from the surrounding ground and
+herbage?  I am inclined to believe in this latter view: firstly, because
+when worms were kept in pots in a room with a fire, in which case cold
+air could not enter the burrows, they plugged them up in a slovenly
+manner; and secondarily, because they often coat the upper part of their
+burrows with leaves, apparently to prevent their bodies from coming into
+close contact with the cold damp earth.  Mr. E. Parfitt has suggested to
+me that the mouths of the burrows are closed in order that the air within
+them may be kept thoroughly damp, and this seems the most probable
+explanation of the habit.  But the plugging-up process may serve for all
+the above purposes.
+
+Whatever the motive may be, it appears that worms much dislike leaving
+the mouths of their burrows open.  Nevertheless they will reopen them at
+night, whether or not they can afterwards close them.  Numerous open
+burrows may be seen on recently-dug ground, for in this case the worms
+eject their castings in cavities left in the ground, or in the old
+burrows instead of piling them over the mouths of their burrows, and they
+cannot collect objects on the surface by which the mouths might be
+protected.  So again on a recently disinterred pavement of a Roman villa
+at Abinger (hereafter to be described) the worms pertinaciously opened
+their burrows almost every night, when these had been closed by being
+trampled on, although they were rarely able to find a few minute stones
+wherewith to protect them.
+
+_Intelligence shown by worms in their manner of plugging up their
+burrows_.—If a man had to plug up a small cylindrical hole, with such
+objects as leaves, petioles or twigs, he would drag or push them in by
+their pointed ends; but if these objects were very thin relatively to the
+size of the hole, he would probably insert some by their thicker or
+broader ends.  The guide in his case would be intelligence.  It seemed
+therefore worth while to observe carefully how worms dragged leaves into
+their burrows; whether by their tips or bases or middle parts.  It seemed
+more especially desirable to do this in the case of plants not natives to
+our country; for although the habit of dragging leaves into their burrows
+is undoubtedly instinctive with worms, yet instinct could not tell them
+how to act in the case of leaves about which their progenitors knew
+nothing.  If, moreover, worms acted solely through instinct or an
+unvarying inherited impulse, they would draw all kinds of leaves into
+their burrows in the same manner.  If they have no such definite
+instinct, we might expect that chance would determine whether the tip,
+base or middle was seized.  If both these alternatives are excluded,
+intelligence alone is left; unless the worm in each case first tries many
+different methods, and follows that alone which proves possible or the
+most easy; but to act in this manner and to try different methods makes a
+near approach to intelligence.
+
+In the first place 227 withered leaves of various kinds, mostly of
+English plants, were pulled out of worm-burrows in several places.  Of
+these, 181 had been drawn into the burrows by or near their tips, so that
+the foot-stalk projected nearly upright from the mouth of the burrow; 20
+had been drawn in by their bases, and in this case the tips projected
+from the burrows; and 26 had been seized near the middle, so that these
+had been drawn in transversely and were much crumpled.  Therefore 80 per
+cent. (always using the nearest whole number) had been drawn in by the
+tip, 9 per cent. by the base or foot-stalk, and 11 per cent. transversely
+or by the middle.  This alone is almost sufficient to show that chance
+does not determine the manner in which leaves are dragged into the
+burrows.
+
+Of the above 227 leaves, 70 consisted of the fallen leaves of the common
+lime-tree, which is almost certainly not a native of England.  These
+leaves are much acuminated towards the tip, and are very broad at the
+base with a well-developed foot-stalk.  They are thin and quite flexible
+when half-withered.  Of the 70, 79 per cent. had been drawn in by or near
+the tip; 4 per cent. by or near the base; and 17 per cent. transversely
+or by the middle.  These proportions agree very closely, as far as the
+tip is concerned, with those before given.  But the percentage drawn in
+by the base is smaller, which may be attributed to the breadth of the
+basal part of the blade.  We here, also, see that the presence of a
+foot-stalk, which it might have been expected would have tempted the
+worms as a convenient handle, has little or no influence in determining
+the manner in which lime leaves are dragged into the burrows.  The
+considerable proportion, viz., 17 per cent., drawn in more or less
+transversely depends no doubt on the flexibility of these half-decayed
+leaves.  The fact of so many having been drawn in by the middle, and of
+some few having been drawn in by the base, renders it improbable that the
+worms first tried to draw in most of the leaves by one or both of these
+methods, and that they afterwards drew in 79 per cent. by their tips; for
+it is clear that they would not have failed in drawing them in by the
+base or middle.
+
+The leaves of a foreign plant were next searched for, the blades of which
+were not more pointed towards the apex than towards the base.  This
+proved to be the case with those of a laburnum (a hybrid between _Cytisus
+alpinus_ and _laburnum_) for on doubling the terminal over the basal
+half, they generally fitted exactly; and when there was any difference,
+the basal half was a little the narrower.  It might, therefore, have been
+expected that an almost equal number of these leaves would have been
+drawn in by the tip and base, or a slight excess in favour of the latter.
+But of 73 leaves (not included in the first lot of 227) pulled out of
+worm-burrows, 63 per cent. had been drawn in by the tip; 27 per cent. by
+the base, and 10 per cent. transversely.  We here see that a far larger
+proportion, viz., 27 per cent. were drawn in by the base than in the case
+of lime leaves, the blades of which are very broad at the base, and of
+which only 4 per cent. had thus been drawn in.  We may perhaps account
+for the fact of a still larger proportion of the laburnum leaves not
+having been drawn in by the base, by worms having acquired the habit of
+generally drawing in leaves by their tips and thus avoiding the
+foot-stalk.  For the basal margin of the blade in many kinds of leaves
+forms a large angle with the foot-stalk; and if such a leaf were drawn in
+by the foot-stalk, the basal margin would come abruptly into contact with
+the ground on each side of the burrow, and would render the drawing in of
+the leaf very difficult.
+
+Nevertheless worms break through their habit of avoiding the foot-stalk,
+if this part offers them the most convenient means for drawing leaves
+into their burrows.  The leaves of the endless hybridised varieties of
+the Rhododendron vary much in shape; some are narrowest towards the base
+and others towards the apex.  After they have fallen off, the blade on
+each side of the midrib often becomes curled up while drying, sometimes
+along the whole length, sometimes chiefly at the base, sometimes towards
+the apex.  Out of 28 fallen leaves on one bed of peat in my garden, no
+less than 23 were narrower in the basal quarter than in the terminal
+quarter of their length; and this narrowness was chiefly due to the
+curling in of the margins.  Out of 36 fallen leaves on another bed, in
+which different varieties of the Rhododendron grew, only 17 were narrower
+towards the base than towards the apex.  My son William, who first called
+my attention to this case, picked up 237 fallen leaves in his garden
+(where the Rhododendron grows in the natural soil) and of these 65 per
+cent. could have been drawn by worms into their burrows more easily by
+the base or foot-stalk than by the tip; and this was partly due to the
+shape of the leaf and in a less degree to the curling in of the margins:
+27 per cent. could have been drawn in more easily by the tip than by the
+base: and 8 per cent. with about equal ease by either end.  The shape of
+a fallen leaf ought to be judged of before one end has been drawn into a
+burrow, for after this has happened, the free end, whether it be the base
+or apex, will dry more quickly than the end imbedded in the damp ground;
+and the exposed margins of the free end will consequently tend to become
+more curled inwards than they were when the leaf was first seized by the
+worm.  My son found 91 leaves which had been dragged by worms into their
+burrows, though not to a great depth; of these 66 per cent. had been
+drawn in by the base or foot-stalk; and 34 per cent. by the tip.  In this
+case, therefore, the worms judged with a considerable degree of
+correctness how best to draw the withered leaves of this foreign plant
+into their burrows; notwithstanding that they had to depart from their
+usual habit of avoiding the foot-stalk.
+
+On the gravel-walks in my garden a very large number of leaves of three
+species of Pinus (_P. austriaca_, _nigricans_ and _sylvestris_) are
+regularly drawn into the mouths of worm burrows.  These leaves consist of
+two so-called needles, which are of considerable length in the two first
+and short in the last named species, and are united to a common base; and
+it is by this part that they are almost invariably drawn into the
+burrows.  I have seen only two or at most three exceptions to this rule
+with worms in a state of nature.  As the sharply pointed needles diverge
+a little, and as several leaves are drawn into the same burrow, each tuft
+forms a perfect _chevaux de frise_.  On two occasions many of these tufts
+were pulled up in the evening, but by the following morning fresh leaves
+had been pulled in, and the burrows were again well protected.  These
+leaves could not be dragged into the burrows to any depth, except by
+their bases, as a worm cannot seize hold of the two needles at the same
+time, and if one alone were seized by the apex, the other would be
+pressed against the ground and would resist the entry of the seized one.
+This was manifest in the above mentioned two or three exceptional cases.
+In order, therefore, that worms should do their work well, they must drag
+pine-leaves into their burrows by their bases, where the two needles are
+conjoined.  But how they are guided in this work is a perplexing
+question.
+
+This difficulty led my son Francis and myself to observe worms in
+confinement during several nights by the aid of a dim light, while they
+dragged the leaves of the above named pines into their burrows.  They
+moved the anterior extremities of their bodies about the leaves, and on
+several occasions when they touched the sharp end of a needle they
+withdrew suddenly as if pricked.  But I doubt whether they were hurt, for
+they are indifferent to very sharp objects, and will swallow even
+rose-thorns and small splinters of glass.  It may also be doubted,
+whether the sharp ends of the needles serve to tell them that this is the
+wrong end to seize; for the points were cut off many leaves for a length
+of about one inch, and fifty-seven of them thus treated were drawn into
+the burrows by their bases, and not one by the cut-off ends.  The worms
+in confinement often seized the needles near the middle and drew them
+towards the mouths of their burrows; and one worm tried in a senseless
+manner to drag them into the burrow by bending them.  They sometimes
+collected many more leaves over the mouths of their burrows (as in the
+case formerly mentioned of lime-leaves) than could enter them.  On other
+occasions, however, they behaved very differently; for as soon as they
+touched the base of a pine-leaf, this was seized, being sometimes
+completely engulfed in their mouths, or a point very near the base was
+seized, and the leaf was then quickly dragged or rather jerked into their
+burrows.  It appeared both to my son and myself as if the worms instantly
+perceived as soon as they had seized a leaf in the proper manner.  Nine
+such cases were observed, but in one of them the worm failed to drag the
+leaf into its burrow, as it was entangled by other leaves lying near.  In
+another case a leaf stood nearly upright with the points of the needles
+partly inserted into a burrow, but how placed there was not seen; and
+then the worm reared itself up and seized the base, which was dragged
+into the mouth of the burrow by bowing the whole leaf.  On the other
+hand, after a worm had seized the base of a leaf, this was on two
+occasions relinquished from some unknown motive.
+
+As already remarked, the habit of plugging up the mouths of the burrows
+with various objects, is no doubt instinctive in worms; and a very young
+one, born in one of my pots, dragged for some little distance a
+Scotch-fir leaf, one needle of which was as long and almost as thick as
+its own body.  No species of pine is endemic in this part of England, it
+is therefore incredible that the proper manner of dragging pine-leaves
+into the burrows can be instinctive with our worms.  But as the worms on
+which the above observations were made, were dug up beneath or near some
+pines, which had been planted there about forty years, it was desirable
+to prove that their actions were not instinctive.  Accordingly,
+pine-leaves were scattered on the ground in places far removed from any
+pine-tree, and 90 of them were drawn into the burrows by their bases.
+Only two were drawn in by the tips of the needles, and these were not
+real exceptions, as one was drawn in for a very short distance, and the
+two needles of the other cohered.  Other pine-leaves were given to worms
+kept in pots in a warm room, and here the result was different; for out
+of 42 leaves drawn into the burrows, no less than 16 were drawn in by the
+tips of the needles.  These worms, however, worked in a careless or
+slovenly manner; for the leaves were often drawn in to only a small
+depth; sometimes they were merely heaped over the mouths of the burrows,
+and sometimes none were drawn in.  I believe that this carelessness may
+be accounted for either by the warmth of the air, or by its dampness, as
+the pots were covered by glass plates; the worms consequently did not
+care about plugging up their holes effectually.  Pots tenanted by worms
+and covered with a net which allowed the free entrance of air, were left
+out of doors for several nights, and now 72 leaves were all properly
+drawn in by their bases.
+
+It might perhaps be inferred from the facts as yet given, that worms
+somehow gain a general notion of the shape or structure of pine-leaves,
+and perceive that it is necessary for them to seize the base where the
+two needles are conjoined.  But the following cases make this more than
+doubtful.  The tips of a large number of needles of _P. austriaca_ were
+cemented together with shell-lac dissolved in alcohol, and were kept for
+some days, until, as I believe, all odour or taste had been lost; and
+they were then scattered on the ground where no pine-trees grew, near
+burrows from which the plugging had been removed.  Such leaves could have
+been drawn into the burrows with equal ease by either end; and judging
+from analogy and more especially from the case presently to be given of
+the petioles of _Clematis montana_, I expected that the apex would have
+been preferred.  But the result was that out of 121 leaves with the tips
+cemented, which were drawn into burrows, 108 were drawn in by their
+bases, and only 13 by their tips.  Thinking that the worms might possibly
+perceive and dislike the smell or taste of the shell-lac, though this was
+very improbable, especially after the leaves had been left out during
+several nights, the tips of the needles of many leaves were tied together
+with fine thread.  Of leaves thus treated 150 were drawn into burrows—123
+by the base and 27 by the tied tips; so that between four and five times
+as many were drawn in by the base as by the tip.  It is possible that the
+short cut-off ends of the thread with which they were tied, may have
+tempted the worms to drag in a larger proportional number by the tips
+than when cement was used.  Of the leaves with tied and cemented tips
+taken together (271 in number) 85 per cent. were drawn in by the base and
+15 per cent. by the tips.  We may therefore infer that it is not the
+divergence of the two needles which leads worms in a state of nature
+almost invariably to drag pine-leaves into their burrows by the base.
+Nor can it be the sharpness of the points of the needles which determines
+them; for, as we have seen, many leaves with the points cut off were
+drawn in by their bases.  We are thus led to conclude, that with
+pine-leaves there must be something attractive to worms in the base,
+notwithstanding that few ordinary leaves are drawn in by the base or
+foot-stalk.
+
+_Petioles_.—We will now turn to the petioles or foot-stalks of compound
+leaves, after the leaflets have fallen off.  Those from _Clematis
+montana_, which grew over a verandah, were dragged early in January in
+large numbers into the burrows on an adjoining gravel-walk, lawn, and
+flower-bed.  These petioles vary from 2½ to 4½ inches in length, are
+rigid and of nearly uniform thickness, except close to the base where
+they thicken rather abruptly, being here about twice as thick as in any
+other part.  The apex is somewhat pointed, but soon withers and is then
+easily broken off.  Of these petioles, 314 were pulled out of burrows in
+the above specified sites; and it was found that 76 per cent. had been
+drawn in by their tips, and 24 per cent by their bases; so that those
+drawn in by the tip were a little more than thrice as many as those drawn
+in by the base.  Some of those extracted from the well-beaten gravel-walk
+were kept separate from the others; and of these (59 in number) nearly
+five times as many had been drawn in by the tip as by the base; whereas
+of those extracted from the lawn and flower-bed, where from the soil
+yielding more easily, less care would be necessary in plugging up the
+burrows, the proportion of those drawn in by the tip (130) to those drawn
+in by the base (48) was rather less than three to one.  That these
+petioles had been dragged into the burrows for plugging them up, and not
+for food, was manifest, as neither end, as far as I could see, had been
+gnawed.  As several petioles are used to plug up the same burrow, in one
+case as many as 10, and in another case as many as 15, the worms may
+perhaps at first draw in a few by the thicker end so as to save labour;
+but afterwards a large majority are drawn in by the pointed end, in order
+to plug up the hole securely.
+
+The fallen petioles of our native ash-tree were next observed, and the
+rule with most objects, viz., that a large majority are dragged into the
+burrows by the more pointed end, had not here been followed; and this
+fact much surprised me at first.  These petioles vary in length from 5 to
+8½ inches; they are thick and fleshy towards the base, whence they taper
+gently towards the apex, which is a little enlarged and truncated where
+the terminal leaflet had been originally attached.  Under some ash-trees
+growing in a grass-field, 229 petioles were pulled out of worm burrows
+early in January, and of these 51.5 per cent. had been drawn in by the
+base, and 48.5 per cent. by the apex.  This anomaly was however readily
+explained as soon as the thick basal part was examined; for in 78 out of
+103 petioles, this part had been gnawed by worms, just above the
+horse-shoe shaped articulation.  In most cases there could be no mistake
+about the gnawing; for ungnawed petioles which were examined after being
+exposed to the weather for eight additional weeks had not become more
+disintegrated or decayed near the base than elsewhere.  It is thus
+evident that the thick basal end of the petiole is drawn in not solely
+for the sake of plugging up the mouths of the burrows, but as food.  Even
+the narrow truncated tips of some few petioles had been gnawed; and this
+was the case in 6 out of 37 which were examined for this purpose.  Worms,
+after having drawn in and gnawed the basal end, often push the petioles
+out of their burrows; and then drag in fresh ones, either by the base for
+food, or by the apex for plugging up the mouth more effectually.  Thus,
+out of 37 petioles inserted by their tips, 5 had been previously drawn in
+by the base, for this part had been gnawed.  Again, I collected a handful
+of petioles lying loose on the ground close to some plugged-up burrows,
+where the surface was thickly strewed with other petioles which
+apparently had never been touched by worms; and 14 out of 47 (_i.e._
+nearly one-third), after having had their bases gnawed had been pushed
+out of the burrows and were now lying on the ground.  From these several
+facts we may conclude that worms draw in some petioles of the ash by the
+base to serve as food, and others by the tip to plug up the mouths of
+their burrows in the most efficient manner.
+
+The petioles of _Robinia pseudo-acacia_ vary from 4 or 5 to nearly 12
+inches in length; they are thick close to the base before the softer
+parts have rotted off, and taper much towards the upper end.  They are so
+flexible that I have seen some few doubled up and thus drawn into the
+burrows of worms.  Unfortunately these petioles were not examined until
+February, by which time the softer parts had completely rotted off, so
+that it was impossible to ascertain whether worms had gnawed the bases,
+though this is in itself probable.  Out of 121 petioles extracted from
+burrows early in February, 68 were imbedded by the base, and 53 by the
+apex.  On February 5 all the petioles which had been drawn into the
+burrows beneath a Robinia, were pulled up; and after an interval of
+eleven days, 35 petioles had been again dragged in, 19 by the base, and
+16 by the apex.  Taking these two lots together, 56 per cent. were drawn
+in by the base, and 44 per cent. by the apex.  As all the softer parts
+had long ago rotted off, we may feel sure, especially in the latter case,
+that none had been drawn in as food.  At this season, therefore, worms
+drag these petioles into their burrows indifferently by either end, a
+slight preference being given to the base.  This latter fact may be
+accounted for by the difficulty of plugging up a burrow with objects so
+extremely thin as are the upper ends.  In support of this view, it may be
+stated that out of the 16 petioles which had been drawn in by their upper
+ends, the more attenuated terminal portion of 7 had been previously
+broken off by some accident.
+
+_Triangles of paper_.—Elongated triangles were cut out of moderately
+stiff writing-paper, which was rubbed with raw fat on both sides, so as
+to prevent their becoming excessively limp when exposed at night to rain
+and dew.  The sides of all the triangles were three inches in length,
+with the bases of 120 one inch, and of the other 183 half an inch in
+length.  These latter triangles were very narrow or much acuminated. {79}
+As a check on the observations presently to be given, similar triangles
+in a damp state were seized by a very narrow pair of pincers at different
+points and at all inclinations with reference to the margins, and were
+then drawn into a short tube of the diameter of a worm-burrow.  If seized
+by the apex, the triangle was drawn straight into the tube, with its
+margins infolded; if seized at some little distance from the apex, for
+instance at half an inch, this much was doubled back within the tube.  So
+it was with the base and basal angles, though in this case the triangles
+offered, as might have been expected, much more resistance to being drawn
+in.  If seized near the middle the triangle was doubled up, with the apex
+and base left sticking out of the tube.  As the sides of the triangles
+were three inches in length, the result of their being drawn into a tube
+or into a burrow in different ways, may be conveniently divided into
+three groups: those drawn in by the apex or within an inch of it; those
+drawn in by the base or within an inch of it; and those drawn in by any
+point in the middle inch.
+
+In order to see how the triangles would be seized by worms, some in a
+damp state were given to worms kept in confinement.  They were seized in
+three different manners in the case of both the narrow and broad
+triangles: viz., by the margin; by one of the three angles, which was
+often completely engulfed in their mouths; and lastly, by suction applied
+to any part of the flat surface.  If lines parallel to the base and an
+inch apart, are drawn across a triangle with the sides three inches in
+length, it will be divided into three parts of equal length.  Now if
+worms seized indifferently by chance any part, they would assuredly seize
+on the basal part or division far oftener than on either of the two other
+divisions.  For the area of the basal to the apical part is as 5 to 1, so
+that the chance of the former being drawn into a burrow by suction, will
+be as 5 to 1, compared with the apical part.  The base offers two angles
+and the apex only one, so that the former would have twice as good a
+chance (independently of the size of the angles) of being engulfed in a
+worm’s mouth, as would the apex.  It should, however, be stated that the
+apical angle is not often seized by worms; the margin at a little
+distance on either side being preferred.  I judge of this from having
+found in 40 out of 46 cases in which triangles had been drawn into
+burrows by their apical ends, that the tip had been doubled back within
+the burrow for a length of between 1/20 of an inch and 1 inch.  Lastly,
+the proportion between the margins of the basal and apical parts is as 3
+to 2 for the broad, and 2½ to 2 for the narrow triangles.  From these
+several considerations it might certainly have been expected, supposing
+that worms seized hold of the triangles by chance, that a considerably
+larger proportion would have been dragged into the burrows by the basal
+than by the apical part; but we shall immediately see how different was
+the result.
+
+Triangles of the above specified sizes were scattered on the ground in
+many places and on many successive nights near worm-burrows, from which
+the leaves, petioles, twigs, &c., with which they had been plugged, were
+removed.  Altogether 303 triangles were drawn by worms into their
+burrows: 12 others were drawn in by both ends, but as it was impossible
+to judge by which end they had been first seized, these are excluded.  Of
+the 303, 62 per cent. had been drawn in by the apex (using this term for
+all drawn in by the apical part, one inch in length); 15 per cent. by the
+middle; and 23 per cent. by the basal part.  If they had been drawn
+indifferently by any point, the proportion for the apical, middle and
+basal parts would have been 33.3 per cent. for each; but, as we have just
+seen, it might have been expected that a much larger proportion would
+have been drawn in by the basal than by any other part.  As the case
+stands, nearly three times as many were drawn in by the apex as by the
+base.  If we consider the broad triangles by themselves, 59 per cent.
+were drawn in by the apex, 25 per cent. by the middle, and 16 per cent.
+by the base.  Of the narrow triangles, 65 per cent. were drawn in by the
+apex, 14 per cent, by the middle, and 21 per cent. by the base; so that
+here those drawn in by the apex were more than 3 times as many as those
+drawn in by the base.  We may therefore conclude that the manner in which
+the triangles are drawn into the burrows is not a matter of chance.
+
+In eight cases, two triangles had been drawn into the same burrow, and in
+seven of these cases, one had been drawn in by the apex and the other by
+the base.  This again indicates that the result is not determined by
+chance.  Worms appear sometimes to revolve in the act of drawing in the
+triangles, for five out of the whole lot had been wound into an irregular
+spire round the inside of the burrow.  Worms kept in a warm room drew 63
+triangles into their burrows; but, as in the case of the pine-leaves,
+they worked in a rather careless manner, for only 44 per cent. were drawn
+in by the apex, 22 per cent. by the middle, and 33 per cent. by the base.
+In five cases, two triangles were drawn into the same burrow.
+
+It may be suggested with much apparent probability that so large a
+proportion of the triangles were drawn in by the apex, not from the worms
+having selected this end as the most convenient for the purpose, but from
+having first tried in other ways and failed.  This notion was
+countenanced by the manner in which worms in confinement were seen to
+drag about and drop the triangles; but then they were working carelessly.
+I did not at first perceive the importance of this subject, but merely
+noticed that the bases of those triangles which had been drawn in by the
+apex, were generally clean and not crumpled.  The subject was afterwards
+attended to carefully.  In the first place several triangles which had
+been drawn in by the basal angles, or by the base, or a little above the
+base, and which were thus much crumpled and dirtied, were left for some
+hours in water and were then well shaken while immersed; but neither the
+dirt nor the creases were thus removed.  Only slight creases could be
+obliterated, even by pulling the wet triangles several times through my
+fingers.  Owing to the slime from the worms’ bodies, the dirt was not
+easily washed off.  We may therefore conclude that if a triangle, before
+being dragged in by the apex, had been dragged into a burrow by its base
+with even a slight degree of force, the basal part would long retain its
+creases and remain dirty.  The condition of 89 triangles (65 narrow and
+24 broad ones), which had been drawn in by the apex, was observed; and
+the bases of only 7 of them were at all creased, being at the same time
+generally dirty.  Of the 82 uncreased triangles, 14 were dirty at the
+base; but it does not follow from this fact that these had first been
+dragged towards the burrows by their bases; for the worms sometimes
+covered large portions of the triangles with slime, and these when
+dragged by the apex over the ground would be dirtied; and during rainy
+weather, the triangles were often dirtied over one whole side or over
+both sides.  If the worms had dragged the triangles to the mouths of
+their burrows by their bases, as often as by their apices, and had then
+perceived, without actually trying to draw them into the burrow, that the
+broader end was not well adapted for this purpose—even in this case a
+large proportion would probably have had their basal ends dirtied.  We
+may therefore infer—improbable as is the inference—that worms are able by
+some means to judge which is the best end by which to draw triangles of
+paper into their burrows.
+
+The percentage results of the foregoing observations on the manner in
+which worms draw various kinds of objects into the mouths of their
+burrows may be abridged as follows:—
+
+   Nature of       Drawn into the   Drawn in, by or   Drawn in, by or
+    Object.        burrows, by or       near the       near the base.
+                   near the apex.       middle.
+Leaves of                       80                11                 9
+various kinds
+—of the Lime,                   79                17                 4
+basal margin of
+blade broad,
+apex acuminated
+—of a Laburnum,                 63                10                27
+basal part of
+blade as narrow
+as, or
+sometimes
+little narrower
+than the apical
+part
+—of the                         34        ...                       66
+Rhododendron,
+basal part of
+blade often
+narrower than
+the apical part
+—of Pine-trees,         ...               ...                      100
+consisting of
+two needles
+arising from a
+common base
+Petioles of a                   76        ...                       24
+Clematis,
+somewhat
+pointed at the
+apex, and blunt
+at the base
+—of the Ash,                  48.5        ...                     51.5
+the thick basal
+end often drawn
+in to serve as
+food
+—of Robinia,                    44        ...                       56
+extremely thin,
+especially
+towards the
+apex, so as to
+be ill-fitted
+for plugging up
+the burrows
+Triangles of                    62                15                23
+paper, of the
+two sizes
+—of the broad                   59                25                16
+ones alone
+—of the narrow                  65                14                21
+ones alone
+
+If we consider these several cases, we can hardly escape from the
+conclusion that worms show some degree of intelligence in their manner of
+plugging up their burrows.  Each particular object is seized in too
+uniform a manner, and from causes which we can generally understand, for
+the result to be attributed to mere chance.  That every object has not
+been drawn in by its pointed end, may be accounted for by labour having
+been saved through some being inserted by their broader or thicker ends.
+No doubt worms are led by instinct to plug up their burrows; and it might
+have been expected that they would have been led by instinct how best to
+act in each particular case, independently of intelligence.  We see how
+difficult it is to judge whether intelligence comes into play, for even
+plants might sometimes be thought to be thus directed; for instance when
+displaced leaves re-direct their upper surfaces towards the light by
+extremely complicated movements and by the shortest course.  With
+animals, actions appearing due to intelligence may be performed through
+inherited habit without any intelligence, although aboriginally thus
+acquired.  Or the habit may have been acquired through the preservation
+and inheritance of beneficial variations of some other habit; and in this
+case the new habit will have been acquired independently of intelligence
+throughout the whole course of its development.  There is no _à priori_
+improbability in worms having acquired special instincts through either
+of these two latter means.  Nevertheless it is incredible that instincts
+should have been developed in reference to objects, such as the leaves of
+petioles of foreign plants, wholly unknown to the progenitors of the
+worms which act in the described manner.  Nor are their actions so
+unvarying or inevitable as are most true instincts.
+
+As worms are not guided by special instincts in each particular case,
+though possessing a general instinct to plug up their burrows, and as
+chance is excluded, the next most probable conclusion seems to be that
+they try in many different ways to draw in objects, and at last succeed
+in some one way.  But it is surprising that an animal so low in the scale
+as a worm should have the capacity for acting in this manner, as many
+higher animals have no such capacity.  For instance, ants may be seen
+vainly trying to drag an object transversely to their course, which could
+be easily drawn longitudinally; though after a time they generally act in
+a wiser manner, M. Fabre states {89a} that a Sphex—an insect belonging to
+the same highly-endowed order with ants—stocks its nest with paralysed
+grass-hoppers, which are invariably dragged into the burrow by their
+antennæ.  When these were cut off close to the head, the Sphex seized the
+palpi; but when these were likewise cut off, the attempt to drag its prey
+into the burrow was given up in despair.  The Sphex had not intelligence
+enough to seize one of the six legs or the ovipositor of the grasshopper,
+which, as M. Fabre remarks, would have served equally well.  So again, if
+the paralysed prey with an egg attached to it be taken out of the cell,
+the Sphex after entering and finding the cell empty, nevertheless closes
+it up in the usual elaborate manner.  Bees will try to escape and go on
+buzzing for hours on a window, one half of which has been left open.
+Even a pike continued during three months to dash and bruise itself
+against the glass sides of an aquarium, in the vain attempt to seize
+minnows on the opposite side. {89b}  A cobra-snake was seen by Mr. Layard
+{90} to act much more wisely than either the pike or the Sphex; it had
+swallowed a toad lying within a hole, and could not withdraw its head;
+the toad was disgorged, and began to crawl away; it was again swallowed
+and again disgorged; and now the snake had learnt by experience, for it
+seized the toad by one of its legs and drew it out of the hole.  The
+instincts of even the higher animals are often followed in a senseless or
+purposeless manner: the weaver-bird will perseveringly wind threads
+through the bars of its cage, as if building a nest: a squirrel will pat
+nuts on a wooden floor, as if he had just buried them in the ground: a
+beaver will cut up logs of wood and drag them about, though there is no
+water to dam up; and so in many other cases.
+
+Mr. Romanes, who has specially studied the minds of animals, believes
+that we can safely infer intelligence, only when we see an individual
+profiting by its own experience.  By this test the cobra showed some
+intelligence; but this would have been much plainer if on a second
+occasion he had drawn a toad out of a hole by its leg.  The Sphex failed
+signally in this respect.  Now if worms try to drag objects into their
+burrows first in one way and then in another, until they at last succeed,
+they profit, at least in each particular instance, by experience.
+
+But evidence has been advanced showing that worms do not habitually try
+to draw objects into their burrows in many different ways.  Thus
+half-decayed lime-leaves from their flexibility could have been drawn in
+by their middle or basal parts, and were thus drawn into the burrows in
+considerable numbers; yet a large majority were drawn in by or near the
+apex.  The petioles of the Clematis could certainly have been drawn in
+with equal ease by the base and apex; yet three times and in certain
+cases five times as many were drawn in by the apex as by the base.  It
+might have been thought that the foot-stalks of leaves would have tempted
+the worms as a convenient handle; yet they are not largely used, except
+when the base of the blade is narrower than the apex.  A large number of
+the petioles of the ash are drawn in by the base; but this part serves
+the worms as food.  In the case of pine-leaves worms plainly show that
+they at least do not seize the leaf by chance; but their choice does not
+appear to be determined by the divergence of the two needles, and the
+consequent advantage or necessity of drawing them into their burrows by
+the base.  With respect to the triangles of paper, those which had been
+drawn in by the apex rarely had their bases creased or dirty; and this
+shows that the worms had not often first tried to drag them in by this
+end.
+
+If worms are able to judge, either before drawing or after having drawn
+an object close to the mouths of their burrows, how best to drag it in,
+they must acquire some notion of its general shape.  This they probably
+acquire by touching it in many places with the anterior extremity of
+their bodies, which serves as a tactile organ.  It may be well to
+remember how perfect the sense of touch becomes in a man when born blind
+and deaf, as are worms.  If worms have the power of acquiring some
+notion, however rude, of the shape of an object and of their burrows, as
+seems to be the case, they deserve to be called intelligent; for they
+then act in nearly the same manner as would a man under similar
+circumstances.
+
+To sum up, as chance does not determine the manner in which objects are
+drawn into the burrows, and as the existence of specialized instincts for
+each particular case cannot be admitted, the first and most natural
+supposition is that worms try all methods until they at last succeed; but
+many appearances are opposed to such a supposition.  One alternative
+alone is left, namely, that worms, although standing low in the scale of
+organization, possess some degree of intelligence.  This will strike
+every one as very improbable; but it may be doubted whether we know
+enough about the nervous system of the lower animals to justify our
+natural distrust of such a conclusion.  With respect to the small size of
+the cerebral ganglia, we should remember what a mass of inherited
+knowledge, with some power of adapting means to an end, is crowded into
+the minute brain of a worker-ant.
+
+_Means by which worms excavate their burrows_.—This is effected in two
+ways; by pushing away the earth on all sides, and by swallowing it.  In
+the former case, the worm inserts the stretched out and attenuated
+anterior extremity of its body into any little crevice, or hole; and
+then, as Perrier remarks, {93} the pharynx is pushed forwards into this
+part, which consequently swells and pushes away the earth on all sides.
+The anterior extremity thus serves as a wedge.  It also serves, as we
+have before seen, for prehension and suction, and as a tactile organ.  A
+worm was placed on loose mould, and it buried itself in between two and
+three minutes.  On another occasion four worms disappeared in 15 minutes
+between the sides of the pot and the earth, which had been moderately
+pressed down.  On a third occasion three large worms and a small one were
+placed on loose mould well mixed with fine sand and firmly pressed down,
+and they all disappeared, except the tail of one, in 35 minutes.  On a
+fourth occasion six large worms were placed on argillaceous mud mixed
+with sand firmly pressed down, and they disappeared, except the extreme
+tips of the tails of two of them, in 40 minutes.  In none of these cases,
+did the worms swallow, as far as could be seen, any earth.  They
+generally entered the ground close to the sides of the pot.
+
+A pot was next filled with very fine ferruginous sand, which was pressed
+down, well watered, and thus rendered extremely compact.  A large worm
+left on the surface did not succeed in penetrating it for some hours, and
+did not bury itself completely until 25 hrs. 40 min. had elapsed.  This
+was effected by the sand being swallowed, as was evident by the large
+quantity ejected from the vent, long before the whole body had
+disappeared.  Castings of a similar nature continued to be ejected from
+the burrow during the whole of the following day.
+
+As doubts have been expressed by some writers whether worms ever swallow
+earth solely for the sake of making their burrows, some additional cases
+may be given.  A mass of fine reddish sand, 23 inches in thickness, left
+on the ground for nearly two years, had been penetrated in many places by
+worms; and their castings consisted partly of the reddish sand and partly
+of black earth brought up from beneath the mass.  This sand had been dug
+up from a considerable depth, and was of so poor a nature that weeds
+could not grow on it.  It is therefore highly improbable that it should
+have been swallowed by the worms as food.  Again in a field near my house
+the castings frequently consist of almost pure chalk, which lies at only
+a little depth beneath the surface; and here again it is very improbable
+that the chalk should have been swallowed for the sake of the very little
+organic matter which could have percolated into it from the poor
+overlying pasture.  Lastly, a casting thrown up through the concrete and
+decayed mortar between the tiles, with which the now ruined aisle of
+Beaulieu Abbey had formerly been paved, was washed, so that the coarser
+matter alone was left.  This consisted of grains of quartz, micaceous
+slate, other rocks, and bricks or tiles, many of them from 1/20 to 1/10
+inch in diameter.  No one will suppose that these grains were swallowed
+as food, yet they formed more than half of the casting, for they weighed
+19 grains, the whole casting having weighed 33 grains.  Whenever a worm
+burrows to a depth of some feet in undisturbed compact ground, it must
+form its passage by swallowing the earth; for it is incredible that the
+ground could yield on all sides to the pressure of the pharynx when
+pushed forwards within the worm’s body.
+
+That worms swallow a larger quantity of earth for the sake of extracting
+any nutritious matter which it may contain than for making their burrows,
+appears to me certain.  But as this old belief has been doubted by so
+high an authority as Claparède, evidence in its favour must be given in
+some detail.  There is no _à priori_ improbability in such a belief, for
+besides other annelids, especially the _Arenicola marina_, which throws
+up such a profusion of castings on our tidal sands, and which it is
+believed thus subsists, there are animals belonging to the most distinct
+classes, which do not burrow, but habitually swallow large quantities of
+sand; namely, the molluscan Onchidium and many Echinoderms. {97}
+
+If earth were swallowed only when worms deepened their burrows or made
+new ones, castings would be thrown up only occasionally; but in many
+places fresh castings may be seen every morning, and the amount of earth
+ejected from the same burrow on successive days is large.  Yet worms do
+not burrow to a great depth, except when the weather is very dry or
+intensely cold.  On my lawn the black vegetable mould or humus is only
+about 5 inches in thickness, and overlies light-coloured or reddish
+clayey soil: now when castings are thrown up in the greatest profusion,
+only a small proportion are light coloured, and it is incredible that the
+worms should daily make fresh burrows in every direction in the thin
+superficial layer of dark-coloured mould, unless they obtained nutriment
+of some kind from it.  I have observed a strictly analogous case in a
+field near my house where bright red clay lay close beneath the surface.
+Again on one part of the Downs near Winchester the vegetable mould
+overlying the chalk was found to be only from 3 to 4 inches in thickness;
+and the many castings here ejected were as black as ink and did not
+effervesce with acids; so that the worms must have confined themselves to
+this thin superficial layer of mould, of which large quantities were
+daily swallowed.  In another place at no great distance the castings were
+white; and why the worms should have burrowed into the chalk in some
+places and not in others, I am unable to conjecture.
+
+Two great piles of leaves had been left to decay in my grounds, and
+months after their removal, the bare surface, several yards in diameter,
+was so thickly covered during several months with castings that they
+formed an almost continuous layer; and the large number of worms which
+lived here must have subsisted during these months on nutritious matter
+contained in the black earth.
+
+The lowest layer from another pile of decayed leaves mixed with some
+earth was examined under a high power, and the number of spores of
+various shapes and sizes which it contained was astonishingly great; and
+these crushed in the gizzards of worms may largely aid in supporting
+them.  Whenever castings are thrown up in the greatest number, few or no
+leaves are drawn into the burrows; for instance the turf along a
+hedgerow, about 200 yards in length, was daily observed in the autumn
+during several weeks, and every morning many fresh castings were seen;
+but not a single leaf was drawn into these burrows.  These castings from
+their blackness and from the nature of the subsoil could not have been
+brought up from a greater depth than 6 or 8 inches.  On what could these
+worms have subsisted during this whole time, if not on matter contained
+in the black earth?  On the other hand, whenever a large number of leaves
+are drawn into the burrows, the worms seem to subsist chiefly on them,
+for few earth-castings are then ejected on the surface.  This difference
+in the behaviour of worms at different times, perhaps explains a
+statement by Claparède, namely, that triturated leaves and earth are
+always found in distinct parts of their intestines.
+
+Worms sometimes abound in places where they can rarely or never obtain
+dead or living leaves; for instance, beneath the pavement in well-swept
+courtyards, into which leaves are only occasionally blown.  My son Horace
+examined a house, one corner of which had subsided; and he found here in
+the cellar, which was extremely damp, many small worm-castings thrown up
+between the stones with which the cellar was paved; and in this case it
+is improbable that the worms could ever have obtained leaves.  Mr. A. C.
+Horner confirms this account, as he has seen castings in the cellars of
+his house, which is an old one at Tonbridge.
+
+But the best evidence, known to me, of worms subsisting for at least
+considerable periods of time solely on the organic matter contained in
+earth, is afforded by some facts communicated to me by Dr. King.  Near
+Nice large castings abound in extraordinary numbers, so that 5 or 6 were
+often found within the space of a square foot.  They consist of fine,
+pale-coloured earth, containing calcareous matter, which after having
+passed through the bodies of worms and being dried, coheres with
+considerable force.  I have reason to believe that these castings had
+been formed by species of Perichæta, which have been naturalized here
+from the East. {101}  They rise like towers, with their summits often a
+little broader than their bases, sometimes to a height of above 3 and
+often to a height of 2½ inches.  The tallest of those which were measured
+was 3.3 inches in height and 1 inch in diameter.  A small cylindrical
+passage runs up the centre of each tower, through which the worm ascends
+to eject the earth which it has swallowed, and thus to add to its height.
+A structure of this kind would not allow leaves being easily dragged from
+the surrounding ground into the burrows; and Dr. King, who looked
+carefully, never saw even a fragment of a leaf thus drawn in.  Nor could
+any trace be discovered of the worms having crawled down the exterior
+surfaces of the towers in search of leaves; and had they done so, tracks
+would almost certainly have been left on the upper part whilst it
+remained soft.  It does not, however, follow that these worms do not draw
+leaves into their burrows during some other season of the year, at which
+time they would not build up their towers.
+
+From the several foregoing cases, it can hardly be doubted that worms
+swallow earth, not only for the sake of making their burrows, but for
+obtaining food.  Hensen, however, concludes from his analyses of mould
+that worms probably could not live on ordinary vegetable mould, though he
+admits that they might be nourished to some extent by leaf-mould. {102}
+But we have seen that worms eagerly devour raw meat, fat, and dead worms;
+and ordinary mould can hardly fail to contain many ova, larvæ, and small
+living or dead creatures, spores of cryptogamic plants, and micrococci,
+such as those which give rise to saltpetre.  These various organisms,
+together with some cellulose from any leaves and roots not utterly
+decayed, might well account for such large quantities of mould being
+swallowed by worms.  It may be worth while here to recall the fact that
+certain species of Utricularia, which grow in damp places in the tropics,
+possess bladders beautifully constructed for catching minute subterranean
+animals; and these traps would not have been developed unless many small
+animals inhabited such soil.
+
+_The depth to which worms penetrate_, _and the construction of their
+burrows_.—Although worms usually live near the surface, yet they burrow
+to a considerable depth during long-continued dry weather and severe
+cold.  In Scandinavia, according to Eisen, and in Scotland, according to
+Mr. Lindsay Carnagie, the burrows run down to a depth of from 7 to 8
+feet; in North Germany, according to Hoffmeister, from 6 to 8 feet, but
+Hensen says, from 3 to 6 feet.  This latter observer has seen worms
+frozen at a depth of 1½ feet beneath the surface.  I have not myself had
+many opportunities for observation, but I have often met with worms at
+depths of 3 to 4 feet.  In a bed of fine sand overlying the chalk, which
+had never been disturbed, a worm was cut into two at 55 inches, and
+another was found here at Down in December at the bottom of its burrow,
+at 61 inches beneath the surface.  Lastly, in earth near an old Roman
+Villa, which had not been disturbed for many centuries, a worm was met
+with at a depth of 66 inches; and this was in the middle of August.
+
+The burrows run down perpendicularly, or more commonly a little
+obliquely.  They are said sometimes to branch, but as far as I have seen
+this does not occur, except in recently dug ground and near the surface.
+They are generally, or as I believe invariably, lined with a thin layer
+of fine, dark-coloured earth voided by the worms; so that they must at
+first be made a little wider than their ultimate diameter.  I have seen
+several burrows in undisturbed sand thus lined at a depth of 4 ft. 6 in.;
+and others close to the surface thus lined in recently dug ground.  The
+walls of fresh burrows are often dotted with little globular pellets of
+voided earth, still soft and viscid; and these, as it appears, are spread
+out on all sides by the worm as it travels up or down its burrow.  The
+lining thus formed becomes very compact and smooth when nearly dry, and
+closely fits the worm’s body.  The minute reflexed bristles which project
+in rows on all sides from the body, thus have excellent points of
+support; and the burrow is rendered well adapted for the rapid movement
+of the animal.  The lining appears also to strengthen the walls, and
+perhaps saves the worm’s body from being scratched.  I think so because
+several burrows which passed through a layer of sifted coal-cinders,
+spread over turf to a thickness of 1½ inch, had been thus lined to an
+unusual thickness.  In this case the worms, judging from the castings,
+had pushed the cinders away on all sides and had not swallowed any of
+them.  In another place, burrows similarly lined, passed through a layer
+of coarse coal-cinders, 3½ inches in thickness.  We thus see that the
+burrows are not mere excavations, but may rather be compared with tunnels
+lined with cement.
+
+The mouths of the burrow are in addition often lined with leaves; and
+this is an instinct distinct from that of plugging them up, and does not
+appear to have been hitherto noticed.  Many leaves of the Scotch-fir or
+pine (_Pinus sylvestris_) were given to worms kept in confinement in two
+pots; and when after several weeks the earth was carefully broken up, the
+upper parts of three oblique burrows were found surrounded for lengths of
+7, 4, and 3½ inches with pine-leaves, together with fragments of other
+leaves which had been given the worms as food.  Glass beads and bits of
+tile, which had been strewed on the surface of the soil, were stuck into
+the interstices between the pine-leaves; and these interstices were
+likewise plastered with the viscid castings voided by the worms.  The
+structures thus formed cohered so well, that I succeeded in removing one
+with only a little earth adhering to it.  It consisted of a slightly
+curved cylindrical case, the interior of which could be seen through
+holes in the sides and at either end.  The pine-leaves had all been drawn
+in by their bases; and the sharp points of the needles had been pressed
+into the lining of voided earth.  Had this not been effectually done, the
+sharp points would have prevented the retreat of the worms into their
+burrows; and these structures would have resembled traps armed with
+converging points of wire, rendering the ingress of an animal easy and
+its egress difficult or impossible.  The skill shown by these worms is
+noteworthy and is the more remarkable, as the Scotch pine is not a native
+of this district.
+
+After having examined these burrows made by worms in confinement, I
+looked at those in a flower-bed near some Scotch pines.  These had all
+been plugged up in the ordinary manner with the leaves of this tree,
+drawn in for a length of from 1 to 1½ inch; but the mouths of many of
+them were likewise lined with them, mingled with fragments of other kinds
+of leaves, drawn in to a depth of 4 or 5 inches.  Worms often remain, as
+formerly stated, for a long time close to the mouths of their burrows,
+apparently for warmth; and the basket-like structures formed of leaves
+would keep their bodies from coming into close contact with the cold damp
+earth.  That they habitually rested on the pine-leaves, was rendered
+probable by their clean and almost polished surfaces.
+
+The burrows which run far down into the ground, generally, or at least
+often, terminate in a little enlargement or chamber.  Here, according to
+Hoffmeister, one or several worms pass the winter rolled up into a ball.
+Mr. Lindsay Carnagie informed me (1838) that he had examined many burrows
+over a stone-quarry in Scotland, where the overlying boulder-clay and
+mould had recently been cleared away, and a little vertical cliff thus
+left.  In several cases the same burrow was a little enlarged at two or
+three points one beneath the other; and all the burrows terminated in a
+rather large chamber, at a depth of 7 or 8 feet from the surface.  These
+chambers contained many small sharp bits of stone and husks of
+flax-seeds.  They must also have contained living seeds, for on the
+following spring Mr. Carnagie saw grass-plants sprouting out of some of
+the intersected chambers.  I found at Abinger in Surrey two burrows
+terminating in similar chambers at a depth of 36 and 41 inches, and these
+were lined or paved with little pebbles, about as large as mustard seeds;
+and in one of the chambers there was a decayed oat-grain, with its husk.
+Hensen likewise states that the bottoms of the burrows are lined with
+little stones; and where these could not be procured, seeds, apparently
+of the pear, had been used, as many as fifteen having been carried down
+into a single burrow, one of which had germinated. {108}  We thus see how
+easily a botanist might be deceived who wished to learn how long deeply
+buried seeds remained alive, if he were to collect earth from a
+considerable depth, on the supposition that it could contain only seeds
+which had long lain buried.  It is probable that the little stones, as
+well as the seeds, are carried down from the surface by being swallowed;
+for a surprising number of glass beads, bits of tile and of glass were
+certainly thus carried down by worms kept in pots; but some may have been
+carried down within their mouths.  The sole conjecture which I can form
+why worms line their winter-quarters with little stones and seeds, is to
+prevent their closely coiled-up bodies from coming into close contact
+with the surrounding cold soil; and such contact would perhaps interfere
+with their respiration which is effected by the skin alone.
+
+A worm after swallowing earth, whether for making its burrow or for food,
+soon comes to the surface to empty its body.  The ejected earth is
+thoroughly mingled with the intestinal secretions, and is thus rendered
+viscid.  After being dried it sets hard.  I have watched worms during the
+act of ejection, and when the earth was in a very liquid state it was
+ejected in little spurts, and by a slow peristaltic movement when not so
+liquid.  It is not cast indifferently on any side, but with some care,
+first on one and then on another side; the tail being used almost like a
+trowel.  When a worm comes to the surface to eject earth, the tail
+protrudes, but when it collects leaves its head must protrude.  Worms
+therefore must have the power of turning round in their closely-fitting
+burrows; and this, as it appears to us, would be a difficult feat.  As
+soon as a little heap has been formed, the worm apparently avoids, for
+the sake of safety, protruding its tail; and the earthy matter is forced
+up through the previously deposited soft mass.  The mouth of the same
+burrow is used for this purpose for a considerable time.  In the case of
+the tower-like castings (see Fig. 2) near Nice, and of the similar but
+still taller towers from Bengal (hereafter to be described and figured),
+a considerable degree of skill is exhibited in their construction.  Dr.
+King also observed that the passage up these towers hardly ever ran in
+the same exact line with the underlying burrow, so that a thin
+cylindrical object such as a haulm of grass, could not be passed down the
+tower into the burrow; and this change of direction probably serves in
+some manner as a protection.
+
+Worms do not always eject their castings on the surface of the ground.
+When they can find any cavity, as when burrowing in newly turned-up
+earth, or between the stems of banked-up plants, they deposit their
+castings in such places.  So again any hollow beneath a large stone lying
+on the surface of the ground, is soon filled up with their castings.
+According to Hensen, old burrows are habitually used for this purpose;
+but as far as my experience serves, this is not the case, excepting with
+those near the surface in recently dug ground.  I think that Hensen may
+have been deceived by the walls of old burrows, lined with black earth,
+having sunk in or collapsed; for black streaks are thus left, and these
+are conspicuous when passing through light-coloured soil, and might be
+mistaken for completely filled-up burrows.
+
+It is certain that old burrows collapse in the course of time; for as we
+shall see in the next chapter, the fine earth voided by worms, if spread
+out uniformly, would form in many places in the course of a year a layer
+0.2 of an inch in thickness; so that at any rate this large amount is not
+deposited within the old unused burrows.  If the burrows did not
+collapse, the whole ground would be first thickly riddled with holes to a
+depth of about ten inches, and in fifty years a hollow unsupported space,
+ten inches in depth, would be left.  The holes left by the decay of
+successively formed roots of trees and plants must likewise collapse in
+the course of time.
+
+The burrows of worms run down perpendicularly or a little obliquely, and
+where the soil is at all argillaceous, there is no difficulty in
+believing that the walls would slowly flow or slide inwards during very
+wet weather.  When, however, the soil is sandy or mingled with many small
+stones, it can hardly be viscous enough to flow inwards during even the
+wettest weather; but another agency may here come into play.  After much
+rain the ground swells, and as it cannot expand laterally, the surface
+rises; during dry weather it sinks again.  For instance, a large flat
+stone laid on the surface of a field sank 3.33 mm. whilst the weather was
+dry between May 9th and June 13th, and rose 1.91 mm, between September
+7th and 19th of the same year, much rain having fallen during the latter
+part of this time.  During frosts and thaws the movements were twice as
+great.  These observations were made by my son Horace, who will hereafter
+publish an account of the movements of this stone during successive wet
+and dry seasons, and of the effects of its being undermined by worms.
+Now when the ground swells, if it be penetrated by cylindrical holes,
+such as worm-burrows, their walls will tend to yield and be pressed
+inwards; and the yielding will be greater in the deeper parts (supposing
+the whole to be equally moistened) from the greater weight of the
+superincumbent soil which has to be raised, than in the parts near the
+surface.  When the ground dries, the walls will shrink a little and the
+burrows will be a little enlarged.  Their enlargement, however, through
+the lateral contraction of the ground, will not be favoured, but rather
+opposed, by the weight of the superincumbent soil.
+
+_Distribution of Worms_.—Earth-worms are found in all parts of the world,
+and some of the genera have an enormous range. {113}  They inhabit the
+most isolated islands; they abound in Iceland, and are known to exist in
+the West Indies, St. Helena, Madagascar, New Caledonia and Tahiti.  In
+the Antarctic regions, worms from Kerguelen Land have been described by
+Ray Lankester; and I found them in the Falkland Islands.  How they reach
+such isolated islands is at present quite unknown.  They are easily
+killed by salt-water, and it does not appear probable that young worms or
+their egg-capsules could be carried in earth adhering to the feet or
+beaks of land-birds.  Moreover Kerguelen Land is not now inhabited by any
+land-bird.
+
+In this volume we are chiefly concerned with the earth cast up by worms,
+and I have gleaned a few facts on this subject with respect to distant
+lands.  Worms throw up plenty of castings in the United States.  In
+Venezuela, castings, probably ejected by species of Urochæta, are common
+in the gardens and fields, but not in the forests, as I hear from Dr.
+Ernst of Caracas.  He collected 156 castings from the court-yard of his
+house, having an area of 200 square yards.  They varied in bulk from half
+a cubic centimeter to five cubic centimeters, and were on an average
+three cubic centimeters.  They were, therefore, of small size in
+comparison with those often found in England; for six large castings from
+a field near my house averaged 16 cubic centimeters.  Several species of
+earth-worms are common in St. Catharina in South Brazil, and Fritz Müller
+informs me “that in most parts of the forests and pasture-lands, the
+whole soil, to a depth of a quarter of a metre, looks as if it had passed
+repeatedly through the intestines of earth-worms, even where hardly any
+castings are to be seen on the surface.”  A gigantic but very rare
+species is found there, the burrows of which are sometimes even two
+centimeters or nearly 0.8 of an inch in diameter, and which apparently
+penetrate the ground to a great depth.
+
+In the dry climate of New South Wales, I hardly expected that worms would
+be common; but Dr. G. Krefft of Sydney, to whom I applied, after making
+inquiries from gardeners and others, and from his own observations,
+informs me that their castings abound.  He sent me some collected after
+heavy rain, and they consisted of little pellets, about 0.15 inch in
+diameter; and the blackened sandy earth of which they were formed still
+cohered with considerable tenacity.
+
+The late Mr. John Scott of the Botanic Gardens near Calcutta made many
+observations for me on worms living under the hot and humid climate of
+Bengal.  The castings abound almost everywhere, in jungles and in the
+open ground, to a greater degree, as he thinks, than in England.  After
+the water has subsided from the flooded rice-fields, the whole surface
+very soon becomes studded with castings—a fact which much surprised Mr.
+Scott, as he did not know how long worms could survive beneath water.
+They cause much trouble in the Botanic garden, “for some of the finest of
+our lawns can be kept in anything like order only by being almost daily
+rolled; if left undisturbed for a few days they become studded with large
+castings.”  These closely resemble those described as abounding near
+Nice; and they are probably the work of a species of Perichæta.  They
+stand up like towers, with an open passage in the centre.
+
+   [Picture: Fig. 3: A tower-like casting.  Fig. 4: A casting from the
+                            Nilgiri Mountains]
+
+A figure of one of these castings from a photograph is here given (Fig.
+3).  The largest received by me was 3½ inches in height and 1.35 inch in
+diameter; another was only ¾ inch in diameter and 2¾ in height.  In the
+following year, Mr. Scott measured several of the largest; one was 6
+inches in height and nearly 1½ in diameter: two others were 5 inches in
+height and respectively 2 and rather more than 2½ inches in diameter.
+The average weight of the 22 castings sent to me was 35 grammes (1¼ oz.);
+and one of them weighed 44.8 grammes (or 2 oz.). All these castings were
+thrown up either in one night or in two.  Where the ground in Bengal is
+dry, as under large trees, castings of a different kind are found in vast
+numbers: these consist of little oval or conical bodies, from about the
+1/20 to rather above 1/10 of an inch in length.  They are obviously
+voided by a distinct species of worms.
+
+The period during which worms near Calcutta display such extraordinary
+activity lasts for only a little over two months, namely, during the cool
+season after the rains.  At this time they are generally found within
+about 10 inches beneath the surface.  During the hot season they burrow
+to a greater depth, and are then found coiled up and apparently
+hybernating.  Mr. Scott has never seen them at a greater depth than 2½
+feet, but has heard of their having been found at 4 feet.  Within the
+forests, fresh castings may be found even during the hot season.  The
+worms in the Botanic garden, during the cool and dry season, draw many
+leaves and little sticks into the mouths of their burrows, like our
+English worms; but they rarely act in this manner during the rainy
+season.
+
+Mr. Scott saw worm-castings on the lofty mountains of Sikkim in North
+India.  In South India Dr. King found in one place, on the plateau of the
+Nilgiris, at an elevation of 7000 feet, “a good many castings,” which are
+interesting for their great size.  The worms which eject them are seen
+only during the wet season, and are reported to be from 12 to 15 inches
+in length, and as thick as a man’s little finger.  These castings were
+collected by Dr. King after a period of 110 days without any rain; and
+they must have been ejected either during the north-east or more probably
+during the previous south-west monsoon; for their surfaces had suffered
+some disintegration and they were penetrated by many fine roots.  A
+drawing is here given (Fig. 4) of one which seems to have best retained
+its original size and appearance.  Notwithstanding some loss from
+disintegration, five of the largest of these castings (after having been
+well sun-dried) weighed each on an average 89.5 grammes, or above 3 oz.;
+and the largest weighed 123.14 grammes, or 4⅓ oz.,—that is, above a
+quarter of a pound!  The largest convolutions were rather more than one
+inch in diameter; but it is probable that they had subsided a little
+whilst soft, and that their diameters had thus been increased.  Some had
+flowed so much that they now consisted of a pile of almost flat confluent
+cakes.  All were formed of fine, rather light-coloured earth, and were
+surprisingly hard and compact, owing no doubt to the animal matter by
+which the particles of earth had been cemented together.  They did not
+disintegrate, even when left for some hours in water.  Although they had
+been cast up on the surface of gravelly soil, they contained extremely
+few bits of rock, the largest of which was only 0.15 inch in diameter.
+
+Dr. King saw in Ceylon a worm about 2 feet in length and ½ inch in
+diameter; and he was told that it was a very common species during the
+wet season.  These worms must throw up castings at least as large as
+those on the Nilgiri Mountains; but Dr. King saw none during his short
+visit to Ceylon.
+
+Sufficient facts have now been given, showing that worms do much work in
+bringing up fine earth to the surface in most or all parts of the world,
+and under the most different climates.
+
+
+
+
+CHAPTER III.
+THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE SURFACE.
+
+
+Rate at which various objects strewed on the surface of grass-fields are
+covered up by the castings of worms—The burial of a paved path—The slow
+subsidence of great stones left on the surface—The number of worms which
+live within a given space—The weight of earth ejected from a burrow, and
+from all the burrows within a given space—The thickness of the layer of
+mould which the castings on a given space would form within a given time
+if uniformly spread out—The slow rate at which mould can increase to a
+great thickness—Conclusion.
+
+WE now come to the more immediate subject of this volume, namely, the
+amount of earth which is brought up by worms from beneath the surface,
+and is afterwards spread out more or less completely by the rain and
+wind.  The amount can be judged of by two methods,—by the rate at which
+objects left on the surface are buried, and more accurately by weighing
+the quantity brought up within a given time.  We will begin with the
+first method, as it was first followed.
+
+Near Mael Hall in Staffordshire, quick-lime had been spread about the
+year 1827 thickly over a field of good pasture-land, which had not since
+been ploughed.  Some square holes were dug in this field in the beginning
+of October 1837; and the sections showed a layer of turf, formed by the
+matted roots of the grasses, ½ inch in thickness, beneath which, at a
+depth of 2½ inches (or 3 inches from the surface), a layer of the lime in
+powder or in small lumps could be distinctly seen running all round the
+vertical sides of the holes.  The soil beneath the layer of lime was
+either gravelly or of a coarse sandy nature, and differed considerably in
+appearance from the overlying dark-coloured fine mould.  Coal-cinders had
+been spread over a part of this same field either in the year 1833 or
+1834; and when the above holes were dug, that is after an interval of 3
+or 4 years, the cinders formed a line of black spots round the holes, at
+a depth of 1 inch beneath the surface, parallel to and above the white
+layer of lime.  Over another part of this field cinders had been strewed,
+only about half-a-year before, and these either still lay on the surface
+or were entangled among the roots of the grasses; and I here saw the
+commencement of the burying process, for worm-castings had been heaped on
+several of the smaller fragments.  After an interval of 4¾ years this
+field was re-examined, and now the two layers of lime and cinders were
+found almost everywhere at a greater depth than before by nearly 1 inch,
+we will say by ¾ of an inch.  Therefore mould to an average thickness of
+0.22 of an inch had been annually brought up by the worms, and had been
+spread over the surface of this field.
+
+Coal-cinders had been strewed over another field, at a date which could
+not be positively ascertained, so thickly that they formed (October,
+1837) a layer, 1 inch in thickness at a depth of about 3 inches from the
+surface.  The layer was so continuous that the over-lying dark vegetable
+mould was connected with the sub-soil of red clay only by the roots of
+the grasses; and when these were broken, the mould and the red clay fell
+apart.  In a third field, on which coal-cinders and burnt marl had been
+strewed several times at unknown dates, holes were dug in 1842; and a
+layer of cinders could be traced at a depth of 3½ inches, beneath which
+at a depth of 9½ inches from the surface there was a line of cinders
+together with burnt marl.  On the sides of one hole there were two layers
+of cinders, at 2 and 3½ inches beneath the surface; and below them at a
+depth in parts of 9½, and in other parts of 10½ inches there were
+fragments of burnt marl.  In a fourth field two layers of lime, one above
+the other, could be distinctly traced, and beneath them a layer of
+cinders and burnt marl at a depth of from 10 to 12 inches below the
+surface.
+
+  [Picture: Fig. 5: Section of the vegetable mould in a field.  Fig. 6:
+                  Traverse section across a large stone]
+
+A piece of waste, swampy land was enclosed, drained, ploughed, harrowed
+and thickly covered in the year 1822 with burnt marl and cinders.  It was
+sowed with grass seeds, and now supports a tolerably good but coarse
+pasture.  Holes were dug in this field in 1837, or 15 years after its
+reclamation, and we see in the accompanying diagram (Fig. 5), reduced to
+half of the natural scale, that the turf was ½ inch thick, beneath which
+there was a layer of vegetable mould 2½ inches thick.  This layer did not
+contain fragments of any kind; but beneath it there was a layer of mould,
+1½ inch in thickness, full of fragments of burnt marl, conspicuous from
+their red colour, one of which near the bottom was an inch in length; and
+other fragments of coal-cinders together with a few white quartz pebbles.
+Beneath this layer and at a depth of 4½ inches from the surface, the
+original black, peaty, sandy soil with a few quartz pebbles was
+encountered.  Here therefore the fragments of burnt marl and cinders had
+been covered in the course of 15 years by a layer of fine vegetable
+mould, only 2½ inches in thickness, excluding the turf.  Six and a half
+years subsequently this field was re-examined, and the fragments were now
+found at from 4 to 5 inches beneath the surface.  So that in this
+interval of 6½ years, about 1½ inch of mould had been added to the
+superficial layer.  I am surprised that a greater quantity had not been
+brought up during the whole 21½ years, for in the closely underlying
+black, peaty soil there were many worms.  It is, however, probable that
+formerly, whilst the land remained poor, worms were scanty; and the mould
+would then have accumulated slowly.  The average annual increase of
+thickness for the whole period is 0.19 of an inch.
+
+Two other cases are worth recording.  In the spring of 1835, a field,
+which had long existed as poor pasture and was so swampy that it trembled
+slightly when stamped on, was thickly covered with red sand so that the
+whole surface appeared at first bright red.  When holes were dug in this
+field after an interval of about 2½ years, the sand formed a layer at a
+depth of ¾ in. beneath the surface.  In 1842 (i.e., 7 years after the
+sand had been laid on) fresh holes were dug, and now the red sand formed
+a distinct layer, 2 inches beneath the surface, or 1½ inch beneath the
+turf; so that on an average, 0.21 inch of mould had been annually brought
+to the surface.  Immediately beneath the layer of red sand, the original
+substratum of black sandy peat extended.
+
+A grass field, likewise not far from Maer Hall, had formerly been thickly
+covered with marl, and was then left for several years as pasture; it was
+afterwards ploughed.  A friend had three trenches dug in this field 28
+years after the application of the marl, {126} and a layer of the marl
+fragments could be traced at a depth, carefully measured, of 12 inches in
+some parts, and of 14 inches in other parts.  This difference in depth
+depended on the layer being horizontal, whilst the surface consisted of
+ridges and furrows from the field having been ploughed.  The tenant
+assured me that it had never been turned up to a greater depth than from
+6 to 8 inches; and as the fragments formed an unbroken horizontal layer
+from 12 to 14 inches beneath the surface, these must have been buried by
+the worms whilst the land was in pasture before it was ploughed, for
+otherwise they would have been indiscriminately scattered by the plough
+throughout the whole thickness of the soil.  Four-and-a-half years
+afterwards I had three holes dug in this field, in which potatoes had
+been lately planted, and the layer of marl-fragments was now found 13
+inches beneath the bottoms of the furrows, and therefore probably 15
+inches beneath the general level of the field.  It should, however, be
+observed that the thickness of the blackish sandy soil, which had been
+thrown up by the worms above the marl-fragments in the course of 32½
+years, would have measured less than 15 inches, if the field had always
+remained as pasture, for the soil would in this case have been much more
+compact.  The fragments of marl almost rested on an undisturbed
+substratum of white sand with quartz pebbles; and as this would be little
+attractive to worms, the mould would hereafter be very slowly increased
+by their action.
+
+We will now give some cases of the action of worms, on land differing
+widely from the dry sandy or the swampy pastures just described.  The
+chalk formation extends all round my house in Kent; and its surface, from
+having been exposed during an immense period to the dissolving action of
+rain-water, is extremely irregular, being abruptly festooned and
+penetrated by many deep well-like cavities. {128}  During the dissolution
+of the chalk, the insoluble matter, including a vast number of unrolled
+flints of all sizes, has been left on the surface and forms a bed of
+stiff red clay, full of flints, and generally from 6 to 14 feet in
+thickness.  Over the red clay, wherever the land has long remained as
+pasture, there is a layer a few inches in thickness, of dark-coloured
+vegetable mould.
+
+A quantity of broken chalk was spread, on December 20, 1842, over a part
+of a field near my house, which had existed as pasture certainly for 30,
+probably for twice or thrice as many years.  The chalk was laid on the
+land for the sake of observing at some future period to what depth it
+would become buried.  At the end of November, 1871, that is after an
+interval of 29 years, a trench was dug across this part of the field; and
+a line of white nodules could be traced on both sides of the trench, at a
+depth of 7 inches from the surface.  The mould, therefore, (excluding the
+turf) had here been thrown up at an average rate of 0.22 inch per year.
+Beneath the line of chalk nodules there was in parts hardly any fine
+earth free of flints, while in other parts there was a layer, 2¼ inches
+in thickness.  In this latter case the mould was altogether 9¼ inches
+thick; and in one such spot a nodule of chalk and a smooth flint pebble,
+both of which must have been left at some former time on the surface,
+were found at this depth.  At from 11 to 12 inches beneath the surface,
+the undisturbed reddish clay, full of flints, extended.  The appearance
+of the above nodules of chalk surprised me, much at first, as they
+closely resembled water-worn pebbles, whereas the freshly-broken
+fragments had been angular.  But on examining the nodules with a lens,
+they no longer appeared water-worn, for their surfaces were pitted
+through unequal corrosion, and minute, sharp points, formed of broken
+fossil shells, projected from them.  It was evident that the corners of
+the original fragments of chalk had been wholly dissolved, from
+presenting a large surface to the carbonic acid dissolved in the
+rain-water and to that generated in soil containing vegetable matter, as
+well as to the humus-acids. {131}  The projecting corners would also,
+relatively to the other parts, have been embraced by a larger number of
+living rootlets; and these have the power of even attacking marble, as
+Sachs has shown.  Thus, in the course of 29 years, buried angular
+fragments of chalk had been converted into well-rounded nodules.
+
+Another part of this same field was mossy, and as it was thought that
+sifted coal-cinders would improve the pasture, a thick layer was spread
+over this part either in 1842 or 1843, and another layer some years
+afterwards.  In 1871 a trench was here dug, and many cinders lay in a
+line at a depth of 7 inches beneath the surface, with another line at a
+depth of 5½ inches parallel to the one beneath.  In another part of this
+field, which had formerly existed as a separate one, and which it was
+believed had been pasture-land for more than a century, trenches were dug
+to see how thick the vegetable mould was.  By chance the first trench was
+made at a spot where at some former period, certainly more than forty
+years before, a large hole had been filled up with coarse red clay,
+flints, fragments of chalk, and gravel; and here the fine vegetable mould
+was only from 4⅛ to 4⅜ inches in thickness.  In another and undisturbed
+place, the mould varied much in thickness, namely, from 6½ to 8½ inches;
+beneath which a few small fragments of brick were found in one place.
+From these several cases, it would appear that during the last 29 years
+mould has been heaped on the surface at an average annual rate of from
+0.2 to 0.22 of an inch.  But in this district when a ploughed field is
+first laid down in grass, the mould accumulates at a much slower rate.
+The rate, also, must become very much slower after a bed of mould,
+several inches in thickness, has been formed; for the worms then live
+chiefly near the surface, and burrow down to a greater depth so as to
+bring up fresh earth from below, only during the winter when the weather
+is very cold (at which time worms were found in this field at a depth of
+26 inches) and during summer, when the weather is very dry.
+
+A field, which adjoins the one just described, slopes in one part rather
+steeply (viz., at from 10° to 15°); this part was last ploughed in 1841,
+was then harrowed and left to become pasture-land.  For several years it
+was clothed with an extremely scant vegetation, and was so thickly
+covered with small and large flints (some of them half as large as a
+child’s head) that the field was always called by my sons “the stony
+field.”  When they ran down the slope the stones clattered together, I
+remember doubting whether I should live to see these larger flints
+covered with vegetable mould and turf.  But the smaller stones
+disappeared before many years had elapsed, as did every one of the larger
+ones after a time; so that after thirty years (1871) a horse could gallop
+over the compact turf from one end of the field to the other, and not
+strike a single stone with his shoes.  To anyone who remembered the
+appearance of the field in 1842, the transformation was wonderful.  This
+was certainly the work of the worms, for though castings were not
+frequent for several years, yet some were thrown up month after month,
+and these gradually increased in numbers as the pasture improved.  In the
+year 1871 a trench was dug on the above slope, and the blades of grass
+were cut off close to the roots, so that the thickness of the turf and of
+the vegetable mould could be measured accurately.  The turf was rather
+less than half an inch, and the mould, which did not contain any stones,
+2½ inches in thickness.  Beneath this lay coarse clayey earth full of
+flints, like that in any of the neighbouring ploughed fields.  This
+coarse earth easily fell apart from the overlying mould when a spit was
+lifted up.  The average rate of accumulation of the mould during the
+whole thirty years was only .083 inch per year (i.e., nearly one inch in
+twelve years); but the rate must have been much slower at first, and
+afterwards considerably quicker.
+
+The transformation in the appearance of this field, which had been
+effected beneath my eyes, was afterwards rendered the more striking, when
+I examined in Knole Park a dense forest of lofty beech-trees, beneath
+which nothing grew.  Here the ground was thickly strewed with large naked
+stones, and worm-castings were almost wholly absent.  Obscure lines and
+irregularities on the surface indicated that the land had been cultivated
+some centuries ago.  It is probable that a thick wood of young
+beech-trees sprung up so quickly, that time enough was not allowed for
+worms to cover up the stones with their castings, before the site became
+unfitted for their existence.  Anyhow the contrast between the state of
+the now miscalled “stony field,” well stocked with worms, and the present
+state of the ground beneath the old beech-trees in Knole Park, where
+worms appeared to be absent, was striking.
+
+A narrow path running across part of my lawn was paved in 1843 with small
+flagstones, set edgeways; but worms threw up many castings and weeds grew
+thickly between them.  During several years the path was weeded and
+swept; but ultimately the weeds and worms prevailed, and the gardener
+ceased to sweep, merely mowing off the weeds, as often as the lawn was
+mowed.  The path soon became almost covered up, and after several years
+no trace of it was left.  On removing, in 1877, the thin overlying layer
+of turf, the small flag-stones, all in their proper places, were found
+covered by an inch of fine mould.
+
+Two recently published accounts of substances strewed on the surface of
+pasture-land, having become buried through the action of worms, may be
+here noticed.  The Rev. H. C. Key had a ditch cut in a field, over which
+coal-ashes had been spread, as it was believed, eighteen years before;
+and on the clean-cut perpendicular sides of the ditch, at a depth of at
+least seven inches, there could be seen, for a length of 60 yards, “a
+distinct, very even, narrow line of coal-ashes, mixed with small coal,
+perfectly parallel with the top-sward.” {136a}  This parallelism and the
+length of the section give interest to the case.  Secondly, Mr. Dancer
+states {136b} that crushed bones had been thickly strewed over a field;
+and “some years afterwards” these were found “several inches below the
+surface, at a uniform depth.”
+
+The Rev. Mr. Zincke informs me that he has lately had an orchard dug to
+the unusual depth of 4 feet.  The upper 18 inches consisted of
+dark-coloured vegetable mould, and the next 18 inches of sandy loam,
+containing in the lower part many rolled pieces of sandstone, with some
+bits of brick and tile, probably of Roman origin, as remains of this
+period have been found close by.  The sandy loam rested on an indurated
+ferruginous pan of yellow clay, on the surface of which two perfect celts
+were found.  If, as seems probable, the celts were originally left on the
+surface of the land, they have since been covered up with earth 3 feet in
+thickness, all of which has probably passed through the bodies of worms,
+excepting the stones which may have been scattered on the surface at
+different times, together with manure or by other means.  It is difficult
+otherwise to understand the source of the 18 inches of sandy loam, which
+differed from the overlying dark vegetable mould, after both had been
+burnt, only in being of a brighter red colour, and in not being quite so
+fine-grained.  But on this view we must suppose that the carbon in
+vegetable mould, when it lies at some little depth beneath the surface
+and does not continually receive decaying vegetable matter from above,
+loses its dark colour in the course of centuries; but whether this is
+probable I do not know.
+
+Worms appear to act in the same manner in New Zealand as in Europe; for
+Professor J. von Haast has described {138a} a section near the coast,
+consisting of mica-schist, “covered by 5 or 6 feet of loess, above which
+about 12 inches of vegetable soil had accumulated.”  Between the loess
+and the mould there was a layer from 3 to 6 inches in thickness,
+consisting of “cores, implements, flakes, and chips, all manufactured
+from hard basaltic rock.”  It is therefore probable that the aborigines,
+at some former period, had left these objects on the surface, and that
+they had afterwards been slowly covered up by the castings of worms.
+
+Farmers in England are well aware that objects of all kinds, left on the
+surface of pasture-land, after a time disappear, or, as they say, work
+themselves downwards.  How powdered lime, cinders, and heavy stones, can
+work down, and at the same rate, through the matted roots of a
+grass-covered surface, is a question which has probably never occurred to
+them. {138b}
+
+_The Sinking of great Stones through the Action of Worms_.—When a stone
+of large size and of irregular shape is left on the surface of the
+ground, it rests, of course, on the more protuberant parts; but worms
+soon fill up with their castings all the hollow spaces on the lower side;
+for, as Hensen remarks, they like the shelter of stones.  As soon as the
+hollows are filled up, the worms eject the earth which they have
+swallowed beyond the circumference of the stones; and thus the surface of
+the ground is raised all round the stone.  As the burrows excavated
+directly beneath the stone after a time collapse, the stone sinks a
+little. {139}  Hence it is, that boulders which at some ancient period
+have rolled down from a rocky mountain or cliff on to a meadow at its
+base, are always somewhat imbedded in the soil; and, when removed, leave
+an exact impression of their lower surfaces in the underlying fine mould.
+If, however, a boulder is of such huge dimensions, that the earth beneath
+is kept dry, such earth will not be inhabited by worms, and the boulder
+will not sink into the ground.
+
+A lime-kiln formerly stood in a grass-field near Leith Hill Place in
+Surrey, and was pulled down 35 years before my visit; all the loose
+rubbish had been carted away, excepting three large stones of quartzose
+sandstone, which it was thought might hereafter be of some use.  An old
+workman remembered that they had been left on a bare surface of broken
+bricks and mortar, close to the foundations of the kiln; but the whole
+surrounding surface is now covered with turf and mould.  The two largest
+of these stones had never since been moved; nor could this easily have
+been done, as, when I had them removed, it was the work of two men with
+levers.  One of these stones, and not the largest, was 64 inches long, 17
+inches broad, and from 9 to 10 inches in thickness.  Its lower surface
+was somewhat protuberant in the middle; and this part still rested on
+broken bricks and mortar, showing the truth of the old workman’s account.
+Beneath the brick rubbish the natural sandy soil, full of fragments of
+sandstone was found; and this could have yielded very little, if at all,
+to the weight of the stone, as might have been expected if the sub-soil
+had been clay.  The surface of the field, for a distance of about 9
+inches round the stone, gradually sloped up to it, and close to the stone
+stood in most places about 4 inches above the surrounding ground.  The
+base of the stone was buried from 1 to 2 inches beneath the general
+level, and the upper surface projected about 8 inches above this level,
+or about 4 inches above the sloping border of turf.  After the removal of
+the stone it became evident that one of its pointed ends must at first
+have stood clear above the ground by some inches, but its upper surface
+was now on a level with the surrounding turf.  When the stone was
+removed, an exact cast of its lower side, forming a shallow crateriform
+hollow, was left, the inner surface of which consisted of fine black
+mould, excepting where the more protuberant parts rested on the
+brick-rubbish.  A transverse section of this stone, together with its
+bed, drawn from measurements made after it had been displaced, is here
+given on a scale of ½ inch to a foot (Fig. 6).  The turf-covered border
+which sloped up to the stone, consisted of fine vegetable mould, in one
+part 7 inches in thickness.  This evidently consisted of worm-castings,
+several of which had been recently ejected.  The whole stone had sunk in
+the thirty-five years, as far as I could judge, about 1½ inch; and this
+must have been due to the brick-rubbish beneath the more protuberant
+parts having been undermined by worms.  At this rate the upper surface of
+the stone, if it had been left undisturbed, would have sunk to the
+general level of the field in 247 years; but before this could have
+occurred, some earth would have been washed down by heavy rain from the
+castings on the raised border of turf over the upper surface of the
+stone.
+
+The second stone was larger that the one just described, viz., 67 inches
+in length, 39 in breadth, and 15 in thickness.  The lower surface was
+nearly flat, so that the worms must soon have been compelled to eject
+their castings beyond its circumference.  The stone as a whole had sunk
+about 2 inches into the ground.  At this rate it would have required 262
+years for its upper surface to have sunk to the general level of the
+field.  The upwardly sloping, turf-covered border round the stone was
+broader than in the last case, viz., from 14 to 16 inches; and why this
+should be so, I could see no reason.  In most parts this border was not
+so high as in the last case, viz., from 2 to 2½ inches, but in one place
+it was as much as 5½.  Its average height close to the stone was probably
+about 3 inches, and it thinned out to nothing.  If so, a layer of fine
+earth, 15 inches in breadth and 1½ inch in average thickness, of
+sufficient length to surround the whole of the much elongated slab, must
+have been brought up by the worms in chief part from beneath the stone in
+the course of 35 years.  This amount would be amply sufficient to account
+for its having sunk about 2 inches into the ground; more especially if we
+bear in mind that a good deal of the finest earth would have been washed
+by heavy rain from the castings ejected on the sloping border down to the
+level of the field.  Some fresh castings were seen close to the stone.
+Nevertheless, on digging a large hole to a depth of 18 inches where the
+stone had lain, only two worms and a few burrows were seen, although the
+soil was damp and seemed favourable for worms.  There were some large
+colonies of ants beneath the stone, and possibly since their
+establishment the worms had decreased in number.
+
+The third stone was only about half as large as the others; and two
+strong boys could together have rolled it over.  I have no doubt that it
+had been rolled over at a moderately recent time, for it now lay at some
+distance from the two other stones at the bottom of a little adjoining
+slope.  It rested also on fine earth, instead of partly on brick-rubbish.
+In agreement with this conclusion, the raised surrounding border of turf
+was only 1 inch high in some parts, and 2 inches in other parts.  There
+were no colonies of ants beneath this stone, and on digging a hole where
+it had lain, several burrows and worms were found.
+
+At Stonehenge, some of the outer Druidical stones are now prostrate,
+having fallen at a remote but unknown period; and these have become
+buried to a moderate depth in the ground.  They are surrounded by sloping
+borders of turf, on which recent castings were seen.  Close to one of
+these fallen stones, which was 17 ft long, 6 ft. broad, and 28½ inches
+thick, a hole was dug; and here the vegetable mould was at least 9½
+inches in thickness.  At this depth a flint was found, and a little
+higher up on one side of the hole a fragment of glass.  The base of the
+stone lay about 9½ inches beneath the level of the surrounding ground,
+and its upper surface 19 inches above the ground.
+
+A hole was also dug close to a second huge stone, which in falling had
+broken into two pieces; and this must have happened long ago, judging
+from the weathered aspect of the fractured ends.  The base was buried to
+a depth of 10 inches, as was ascertained by driving an iron skewer
+horizontally into the ground beneath it.  The vegetable mould forming the
+turf-covered sloping border round the stone, on which many castings had
+recently been ejected, was 10 inches in thickness; and most of this mould
+must have been brought up by worms from beneath its base.  At a distance
+of 8 yards from the stone, the mould was only 5½ inches in thickness
+(with a piece of tobacco pipe at a depth of 4 inches), and this rested on
+broken flint and chalk which could not have easily yielded to the
+pressure or weight of the stone.
+
+A straight rod was fixed horizontally (by the aid of a spirit-level)
+across a third fallen stone, which was 7 feet 9 inches long; and the
+contour of the projecting parts and of the adjoining ground, which was
+not quite level, was thus ascertained, as shown in the accompanying
+diagram (Fig. 7) on a scale of ½ inch to a foot.  The turf-covered border
+sloped up to the stone on one side to a height of 4 inches, and on the
+opposite side to only 2½ inches above the general level.  A hole was dug
+on the eastern side, and the base of the stone was here found to lie at a
+depth of 4 inches beneath the general level of the ground, and of 8
+inches beneath the top of the sloping turf-covered border.
+
+                                * * * * *
+
+Sufficient evidence has now been given showing that small objects left on
+the surface of the land where worms abound soon get buried, and that
+large stones sink slowly downwards through the same means.  Every step of
+the process could be followed, from the accidental deposition of a single
+casting on a small object lying loose on the surface, to its being
+entangled amidst the matted roots of the turf, and lastly to its being
+embedded in the mould at various depths beneath the surface.  When the
+same field was re-examined after the interval of a few years, such
+objects were found at a greater depth than before.  The straightness and
+regularity of the lines formed by the imbedded objects, and their
+parallelism with the surface of the land, are the most striking features
+of the case; for this parallelism shows how equably the worms must have
+worked; the result being, however, partly the effect of the washing down
+of the fresh castings by rain.  The specific gravity of the objects does
+not affect their rate of sinking, as could be seen by porous cinders,
+burnt marl, chalk and quartz pebbles, having all sunk to the same depth
+within the same time.  Considering the nature of the substratum, which at
+Leith Hill Place was sandy soil including many bits of rock, and at
+Stonehenge, chalk-rubble with broken flints; considering, also, the
+presence of the turf-covered sloping border of mould round the great
+fragments of stone at both these places, their sinking does not appear to
+have been sensibly aided by their weight, though this was considerable.
+{147}
+
+_On the number of worms which live within a given space_.—We will now
+show, firstly, what a vast number of worms live unseen by us beneath our
+feet, and, secondly, the actual weight of the earth which they bring up
+to the surface within a given space and within a given time.  Hensen, who
+has published so full and interesting an account of the habits of worms,
+{148} calculates, from the number which he found in a measured space,
+that there must exist 133,000 living worms in a hectare of land, or
+53,767 in an acre.  This latter number of worms would weigh 356 pounds,
+taking Hensen’s standard of the weight of a single worm, namely, three
+grams.  It should, however, be noted that this calculation is founded on
+the numbers found in a garden, and Hensen believes that worms are here
+twice as numerous as in corn-fields.  The above result, astonishing
+though it be, seems to me credible, judging from the number of worms
+which I have sometimes seen, and from the number daily destroyed by birds
+without the species being exterminated.  Some barrels of bad ale were
+left on Mr. Miller’s land, {149} in the hope of making vinegar, but the
+vinegar proved bad, and the barrels were upset.  It should be premised
+that acetic acid is so deadly a poison to worms that Perrier found that a
+glass rod dipped into this acid and then into a considerable body of
+water in which worms were immersed, invariably killed them quickly.  On
+the morning after the barrels had been upset, “the heaps of worms which
+lay dead on the ground were so amazing, that if Mr. Miller had not seen
+them, he could not have thought it possible for such numbers to have
+existed in the space.”  As further evidence of the large number of worms
+which live in the ground, Hensen states that he found in a garden
+sixty-four open burrows in a space of 14½ square feet, that is, nine in 2
+square feet.  But the burrows are sometimes much more numerous, for when
+digging in a grass-field near Maer Hall, I found a cake of dry earth, as
+large as my two open hands, which was penetrated by seven burrows, as
+large as goose-quills.
+
+_Weight of the earth ejected from a single burrow_, _and from all the
+burrows within a given space_.—With respect to the weight of the earth
+daily ejected by worms, Hensen found that it amounted, in the case of
+some worms which he kept in confinement, and which he appears to have fed
+with leaves, to only 0.5 gram, or less than 8 grains per diem.  But a
+very much larger amount must be ejected by worms in their natural state,
+at the periods when they consume earth as food instead of leaves, and
+when they are making deep burrows.  This is rendered almost certain by
+the following weights of the castings thrown up at the mouths of single
+burrows; the whole of which appeared to have been ejected within no long
+time, as was certainly the case in several instances.  The castings were
+dried (excepting in one specified instance) by exposure during many days
+to the sun or before a hot fire.
+
+ WEIGHT OF THE CASTINGS ACCUMULATED AT THE MOUTH OF A SINGLE BURROW.
+(1.)  Down, Kent (sub-soil red clay, full of flints,              3.98
+over-lying the chalk).  The largest casting which I could
+find on the flanks of a steep valley, the sub-soil being
+here shallow.  In this one case, the casting was not well
+dried
+(2.)  Down.—Largest casting which I could find (consisting        3.87
+chiefly of calcareous matter), on extremely poor pasture
+land at the bottom of the valley mentioned under (1.)
+(3.)  Down.—A large casting, but not of unusual size, from        1.22
+a nearly level field, poor pasture, laid down in a grass
+about 35 years before
+(4.)  Down.  Average weight of 11 not large castings               0.7
+ejected on a sloping surface on my lawn, after they had
+suffered some loss of weight from being exposed during a
+considerable length of time to rain
+(5.)  Near Nice in France.—Average weight of 12 castings of       1.37
+ordinary dimensions, collected by Dr. King on land which
+had not been mown for a long time and where worms abounded,
+viz., a lawn protected by shrubberies near the sea; soil
+sandy and calcareous; these castings had been exposed for
+some time to rain, before being collected, and must have
+lost some weight by disintegration, but they still retained
+their form
+(6.)  The heaviest of the above twelve castings                   1.76
+(7.)   Lower Bengal.—Average weight of 22 castings,               1.24
+collected by Mr. J. Scott, and stated by him to have been
+thrown up in the course of one or two nights
+(8.)  The heaviest of the above 22 castings                       2.09
+(9.)  Nilgiri Mountains, S. India; average weight of the 5        3.15
+largest castings collected by Dr. King.  They had been
+exposed to the rain of the last monsoon, and must have lost
+some weight
+(10.)  The heaviest of the above 5 castings                       4.34
+
+In this table we see that castings which had been ejected at the mouth of
+the same burrow, and which in most cases appeared fresh and always
+retained their vermiform configuration, generally exceeded an ounce in
+weight after being dried, and sometimes nearly equalled a quarter of a
+pound.  On the Nilgiri mountains one casting even exceeded this latter
+weight.  The largest castings in England were found on extremely poor
+pasture-land; and these, as far as I have seen, are generally larger than
+those on land producing a rich vegetation.  It would appear that worms
+have to swallow a greater amount of earth on poor than on rich land, in
+order to obtain sufficient nutriment.
+
+With respect to the tower-like castings near Nice (Nos. 5 and 6 in the
+above table), Dr. King often found five or six of them on a square foot
+of surface; and these, judging from their average weight, would have
+weighed together 7½ ounces; so that the weight of those on a square yard
+would have been 4 lb. 3½ oz.  Dr. King collected, near the close of the
+year 1872, all the castings which still retained their vermiform shape,
+whether broken down or not, from a square foot, in a place abounding with
+worms, on the summit of a bank, where no castings could have rolled down
+from above.  These castings must have been ejected, as he judged from
+their appearance in reference to the rainy and dry periods near Nice,
+within the previous five or six months; they weighed 9½ oz., or 5 lb. 5½
+oz. per square yard.  After an interval of four months, Dr. King
+collected all the castings subsequently ejected on the same square foot
+of surface, and they weighed 2½ oz., or 1 lb. 6½ oz. per square yard.
+Therefore within about ten months, or we will say for safety’s sake
+within a year, 12 oz. of castings were thrown up on this one square foot,
+or 6.75 pounds on the square yard; and this would give 14.58 tons per
+acre.
+
+In a field at the bottom of a valley in the chalk (see No. 2 in the
+foregoing table), a square yard was measured at a spot where very large
+castings abounded; they appeared, however, almost equally numerous in a
+few other places.  These castings, which retained perfectly their
+vermiform shape, were collected; and they weighed when partially dried, 1
+lb. 13½ oz.  This field had been rolled with a heavy agricultural roller
+fifty-two days before, and this would certainly have flattened every
+single casting on the land.  The weather had been very dry for two or
+three weeks before the day of collection, so that not one casting
+appeared fresh or had been recently ejected.  We may therefore assume
+that those which were weighed had been ejected within, we will say, forty
+days from the time when the field was rolled,—that is, twelve days short
+of the whole intervening period.  I had examined the same part of the
+field shortly before it was rolled, and it then abounded with fresh
+castings.  Worms do not work in dry weather during the summer, or in
+winter during severe frosts.  If we assume that they work for only half
+the year—though this is too low an estimate—then the worms in this field
+would eject during the year, 8.387 pounds per square yard; or 18.12 tons
+per acre, assuming the whole surface to be equally productive in
+castings.
+
+In the foregoing cases some of the necessary data had to be estimated,
+but in the two following cases the results are much more trustworthy.  A
+lady, on whose accuracy I can implicitly rely, offered to collect during
+a year all the castings thrown up on two separate square yards, near
+Leith Hill Place, in Surrey.  The amount collected was, however, somewhat
+less than that originally ejected by the worms; for, as I have repeatedly
+observed, a good deal of the finest earth is washed away, whenever
+castings are thrown up during or shortly before heavy rain.  Small
+portions also adhered to the surrounding blades of grass, and it required
+too much time to detach every one of them.
+
+On sandy soil, as in the present instance, castings are liable to crumble
+after dry weather, and particles were thus often lost.  The lady also
+occasionally left home for a week or two, and at such times the castings
+must have suffered still greater loss from exposure to the weather.
+These losses were, however, compensated to some extent by the collections
+having been made on one of the squares for four days, and on the other
+square for two days more than the year.
+
+A space was selected (October 9th, 1870) for one of the squares on a
+broad, grass-covered terrace, which had been mowed and swept during many
+years.  It faced the south, but was shaded during part of the day by
+trees.  It had been formed at least a century ago by a great accumulation
+of small and large fragments of sandstone, together with some sandy
+earth, rammed down level.  It is probable that it was at first protected
+by being covered with turf.  This terrace, judging from the number of
+castings on it, was rather unfavourable for the existence of worms, in
+comparison with the neighbouring fields and an upper terrace.  It was
+indeed surprising that as many worms could live here as were seen; for on
+digging a hole in this terrace, the black vegetable mould together with
+the turf was only four inches in thickness, beneath which lay the level
+surface of light-coloured sandy soil, with many fragments of sandstone.
+Before any castings were collected all the previously existing ones were
+carefully removed.  The last day’s collection was on October 14th, 1871.
+The castings were then well dried before a fire; and they weighed exactly
+3½ lbs.  This would give for an acre of similar land 7.56 tons of dry
+earth annually ejected by worms.
+
+The second square was marked on unenclosed common land, at a height of
+about 700 ft. above the sea, at some little distance from Leith Hill
+Tower.  The surface was clothed with short, fine turf, and had never been
+disturbed by the hand of man.  The spot selected appeared neither
+particularly favourable nor the reverse for worms; but I have often
+noticed that castings are especially abundant on common land, and this
+may, perhaps, be attributed to the poorness of the soil.  The vegetable
+mould was here between three and four inches in thickness.  As this spot
+was at some distance from the house where the lady lived, the castings
+were not collected at such short intervals of time as those on the
+terrace; consequently the loss of fine earth during rainy weather must
+have been greater in this than in the last case.  The castings moreover
+were more sandy, and in collecting them during dry weather they sometimes
+crumbled into dust, and much was thus lost.  Therefore it is certain that
+the worms brought up to the surface considerably more earth than that
+which was collected.  The last collection was made on October 27th, 1871;
+i.e., 367 days after the square had been marked out and the surface
+cleared of all pre-existing castings.  The collected castings, after
+being well dried, weighed 7.453 pounds; and this would give, for an acre
+of the same kind of land, 16.1 tons of annually ejected dry earth.
+
+                 SUMMARY OF THE FOUR FOREGOING CASES.
+(1.)  Castings ejected near Nice within about a year, collected by Dr.
+King on a square foot of surface, calculated to yield per acre 14.58
+tons.
+(2.)  Castings ejected during about 40 days on a square yard, in a
+field of poor pasture at the bottom of a large valley in the Chalk,
+calculated to yield annually per acre 18.12 tons.
+(3.)  Castings collected from a square yard on an old terrace at Leith
+Hill Place, during 369 days, calculated to yield annually per acre
+7.56 tons.
+(4.)  Castings collected from a square yard on Leith Hill Common
+during 367 days, calculated to yield annually per acre 16.1 tons.
+
+_The thickness of the layer of mould_, _which castings ejected during a
+year would form if uniformly spread out_.—As we know, from the two last
+cases in the above summary, the weight of the dried castings ejected by
+worms during a year on a square yard of surface, I wished to learn how
+thick a layer of ordinary mould this amount would form if spread
+uniformly over a square yard.  The dry castings were therefore broken
+into small particles, and whilst being placed in a measure were well
+shaken and pressed down.  Those collected on the Terrace amounted to
+124.77 cubic inches; and this amount, if spread out over a square yard,
+would make a layer 0.9627 inch in thickness.  Those collected on the
+Common amounted to 197.56 cubic inches, and would make a similar layer
+0.1524 inch in thickness.
+
+These thicknesses must, however, be corrected, for the triturated
+castings, after being well shaken down and pressed, did not make nearly
+so compact a mass as vegetable mould, though each separate particle was
+very compact.  Yet mould is far from being compact, as is shown by the
+number of air-bubbles which rise up when the surface is flooded with
+water.  It is moreover penetrated by many fine roots.  To ascertain
+approximately by how much ordinary vegetable mould would be increased in
+bulk by being broken up into small particles and then dried, a thin
+oblong block of somewhat argillaceous mould (with the turf pared off) was
+measured before being broken up, was well dried and again measured.  The
+drying caused it to shrink by 1/7 of its original bulk, judging from
+exterior measurements alone.  It was then triturated and partly reduced
+to powder, in the same manner as the castings had been treated, and its
+bulk now exceeded (notwithstanding shrinkage from drying) by 1/16 that of
+the original block of damp mould.  Therefore the above calculated
+thickness of the layer, formed by the castings from the Terrace, after
+being damped and spread over a square yard, would have to be reduced by
+1/16; and this will reduce the layer to 0.09 of an inch, so that a layer
+0.9 inch in thickness would be formed in the course of ten years.  On the
+same principle the castings from the Common would make in the course of a
+single year a layer 0.1429 inch, or in the course of 10 years 1.429 inch,
+in thickness.  We may say in round numbers that the thickness in the
+former case would amount to nearly 1 inch, and in the second case to
+nearly 1½ inch in 10 years.
+
+In order to compare these results with those deduced from the rates at
+which small objects left on the surfaces of grass-fields become buried
+(as described in the early part of this chapter), we will give the
+following summary:—
+
+  SUMMARY OF THE THICKNESS OF THE MOULD ACCUMULATED OVER OBJECTS LEFT
+          STREWED ON THE SURFACE, IN THE COURSE OF TEN YEARS.
+The accumulation of mould during 14¾ years on the surface of a dry,
+sandy, grass-field near Maer Hall, amounted to 2.2 inches in 10 years.
+The accumulation during 21½ years on a swampy field near Maer Hall,
+amounted to nearly 1.9 inch in 10 years.
+The accumulation during 7 years on a very swampy field near Maer Hall
+amounted to 2.1 inches in 10 years.
+The accumulation during 29 years, on good, argillaceous pasture-land
+over the Chalk at Down, amounted to 2.2 inches in 10 years.
+The accumulation during 30 years on the side of a valley over the
+Chalk at Down, the soil being argillaceous, very poor, and only just
+converted into pasture (so that it was for some years unfavourable for
+worms), amounted to 0.83 inch in 10 years.
+
+In these cases (excepting the last) it may be seen that the amount of
+earth brought to the surface during 10 years is somewhat greater than
+that calculated from the castings which were actually weighed.  This
+excess may be partly accounted for by the loss which the weighed castings
+had previously undergone through being washed by rain, by the adhesion of
+particles to the blades of the surrounding grass, and by their crumbling
+when dry.  Nor must we overlook other agencies which in all ordinary
+cases add to the amount of mould, and which would not be included in the
+castings that were collected, namely, the fine earth brought up to the
+surface by burrowing larvæ and insects, especially by ants.  The earth
+brought up by moles generally has a somewhat different appearance from
+vegetable mould; but after a time would not be distinguishable from it.
+In dry countries, moreover, the wind plays an important part in carrying
+dust from one place to another, and even in England it must add to the
+mould on fields near great roads.  But in our country these latter
+several agencies appear to be of quite subordinate importance in
+comparison with the action of worms.
+
+We have no means of judging how great a weight of earth a single
+full-sized worm ejects during a year.  Hensen estimates that 53,767 worms
+exist in an acre of land; but this is founded on the number found in
+gardens, and he believes that only about half as many live in
+corn-fields.  How many live in old pasture land is unknown; but if we
+assume that half the above number, or 26,886 worms live on such land,
+then taking from the previous summary 15 tons as the weight of the
+castings annually thrown up on an acre of land, each worm must annually
+eject 20 ounces.  A full-sized casting at the mouth of a single burrow
+often exceeds, as we have seen, an ounce in weight; and it is probable
+that worms eject more than 20 full-sized castings during a year.  If they
+eject annually more than 20 ounces, we may infer that the worms which
+live in an acre of pasture land must be less than 26,886 in number.
+
+Worms live chiefly in the superficial mould, which is usually from 4 or 5
+to 10 and even 12 inches in thickness; and it is this mould which passes
+over and over again through their bodies and is brought to the surface.
+But worms occasionally burrow into the subsoil to a much greater depth,
+and on such occasions they bring up earth from this greater depth; and
+this process has gone on for countless ages.  Therefore the superficial
+layer of mould would ultimately attain, though at a slower and slower
+rate, a thickness equal to the depth to which worms ever burrow, were
+there not other opposing agencies at work which carry away to a lower
+level some of the finest earth which is continually being brought to the
+surface by worms.  How great a thickness vegetable mould ever attains, I
+have not had good opportunities for observing; but in the next chapter,
+when we consider the burial of ancient buildings, some facts will be
+given on this head.  In the two last chapters we shall see that the soil
+is actually increased, though only to a small degree, through the agency
+of worms; but their chief work is to sift the finer from the coarser
+particles, to mingle the whole with vegetable débris, and to saturate it
+with their intestinal secretions.
+
+Finally, no one who considers the facts given in this chapter—on the
+burying of small objects and on the sinking of great stones left on the
+surface—on the vast number of worms which live within a moderate extent
+of ground on the weight of the castings ejected from the mouth of the
+same burrow—on the weight of all the castings ejected within a known time
+on a measured space—will hereafter, as I believe, doubt that worms play
+an important part in nature.
+
+
+
+
+CHAPTER IV.
+THE PART WHICH WORMS HAVE PLAYED IN THE BURIAL OF ANCIENT BUILDINGS.
+
+
+The accumulation of rubbish on the sites of great cities independent of
+the action of worms—The burial of a Roman villa at Abinger—The floors and
+walls penetrated by worms—Subsidence of a modern pavement—The buried
+pavement at Beaulieu Abbey—Roman villas at Chedworth and Brading—The
+remains of the Roman town at Silchester—The nature of the débris by which
+the remains are covered—The penetration of the tesselated floors and
+walls by worms—Subsidence of the floors—Thickness of the mould—The old
+Roman city of Wroxeter—Thickness of the mould—Depth of the foundations of
+some of the Buildings—Conclusion.
+
+ARCHÆOLOGISTS are probably not aware how much they owe to worms for the
+preservation of many ancient objects.  Coins, gold ornaments, stone
+implements, &c., if dropped on the surface of the ground, will infallibly
+be buried by the castings of worms in a few years, and will thus be
+safely preserved, until the land at some future time is turned up.  For
+instance, many years ago a grass-field was ploughed on the northern side
+of the Severn, not far from Shrewsbury; and a surprising number of iron
+arrow-heads were found at the bottom of the furrows, which, as Mr.
+Blakeway, a local antiquary, believed, were relics of the battle of
+Shrewsbury in the year 1403, and no doubt had been originally left
+strewed on the battle-field.  In the present chapter I shall show that
+not only implements, &c., are thus preserved, but that the floors and the
+remains of many ancient buildings in England have been buried so
+effectually, in large part through the action of worms, that they have
+been discovered in recent times solely through various accidents.  The
+enormous beds of rubbish, several yards in thickness, which underlie many
+cities, such as Rome, Paris, and London, the lower ones being of great
+antiquity, are not here referred to, as they have not been in any way
+acted on by worms.  When we consider how much matter is daily brought
+into a great city for building, fuel, clothing and food, and that in old
+times when the roads were bad and the work of the scavenger was
+neglected, a comparatively small amount was carried away, we may agree
+with Élie de Beaumont, who, in discussing this subject, says, “pour une
+voiture de matériaux qui en sort, on y en fait entrer cent.” {166a}  Nor
+should we overlook the effects of fires, the demolition of old buildings,
+and the removal of rubbish to the nearest vacant space.
+
+_Abinger_, _Surrey_.—Late in the autumn of 1876, the ground in an old
+farm-yard at this place was dug to a depth of 2 to 2½ feet, and the
+workmen found various ancient remains.  This led Mr. T. H. Farrer of
+Abinger Hall to have an adjoining ploughed field searched.  On a trench
+being dug, a layer of concrete, still partly covered with tesseræ (small
+red tiles), and surrounded on two sides by broken-down walls, was soon
+discovered.  It is believed, {166b} that this room formed part of the
+atrium or reception-room of a Roman villa.  The walls of two or three
+other small rooms were afterwards discovered.  Many fragments of pottery,
+other objects, and coins of several Roman emperors, dating from 133 to
+361, and perhaps to 375 A.D., were likewise found.  Also a half-penny of
+George I., 1715.  The presence of this latter coin seems an anomaly; but
+no doubt it was dropped on the ground during the last century, and since
+then there has been ample time for its burial under a considerable depth
+of the castings of worms.  From the different dates of the Roman coins we
+may infer that the building was long inhabited.  It was probably ruined
+and deserted 1400 or 1500 years ago.
+
+I was present during the commencement of the excavations (August 20,
+1877) and Mr. Farrer had two deep trenches dug at opposite ends of the
+atrium, so that I might examine the nature of the soil near the remains.
+The field sloped from east to west at an angle of about 7°; and one of
+the two trenches, shown in the accompanying section (Fig. 8) was at the
+upper or eastern end.  The diagram is on a scale of 1/20 of an inch to an
+inch; but the trench, which was between 4 and 5 feet broad, and in parts
+above 5 feet deep, has necessarily been reduced out of all proportion.
+The fine mould over the floor of the atrium varied in thickness from 11
+to 16 inches; and on the side of the trench in the section was a little
+over 13 inches.  After the mould had been removed, the floor appeared as
+a whole moderately level; but it sloped in parts at an angle of 1°, and
+in one place near the outside at as much as 8° 30′.  The wall surrounding
+the pavement was built of rough stones, and was 23 inches in thickness
+where the trench was dug.  Its broken summit was here 13 inches, but in
+another part 15 inches, beneath the surface of the field, being covered
+by this thickness of mould.  In one spot, however, it rose to within 6
+inches of the surface.  On two sides of the room, where the junction of
+the concrete floor with the bounding walls could be carefully examined,
+there was no crack or separation.  This trench afterwards proved to have
+been dug within an adjoining room (11 ft. by 11 ft. 6 in. in size), the
+existence of which was not even suspected whilst I was present.
+
+   [Picture: Fig. 8: Section through the foundations of a buried Roman
+                                  villa]
+
+On the side of the trench farthest from the buried wall (W), the mould
+varied from 9 to 14 inches in thickness; it rested on a mass (B) 23
+inches thick of blackish earth, including many large stones.  Beneath
+this was a thin bed of very black mould (C), then a layer of earth full
+of fragments of mortar (D), and then another thin bed (about 3 inches
+thick) (E) of very black mould, which rested on the undisturbed subsoil
+(F) of firm, yellowish, argillaceous sand.  The 23-inch bed (B) was
+probably made ground, as this would have brought up the floor of the room
+to a level with that of the atrium.  The two thin beds of black mould at
+the bottom of the trench evidently marked two former land-surfaces.
+Outside the walls of the northern room, many bones, ashes, oyster-shells,
+broken pottery and an entire pot were subsequently found at a depth of 16
+inches beneath the surface.
+
+The second trench was dug on the western or lower side of the villa: the
+mould was here only 6½ inches in thickness, and it rested on a mass of
+fine earth full of stones, broken tiles and fragments of mortar, 34
+inches in thickness, beneath which was the undisturbed sand.  Most of
+this earth had probably been washed down from the upper part of the
+field, and the fragments of stones, tiles, &c., must have come from the
+immediately adjoining ruins.
+
+It appears at first sight a surprising fact that this field of light
+sandy soil should have been cultivated and ploughed during many years,
+and that not a vestige of these buildings should have been discovered.
+No one even suspected that the remains of a Roman villa lay hidden close
+beneath the surface.  But the fact is less surprising when it is known
+that the field, as the bailiff believed, had never been ploughed to a
+greater depth than 4 inches.  It is certain that when the land was first
+ploughed, the pavement and the surrounding broken walls must have been
+covered by at least 4 inches of soil, for otherwise the rotten concrete
+floor would have been scored by the ploughshare, the tesseræ torn up, and
+the tops of the old walls knocked down.
+
+When the concrete and tesseræ were first cleared over a space of 14 by 9
+ft., the floor which was coated with trodden-down earth exhibited no
+signs of having been penetrated by worms; and although the overlying fine
+mould closely resembled that which in many places has certainly been
+accumulated by worms, yet it seemed hardly possible that this mould could
+have been brought up by worms from beneath the apparently sound floor.
+It seemed also extremely improbable that the thick walls, surrounding the
+room and still united to the concrete, had been undermined by worms, and
+had thus been caused to sink, being afterwards covered up by their
+castings.  I therefore at first concluded that all the fine mould above
+the ruins had been washed down from the upper parts of the field; but we
+shall soon see that this conclusion was certainly erroneous, though much
+fine earth is known to be washed down from the upper part of the field in
+its present ploughed state during heavy rains.
+
+Although the concrete floor did not at first appear to have been anywhere
+penetrated by worms, yet by the next morning little cakes of the
+trodden-down earth had been lifted up by worms over the mouths of seven
+burrows, which passed through the softer parts of the naked concrete, or
+between the interstices of the tesseræ.  On the third morning twenty-five
+burrows were counted; and by suddenly lifting up the little cakes of
+earth, four worms were seen in the act of quickly retreating.  Two
+castings were thrown up during the third night on the floor, and these
+were of large size.  The season was not favourable for the full activity
+of worms, and the weather had lately been hot and dry, so that most of
+the worms now lived at a considerable depth.  In digging the two trenches
+many open burrows and some worms were encountered at between 30 and 40
+inches beneath the surface; but at a greater depth they became rare.  One
+worm, however, was cut through at 48½, and another at 51½ inches beneath
+the surface.  A fresh humus-lined burrow was also met with at a depth of
+57 and another at 65½ inches.  At greater depths than this, neither
+burrows nor worms were seen.
+
+As I wished to learn how many worms lived beneath the floor of the
+atrium—a space of about 14 by 9 feet—Mr. Farrer was so kind as to make
+observations for me, during the next seven weeks, by which time the worms
+in the surrounding country were in full activity, and were working near
+the surface.  It is very improbable that worms should have migrated from
+the adjoining field into the small space of the atrium, after the
+superficial mould in which they prefer to live, had been removed.  We may
+therefore conclude that the burrows and the castings which were seen here
+during the ensuing seven weeks were the work of the former inhabitants of
+the space.  I will now give a few extracts from Mr. Farrer’s notes.
+
+Aug. 26th, 1877; that is, five days after the floor had been cleared.  On
+the previous night there had been some heavy rain, which washed the
+surface clean, and now the mouths of forty burrows were counted.  Parts
+of the concrete were seen to be solid, and had never been penetrated by
+worms, and here the rain-water lodged.
+
+Sept. 5th.—Tracks of worms, made during the previous night, could be seen
+on the surface of the floor, and five or six vermiform castings had been
+thrown up.  These were defaced.
+
+Sept. 12th.—During the last six days, the worms have not been active,
+though many castings have been ejected in the neighbouring fields; but on
+this day the earth was a little raised over the mouths of the burrows, or
+castings were ejected, at ten fresh points.  These were defaced.  It
+should be understood that when a fresh burrow is spoken of, this
+generally means only that an old burrow has been re-opened.  Mr. Farrer
+was repeatedly struck with the pertinacity with which the worms re-opened
+their old burrows, even when no earth was ejected from them.  I have
+often observed the same fact, and generally the mouths of the burrows are
+protected by an accumulation of pebbles, sticks or leaves.  Mr. Farrer
+likewise observed that the worms living beneath the floor of the atrium
+often collected coarse grains of sand, and such little stones as they
+could find, round the mouths of their burrows.
+
+Sept. 13th; soft wet weather.  The mouths of the burrows were re-opened,
+or castings were ejected, at 31 points; these were all defaced.
+
+Sept. 14th; 34 fresh holes or castings; all defaced.
+
+Sept. 15th; 44 fresh holes, only 5 castings; all defaced.
+
+Sept. 18th; 43 fresh holes, 8 castings; all defaced.
+
+The number of castings on the surrounding fields was now very large.
+
+Sept. 19th; 40 holes, 8 castings; all defaced.
+
+Sept. 22nd; 43 holes, only a few fresh castings; all defaced.
+
+Sept. 23rd; 44 holes, 8 castings.
+
+Sept. 25th; 50 holes, no record of the number of castings.
+
+Oct. 13th;  61 holes, no record of the number of castings.
+
+After an interval of three years, Mr. Farrer, at my request, again looked
+at the concrete floor, and found the worms still at work.
+
+Knowing what great muscular power worms possess, and seeing how soft the
+concrete was in many parts, I was not surprised at its having been
+penetrated by their burrows; but it is a more surprising fact that the
+mortar between the rough stones of the thick walls, surrounding the
+rooms, was found by Mr. Farrer to have been penetrated by worms.  On
+August 26th, that is, five days after the ruins had been exposed, he
+observed four open burrows on the broken summit of the eastern wall (W in
+Fig. 8); and, on September 15th, other burrows similarly situated were
+seen.  It should also be noted that in the perpendicular side of the
+trench (which was much deeper than is represented in Fig. 8) three recent
+burrows were seen, which ran obliquely far down beneath the base of the
+old wall.
+
+We thus see that many worms lived beneath the floor and the walls of the
+atrium at the time when the excavations were made; and that they
+afterwards almost daily brought up earth to the surface from a
+considerable depth.  There is not the slightest reason to doubt that
+worms have acted in this manner ever since the period when the concrete
+was sufficiently decayed to allow them to penetrate it; and even before
+that period they would have lived beneath the floor, as soon as it became
+pervious to rain, so that the soil beneath was kept damp.  The floor and
+the walls must therefore have been continually undermined; and fine earth
+must have been heaped on them during many centuries, perhaps for a
+thousand years.  If the burrows beneath the floor and walls, which it is
+probable were formerly as numerous as they now are, had not collapsed in
+the course of time in the manner formerly explained, the underlying earth
+would have been riddled with passages like a sponge; and as this was not
+the case, we may feel sure that they have collapsed.  The inevitable
+result of such collapsing during successive centuries, will have been the
+slow subsidence of the floor and of the walls, and their burial beneath
+the accumulated worm-castings.  The subsidence of a floor, whilst it
+still remains nearly horizontal, may at first appear improbable; but the
+case presents no more real difficulty than that of loose objects strewed
+on the surface of a field, which, as we have seen, become buried several
+inches beneath the surface in the course of a few years, though still
+forming a horizontal layer parallel to the surface.  The burial of the
+paved and level path on my lawn, which took place under my own
+observation, is an analogous case.  Even those parts of the concrete
+floor which the worms could not penetrate would almost certainly have
+been undermined, and would have sunk, like the great stones at Leith Hill
+Place and Stonehenge, for the soil would have been damp beneath them.
+But the rate of sinking of the different parts would not have been quite
+equal, and the floor was not quite level.  The foundations of the
+boundary walls lie, as shown in the section, at a very small depth
+beneath the surface; they would therefore have tended to subside at
+nearly the same rate as the floor.  But this would not have occurred if
+the foundations had been deep, as in the case of some other Roman ruins
+presently to be described.
+
+Finally, we may infer that a large part of the fine vegetable mould,
+which covered the floor and the broken-down walls of this villa, in some
+places to a thickness of 16 inches, was brought up from below by worms.
+From facts hereafter to be given there can be no doubt that some of the
+finest earth thus brought up will have been washed down the sloping
+surface of the field during every heavy shower of rain.  If this had not
+occurred a greater amount of mould would have accumulated over the ruins
+than that now present.  But beside the castings of worms and some earth
+brought up by insects, and some accumulation of dust, much fine earth
+will have been washed over the ruins from the upper parts of the field,
+since it has been under cultivation; and from over the ruins to the lower
+parts of the slope; the present thickness of the mould being the
+resultant of these several agencies.
+
+                                * * * * *
+
+I may here append a modern instance of the sinking of a pavement,
+communicated to me in 1871 by Mr. Ramsay, Director of the Geological
+Survey of England.  A passage without a roof, 7 feet in length by 3 feet
+2 inches in width, led from his house into the garden, and was paved with
+slabs of Portland stone.  Several of these slabs were 16 inches square,
+others larger, and some a little smaller.  This pavement had subsided
+about 3 inches along the middle of the passage, and two inches on each
+side, as could be seen by the lines of cement by which the slabs had been
+originally joined to the walls.  The pavement had thus become slightly
+concave along the middle; but there was no subsidence at the end close to
+the house.  Mr. Ramsay could not account for this sinking, until he
+observed that castings of black mould were frequently ejected along the
+lines of junction between the slabs; and these castings were regularly
+swept away.  The several lines of junction, including those with the
+lateral walls, were altogether 39 feet 2 inches in length.  The pavement
+did not present the appearance of ever having been renewed, and the house
+was believed to have been built about eighty-seven years ago.
+Considering all these circumstances, Mr. Ramsay does not doubt that the
+earth brought up by the worms since the pavement was first laid down, or
+rather since the decay of the mortar allowed the worms to burrow through
+it, and therefore within a much shorter time than the eighty-seven years,
+has sufficed to cause the sinking of the pavement to the above amount,
+except close to the house, where the ground beneath would have been kept
+nearly dry.
+
+Beaulieu Abbey, Hampshire.—This abbey was destroyed by Henry VIII., and
+there now remains only a portion of the southern aisle-wall.  It is
+believed that the king had most of the stones carried away for building a
+castle; and it is certain that they have been removed.  The positions of
+the nave and transepts were ascertained not long ago by the foundations
+having been found; and the place is now marked by stones let into the
+ground.  Where the abbey formerly stood, there now extends a smooth
+grass-covered surface, which resembles in all respects the rest of the
+field.  The guardian, a very old man, said the surface had never been
+levelled in his time.  In the year 1853, the Duke of Buccleuch had three
+holes dug in the turf within a few yards of one another, at the western
+end of the nave; and the old tesselated pavement of the abbey was thus
+discovered.  These holes were afterwards surrounded by brickwork, and
+protected by trap-doors, so that the pavement might be readily inspected
+and preserved.  When my son William examined the place on January 5,
+1872, he found that the pavement in the three holes lay at depths of 6¾,
+10 and 11½ inches beneath the surrounding turf-covered surface.  The old
+guardian asserted that he was often forced to remove worm-castings from
+the pavement; and that he had done so about six months before.  My son
+collected all from one of the holes, the area of which was 5.32 square
+feet, and they weighed 7.97 ounces.  Assuming that this amount had
+accumulated in six months, the accumulation during a year on a square
+yard would be 1.68 pounds, which, though a large amount, is very small
+compared with what, as we have seen, is often ejected on fields and
+commons.  When I visited the abbey on June 22, 1877, the old man said
+that he had cleared out the holes about a month before, but a good many
+castings had since been ejected.  I suspect that he imagined that he
+swept the pavements oftener than he really did, for the conditions were
+in several respects very unfavourable for the accumulation of even a
+moderate amount of castings.  The tiles are rather large, viz., about 5½
+inches square, and the mortar between them was in most places sound, so
+that the worms were able to bring up earth from below only at certain
+points.  The tiles rested on a bed of concrete, and the castings in
+consequence consisted in large part (viz., in the proportion of 19 to 33)
+of particles of mortar, grains of sand, little fragments of rock, bricks
+or tile; and such substances could hardly be agreeable, and certainly not
+nutritious, to worms.
+
+My son dug holes in several places within the former walls of the abbey,
+at a distance of several yards from the above described bricked squares.
+He did not find any tiles, though these are known to occur in some other
+parts, but he came in one spot to concrete on which tiles had once
+rested.  The fine mould beneath the turf on the sides of the several
+holes, varied in thickness from only 2 to 2¾ inches, and this rested on a
+layer from 8¾ to above 11 inches in thickness, consisting of fragments of
+mortar and stone-rubbish with the interstices compactly filled up with
+black mould.  In the surrounding field, at a distance of 20 yards from
+the abbey, the fine vegetable mould was 11 inches thick.
+
+We may conclude from these facts that when the abbey was destroyed and
+the stones removed, a layer of rubbish was left over the whole surface,
+and that as soon as the worms were able to penetrate the decayed concrete
+and the joints between the tiles, they slowly filled up the interstices
+in the overlying rubbish with their castings, which were afterwards
+accumulated to a thickness of nearly three inches over the whole surface.
+If we add to this latter amount the mould between the fragments of
+stones, some five or six inches of mould must have been brought up from
+beneath the concrete or tiles.  The concrete or tiles will consequently
+have subsided to nearly this amount.  The bases of the columns of the
+aisles are now buried beneath mould and turf.  It is not probable that
+they can have been undermined by worms, for their foundations would no
+doubt have been laid at a considerable depth.  If they have not subsided,
+the stones of which the columns were constructed must have been removed
+from beneath the former level of the floor.
+
+_Chedworth_, _Gloucestershire_.—The remains of a large Roman villa were
+discovered here in 1866, on ground which had been covered with wood from
+time immemorial.  No suspicion seems ever to have been entertained that
+ancient buildings lay buried here, until a gamekeeper, in digging for
+rabbits, encountered some remains. {183}  But subsequently the tops of
+some stone walls were detected in parts of the wood, projecting a little
+above the surface of the ground.  Most of the coins found here belonged
+to Constans (who died 350 A.D.) and the Constantine family.  My sons
+Francis and Horace visited the place in November 1877, for the sake of
+ascertaining what part worms may have played in the burial of these
+extensive remains.  But the circumstances were not favourable for this
+object, as the ruins are surrounded on three sides by rather steep banks,
+down which earth is washed during rainy weather.  Moreover most of the
+old rooms have been covered with roofs, for the protection of the elegant
+tesselated pavements.
+
+A few facts may, however, be given on the thickness of the soil over
+these ruins.  Close outside the northern rooms there is a broken wall,
+the summit of which was covered by 5 inches of black mould; and in a hole
+dug on the outer side of this wall, where the ground had never before
+been disturbed, black mould, full of stones, 26 inches in thickness, was
+found, resting on the undisturbed sub-soil of yellow clay.  At a depth of
+22 inches from the surface a pig’s jaw and a fragment of a tile were
+found.  When the excavations were first made, some large trees grew over
+the ruins; and the stump of one has been left directly over a party-wall
+near the bath-room, for the sake of showing the thickness of the
+superincumbent soil, which was here 38 inches.  In one small room, which,
+after being cleared out, had not been roofed over, my sons observed the
+hole of a worm passing through the rotten concrete, and a living worm was
+found within the concrete.  In another open room worm-castings were seen
+on the floor, over which some earth had by this means been deposited, and
+here grass now grew.
+
+_Brading_, _Isle of Wight_.—A fine Roman villa was discovered here in
+1880; and by the end of October no less than 18 chambers had been more or
+less cleared.  A coin dated 337 A.D. was found.  My son William visited
+the place before the excavations were completed; and he informs me that
+most of the floors were at first covered with much rubbish and fallen
+stones, having their interstices completely filled up with mould,
+abounding, as the workmen said, with worms, above which there was mould
+without any stones.  The whole mass was in most places from 3 to above 4
+ft. in thickness.  In one very large room the overlying earth was only 2
+ft. 6 in. thick; and after this had been removed, so many castings were
+thrown up between the tiles that the surface had to be almost daily
+swept.  Most of the floors were fairly level.  The tops of the
+broken-down walls were covered in some places by only 4 or 5 inches of
+soil, so that they were occasionally struck by the plough, but in other
+places they were covered by from 13 to 18 inches of soil.  It is not
+probable that these walls could have been undermined by worms and
+subsided, as they rested on a foundation of very hard red sand, into
+which worms could hardly burrow.  The mortar, however, between the stones
+of the walls of a hypocaust was found by my son to have been penetrated
+by many worm-burrows.  The remains of this villa stand on land which
+slopes at an angle of about 3°; and the land appears to have been long
+cultivated.  Therefore no doubt a considerable quantity of fine earth has
+been washed down from the upper parts of the field, and has largely aided
+in the burial of these remains.
+
+_Silchester_, _Hampshire_.—The ruins of this small Roman town have been
+better preserved than any other remains of the kind in England.  A broken
+wall, in most parts from 15 to 18 feet in height and about 1½ mile in
+compass, now surrounds a space of about 100 acres of cultivated land, on
+which a farm-house and a church stand. {187}  Formerly, when the weather
+was dry, the lines of the buried walls could be traced by the appearance
+of the crops; and recently very extensive excavations have been
+undertaken by the Duke of Wellington, under the superintendence of the
+late Rev. J. G. Joyce, by which means many large buildings have been
+discovered.  Mr. Joyce made careful coloured sections, and measured the
+thickness of each bed of rubbish, whilst the excavations were in
+progress; and he has had the kindness to send me copies of several of
+them.  When my sons Francis and Horace visited these ruins, he
+accompanied them, and added his notes to theirs.
+
+Mr. Joyce estimates that the town was inhabited by the Romans for about
+three centuries; and no doubt much matter must have accumulated within
+the walls during this long period.  It appears to have been destroyed by
+fire, and most of the stones used in the buildings have since been
+carried away.  These circumstances are unfavourable for ascertaining the
+part which worms have played in the burial of the ruins; but as careful
+sections of the rubbish overlying an ancient town have seldom or never
+before been made in England, I will give copies of the most
+characteristic portions of some of those made by Mr. Joyce.  They are of
+too great length to be here introduced entire.
+
+An east and west section, 30 ft. in length, was made across a room in the
+Basilica, now called the Hall of the Merchants (Fig. 9).  The hard
+concrete floor, still covered here and there with tesseræ, was found at 3
+ft. beneath the surface of the field, which was here level.  On the floor
+there were two large piles of charred wood, one alone of which is shown
+in the part of the section here given.  This pile was covered by a thin
+white layer of decayed stucco or plaster, above which was a mass,
+presenting a singularly disturbed appearance, of broken tiles, mortar,
+rubbish and fine gravel, together 27 inches in thickness.  Mr. Joyce
+believes that the gravel was used in making the mortar or concrete, which
+has since decayed, some of the lime probably having been dissolved.  The
+disturbed state of the rubbish may have been due to its having been
+searched for building stones.  This bed was capped by fine vegetable
+mould, 9 inches in thickness.  From these facts we may conclude that the
+Hall was burnt down, and that much rubbish fell on the floor, through and
+from which the worms slowly brought up the mould, now forming the surface
+of the level field.
+
+ [Picture: Fig. 7: Section through one of the fallen Druidical stones at
+Stonehenge.  Fig. 9: Section within a room in the Basilica at Silchester]
+
+A section across the middle of another hall in the Basilica, 32 feet 6
+inches in length, called the Ærarium, is shown in Fig. 10.  It appears
+that we have here evidence of two fires, separated by an interval of
+time, during which the 6 inches of “mortar and concrete with broken
+tiles” was accumulated.  Beneath one of the layers of charred wood, a
+valuable relic, a bronze eagle, was found; and this shows that the
+soldiers must have deserted the place in a panic.  Owing to the death of
+Mr. Joyce, I have not been able to ascertain beneath which of the two
+layers the eagle was found.  The bed of rubble overlying the undisturbed
+gravel originally formed, as I suppose, the floor, for it stands on a
+level with that of a corridor, outside the walls of the Hall; but the
+corridor is not shown in the section as here given.  The vegetable mould
+was 16 inches thick in the thickest part; and the depth from the surface
+of the field, clothed with herbage, to the undisturbed gravel, was 40
+inches.
+
+ [Picture: Fig. 10: Section within a hall in the Basilica of Silchester]
+
+The section shown in Fig. 11 represents an excavation made in the middle
+of the town, and is here introduced because the bed of “rich mould”
+attained, according to Mr. Joyce, the unusual thickness of 20 inches.
+Gravel lay at the depth of 48 inches from the surface; but it was not
+ascertained whether this was in its natural state, or had been brought
+here and had been rammed down, as occurs in some other places.
+
+ [Picture: Fig. 11: Section in a block of buildings in the middle of the
+                           town of Silchester]
+
+The section shown in Fig. 12 was taken in the centre of the Basilica, and
+though it was 5 feet in depth, the natural sub-soil was not reached.  The
+bed marked “concrete” was probably at one time a floor; and the beds
+beneath seem to be the remnants of more ancient buildings.  The vegetable
+mould was here only 9 inches thick.  In some other sections, not copied,
+we likewise have evidence of buildings having been erected over the ruins
+of older ones.  In one case there was a layer of yellow clay of very
+unequal thickness between two beds of débris, the lower one of which
+rested on a floor with tesseræ.  The ancient broken walls appear to have
+been sometimes roughly cut down to a uniform level, so as to serve as the
+foundations for a temporary building; and Mr. Joyce suspects that some of
+these buildings were wattled sheds, plastered with clay, which would
+account for the above-mentioned layer of clay.
+
+ [Picture: Fig. 12: Section in the centre of the Basilica at Silchester]
+
+Turning now to the points which more immediately concern us.
+Worm-castings were observed on the floors of several of the rooms, in one
+of which the tesselation was unusually perfect.  The tesseræ here
+consisted of little cubes of hard sandstone of about 1 inch, several of
+which were loose or projected slightly above the general level.  One or
+occasionally two open worm-burrows were found beneath all the loose
+tesseræ.  Worms have also penetrated the old walls of these ruins.  A
+wall, which had just been exposed to view during the excavations then in
+progress, was examined; it was built of large flints, and was 18 inches
+in thickness.  It appeared sound, but when the soil was removed from
+beneath, the mortar in the lower part was found to be so much decayed
+that the flints fell apart from their own weight.  Here, in the middle of
+the wall, at a depth of 29 inches beneath the old floor and of 49½ inches
+beneath the surface of the field, a living worm was found, and the mortar
+was penetrated by several burrows.
+
+A second wall was exposed to view for the first time, and an open burrow
+was seen on its broken summit.  By separating the flints this burrow was
+traced far down in the interior of the wall; but as some of the flints
+cohered firmly, the whole mass was disturbed in pulling down the wall,
+and the burrow could not be traced to the bottom.  The foundations of a
+third wall, which appeared quite sound, lay at a depth of 4 feet beneath
+one of the floors, and of course at a considerably greater depth beneath
+the level of the ground.  A large flint was wrenched out of the wall at
+about a foot from the base, and this required much force, as the mortar
+was sound; but behind the flint in the middle of the wall, the mortar was
+friable, and here there were worm-burrows.  Mr. Joyce and my sons were
+surprised at the blackness of the mortar in this and in several other
+cases, and at the presence of mould in the interior of the walls.  Some
+may have been placed there by the old builders instead of mortar; but we
+should remember that worms line their burrows with black humus.  Moreover
+open spaces would almost certainly have been occasionally left between
+the large irregular flints; and these spaces, we may feel sure, would be
+filled up by the worms with their castings, as soon as they were able to
+penetrate the wall.  Rain-water, oozing down the burrows would also carry
+fine dark-coloured particles into every crevice.  Mr. Joyce was at first
+very sceptical about the amount of work which I attributed to worms; but
+he ends his notes with reference to the last-mentioned wall by saying,
+“This case caused me more surprise and brought more conviction to me than
+any other.  I should have said, and did say, that it was quite impossible
+such a wall could have been penetrated by earth-worms.”
+
+In almost all the rooms the pavement has sunk considerably, especially
+towards the middle; and this is shown in the three following sections.
+The measurements were made by stretching a string tightly and
+horizontally over the floor.  The section, Fig. 13, was taken from north
+to south across a room, 18 feet 4 inches in length, with a nearly perfect
+pavement, next to the “Red Wooden Hut.”  In the northern half, the
+subsidence amounted to 5¾ inches beneath the level of the floor as it now
+stands close to the walls; and it was greater in the northern than in the
+southern half; but, according to Mr. Joyce, the entire pavement has
+obviously subsided.  In several places, the tesseræ appeared as if drawn
+a little away from the walls; whilst in other places they were still in
+close contact with them.
+
+ [Picture: Fig. 14: A north and south section through the subsided floor
+                              of a corridor]
+
+In Fig. 14, we see a section across the paved floor of the southern
+corridor or ambulatory of a quadrangle, in an excavation made near “The
+Spring.”  The floor is 7 feet 9 inches wide, and the broken-down walls
+now project only ¾ of an inch above its level.  The field, which was in
+pasture, here sloped from north to south, at an angle of 30°, 40′.  The
+nature of the ground at some little distance on each side of the corridor
+is shown in the section.  It consisted of earth full of stones and other
+débris, capped with dark vegetable mould which was thicker on the lower
+or southern than on the northern side.  The pavement was nearly level
+along lines parallel to the side-walls, but had sunk in the middle as
+much as 7¾ inches.
+
+A small room at no great distance from that represented in Fig. 13, had
+been enlarged by the Roman occupier on the southern side, by an addition
+of 5 feet 4 inches in breadth.  For this purpose the southern wall of the
+house had been pulled down, but the foundations of the old wall had been
+left buried at a little depth beneath the pavement of the enlarged room.
+Mr. Joyce believes that this buried wall must have been built before the
+reign of Claudius II., who died 270 A.D.  We see in the accompanying
+section, Fig. 15, that the tesselated pavement has subsided to a less
+degree over the buried wall than elsewhere; so that a slight convexity or
+protuberance here stretched in a straight line across the room.  This led
+to a hole being dug, and the buried wall was thus discovered.
+
+          [Picture: Fig. 15: Section through the subsided floor]
+
+We see in these three sections, and in several others not given, that the
+old pavements have sunk or sagged considerably.  Mr. Joyce formerly
+attributed this sinking solely to the slow settling of the ground.  That
+there has been some settling is highly probable, and it may be seen in
+Fig. 15 that the pavement for a width of 5 feet over the southern
+enlargement of the room, which must have been built on fresh ground, has
+sunk a little more than on the old northern side.  But this sinking may
+possibly have had no connection with the enlargement of the room; for in
+Fig. 13 one half of the pavement has subsided more than the other half
+without any assignable cause.  In a bricked passage to Mr. Joyce’s own
+house, laid down only about six years ago, the same kind of sinking has
+occurred as in the ancient buildings.  Nevertheless it does not appear
+probable that the whole amount of sinking can be thus accounted for.  The
+Roman builders excavated the ground to an unusual depth for the
+foundations of their walls, which were thick and solid; it is therefore
+hardly credible that they should have been careless about the solidity of
+the bed on which their tesselated and often ornamented pavements were
+laid.  The sinking must, as it appears to me, be attributed in chief part
+to the pavement having been undermined by worms, which we know are still
+at work.  Even Mr. Joyce at last admitted that this could not have failed
+to have produced a considerable effect.  Thus also the large quantity of
+fine mould overlying the pavements can be accounted for, the presence of
+which would otherwise be inexplicable.  My sons noticed that in one room
+in which the pavement had sagged very little, there was an unusually
+small amount of overlying mould.
+
+As the foundations of the walls generally lie at a considerable depth,
+they will either have not subsided at all through the undermining action
+of worms, or they will have subsided much less than the floor.  This
+latter result would follow from worms not often working deep down beneath
+the foundations; but more especially from the walls not yielding when
+penetrated by worms, whereas the successively formed burrows in a mass of
+earth, equal to one of the walls in depth and thickness, would have
+collapsed many times since the desertion of the ruins, and would
+consequently have shrunk or subsided.  As the walls cannot have sunk much
+or at all, the immediately adjoining pavement from adhering to them will
+have been prevented from subsiding; and thus the present curvature of the
+pavement is intelligible.
+
+The circumstance which has surprised me most with respect to Silchester
+is that during the many centuries which have elapsed since the old
+buildings were deserted, the vegetable mould has not accumulated over
+them to a greater thickness than that here observed.  In most places it
+is only about 9 inches in thickness, but in some places 12 or even more
+inches.  In Fig. 11, it is given as 20 inches, but this section was drawn
+by Mr. Joyce before his attention was particularly called to this
+subject.  The land enclosed within the old walls is described as sloping
+slightly to the south; but there are parts which, according to Mr. Joyce,
+are nearly level, and it appears that the mould is here generally thicker
+than elsewhere.  The surface slopes in other parts from west to east, and
+Mr. Joyce describes one floor as covered at the western end by rubbish
+and mould to a thickness of 28½ inches, and at the eastern end by a
+thickness of only 11½ inches.  A very slight slope suffices to cause
+recent castings to flow downwards during heavy rain, and thus much earth
+will ultimately reach the neighbouring rills and streams and be carried
+away.  By this means, the absence of very thick beds of mould over these
+ancient ruins may, as I believe, be explained.  Moreover most of the land
+here has long been ploughed, and this would greatly aid the washing away
+of the finer earth during rainy weather.
+
+The nature of the beds immediately beneath the vegetable mould in some of
+the sections is rather perplexing.  We see, for instance, in the section
+of an excavation in a grass meadow (Fig. 14), which sloped from north to
+south at an angle of 3° 40′, that the mould on the upper side is only six
+inches and on the lower side nine inches in thickness.  But this mould
+lies on a mass (25½ inches in thickness on the upper side) “of dark brown
+mould,” as described by Mr. Joyce, “thickly interspersed with small
+pebbles and bits of tiles, which present a corroded or worn appearance.”
+The state of this dark-coloured earth is like that of a field which has
+long been ploughed, for the earth thus becomes intermingled with stones
+and fragments of all kinds which have been much exposed to the weather.
+If during the course of many centuries this grass meadow and the other
+now cultivated fields have been at times ploughed, and at other times
+left as pasture, the nature of the ground in the above section is
+rendered intelligible.  For worms will continually have brought up fine
+earth from below, which will have been stirred up by the plough whenever
+the land was cultivated.  But after a time a greater thickness of fine
+earth will thus have been accumulated than could be reached by the
+plough; and a bed like the 25½-inch mass, in Fig. 14, will have been
+formed beneath the superficial mould, which latter will have been brought
+to the surface within more recent times, and have been well sifted by the
+worms.
+
+_Wroxeter_, _Shropshire_.—The old Roman city of Uriconium was founded in
+the early part of the second century, if not before this date; and it was
+destroyed, according to Mr. Wright, probably between the middle of the
+fourth and fifth century.  The inhabitants were massacred, and skeletons
+of women were found in the hypocausts.  Before the year 1859, the sole
+remnant of the city above ground, was a portion of a massive wall about
+20 ft. in height.  The surrounding land undulates slightly, and has long
+been under cultivation.  It had been noticed that the corn-crops ripened
+prematurely in certain narrow lines, and that the snow remained unmelted
+in certain places longer than in others.  These appearances led, as I was
+informed, to extensive excavations being undertaken.  The foundations of
+many large buildings and several streets have thus been exposed to view.
+The space enclosed within the old walls is an irregular oval, about 1¾
+mile in length.  Many of the stones or bricks used in the buildings must
+have been carried away; but the hypocausts, baths, and other underground
+buildings were found tolerably perfect, being filled with stones, broken
+tiles, rubbish and soil.  The old floors of various rooms were covered
+with rubble.  As I was anxious to know how thick the mantle of mould and
+rubbish was, which had so long concealed these ruins, I applied to Dr. H.
+Johnson, who had superintended the excavations; and he, with the greatest
+kindness, twice visited the place to examine it in reference to my
+questions, and had many trenches dug in four fields which had hitherto
+been undisturbed.  The results of his observations are given in the
+following Table.  He also sent me specimens of the mould, and answered,
+as far as he could, all my questions.
+
+
+
+MEASUREMENTS BY DR. H. JOHNSON OF THE THICKNESS OF THE VEGETABLE MOULD
+OVER THE ROMAN RUINS AT WROXETER.
+
+
+               Trenches dug in a field called “Old Works.”
+
+                                    Thickness of mould in inches.
+1.  At a depth of 36 inches                                         20
+undisturbed sand was reached
+2.  At a depth of 33 inches                                         21
+concrete was reached
+3. At a depth of 9 inches                                            9
+concrete was reached
+
+Trenches dug in a field called “Shop Leasows;” this is the highest field
+within the old walls, and slopes down from a sub-central point on all
+sides at about an angle of 2°.
+
+                                    Thickness of mould in inches.
+4.  Summit of field, trench 45                                      40
+inches deep
+5.  Close to summit of field,                                       26
+trench 36 inches deep
+6.  Close to summit of field,                                       28
+trench 28 inches deep
+7.  Near summit of field, trench                                    24
+36 inches deep
+8.  Near summit of field, trench                                    24
+at one end 39 inches deep; the
+mould here graduated into the
+underlying undisturbed sand, and
+its thickness (24 inches) is
+somewhat arbitrary.  At the other
+end of the trench, a causeway was
+encountered at a depth of only 7
+inches, and the mould was here
+only 7 inches thick
+9.  Trench close to the last, 28                                    24
+inches in depth
+10.  Lower part of same field,                                      15
+trench 30 inches deep
+11.  Lower part of same field,                                      17
+trench 31 inches deep
+12.  Lower part of same field,                                      28
+trench 36 inches deep, at which
+depth undisturbed sand was
+reached
+13.  In another part of same                                        9½
+field, trench 9½ inches deep
+stopped by concrete
+14.  In another part of same                                         9
+field, trench 9 inches deep,
+stopped by concrete
+15.  In another part of the same                                    16
+field, trench 24 inches deep,
+when sand was reached
+16.  In another part of same                                        13
+field, trench 30 inches deep,
+when stones were reached; at one
+end of the trench mould 12
+inches, at the other end 14
+inches thick
+
+Small field between “Old Works” and “Shop Leasows,” I believe nearly as
+high as the upper part of the latter field.
+
+                                    Thickness of mould in inches.
+17.  Trench 26 inches deep                                          24
+18.  Trench 10 inches deep, and                                     10
+then came upon a causeway
+19.  Trench 34 inches deep                                          30
+20. Trench 31 inches deep                                           31
+
+Field on the western side of the space enclosed within the old walls.
+
+                                    Thickness of mould in inches.
+21.  Trench 28 inches deep, when                                    16
+undisturbed sand was reached
+22.  Trench 29 inches deep, when                                    15
+undisturbed sand was reached
+23.  Trench 14 inches deep, and                                     14
+then came upon a building
+
+Dr. Johnson distinguished as mould the earth which differed, more or less
+abruptly, in its dark colour and in its texture from the underlying sand
+or rubble.  In the specimens sent to me, the mould resembled that which
+lies immediately beneath the turf in old pasture-land, excepting that it
+often contained small stones, too large to have passed through the bodies
+of worms.  But the trenches above described were dug in fields, none of
+which were in pasture, and all had been long cultivated.  Bearing in mind
+the remarks made in reference to Silchester on the effects of
+long-continued culture, combined with the action of worms in bringing up
+the finer particles to the surface, the mould, as so designated by Dr.
+Johnson, seems fairly well to deserve its name.  Its thickness, where
+there was no causeway, floor or walls beneath, was greater than has been
+elsewhere observed, namely, in many places above 2 ft., and in one spot
+above 3 ft.  The mould was thickest on and close to the nearly level
+summit of the field called “Shop Leasows,” and in a small adjoining
+field, which, as I believe, is of nearly the same height.  One side of
+the former field slopes at an angle of rather above 2°, and I should have
+expected that the mould, from being washed down during heavy rain, would
+have been thicker in the lower than in the upper part; but this was not
+the case in two out of the three trenches here dug.
+
+In many places, where streets ran beneath the surface, or where old
+buildings stood, the mould was only 8 inches in thickness; and Dr.
+Johnson was surprised that in ploughing the land, the ruins had never
+been struck by the plough as far as he had heard.  He thinks that when
+the land was first cultivated the old walls were perhaps intentionally
+pulled down, and that hollow places were filled up.  This may have been
+the case; but if after the desertion of the city the land was left for
+many centuries uncultivated, worms would have brought up enough fine
+earth to have covered the ruins completely; that is if they had subsided
+from having been undermined.  The foundations of some of the walls, for
+instance those of the portion still standing about 20 feet above the
+ground, and those of the marketplace, lie at the extraordinary depth of
+14 feet; but it is highly improbable that the foundations were generally
+so deep.  The mortar employed in the buildings must have been excellent,
+for it is still in parts extremely hard.  Wherever walls of any height
+have been exposed to view, they are, as Dr. Johnson believes, still
+perpendicular.  The walls with such deep foundations cannot have been
+undermined by worms, and therefore cannot have subsided, as appears to
+have occurred at Abinger and Silchester.  Hence it is very difficult to
+account for their being now completely covered with earth; but how much
+of this covering consists of vegetable mould and how much of rubble I do
+not know.  The market-place, with the foundations at a depth of 14 feet,
+was covered up, as Dr. Johnson believes, by between 6 and 24 inches of
+earth.  The tops of the broken-down walls of a caldarium or bath, 9 feet
+in depth, were likewise covered up with nearly 2 feet of earth.  The
+summit of an arch, leading into an ash-pit 7 feet in depth, was covered
+up with not more than 8 inches of earth.  Whenever a building which has
+not subsided is covered with earth, we must suppose, either that the
+upper layers of stone have been at some time carried away by man, or that
+earth has since been washed down during heavy rain, or blown down during
+storms, from the adjoining land; and this would be especially apt to
+occur where the land has long been cultivated.  In the above cases the
+adjoining land is somewhat higher than the three specified sites, as far
+as I can judge by maps and from information given me by Dr. Johnson.  If;
+however, a great pile of broken stones, mortar, plaster, timber and ashes
+fell over the remains of any building, their disintegration in the course
+of time, and the sifting action of worms, would ultimately conceal the
+whole beneath fine earth.
+
+                                * * * * *
+
+_Conclusion_.—The cases given in this chapter show that worms have played
+a considerable part in the burial and concealment of several Roman and
+other old buildings in England; but no doubt the washing down of soil
+from the neighbouring higher lands, and the deposition of dust, have
+together aided largely in the work of concealment.  Dust would be apt to
+accumulate wherever old broken-down walls projected a little above the
+then existing surface and thus afforded some shelter.  The floors of the
+old rooms, halls and passages have generally sunk, partly from the
+settling of the ground, but chiefly from having been undermined by worms;
+and the sinking has commonly been greater in the middle than near the
+walls.  The walls themselves, whenever their foundations do not lie at a
+great depth, have been penetrated and undermined by worms, and have
+consequently subsided.  The unequal subsidence thus caused, probably
+explains the great cracks which may be seen in many ancient walls, as
+well as their inclination from the perpendicular.
+
+
+
+
+CHAPTER V.
+THE ACTION OF WORMS IN THE DENUDATION OF THE LAND.
+
+
+Evidence of the amount of denudation which the land has
+undergone—Sub-aerial denudation—The deposition of dust—Vegetable mould,
+its dark colour and fine texture largely due to the action of worms—The
+disintegration of rocks by the humus-acids—Similar acids apparently
+generated within the bodies of worms—The action of these acids
+facilitated by the continued movement of the particles of earth—A thick
+bed of mould checks the disintegration of the underlying soil and rocks.
+Particles of stone worn or triturated in the gizzards of worms—Swallowed
+stones serve as mill-stones—The levigated state of the castings—Fragments
+of brick in the castings over ancient buildings well rounded.  The
+triturating power of worms not quite insignificant under a geological
+point of view.
+
+NO one doubts that our world at one time consisted of crystalline rocks,
+and that it is to their disintegration through the action of air, water,
+changes of temperature, rivers, waves of the sea, earthquakes and
+volcanic outbursts, that we owe our sedimentary formations.  These after
+being consolidated and sometimes recrystallized, have often been again
+disintegrated.  Denudation means the removal of such disintegrated matter
+to a lower level.  Of the many striking results due to the modern
+progress of geology there are hardly any more striking than those which
+relate to denudation.  It was long ago seen that there must have been an
+immense amount of denudation; but until the successive formations were
+carefully mapped and measured, no one fully realised how great was the
+amount.  One of the first and most remarkable memoirs ever published on
+this subject was that by Ramsay, {210} who in 1846 showed that in Wales
+from 9000 to 11,000 feet in thickness of solid rock had been stripped off
+large tracks of country.  Perhaps the plainest evidence of great
+denudation is afforded by faults or cracks, which extend for many miles
+across certain districts, with the strata on one side raised even ten
+thousand feet above the corresponding strata on the opposite side; and
+yet there is not a vestige of this gigantic displacement visible on the
+surface of the land.  A huge pile of rock has been planed away on one
+side and not a remnant left.
+
+Until the last twenty or thirty years, most geologists thought that the
+waves of the sea were the chief agents in the work of denudation; but we
+may now feel sure that air and rain, aided by streams and rivers, are
+much more powerful agents,—that is if we consider the whole area of the
+land.  The long lines of escarpment which stretch across several parts of
+England were formerly considered to be undoubtedly ancient coast-lines;
+but we now know that they stand up above the general surface merely from
+resisting air, rain and frost better than the adjoining formations.  It
+has rarely been the good fortune of a geologist to bring conviction to
+the minds of his fellow-workers on a disputed point by a single memoir;
+but Mr. Whitaker, of the Geological Survey of England, was so fortunate
+when, in 1867, he published his paper “On sub-aerial Denudation, and on
+Cliffs and Escarpments of the Chalk.” {211}  Before this paper appeared,
+Mr. A. Tylor had adduced important evidence on sub-aerial denudation, by
+showing that the amount of matter brought down by rivers must infallibly
+lower the level of their drainage basins by many feet in no immense lapse
+of time.  This line of argument has since been followed up in the most
+interesting manner by Archibald Geikie, Croll and others, in a series of
+valuable memoirs. {212}  For the sake of those who have never attended to
+this subject, a single instance may be here given, namely, that of the
+Mississippi, which is chosen because the amount of sediment brought down
+by this great river has been investigated with especial care by order of
+the United States Government.  The result is, as Mr. Croll shows, that
+the mean level of its enormous area of drainage must be lowered 1/4566 of
+a foot annually, or 1 foot in 4566 years.  Consequently, taking the best
+estimate of the mean height of the North American continent, viz. 748
+feet, and looking to the future, the whole of the great Mississippi basin
+will be washed away, and “brought down to the sea-level in less than
+4,500,000 years, if no elevation of the land takes place.”  Some rivers
+carry down much more sediment relatively to their size, and some much
+less than the Mississippi.
+
+Disintegrated matter is carried away by the wind as well as by running
+water.  During volcanic outbursts much rock is triturated and is thus
+widely dispersed; and in all arid countries the wind plays an important
+part in the removal of such matter.  Wind-driven sand also wears down the
+hardest rocks.  I have shown {213} that during four months of the year a
+large quantity of dust is blown from the north-western shores of Africa,
+and falls on the Atlantic over a space of 1600 miles in latitude, and for
+a distance of from 300 to 600 miles from the coast.  But dust has been
+seen to fall at a distance of 1030 miles from the shores of Africa.
+During a stay of three weeks at St. Jago in the Cape Verde Archipelago,
+the atmosphere was almost always hazy, and extremely fine dust coming
+from Africa was continually falling.  In some of this dust which fell in
+the open ocean at a distance of between 330 and 380 miles from the
+African coast, there were many particles of stone, about 1/1000 of an
+inch square.  Nearer to the coast the water has been seen to be so much
+discoloured by the falling dust, that a sailing vessel left a track
+behind her.  In countries, like the Cape Verde Archipelago, where it
+seldom rains and there are no frosts, the solid rock nevertheless
+disintegrates; and in conformity with the views lately advanced by a
+distinguished Belgian geologist, De Koninck, such disintegration may be
+attributed in chief part to the action of the carbonic and nitric acids,
+together with the nitrates and nitrites of ammonia, dissolved in the dew.
+
+In all humid, even moderately humid, countries, worms aid in the work of
+denudation in several ways.  The vegetable mould which covers, as with a
+mantle, the surface of the land, has all passed many times through their
+bodies.  Mould differs in appearance from the subsoil only in its dark
+colour, and in the absence of fragments or particles of stone (when such
+are present in the subsoil), larger than those which can pass through the
+alimentary canal of a worm.  This sifting of the soil is aided, as has
+already been remarked, by burrowing animals of many kinds, especially by
+ants.  In countries where the summer is long and dry, the mould in
+protected places must be largely increased by dust blown from other and
+more exposed places.  For instance, the quantity of dust sometimes blown
+over the plains of La Plata, where there are no solid rocks, is so great,
+that during the “gran seco,” 1827 to 1830, the appearance of the land,
+which is here unenclosed, was so completely changed that the inhabitants
+could not recognise the limits of their own estates, and endless lawsuits
+arose.  Immense quantities of dust are likewise blown about in Egypt and
+in the south of France.  In China, as Richthofen maintains, beds
+appearing like fine sediment, several hundred feet in thickness and
+extending over an enormous area, owe their origin to dust blown from the
+high lands of central Asia. {215}  In humid countries like Great Britain,
+as long as the land remains in its natural state clothed with vegetation,
+the mould in any one place can hardly be much increased by dust; but in
+its present condition, the fields near high roads, where there is much
+traffic, must receive a considerable amount of dust, and when fields are
+harrowed during dry and windy weather, clouds of dust may be seen to be
+blown away.  But in all these cases the surface-soil is merely
+transported from one place to another.  The dust which falls so thickly
+within our houses consists largely of organic matter, and if spread over
+the land would in time decay and disappear almost entirely.  It appears,
+however, from recent observations on the snow-fields of the Arctic
+regions, that some little meteoric dust of extra mundane origin is
+continually falling.
+
+The dark colour of ordinary mould is obviously due to the presence of
+decaying organic matter, which, however, is present in but small
+quantities.  The loss of weight which mould suffers when heated to
+redness seems to be in large part due to water in combination being
+dispelled.  In one sample of fertile mould the amount of organic matter
+was ascertained to be only 1.76 per cent.; in some artificially prepared
+soil it was as much as 5.5 per cent., and in the famous black soil of
+Russia from 5 to even 12 per cent. {217a}  In leaf-mould formed
+exclusively by the decay of leaves the amount is much greater, and in
+peat the carbon alone sometimes amounts to 64 per cent.; but with these
+latter cases we are not here concerned.  The carbon in the soil tends
+gradually to oxidise and to disappear, except where water accumulates and
+the climate is cool; {217b} so that in the oldest pasture-land there is
+no great excess of organic matter, notwithstanding the continued decay of
+the roots and the underground stems of plants, and the occasional
+addition of manure.  The disappearance of the organic matter from mould
+is probably much aided by its being brought again and again to the
+surface in the castings of worms.
+
+Worms, on the other hand, add largely to the organic matter in the soil
+by the astonishing number of half-decayed leaves which they draw into
+their burrows to a depth of 2 or 3 inches.  They do this chiefly for
+obtaining food, but partly for closing the mouths of their burrows and
+for lining the upper part.  The leaves which they consume are moistened,
+torn into small shreds, partially digested, and intimately commingled
+with earth; and it is this process which gives to vegetable mould its
+uniform dark tint.  It is known that various kinds of acids are generated
+by the decay of vegetable matter; and from the contents of the intestines
+of worms and from their castings being acid, it seems probable that the
+process of digestion induces an analogous chemical change in the
+swallowed, triturated, and half-decayed leaves.  The large quantity of
+carbonate of lime secreted by the calciferous glands apparently serves to
+neutralise the acids thus generated; for the digestive fluid of worms
+will not act unless it be alkaline.  As the contents of the upper part of
+their intestines are acid, the acidity can hardly be due to the presence
+of uric acid.  We may therefore conclude that the acids in the alimentary
+canal of worms are formed during the digestive process; and that probably
+they are nearly of the same nature as those in ordinary mould or humus.
+The latter are well known to have the power of de-oxidising or dissolving
+per-oxide of iron, as may be seen wherever peat overlies red sand, or
+where a rotten root penetrates such sand.  Now I kept some worms in a pot
+filled with very fine reddish sand, consisting of minute particles of
+silex coated with the red oxide of iron; and the burrows, which the worms
+made through this sand, were lined or coated in the usual manner with
+their castings, formed of the sand mingled with their intestinal
+secretions and the refuse of the digested leaves; and this sand had
+almost wholly lost its red colour.  When small portions of it were placed
+under the microscope, most of the grains were seen to be transparent and
+colourless, owing to the dissolution of the oxide; whilst almost all the
+grains taken from other parts of the pot were coated with the oxide.
+Acetic acid produced hardly any effect on his sand; and even
+hydrochloric, nitric and sulphuric acids, diluted as in the
+Pharmacopoeia, produced less effect than did the acids in the intestines
+of the worms.
+
+Mr. A. A. Julien has lately collected all the extant information about
+the acids generated in humus, which, according to some chemists, amount
+to more than a dozen different kinds.  These acids, as well as their acid
+salts (i.e., in combination with potash, soda, and ammonia), act
+energetically on carbonate of lime and on the oxides of iron.  It is also
+known that some of these acids, which were called long ago by Thénard
+azohumic, are enabled to dissolve colloid silica in proportion to the
+nitrogen which they contain. {220}  In the formation of these latter
+acids worms probably afford some aid, for Dr. H. Johnson informs me that
+by Nessler’s test he found 0.018 per cent. of ammonia in their castings.
+
+It may be here added that I have recently been informed by Dr. Gilbert
+“that several square yards on his lawn were swept clean, and after two or
+three weeks all the worm-castings on the space were collected and dried.
+These were found to contain 0.35 of nitrogen.  This is from two to three
+times as much as we find in our ordinary arable surface-soil; more than
+in our ordinary pasture surface-soil; but less than in rich
+kitchen-garden mould.  Supposing a quantity of castings equal to 10 tons
+in the dry state were annually deposited on an acre, this would represent
+a manuring of 78 lbs. of nitrogen per acre per annum; and this is very
+much more than the amount of nitrogen in the annual yield of hay per
+acre, if raised without any nitrogenous manure.  Obviously, so far as the
+nitrogen in the castings is derived from surface-growth or from
+surface-soil, it is not a gain to the latter; but so far as it is derived
+from below, it is a gain.”
+
+The several humus-acids, which appear, as we have just seen, to be
+generated within the bodies of worms during the digestive process, and
+their acid salts, play a highly important part, according to the recent
+observations of Mr. Julien, in the disintegration of various kinds of
+rocks.  It has long been known that the carbonic acid, and no doubt
+nitric and nitrous acids, which are present in rain-water, act in like
+manner.  There is, also, a great excess of carbonic acid in all soils,
+especially in rich soils, and this is dissolved by the water in the
+ground.  The living roots of plants, moreover, as Sachs and others have
+shown, quickly corrode and leave their impressions on polished slabs of
+marble, dolomite and phosphate of lime.  They will attack even basalt and
+sandstone. {222}  But we are not here concerned with agencies which are
+wholly independent of the action of worms.
+
+The combination of any acid with a base is much facilitated by agitation,
+as fresh surfaces are thus continually brought into contact.  This will
+be thoroughly effected with the particles of stone and earth in the
+intestines of worms, during the digestive process; and it should be
+remembered that the entire mass of the mould over every field, passes, in
+the course of a few years, through their alimentary canals.  Moreover as
+the old burrows slowly collapse, and as fresh castings are continually
+brought to the surface, the whole superficial layer of mould slowly
+revolves or circulates; and the friction of the particles one with
+another will rub off the finest films of disintegrated matter as soon as
+they are formed.  Through these several means, minute fragments of rocks
+of many kinds and mere particles in the soil will be continually exposed
+to chemical decomposition; and thus the amount of soil will tend to
+increase.
+
+As worms line their burrows with their castings, and as the burrows
+penetrate to a depth of 5 or 6, or even more feet, some small amount of
+the humus-acids will be carried far down, and will there act on the
+underlying rocks and fragments of rock.  Thus the thickness of the soil,
+if none be removed from the surface, will steadily though slowly tend to
+increase; but the accumulation will after a time delay the disintegration
+of the underlying rocks and of the more deeply seated particles.  For the
+humus-acids which are generated chiefly in the upper layer of vegetable
+mould, are extremely unstable compounds, and are liable to decomposition
+before they reach any considerable depth. {223}  A thick bed of overlying
+soil will also check the downward extension of great fluctuations of
+temperature, and in cold countries will check the powerful action of
+frost.  The free access of air will likewise be excluded.  From these
+several causes disintegration would be almost arrested, if the overlying
+mould were to increase much in thickness, owing to none or little being
+removed from the surface. {224a}  In my own immediate neighbourhood we
+have a curious proof how effectually a few feet of clay checks some
+change which goes on in flints, lying freely exposed; for the large ones
+which have lain for some time on the surface of ploughed fields cannot be
+used for building; they will not cleave properly, and are said by the
+workmen to be rotten. {224b}  It is therefore necessary to obtain flints
+for building purposes from the bed of red clay overlying the chalk (the
+residue of its dissolution by rain-water) or from the chalk itself.
+
+Not only do worms aid directly in the chemical disintegration of rocks,
+but there is good reason to believe that they likewise act in a direct
+and mechanical manner on the smaller particles.  All the species which
+swallow earth are furnished with gizzards; and these are lined with so
+thick a chitinous membrane, that Perrier speaks of it, {225a} as “une
+véritable armature.”  The gizzard is surrounded by powerful transverse
+muscles, which, according to Claparède, are about ten times as thick as
+the longitudinal ones; and Perrier saw them contracting energetically.
+Worms belonging to one genus, Digaster, have two distinct but quite
+similar gizzards; and in another genus, Moniligaster, the second gizzard
+consists of four pouches, one succeeding the other, so that it may almost
+be said to have five gizzards. {225b}  In the same manner as gallinaceous
+and struthious birds swallow stones to aid in the trituration of their
+food, so it appears to be with terricolous worms.  The gizzards of
+thirty-eight of our common worms were opened, and in twenty-five of them
+small stones or grains of sand, sometimes together with the hard
+calcareous concretions formed within the anterior calciferous glands,
+were found, and in two others concretions alone.  In the gizzards of the
+remaining worms there were no stones; but some of these were not real
+exceptions, as the gizzards were opened late in the autumn, when the
+worms had ceased to feed and their gizzards were quite empty. {226}
+
+When worms make their burrows through earth abounding with little stones,
+no doubt many will be unavoidably swallowed; but it must not be supposed
+that this fact accounts for the frequency with which stones and sand are
+found in their gizzards.  For beads of glass and fragments of brick and
+of hard tiles were scattered over the surface of the earth, in pots in
+which worms were kept and had already made their burrows; and very many
+of these beads and fragments were picked up and swallowed by the worms,
+for they were found in their castings, intestines, and gizzards.  They
+even swallowed the coarse red dust, formed by the pounding of the tiles.
+Nor can it be supposed that they mistook the beads and fragments for
+food; for we have seen that their taste is delicate enough to distinguish
+between different kinds of leaves.  It is therefore manifest that they
+swallow hard objects, such as bits of stone, beads of glass and angular
+fragments of bricks or tiles for some special purpose; and it can hardly
+be doubted that this is to aid their gizzards in crushing and grinding
+the earth, which they so largely consume.  That such hard objects are not
+necessary for crushing leaves, may be inferred from the fact that certain
+species, which live in mud or water and feed on dead or living vegetable
+matter, but which do not swallow earth, are not provided with gizzards,
+{227} and therefore cannot have the power of utilising stones.
+
+During the grinding process, the particles of earth must be rubbed
+against one another, and between the stones and the tough lining membrane
+of the gizzard.  The softer particles will thus suffer some attrition,
+and will perhaps even be crushed.  This conclusion is supported by the
+appearance of freshly ejected castings, for these often reminded me of
+the appearance of paint which has just been ground by a workman between
+two flat stones.  Morren remarks that the intestinal canal is “impleta
+tenuissimâ terrâ, veluti in pulverem redactâ.” {228a}  Perrier also
+speaks of “l’état de pâte excessivement fine à laquelle est réduite la
+terre qu’ils rejettent,” &c. {228b}
+
+As the amount of trituration which the particles of earth undergo in the
+gizzards of worms possesses some interest (as we shall hereafter see), I
+endeavoured to obtain evidence on this head by carefully examining many
+of the fragments which had passed through their alimentary canals.  With
+worms living in a state of nature, it is of course impossible to know how
+much the fragments may have been worn before they were swallowed.  It is,
+however, clear that worms do not habitually select already rounded
+particles, for sharply angular bits of flint and of other hard rocks were
+often found in their gizzards or intestines.  On three occasions sharp
+spines from the stems of rose-bushes were thus found.  Worms kept in
+confinement repeatedly swallowed angular fragments of hard tile, coal,
+cinders, and even the sharpest fragments of glass.  Gallinaceous and
+struthious birds retain the same stones in their gizzards for a long
+time, which thus become well rounded; but this does not appear to be the
+case with worms, judging from the large number of the fragments of tiles,
+glass beads, stones, &c., commonly found in their castings and
+intestines.  So that unless the same fragments were to pass repeatedly
+through their gizzards, visible signs of attrition in the fragments could
+hardly be expected, except perhaps in the case of very soft stones.
+
+I will now give such evidence of attrition as I have been able to
+collect.  In the gizzards of some worms dug out of a thin bed of mould
+over the chalk, there were many well-rounded small fragments of chalk,
+and two fragments of the shells of a land-mollusc (as ascertained by
+their microscopical structure), which latter were not only rounded but
+somewhat polished.  The calcareous concretions formed in the calciferous
+glands, which are often found in their gizzards, intestines, and
+occasionally in their castings, when of large size, sometimes appeared to
+have been rounded; but with all calcareous bodies the rounded appearance
+may be partly or wholly due to their corrosion by carbonic acid and the
+humus-acids.  In the gizzards of several worms collected in my kitchen
+garden near a hothouse, eight little fragments of cinders were found, and
+of these, six appeared more or less rounded, as were two bits of brick;
+but some other bits were not at all rounded.  A farm-road near Abinger
+Hall had been covered seven years before with brick-rubbish to the depth
+of about 6 inches; turf had grown over this rubbish on both sides of the
+road for a width of 18 inches, and on this turf there were innumerable
+castings.  Some of them were coloured of a uniform red owing to the
+presence of much brick-dust, and they contained many particles of brick
+and of hard mortar from 1 to 3 mm. in diameter, most of which were
+plainly rounded; but all these particles may have been rounded before
+they were protected by the turf and were swallowed, like those on the
+bare parts of the road which were much worn.  A hole in a pasture-field
+had been filled up with brick-rubbish at the same time, viz., seven years
+ago, and was now covered with turf; and here the castings contained very
+many particles of brick, all more or less rounded; and this
+brick-rubbish, after being shot into the hole, could not have undergone
+any attrition.  Again, old bricks very little broken, together with
+fragments of mortar, were laid down to form walks, and were then covered
+with from 4 to 6 inches of gravel; six little fragments of brick were
+extracted from castings collected on these walks, three of which were
+plainly worn.  There were also very many particles of hard mortar, about
+half of which were well rounded; and it is not credible that these could
+have suffered so much corrosion from the action of carbonic acid in the
+course of only seven years.
+
+Much better evidence of the attrition of hard objects in the gizzards of
+worms, is afforded by the state of the small fragments of tiles or
+bricks, and of concrete in the castings thrown up where ancient buildings
+once stood.  As all the mould covering a field passes every few years
+through the bodies of worms, the same small fragments will probably be
+swallowed and brought to the surface many times in the course of
+centuries.  It should be premised that in the several following cases,
+the finer matter was first washed away from the castings, and then _all_
+the particles of bricks, tiles and concrete were collected without any
+selection, and were afterwards examined.  Now in the castings ejected
+between the tesseræ on one of the buried floors of the Roman villa at
+Abinger, there were many particles (from ½ to 2 mm. in diameter) of tiles
+and concrete, which it was impossible to look at with the naked eye or
+through a strong lens, and doubt for a moment that they had almost all
+undergone much attrition.  I speak thus after having examined small
+water-worn pebbles, formed from Roman bricks, which M. Henri de Saussure
+had the kindness to send me, and which he had extracted from sand and
+gravel beds, deposited on the shores of the Lake of Geneva, at a former
+period when the water stood at about two metres above its present level.
+The smallest of these water-worn pebbles of brick from Geneva resembled
+closely many of those extracted from the gizzards of worms, but the
+larger ones were somewhat smoother.
+
+Four castings found on the recently uncovered, tesselated floor of the
+great room in the Roman villa at Brading, contained many particles of
+tile or brick, of mortar, and of hard white cement; and the majority of
+these appeared plainly worn.  The particles of mortar, however, seemed to
+have suffered more corrosion than attrition, for grains of silex often
+projected from their surfaces.  Castings from within the nave of Beaulieu
+Abbey, which was destroyed by Henry VIII., were collected from a level
+expanse of turf, overlying the buried tesselated pavement, through which
+worm-burrows passed; and these castings contained innumerable particles
+of tiles and bricks, of concrete and cement, the majority of which had
+manifestly undergone some or much attrition.  There were also many minute
+flakes of a micaceous slate, the points of which were rounded.  If the
+above supposition, that in all these cases the same minute fragments have
+passed several times through the gizzards of worms, be rejected,
+notwithstanding its inherent probability, we must then assume that in all
+the above cases the many rounded fragments found in the castings had all
+accidentally undergone much attrition before they were swallowed; and
+this is highly improbable.
+
+On the other hand it must be stated that fragments of ornamental tiles,
+somewhat harder than common tiles or bricks, which had been swallowed
+only once by worms kept in confinement, were with the doubtful exception
+of one or two of the smallest grains, not at all rounded.  Nevertheless
+some of them appeared a little worn, though not rounded.  Notwithstanding
+these cases, if we consider the evidence above given, there can be little
+doubt that the fragments, which serve as millstones in the gizzards of
+worms, suffer, when of a not very hard texture, some amount of attrition;
+and that the smaller particles in the earth, which is habitually
+swallowed in such astonishingly large quantities by worms, are ground
+together and are thus levigated.  If this be the case, the “terra
+tenuissima,”—the “pâte excessivement fine,”—of which the castings largely
+consist, is in part due to the mechanical action of the gizzard; {234}
+and this fine matter, as we shall see in the next chapter, is that which
+is chiefly washed away from the innumerable castings on every field
+during each heavy shower of rain.  If the softer stones yield at all, the
+harder ones will suffer some slight amount of wear and tear.
+
+The trituration of small particles of stone in the gizzards of worms is
+of more importance under a geological point of view than may at first
+appear to be the case; for Mr. Sorby has clearly shown that the ordinary
+means of disintegration, namely, running water and the waves of the sea,
+act with less and less power on fragments of rock the smaller they are.
+“Hence,” as he remarks, “even making no allowance for the extra buoying
+up of very minute particles by a current of water, depending on surface
+cohesion, the effects of wearing on the form of the grains must vary
+directly as their diameter or thereabouts.  If so, a grain of 1/10 an
+inch in diameter would be worn ten times as much as one of an inch in
+diameter, and at least a hundred times as much as one of 1/100 an inch in
+diameter.  Perhaps, then, we may conclude that a grain 1/10 of an inch in
+diameter would be worn as much or more in drifting a mile as a grain
+1/1000 of an inch in being drifted 100 miles.  On the same principle a
+pebble one inch in diameter would be worn relatively more by being
+drifted only a few hundred yards.” {236}  Nor should we forget, in
+considering the power which worms exert in triturating particles of rock,
+that there is good evidence that on each acre of land, which is
+sufficiently damp and not too sandy, gravelly or rocky for worms to
+inhabit, a weight of more than ten tons of earth annually passes through
+their bodies and is brought to the surface.  The result for a country of
+the size of Great Britain, within a period not very long in a geological
+sense, such as a million years, cannot be insignificant; for the ten tons
+of earth has to be multiplied first by the above number of years, and
+then by the number of acres fully stocked with worms; and in England,
+together with Scotland, the land which is cultivated and is well fitted
+for these animals, has been estimated at above 32 million acres.  The
+product is 320 million million tons of earth.
+
+
+
+CHAPTER VI.
+THE DENUDATION OF THE LAND—_continued_.
+
+
+Denudation aided by recently ejected castings flowing down inclined
+grass-covered surfaces—The amount of earth which annually flows
+downwards—The effect of tropical rain on worm castings—The finest
+particles of earth washed completely away from castings—The
+disintegration of dried castings into pellets, and their rolling down
+inclined surfaces—The formation of little ledges on hill-sides, in part
+due to the accumulation of disintegrated castings—Castings blown to
+leeward over level land—An attempt to estimate the amount thus blown—The
+degradation of ancient encampments and tumuli—The preservation of the
+crowns and furrows on land anciently ploughed—The formation and amount of
+mould over the Chalk formation.
+
+WE are now prepared to consider the more direct part which worms take in
+the denudation of the land.  When reflecting on sub-aerial denudation, it
+formerly appeared to me, as it has to others, that a nearly level or very
+gently inclined surface, covered with turf, could suffer no loss during
+even a long lapse of time.  It may, however, be urged that at long
+intervals, debacles of rain or water-spouts would remove all the mould
+from a very gentle slope; but when examining the steep, turf-covered
+slopes in Glen Roy, I was struck with the fact how rarely any such event
+could have happened since the Glacial period, as was plain from the
+well-preserved state of the three successive “roads” or lake-margins.
+But the difficulty in believing that earth in any appreciable quantity
+can be removed from a gently inclined surface, covered with vegetation
+and matted with roots, is removed through the agency of worms.  For the
+many castings which are thrown up during rain, and those thrown up some
+little time before heavy rain, flow for a short distance down an inclined
+surface.  Moreover much of the finest levigated earth is washed
+completely away from the castings.  During dry weather castings often
+disintegrate into small rounded pellets, and these from their weight
+often roll down any slope.  This is more especially apt to occur when
+they are started by the wind, and probably when started by the touch of
+an animal, however small.  We shall also see that a strong wind blows all
+the castings, even on a level field, to leeward, whilst they are soft;
+and in like manner the pellets when they are dry.  If the wind blows in
+nearly the direction of an inclined surface, the flowing down of the
+castings is much aided.
+
+The observations on which these several statements are founded must now
+be given in some detail.  Castings when first ejected are viscid and
+soft; during rain, at which time worms apparently prefer to eject them,
+they are still softer; so that I have sometimes thought that worms must
+swallow much water at such times.  However this may be, rain, even when
+not very heavy, if long continued, renders recently-ejected castings
+semi-fluid; and on level ground they then spread out into thin, circular,
+flat discs, exactly as would so much honey or very soft mortar, with all
+traces of their vermiform structure lost.  This latter fact was sometimes
+made evident, when a worm had subsequently bored through a flat circular
+disc of this kind, and heaped up a fresh vermiform mass in the centre.
+These flat subsided discs have been repeatedly seen by me after heavy
+rain, in many places on land of all kinds.
+
+_On the flowing of wet castings_, _and the rolling of dry disintegrated
+castings down inclined surfaces_.—When castings are ejected on an
+inclined surface during or shortly before heavy rain, they cannot fail to
+flow a little down the slope.  Thus, on some steep slopes in Knole Park,
+which were covered with coarse grass and had apparently existed in this
+state from time immemorial, I found (Oct. 22, 1872) after several wet
+days that almost all the many castings were considerably elongated in the
+line of the slope; and that they now consisted of smooth, only slightly
+conical masses.  Whenever the mouths of the burrows could be found from
+which the earth had been ejected, there was more earth below than above
+them.  After some heavy storms of rain (Jan. 25, 1872) two rather steeply
+inclined fields near Down, which had formerly been ploughed and were now
+rather sparsely clothed with poor grass, were visited, and many castings
+extended down the slopes for a length of 5 inches, which was twice or
+thrice the usual diameter of the castings thrown up on the level parts of
+these same fields.  On some fine grassy slopes in Holwood Park, inclined
+at angles between 8° and 11° 30′ with the horizon, where the surface
+apparently had never been disturbed by the hand of man, castings abounded
+in extraordinary numbers: and a space 16 inches in length transversely to
+the slope and 6 inches in the line of the slope, was completely coated,
+between the blades of grass, with a uniform sheet of confluent and
+subsided castings.  Here also in many places the castings had flowed down
+the slope, and now formed smooth narrow patches of earth, 6, 7, and 7½
+inches in length.  Some of these consisted of two castings, one above the
+other, which had become so completely confluent that they could hardly be
+distinguished.  On my lawn, clothed with very fine grass, most of the
+castings are black, but some are yellowish from earth having been brought
+up from a greater depth than usual, and the flowing-down of these yellow
+castings after heavy rain, could be clearly seen where the slope was 5°;
+and where it was less than 1° some evidence of their flowing down could
+still be detected.  On another occasion, after rain which was never
+heavy, but which lasted for 18 hours, all the castings on this same
+gently inclined lawn had lost their vermiform structure; and they had
+flowed, so that fully two-thirds of the ejected earth lay below the
+mouths of the burrows.
+
+These observations led me to make others with more care. Eight castings
+were found on my lawn, where the grass-blades are fine and close
+together, and three others on a field with coarse grass. The
+inclination of the surface at the eleven places where these castings
+were collected varied between 4° 30′ and 17° 30′; the mean of the
+eleven inclinations being 9° 26′. The length of the castings in the
+direction of the slope was first measured with as much accuracy as
+their irregularities would permit. It was found possible to make these
+measurements within about ⅛ of an inch, but one of the castings was too
+irregular to admit of measurement. The average length in the direction
+of the slope of the remaining ten castings was 2.03 inches. The
+castings were then divided with a knife into two parts along a
+horizontal line passing through the mouth of the burrow, which was
+discovered by slicing off the turf; and all the ejected earth was
+separately collected, namely, the part above the hole and the part
+below. Afterwards these two parts were weighed. In every case there was
+much more earth below than above; the mean weight of that above being
+103 grains, and of that below 205 grains; so that the latter was very
+nearly double the former. As on level ground castings are commonly
+thrown up almost equally round the mouths of the burrows, this
+difference in weight indicates the amount of ejected earth which had
+flowed down the slope. But very many more observations would be
+requisite to arrive at any general result; for the nature of the
+vegetation and other accidental circumstances, such as the heaviness of
+the rain, the direction and force of the wind, &c., appear to be more
+important in determining the quantity of the earth which flows down a
+slope than its angle. Thus with four castings on my lawn (included in
+the above eleven) where the mean slope was 7° 19′, the difference in
+the amount of earth above and below the burrows was greater than with
+three other castings on the same lawn where the mean slope was 12° 5′.
+
+We may, however, take the above eleven cases, which are accurate as far
+as they go, and calculate the weight of the ejected earth which annually
+flows down a slope having a mean inclination of 9° 26′.  This was done by
+my son George.  It has been shown that almost exactly two-thirds of the
+ejected earth is found below the mouth of the burrow and one-third above
+it.  Now if the two-thirds which is below the hole be divided into two
+equal parts, the upper half of this two-thirds exactly counterbalances
+the one-third which is above the hole, so that as far as regards the
+one-third above and the upper half of the two-thirds below, there is no
+flow of earth down the hill-side.  The earth constituting the lower half
+of the two-thirds is, however, displaced through distances which are
+different for every part of it, but which may be represented by the
+distance between the middle point of the lower half of the two-thirds and
+the hole.  So that the average distance of displacement is a half of the
+whole length of the worm-casting.  Now the average length of ten out of
+the above eleven castings was 2.03 inches, and half of this we may take
+as being 1 inch.  It may therefore be concluded that one-third of the
+whole earth brought to the surface was in these cases carried down the
+slope through 1 inch. {244}
+
+It was shown in the third chapter that on Leith Hill Common, dry earth
+weighing at least 7.453 lbs. was brought up by worms to the surface on a
+square yard in the course of a year.  If a square yard be drawn on a
+hillside with two of its sides horizontal, then it is clear that only
+1/36 part of the earth brought up on that square yard would be near
+enough to its lower side to cross it, supposing the displacement of the
+earth to be through one inch.  But it appears that only ⅓ of the earth
+brought up can be considered to flow downwards; hence ⅓ of 1/36 or 1/108
+of 7.453 lbs. will cross the lower side of our square yard in a year.
+Now 1/108 of 7.453 lbs. is 1.1 oz.  Therefore 1.1 oz. of dry earth will
+annually cross each linear yard running horizontally along a slope having
+the above inclination; or very nearly 7 lbs. will annually cross a
+horizontal line, 100 yards in length, on a hill-side having this
+inclination.
+
+A more accurate, though still very rough, calculation can be made of the
+bulk of earth, which in its natural damp state annually flows down the
+same slope over a yard-line drawn horizontally across it.  From the
+several cases given in the third chapter, it is known that the castings
+annually brought to the surface on a square yard, if uniformly spread out
+would form a layer 0.2 of an inch in thickness: it therefore follows by a
+calculation similar to the one already given, that ⅓ of 0.2 × 36, or 2.4
+cubic inches of damp earth will annually cross a horizontal line one yard
+in length on a hillside with the above inclination.  This bulk of damp
+castings was found to weigh 1.85 oz.  Therefore 11.56 lbs. of damp earth,
+instead of 7 lbs. of dry earth as by the former calculation, would
+annually cross a line 100 yards in length on our inclined surface.
+
+In these calculations it has been assumed that the castings flow a short
+distance downwards during the whole year, but this occurs only with those
+ejected during or shortly before rain; so that the above results are thus
+far exaggerated.  On the other hand, during rain much of the finest earth
+is washed to a considerable distance from the castings, even where the
+slope is an extremely gentle one, and is thus wholly lost as far as the
+above calculations are concerned.  Castings ejected during dry weather
+and which have set hard, lose in the same manner a considerable quantity
+of fine earth.  Dried castings, moreover, are apt to disintegrate into
+little pellets, which often roll or are blown down any inclined surface.
+Therefore the above result, namely, that 24 cubic inches of earth
+(weighing 1.85 oz. whilst damp) annually crosses a yard-line of the
+specified kind, is probably not much if at all exaggerated.
+
+This amount is small; but we should bear in mind how many branching
+valleys intersect most countries, the whole length of which must be very
+great; and that earth is steadily travelling down both turf-covered sides
+of each valley.  For every 100 yards in length in a valley with sides
+sloping as in the foregoing cases, 480 cubic inches of damp earth,
+weighing above 23 pounds, will annually reach the bottom.  Here a thick
+bed of alluvium will accumulate, ready to be washed away in the course of
+centuries, as the stream in the middle meanders from side to side.
+
+If it could be shown that worms generally excavate their burrows at right
+angles to an inclined surface, and this would be their shortest course
+for bringing up earth from beneath, then as the old burrows collapsed
+from the weight of the superincumbent soil, the collapsing would
+inevitably cause the whole bed of vegetable mould to sink or slide slowly
+down the inclined surface.  But to ascertain the direction of many
+burrows was found too difficult and troublesome.  A straight piece of
+wire was, however, pushed into twenty-five burrows on several sloping
+fields, and in eight cases the burrows were nearly at right angles to the
+slope; whilst in the remaining cases they were indifferently directed at
+various angles, either upwards or downwards with respect to the slope.
+
+In countries where the rain is very heavy, as in the tropics, the
+castings appear, as might have been expected, to be washed down in a
+greater degree than in England.  Mr. Scott informs me that near Calcutta
+the tall columnar castings (previously described), the diameter of which
+is usually between 1 and 1½ inch, subside on a level surface, after heavy
+rain, into almost circular, thin, flat discs, between 3 and 4 and
+sometimes 5 inches in diameter.  Three fresh castings, which had been
+ejected in the Botanic Gardens “on a slightly inclined, grass-covered,
+artificial bank of loamy clay,” were carefully measured, and had a mean
+height of 2.17, and a mean diameter of 1.43 inches; these after heavy
+rain, formed elongated patches of earth, with a mean length in the
+direction of the slope of 5.83 inches.  As the earth had spread very
+little up the slope, a large part, judging from the original diameter of
+these castings, must have flowed bodily downwards about 4 inches.
+Moreover some of the finest earth of which they were composed must have
+been washed completely away to a still greater distance.  In drier sites
+near Calcutta, a species of worm ejects its castings, not in vermiform
+masses, but in little pellets of varying sizes: these are very numerous
+in some places, and Mr. Scott says that they “are washed away by every
+shower.”
+
+I was led to believe that a considerable quantity of fine earth is washed
+quite away from castings during rain, from the surfaces of old ones being
+often studded with coarse particles.  Accordingly a little fine
+precipitated chalk, moistened with saliva or gum-water, so as to be
+slightly viscid and of the same consistence as a fresh casting, was
+placed on the summits of several castings and gently mixed with them.
+These castings were then watered through a very fine rose, the drops from
+which were closer together than those of rain, but not nearly so large as
+those in a thunderstorm; nor did they strike the ground with nearly so
+much force as drops during heavy rain.  A casting thus treated subsided
+with surprising slowness, owing as I suppose to its viscidity.  It did
+not flow bodily down the grass-covered surface of the lawn, which was
+here inclined at an angle of 16° 20′; nevertheless many particles of the
+chalk were found three inches below the casting.  The experiment was
+repeated on three other castings on different parts of the lawn, which
+sloped at 2° 30′, 3° and 6°; and particles of chalk could be seen between
+4 and 5 inches below the casting; and after the surface had become dry,
+particles were found in two cases at a distance of 5 and 6 inches.
+Several other castings with precipitated chalk placed on their summits
+were left to the natural action of the rain.  In one case, after rain
+which was not heavy, the casting was longitudinally streaked with white.
+In two other cases the surface of the ground was rendered somewhat white
+for a distance of one inch from the casting; and some soil collected at a
+distance of 2½ inches, where the slope was 7°, effervesced slightly when
+placed in acid.  After one or two weeks, the chalk was wholly or almost
+wholly washed away from all the castings on which it had been placed, and
+these had recovered their natural colour.
+
+It may be here remarked that after very heavy rain shallow pools may be
+seen on level or nearly level fields, where the soil is not very porous,
+and the water in them is often slightly muddy; when such little pools
+have dried, the leaves and blades of grass at their bottoms are generally
+coated with a thin layer of mud.  This mud I believe is derived in large
+part from recently ejected castings.
+
+Dr. King informs me that the majority of the before described gigantic
+castings, which he found on a fully exposed, bare, gravelly knoll on the
+Nilgiri Mountains in India, had been more or less weathered by the
+previous north-east monsoon; and most of them presented a subsided
+appearance.  The worms here eject their castings only during the rainy
+season; and at the time of Dr. King’s visit no rain had fallen for 110
+days.  He carefully examined the ground between the place where these
+huge castings lay, and a little watercourse at the base of the knoll, and
+nowhere was there any accumulation of fine earth, such as would
+necessarily have been left by the disintegration of the castings if they
+had not been wholly removed.  He therefore has no hesitation in asserting
+that the whole of these huge castings are annually washed during the two
+monsoons (when about 100 inches of rain fall) into the little
+water-course, and thence into the plains lying below at a depth of 3000
+or 4000 feet.
+
+Castings ejected before or during dry weather become hard, sometimes
+surprisingly hard, from the particles of earth having been cemented
+together by the intestinal secretions.  Frost seems to be less effective
+in their disintegration than might have been expected.  Nevertheless they
+readily disintegrate into small pellets, after being alternately
+moistened with rain and again dried.  Those which have flowed during rain
+down a slope, disintegrate in the same manner.  Such pellets often roll a
+little down any sloping surface; their descent being sometimes much aided
+by the wind.  The whole bottom of a broad dry ditch in my grounds, where
+there were very few fresh castings, was completely covered with these
+pellets or disintegrated castings, which had rolled down the steep sides,
+inclined at an angle of 27°.
+
+Near Nice, in places where the great cylindrical castings, previously
+described, abound, the soil consists of very fine arenaceo-calcareous
+loam; and Dr. King informs me that these castings are extremely liable to
+crumble during dry weather into small fragments, which are soon acted on
+by rain, and then sink down so as to be no longer distinguishable from
+the surrounding soil.  He sent me a mass of such disintegrated castings,
+collected on the top of a bank, where none could have rolled down from
+above.  They must have been ejected within the previous five or six
+months, but they now consisted of more or less rounded fragments of all
+sizes, from ¾ of an inch in diameter to minute grains and mere dust.  Dr.
+King witnessed the crumbling process whilst drying some perfect castings,
+which he afterwards sent me.  Mr. Scott also remarks on the crumbling of
+the castings near Calcutta and on the mountains of Sikkim during the hot
+and dry season.
+
+When the castings near Nice had been ejected on an inclined surface, the
+disintegrated fragments rolled downwards, without losing their
+distinctive shape; and in some places could “be collected in basketfuls.”
+Dr. King observed a striking instance of this fact on the Corniche road,
+where a drain, about 2½ feet wide and 9 inches deep, had been made to
+catch the surface drainage from the adjoining hill-side.  The bottom of
+this drain was covered for a distance of several hundred yards, to a
+depth of from 1½ to 3 inches, by a layer of broken castings, still
+retaining their characteristic shape.  Nearly all these innumerable
+fragments had rolled down from above, for extremely few castings had been
+ejected in the drain itself.  The hill-side was steep, but varied much in
+inclination, which Dr. King estimated at from 30° to 60° with the
+horizon.  He climbed up the slope, and “found every here and there little
+embankments, formed by fragments of the castings that had been arrested
+in their downward progress by irregularities of the surface, by stones,
+twigs, &c.  One little group of plants of _Anemone hortensis_ had acted
+in this manner, and quite a small bank of soil had collected round it.
+Much of this soil had crumbled down, but a great deal of it still
+retained the form of castings.”  Dr. King dug up this plant, and was
+struck with the thickness of the soil which must have recently
+accumulated over the crown of the rhizoma, as shown by the length of the
+bleached petioles, in comparison with those of other plants of the same
+kind, where there had been no such accumulation.  The earth thus
+accumulated had no doubt been secured (as I have everywhere seen) by the
+smaller roots of the plants.  After describing this and other analogous
+cases, Dr. King concludes: “I can have no doubt that worms help greatly
+in the process of denudation.”
+
+_Ledges of earth on steep hill-sides_.—Little horizontal ledges, one
+above another, have been observed on steep grassy slopes in many parts of
+the world.  The formation has been attributed to animals travelling
+repeatedly along the slope in the same horizontal lines while grazing,
+and that they do thus move and use the ledges is certain; but Professor
+Henslow (a most careful observer) told Sir J. Hooker that he was
+convinced that this was not the sole cause of their formation.  Sir J.
+Hooker saw such ledges on the Himalayan and Atlas ranges, where there
+were no domesticated animals and not many wild ones; but these latter
+would, it is probable, use the ledges at night while grazing like our
+domesticated animals.  A friend observed for me the ledges on the Alps of
+Switzerland, and states that they ran at 3 or 4 ft. one above the other,
+and were about a foot in breadth.  They had been deeply pitted by the
+feet of grazing cows.  Similar ledges were observed by the same friend on
+our Chalk downs, and on an old talus of chalk-fragments (thrown out of a
+quarry) which had become clothed with turf.
+
+My son Francis examined a Chalk escarpment near Lewes; and here on a part
+which was very steep, sloping at 40° with the horizon, about 30 flat
+ledges extended horizontally for more than 100 yards, at an average
+distance of about 20 inches, one beneath the other.  They were from 9 to
+10 inches in breadth.  When viewed from a distance they presented a
+striking appearance, owing to their parallelism; but when examined
+closely, they were seen to be somewhat sinuous, and one often ran into
+another, giving the appearance of the ledge having forked into two.  They
+are formed of light-coloured earth, which on the outside, where thickest,
+was in one case 9 inches, and in another case between 6 and 7 inches in
+thickness.  Above the ledges, the thickness of the earth over the chalk
+was in the former case 4 and in the latter only 3 inches.  The grass grew
+more vigorously on the outer edges of the ledges than on any other part
+of the slope, and here formed a tufted fringe.  Their middle part was
+bare, but whether this had been caused by the trampling of sheep, which
+sometimes frequent the ledges, my son could not ascertain.  Nor could he
+feel sure how much of the earth on the middle and bare parts, consisted
+of disintegrated worm-castings which had rolled down from above; but he
+felt convinced that some had thus originated; and it was manifest that
+the ledges with their grass-fringed edges would arrest any small object
+rolling down from above.
+
+At one end or side of the bank bearing these ledges, the surface
+consisted in parts of bare chalk, and here the ledges were very
+irregular.  At the other end of the bank, the slope suddenly became less
+steep, and here the ledges ceased rather abruptly; but little embankments
+only a foot or two in length were still present.  The slope became
+steeper lower down the hill, and the regular ledges then reappeared.
+Another of my sons observed, on the inland side of Beachy Head, where the
+surface sloped at about 25°, many short little embankments like those
+just mentioned.  They extended horizontally and were from a few inches to
+two or three feet in length.  They supported tufts of grass growing
+vigorously.  The average thickness of the mould of which they were
+formed, taken from nine measurements, was 4.5 inches; while that of the
+mould above and beneath them was on an average only 3.2 inches, and on
+each side, on the same level, 3.1 inches.  On the upper parts of the
+slope, these embankments showed no signs of having been trampled on by
+sheep, but in the lower parts such signs were fairly plain.  No long
+continuous ledges had here been formed.
+
+If the little embankments above the Corniche road, which Dr. King saw in
+the act of formation by the accumulation of disintegrated and rolled
+worm-castings, were to become confluent along horizontal lines, ledges
+would be formed.  Each embankment would tend to extend laterally by the
+lateral extension of the arrested castings; and animals grazing on a
+steep slope would almost certainly make use of every prominence at nearly
+the same level, and would indent the turf between them; and such
+intermediate indentations would again arrest the castings.  An irregular
+ledge when once formed would also tend to become more regular and
+horizontal by some of the castings rolling laterally from the higher to
+the lower parts, which would thus be raised.  Any projection beneath a
+ledge would not afterwards receive disintegrated matter from above, and
+would tend to be obliterated by rain and other atmospheric agencies.
+There is some analogy between the formation, as here supposed, of these
+ledges, and that of the ripples of wind-drifted sand as described by
+Lyell. {259}
+
+The steep, grass-covered sides of a mountainous valley in Westmoreland,
+called Grisedale, was marked in many places with innumerable lines of
+miniature cliffs, with almost horizontal, little ledges at their bases.
+Their formation was in no way connected with the action of worms, for
+castings could not anywhere be seen (and their absence is an inexplicable
+fact), although the turf lay in many places over a considerable thickness
+of boulder-clay and moraine rubbish.  Nor, as far as I could judge, was
+the formation of these little cliffs at all closely connected with the
+trampling of cows or sheep.  It appeared as if the whole superficial,
+somewhat argillaceous earth, while partially held together by the roots
+of the grasses, had slided a little way down the mountain sides; and in
+thus sliding, had yielded and cracked in horizontal lines, transversely
+to the slope.
+
+_Castings blown to leeward by the wind_.—We have seen that moist castings
+flow, and that disintegrated castings roll down any inclined surface; and
+we shall now see that castings, recently ejected on level grass-covered
+surfaces, are blown during gales of wind accompanied by rain to leeward.
+This has been observed by me many times on many fields during several
+successive years.  After such gales, the castings present a gently
+inclined and smooth, or sometimes furrowed, surface to windward, while
+they are steeply inclined or precipitous to leeward, so that they
+resemble on a miniature scale glacier-ground hillocks of rock.  They are
+often cavernous on the leeward side, from the upper part having curled
+over the lower part.  During one unusually heavy south-west gale with
+torrents of rain, many castings were wholly blown to leeward, so that the
+mouths of the burrows were left naked and exposed on the windward side.
+Recent castings naturally flow down an inclined surface, but on a grassy
+field, which sloped between 10° and 15°, several were found after a heavy
+gale blown up the slope.  This likewise occurred on another occasion on a
+part of my lawn where the slope was somewhat less.  On a third occasion,
+the castings on the steep, grass-covered sides of a valley, down which a
+gale had blown, were directed obliquely instead of straight down the
+slope; and this was obviously due to the combined action of the wind and
+gravity.  Four castings on my lawn, where the downward inclination was 0°
+45′, 1°, 3° and 3° 30′ (mean 2° 45′) towards the north-east, after a
+heavy south-west gale with rain, were divided across the mouths of the
+burrows and weighed in the manner formerly described.  The mean weight of
+the earth below the mouths of burrows and to leeward, was to that above
+the mouths and on the windward side as 2¾ to 1; whereas we have seen that
+with several castings which had flowed down slopes having a mean
+inclination of 9° 26′, and with three castings where the inclination was
+above 12°; the proportional weight of the earth below to that above the
+burrows was as only 2 to 1.  These several cases show how efficiently
+gales of wind accompanied by rain act in displacing recently ejected
+castings.  We may therefore conclude that even a moderately strong wind
+will produce some slight effect on them.
+
+Dry and indurated castings, after their disintegration into small
+fragments or pellets, are sometimes, probably often, blown by a strong
+wind to leeward.  This was observed on four occasions, but I did not
+sufficiently attend to this point.  One old casting on a gently sloping
+bank was blown quite away by a strong south-west wind.  Dr. King believes
+that the wind removes the greater part of the old crumbling castings near
+Nice.  Several old castings on my lawn were marked with pins and
+protected from any disturbance.  They were examined after an interval of
+10 weeks, during which time the weather had been alternately dry and
+rainy.  Some, which were of a yellowish colour had been washed almost
+completely away, as could be seen by the colour of the surrounding
+ground.  Others had completely disappeared, and these no doubt had been
+blown away.  Lastly, others still remained and would long remain, as
+blades of grass had grown through them.  On poor pasture-land, which has
+never been rolled and has not been much trampled on by animals, the whole
+surface is sometimes dotted with little pimples, through and on which
+grass grows; and these pimples consist of old worm-castings.
+
+In all the many observed cases of soft castings blown to leeward, this
+had been effected by strong winds accompanied by rain.  As such winds in
+England generally blow from the south and south-west, earth must on the
+whole tend to travel over our fields in a north and north-east direction.
+This fact is interesting, because it might be thought that none could be
+removed from a level, grass-covered surface by any means.  In thick and
+level woods, protected from the wind, castings will never be removed as
+long as the wood lasts; and mould will here tend to accumulate to the
+depth at which worms can work.  I tried to procure evidence as to how
+much mould is blown, whilst in the state of castings, by our wet southern
+gales to the north-east, over open and flat land, by looking to the level
+of the surface on opposite sides of old trees and hedge-rows; but I
+failed owing to the unequal growth of the roots of trees and to most
+pasture-land having been formerly ploughed.
+
+On an open plain near Stonehenge, there exist shallow circular trenches,
+with a low embankment outside, surrounding level spaces 50 yards in
+diameter.  These rings appear very ancient, and are believed to be
+contemporaneous with the Druidical stones.  Castings ejected within these
+circular spaces, if blown to the north-east by south-west winds would
+form a layer of mould within the trench, thicker on the north-eastern
+than on any other side.  But the site was not favourable for the action
+of worms, for the mould over the surrounding Chalk formation with flints,
+was only 3.37 inches in thickness, from a mean of six observations made
+at a distance of 10 yards outside the embankment.  The thickness of the
+mould within two of the circular trenches was measured every 5 yards all
+round, on the inner sides near the bottom.  My son Horace protracted
+these measurements on paper; and though the curved line representing the
+thickness of the mould was extremely irregular, yet in both diagrams it
+could be seen to be thicker on the north-eastern side than elsewhere.
+When a mean of all the measurements in both the trenches was laid down
+and the line smoothed, it was obvious that the mould was thickest in the
+quarter of the circle between north-west and north-east; and thinnest in
+the quarter between south-east and south-west, especially at this latter
+point.  Besides the foregoing measurements, six others were taken near
+together in one of the circular trenches, on the north-east side; and the
+mould here had a mean thickness of 2.29 inches; while the mean of six
+other measurements on the south-west side was only 1.46 inches.  These
+observations indicate that the castings had been blown by the south-west
+winds from the circular enclosed space into the trench on the north-east
+side; but many more measurements in other analogous cases would be
+requisite for a trustworthy result.
+
+The amount of fine earth brought to the surface under the form of
+castings, and afterwards transported by the winds accompanied by rain, or
+that which flows and rolls down an inclined surface, no doubt is small in
+the course of a few scores of years; for otherwise all the inequalities
+in our pasture fields would be smoothed within a much shorter period than
+appears to be the case.  But the amount which is thus transported in the
+course of thousands of years cannot fail to be considerable and deserves
+attention.  É. de Beaumont looks at the vegetable mould which everywhere
+covers the land as a fixed line, from which the amount of denudation may
+be measured. {265}  He ignores the continued formation of fresh mould by
+the disintegration of the underlying rocks and fragments of rock; and it
+is curious to find how much more philosophical were the views maintained
+long ago, by Playfair, who, in 1802, wrote, “In the permanence of a coat
+of vegetable mould on the surface of the earth, we have a demonstrative
+proof of the continued destruction of the rocks.” {266}
+
+_Ancient encampments and tumuli_.—É. de Beaumont adduces the present
+state of many ancient encampments and tumuli and of old ploughed fields,
+as evidence that the surface of the land undergoes hardly any
+degradation.  But it does not appear that he ever examined the thickness
+of the mould over different parts of such old remains.  He relies chiefly
+on indirect, but apparently trustworthy, evidence that the slopes of the
+old embankments are the same as they originally were; and it is obvious
+that he could know nothing about their original heights.  In Knole Park a
+mound had been thrown up behind the rifle-targets, which appeared to have
+been formed of earth originally supported by square blocks of turf.  The
+sides sloped, as nearly as I could estimate them, at an angle of 45° or
+50° with the horizon, and they were covered, especially on the northern
+side, with long coarse grass, beneath which many worm-castings were
+found.  These had flowed bodily downwards, and others had rolled down as
+pellets.  Hence it is certain that as long as a mound of this kind is
+tenanted by worms, its height will be continually lowered.  The fine
+earth which flows or rolls down the sides of such a mound accumulates at
+its base in the form of a talus.  A bed, even a very thin bed, of fine
+earth is eminently favourable for worms; so that a greater number of
+castings would tend to be ejected on a talus thus formed than elsewhere;
+and these would be partially washed away by every heavy shower and be
+spread over the adjoining level ground.  The final result would be the
+lowering of the whole mound, whilst the inclination of the sides would
+not be greatly lessened.  The same result would assuredly follow with
+ancient embankments and tumuli; except where they had been formed of
+gravel or of nearly pure sand, as such matter is unfavourable for worms.
+Many old fortifications and tumuli are believed to be at least 2000 years
+old; and we should bear in mind that in many places about one inch of
+mould is brought to the surface in 5 years or two inches in 10 years.
+Therefore in so long a period as 2000 years, a large amount of earth will
+have been repeatedly brought to the surface on most old embankments and
+tumuli, especially on the talus round their bases, and much of this earth
+will have been washed completely away.  We may therefore conclude that
+all ancient mounds, when not formed of materials unfavourable to worms,
+will have been somewhat lowered in the course of centuries, although
+their inclinations may not have been greatly changed.
+
+_Fields formerly ploughed_.—From a very remote period and in many
+countries, land has been ploughed, so that convex beds, called crowns or
+ridges, usually about 8 feet across and separated by furrows, have been
+thrown up.  The furrows are directed so as to carry off the surface
+water.  In my attempts to ascertain how long a time these crowns and
+furrows last, when ploughed land has been converted into pasture,
+obstacles of many kinds were encountered.  It is rarely known when a
+field was last ploughed; and some fields which were thought to have been
+in pasture from time immemorial were afterwards discovered to have been
+ploughed only 50 or 60 years before.  During the early part of the
+present century, when the price of corn was very high, land of all kinds
+seems to have been ploughed in Britain.  There is, however, no reason to
+doubt that in many cases the old crowns and furrows have been preserved
+from a very ancient period. {269}  That they should have been preserved
+for very unequal lengths of time would naturally follow from the crowns,
+when first thrown up, having differed much in height in different
+districts, as is now the case with recently ploughed land.
+
+In old pasture fields, the mould, wherever measurements were made, was
+found to be from ½ to 2 inches thicker in the furrows than on the crowns;
+but this would naturally follow from the finer earth having been washed
+from the crowns into the furrows before the land was well clothed with
+turf; and it is impossible to tell what part worms may have played in the
+work.  Nevertheless from what we have seen, castings would certainly tend
+to flow and to be washed during heavy rain from the crowns into the
+furrows.  But as soon as a bed of fine earth had by any means been
+accumulated in the furrows, it would be more favourable for worms than
+the other parts, and a greater number of castings would be thrown up here
+than elsewhere; and as the furrows on sloping land are usually directed
+so as to carry off the surface water, some of the finest earth would be
+washed from the castings which had been here ejected and be carried
+completely away.  The result would be that the furrows would be filled up
+very slowly, while the crowns would be lowered perhaps still more slowly
+by the flowing and rolling of the castings down their gentle inclinations
+into the furrows.
+
+Nevertheless it might be expected that old furrows, especially those on a
+sloping surface, would in the course of time be filled up and disappear.
+Some careful observers, however, who examined fields for me in
+Gloucestershire and Staffordshire could not detect any difference in the
+state of the furrows in the upper and lower parts of sloping fields,
+supposed to have been long in pasture; and they came to the conclusion
+that the crowns and furrows would last for an almost endless number of
+centuries.  On the other hand the process of obliteration seems to have
+commenced in some places.  Thus in a grass field in North Wales, known to
+have been ploughed about 65 years ago, which sloped at an angle of 15° to
+the north-east, the depth of the furrows (only 7 feet apart) was
+carefully measured, and was found to be about 4½ inches in the upper part
+of the slope, and only 1 inch near the base, where they could be traced
+with difficulty.  On another field sloping at about the same angle to the
+south-west, the furrows were scarcely perceptible in the lower part;
+although these same furrows when followed on to some adjoining level
+ground were from 2½ to 3½ inches in depth.  A third and closely similar
+case was observed.  In a fourth case, the mould in a furrow in the upper
+part of a sloping field was 2½ inches, and in the lower part 4½ inches in
+thickness.
+
+On the Chalk Downs at about a mile distance from Stonehenge, my son
+William examined a grass-covered, furrowed surface, sloping at from 8° to
+10 °, which an old shepherd said had not been ploughed within the memory
+of man.  The depth of one furrow was measured at 16 points in a length of
+68 paces, and was found to be deeper where the slope was greatest and
+where less earth would naturally tend to accumulate, and at the base it
+almost disappeared.  The thickness of the mould in this furrow in the
+upper part was 2½ inches, which increased to 5 inches, a little above the
+steepest part of the slope; and at the base, in the middle of the narrow
+valley, at a point which the furrow if continued would have struck, it
+amounted to 7 inches.  On the opposite side of the valley, there were
+very faint, almost obliterated, traces of furrows.  Another analogous but
+not so decided a case was observed at a few miles’ distance from
+Stonehenge.  On the whole it appears that the crowns and furrows on land
+formerly ploughed, but now covered with grass, tend slowly to disappear
+when the surface is inclined; and this is probably in large part due to
+the action of worms; but that the crowns and furrows last for a very long
+time when the surface is nearly level.
+
+_Formation and amount of mould over the Chalk Formation_.—Worm-castings
+are often ejected in extraordinary numbers on steep, grass-covered
+slopes, where the Chalk comes close to the surface, as my son William
+observed near Winchester and elsewhere.  If such castings are largely
+washed away during heavy rains, it is difficult to understand at first
+how any mould can still remain on our Downs, as there does not appear any
+evident means for supplying the loss.  There is, moreover, another cause
+of loss, namely, in the percolation of the finer particles of earth into
+the fissures in the chalk and into the chalk itself.  These
+considerations led me to doubt for a time whether I had not exaggerated
+the amount of fine earth which flows or rolls down grass-covered slopes
+under the form of castings; and I sought for additional information.  In
+some places, the castings on Chalk Downs consist largely of calcareous
+matter, and here the supply is of course unlimited.  But in other places,
+for instance on a part of Teg Down near Winchester, the castings were all
+black and did not effervesce with acids.  The mould over the chalk was
+here only from 3 to 4 inches in thickness.  So again on the plain near
+Stonehenge, the mould, apparently free from calcareous matter, averaged
+rather less than 3½ inches in thickness.  Why worms should penetrate and
+bring up chalk in some places and not in others I do not know.
+
+In many districts where the land is nearly level, a bed several feet in
+thickness of red clay full of unworn flints overlies the Upper Chalk.
+This overlying matter, the surface of which has been converted into
+mould, consists of the undissolved residue from the chalk.  It may be
+well here to recall the case of the fragments of chalk buried beneath
+worm-castings on one of my fields, the angles of which were so completely
+rounded in the course of 29 years that the fragments now resembled
+water-worn pebbles.  This must have been effected by the carbonic acid in
+the rain and in the ground, by the humus-acids, and by the corroding
+power of living roots.  Why a thick mass of residue has not been left on
+the Chalk, wherever the land is nearly level, may perhaps be accounted
+for by the percolation of the fine particles into the fissures, which are
+often present in the chalk and are either open or are filled up with
+impure chalk, or into the solid chalk itself.  That such percolation
+occurs can hardly be doubted.  My son collected some powdered and
+fragmentary chalk beneath the turf near Winchester; the former was found
+by Colonel Parsons, R. E., to contain 10 per cent., and the fragments 8
+per cent. of earthy matter.  On the flanks of the escarpment near Abinger
+in Surrey, some chalk close beneath a layer of flints, 2 inches in
+thickness and covered by 8 inches of mould, yielded a residue of 3.7 per
+cent. of earthy matter.  On the other hand the Upper Chalk properly
+contains, as I was informed by the late David Forbes who had made many
+analyses, only from 1 to 2 per cent. of earthy matter; and two samples
+from pits near my house contained 1.3 and 0.6 per cent.  I mention these
+latter cases because, from the thickness of the overlying bed of red clay
+with flints, I had imagined that the underlying chalk might here be less
+pure than elsewhere.  The cause of the residue accumulating more in some
+places than in others, may be attributed to a layer of argillaceous
+matter having been left at an early period on the chalk, and this would
+check the subsequent percolation of earthy matter into it.
+
+From the facts now given we may conclude that castings ejected on our
+Chalk Downs suffer some loss by the percolation of their finer matter
+into the chalk.  But such impure superficial chalk, when dissolved, would
+leave a larger supply of earthy matter to be added to the mould than in
+the case of pure chalk.  Besides the loss caused by percolation, some
+fine earth is certainly washed down the sloping grass-covered surfaces of
+our Downs.  The washing-down process, however, will be checked in the
+course of time; for although I do not know how thin a layer of mould
+suffices to support worms, yet a limit must at last be reached; and then
+their castings would cease to be ejected or would become scanty.
+
+The following cases show that a considerable quantity of fine earth is
+washed down.  The thickness of the mould was measured at points 12 yards
+apart across a small valley in the Chalk near Winchester.  The sides
+sloped gently at first; then became inclined at about 20°; then more
+gently to near the bottom, which transversely was almost level and about
+50 yards across.  In the bottom, the mean thickness of the mould from
+five measurements was 8.3 inches; whilst on the sides of the valley,
+where the inclination varied between 14° and 20°, its mean thickness was
+rather less than 3.5 inches.  As the turf-covered bottom of the valley
+sloped at an angle of only between 2° and 3°, it is probable that most of
+the 8.3-inch layer of mould had been washed down from the flanks of the
+valley, and not from the upper part.  But as a shepherd said that he had
+seen water flowing in this valley after the sudden thawing of snow, it is
+possible that some earth may have been brought down from the upper part;
+or, on the other hand, that some may have been carried further down the
+valley.  Closely similar results, with respect to the thickness of the
+mould, were obtained in a neighbouring valley.
+
+St. Catherine’s Hill, near Winchester, is 327 feet in height, and
+consists of a steep cone of chalk about ¼ of a mile in diameter.  The
+upper part was converted by the Romans, or, as some think, by the ancient
+Britons, into an encampment, by the excavation of a deep and broad ditch
+all round it.  Most of the chalk removed during the work was thrown
+upwards, by which a projecting bank was formed; and this effectually
+prevents worm-castings (which are numerous in parts), stones, and other
+objects from being washed or rolled into the ditch.  The mould on the
+upper and fortified part of the hill was found to be in most places only
+from 2½ to 3½ inches in thickness; whereas it had accumulated at the foot
+of the embankment above the ditch to a thickness in most places of from 8
+to 9½ inches.  On the embankment itself the mould was only 1 to 1½ inch
+in thickness; and within the ditch at the bottom it varied from 2½ to 3½,
+but was in one spot 6 inches in thickness.  On the north-west side of the
+hill, either no embankment had ever been thrown up above the ditch, or it
+had subsequently been removed; so that here there was nothing to prevent
+worm-castings, earth and stones being washed into the ditch, at the
+bottom of which the mould formed a layer from 11 to 22 inches in
+thickness.  It should however be stated that here and on other parts of
+the slope, the bed of mould often contained fragments of chalk and flint
+which had obviously rolled down at different times from above.  The
+interstices in the underlying fragmentary chalk were also filled up with
+mould.
+
+My son examined the surface of this hill to its base in a south-west
+direction.  Beneath the great ditch, where the slope was about 24°, the
+mould was very thin, namely, from 1½ to 2½ inches; whilst near the base,
+where the slope was only 3° to 4°, it increased to between 8 and 9 inches
+in thickness.  We may therefore conclude that on this artificially
+modified hill, as well as in the natural valleys of the neighbouring
+Chalk Downs, some fine earth, probably derived in large part from
+worm-castings, is washed down, and accumulates in the lower parts,
+notwithstanding the percolation of an unknown quantity into the
+underlying chalk; a supply of fresh earthy matter being afforded by the
+dissolution of the chalk through atmospheric and other agencies.
+
+
+
+
+CHAPTER VII.
+CONCLUSION.
+
+
+Summary of the part which worms have played in the history of the
+world—Their aid in the disintegration of rocks—In the denudation of the
+land—In the preservation of ancient remains—In the preparation of the
+soil for the growth of plants—Mental powers of worms—Conclusion.
+
+WORMS have played a more important part in the history of the world than
+most persons would at first suppose.  In almost all humid countries they
+are extraordinarily numerous, and for their size possess great muscular
+power.  In many parts of England a weight of more than ten tons (10,516
+kilogrammes) of dry earth annually passes through their bodies and is
+brought to the surface on each acre of land; so that the whole
+superficial bed of vegetable mould passes through their bodies in the
+course of every few years.  From the collapsing of the old burrows the
+mould is in constant though slow movement, and the particles composing it
+are thus rubbed together.  By these means fresh surfaces are continually
+exposed to the action of the carbonic acid in the soil, and of the
+humus-acids which appear to be still more efficient in the decomposition
+of rocks.  The generation of the humus-acids is probably hastened during
+the digestion of the many half-decayed leaves which worms consume.  Thus
+the particles of earth, forming the superficial mould, are subjected to
+conditions eminently favourable for their decomposition and
+disintegration.  Moreover, the particles of the softer rocks suffer some
+amount of mechanical trituration in the muscular gizzards of worms, in
+which small stones serve as mill-stones.
+
+The finely levigated castings, when brought to the surface in a moist
+condition, flow during rainy weather down any moderate slope; and the
+smaller particles are washed far down even a gently inclined surface.
+Castings when dry often crumble into small pellets and these are apt to
+roll down any sloping surface.  Where the land is quite level and is
+covered with herbage, and where the climate is humid so that much dust
+cannot be blown away, it appears at first sight impossible that there
+should be any appreciable amount of sub-aerial denudation; but
+worm-castings are blown, especially whilst moist and viscid, in one
+uniform direction by the prevalent winds which are accompanied by rain.
+By these several means the superficial mould is prevented from
+accumulating to a great thickness; and a thick bed of mould checks in
+many ways the disintegration of the underlying rocks and fragments of
+rock.
+
+The removal of worm-castings by the above means leads to results which
+are far from insignificant.  It has been shown that a layer of earth, 0.2
+of an inch in thickness, is in many places annually brought to the
+surface; and if a small part of this amount flows, or rolls, or is
+washed, even for a short distance, down every inclined surface, or is
+repeatedly blown in one direction, a great effect will be produced in the
+course of ages.  It was found by measurements and calculations that on a
+surface with a mean inclination of 9° 26′, 2.4 cubic inches of earth
+which had been ejected by worms crossed, in the course of a year, a
+horizontal line one yard in length; so that 240 cubic inches would cross
+a line 100 yards in length.  This latter amount in a damp state would
+weigh 11½ pounds.  Thus a considerable weight of earth is continually
+moving down each side of every valley, and will in time reach its bed.
+Finally this earth will be transported by the streams flowing in the
+valleys into the ocean, the great receptacle for all matter denuded from
+the land.  It is known from the amount of sediment annually delivered
+into the sea by the Mississippi, that its enormous drainage-area must on
+an average be lowered .00263 of an inch each year; and this would suffice
+in four and half million years to lower the whole drainage-area to the
+level of the sea-shore.  So that, if a small fraction of the layer of
+fine earth, 0.2 of an inch in thickness, which is annually brought to the
+surface by worms, is carried away, a great result cannot fail to be
+produced within a period which no geologist considers extremely long.
+
+                                * * * * *
+
+Archæologists ought to be grateful to worms, as they protect and preserve
+for an indefinitely long period every object, not liable to decay, which
+is dropped on the surface of the land, by burying it beneath their
+castings.  Thus, also, many elegant and curious tesselated pavements and
+other ancient remains have been preserved; though no doubt the worms have
+in these cases been largely aided by earth washed and blown from the
+adjoining land, especially when cultivated.  The old tesselated pavements
+have, however, often suffered by having subsided unequally from being
+unequally undermined by the worms.  Even old massive walls may be
+undermined and subside; and no building is in this respect safe, unless
+the foundations lie 6 or 7 feet beneath the surface, at a depth at which
+worms cannot work.  It is probable that many monoliths and some old walls
+have fallen down from having been undermined by worms.
+
+                                * * * * *
+
+Worms prepare the ground {284} in an excellent manner for the growth of
+fibrous-rooted plants and for seedlings of all kinds.  They periodically
+expose the mould to the air, and sift it so that no stones larger than
+the particles which they can swallow are left in it.  They mingle the
+whole intimately together, like a gardener who prepares fine soil for his
+choicest plants.  In this state it is well fitted to retain moisture and
+to absorb all soluble substances, as well as for the process of
+nitrification.  The bones of dead animals, the harder parts of insects,
+the shells of land-molluscs, leaves, twigs, &c., are before long all
+buried beneath the accumulated castings of worms, and are thus brought in
+a more or less decayed state within reach of the roots of plants.  Worms
+likewise drag an infinite number of dead leaves and other parts of plants
+into their burrows, partly for the sake of plugging them up and partly as
+food.
+
+The leaves which are dragged into the burrows as food, after being torn
+into the finest shreds, partially digested, and saturated with the
+intestinal and urinary secretions, are commingled with much earth.  This
+earth forms the dark coloured, rich humus which almost everywhere covers
+the surface of the land with a fairly well-defined layer or mantle.
+Hensen {285} placed two worms in a vessel 18 inches in diameter, which
+was filled with sand, on which fallen leaves were strewed; and these were
+soon dragged into their burrows to a depth of 3 inches.  After about 6
+weeks an almost uniform layer of sand, a centimeter (0.4 inch) in
+thickness, was converted into humus by having passed through the
+alimentary canals of these two worms.  It is believed by some persons
+that worm-burrows, which often penetrate the ground almost
+perpendicularly to a depth of 5 or 6 feet, materially aid in its
+drainage; notwithstanding that the viscid castings piled over the mouths
+of the burrows prevent or check the rain-water directly entering them.
+They allow the air to penetrate deeply into the ground.  They also
+greatly facilitate the downward passage of roots of moderate size; and
+these will be nourished by the humus with which the burrows are lined.
+Many seeds owe their germination to having been covered by castings; and
+others buried to a considerable depth beneath accumulated castings lie
+dormant, until at some future time they are accidentally uncovered and
+germinate.
+
+Worms are poorly provided with sense-organs, for they cannot be said to
+see, although they can just distinguish between light and darkness; they
+are completely deaf, and have only a feeble power of smell; the sense of
+touch alone is well developed.  They can therefore learn but little about
+the outside world, and it is surprising that they should exhibit some
+skill in lining their burrows with their castings and with leaves, and in
+the case of some species in piling up their castings into tower-like
+constructions.  But it is far more surprising that they should apparently
+exhibit some degrees of intelligence instead of a mere blind instinctive
+impulse, in their manner of plugging up the mouths of their burrows.
+They act in nearly the same manner as would a man, who had to close a
+cylindrical tube with different kinds of leaves, petioles, triangles of
+paper, &c., for they commonly seize such objects by their pointed ends.
+But with thin objects a certain number are drawn in by their broader
+ends.  They do not act in the same unvarying manner in all cases, as do
+most of the lower animals; for instance, they do not drag in leaves by
+their foot-stalks, unless the basal part of the blade is as narrow as the
+apex, or narrower than it.
+
+                                * * * * *
+
+When we behold a wide, turf-covered expanse, we should remember that its
+smoothness, on which so much of its beauty depends, is mainly due to all
+the inequalities having been slowly levelled by worms.  It is a
+marvellous reflection that the whole of the superficial mould over any
+such expanse has passed, and will again pass, every few years through the
+bodies of worms.  The plough is one of the most ancient and most valuable
+of man’s inventions; but long before he existed the land was in fact
+regularly ploughed, and still continues to be thus ploughed by
+earth-worms.  It may be doubted whether there are many other animals
+which have played so important a part in the history of the world, as
+have these lowly organized creatures.  Some other animals, however, still
+more lowly organized, namely corals, have done far more conspicuous work
+in having constructed innumerable reefs and islands in the great oceans;
+but these are almost confined to the tropical zones.
+
+
+
+
+FOOTNOTES.
+
+
+{2}  ‘Leçons de Géologie Pratique,’ tom. i. 1845, p. 140.
+
+{3}  ‘Transactions Geolog. Soc.’ vol. v. p. 505.  Read November 1, 1837.
+
+{4a}  ‘Histoire des progrès de la Géologie,’ tom. i. 1847, p. 224.
+
+{4b}  ‘Zeitschrift für wissenschaft.  Zoologie,’ B. xxviii. 1877, p. 361.
+
+{5}  ‘Gardeners’ Chronicle,’ April 17, 1869, p. 418.
+
+{6}  Mr. Darwin’s attention was called by Professor Hensen to P. E.
+Müller’s work on Humus in ‘Tidsskrift for Skovbrug,’ Band iii. Heft 1 and
+2, Copenhagen, 1878.  He had, however, no opportunity of consulting
+Müller’s work.  Dr. Müller published a second paper in 1884 in the same
+periodical—a Danish journal of forestry.  His results have also been
+published in German, in a volume entitled ‘Studien über die natürlichen
+Humusformen, unter deren Einwirkung auf Vegetation und Boden,’ 8vo.,
+Berlin, 1887.
+
+{8a}  ‘Bidrag till Skandinaviens Oligochætfauna,’ 1871.
+
+{8b}  ‘Die bis jetzt bekannten Arten aus der Familie der Regenwürmer,’
+1845.
+
+{9b}  There is even some reason to believe that pressure is actually
+favourable to the growth of grasses, for Professor Buckman, who made many
+observations on their growth in the experimental gardens of the Royal
+Agricultural College, remarks (‘Gardeners’ Chronicle,’ 1854, p. 619):
+“Another circumstance in the cultivation of grasses in the separate form
+or small patches, is the impossibility of rolling or treading them
+firmly, without which no pasture can continue good.”
+
+{11}  I shall have occasion often to refer to M. Perrier’s admirable
+memoir, ‘Organisation des Lombriciens terrestres’ in ‘Archives de Zoolog.
+expér.’ tom. iii. 1874, p. 372.  C. F. Morren (‘De Lumbrici terrestris
+Hist. Nat.’ 1829, p. 14) found that worms endured immersion for fifteen
+to twenty days in summer, but that in winter they died when thus treated.
+
+{12}  Morren, ‘De Lumbrici terrestris Hist. Nat.’ &c., 1829, p. 67.
+
+{14}  ‘De Lumbrici terrestris Hist. Nat.’ &c., p. 14.
+
+{17}  Histolog.  Untersuchungen über die Regenwürmer.  ‘Zeitschrift für
+wissenschaft.  Zoologie,’ B. xix., 1869, p. 611.
+
+{18a}  For instance, Mr. Bridgman and Mr. Newman (‘The Zoologist,’ vol.
+vii. 1849, p. 2576), and some friends who observed worms for me.
+
+{18b}  ‘Familie der Regenwürmer,’ 1845, p. 18.
+
+{31}  ‘The Zoologist,’ vol. vii. 1849, p. 2576.
+
+{32}  ‘Familie der Regenwürmer,’ p. 13.  Dr. Sturtevant states in the
+‘New York Weekly Tribune’ (May 19, 1880) that he kept three worms in a
+pot, which was allowed to become extremely dry; and these worms were
+found “all entwined together, forming a round mass and in good
+condition.”
+
+{33}  ‘De Lumbrici terrestris Hist. Nat.’ p. 19.
+
+{34}  ‘Archives de Zoologie expérimentale,’ tom. vii. 1878, p. 394.  When
+I wrote the above passage, I was not aware that Krukenberg
+(‘Untersuchungen a. d. physiol.  Inst. d. Univ.  Heidelberg,’ Bd. ii. p.
+37, 1877) had previously investigated the digestive juice of Lumbricus.
+He states that it contains a peptic, and diastatic, as well as a tryptic
+ferment.
+
+{35a}  On the action of the pancreatic ferment, see ‘A Text-Book of
+Physiology,’ by Michael Foster, 2nd edit. pp. 198–203.  1878.
+
+{35b}  Schmulewitsch, ‘Action des Sucs digestifs sur la Cellulose.’
+Bull. de l’Acad. Imp. de St. Pétersbourg, tom. xxv. p. 549.  1879.
+
+{40}  Claparède doubts whether saliva is secreted by worms: see
+‘Zeitschrift für wissenschaft.  Zoologie,’ B. xix. 1869, p. 601.
+
+{41a}  Perrier, ‘Archives de Zoolog. expér.’ July, 1874, pp. 416, 419.
+
+{41b}  ‘Zeitschrift für wissenschaft.  Zoologie,’ B. xix, 1869, pp.
+603–606.
+
+{46}  De Vries, ‘Landwirth. Jahrbücher,’ 1881, p. 77.
+
+{49}  M. Foster, ‘A Text-Book of Physiology,’ 2nd edit. 1878, p. 243.
+
+{50}  M. Foster, _ut sup._ p. 200.
+
+{53}  Claparède remarks (‘Zeitschrift für wisseuschaft.  Zoolog.’ B. 19,
+1869, p. 602) that the pharynx appears from its structure to be adapted
+for suction.
+
+{58}  An account of her observations is given in the ‘Gardeners’
+Chronicle,’ March 28th, 1868, p. 324.
+
+{59a}  London’s ‘Gard. Mag.’ xvii. p. 216, as quoted in the ‘Catalogue of
+the British Museum Worms,’ 1865, p. 327.
+
+{59b}  ‘Familie der Regenwürmer,’ p. 19.
+
+{79}  In these narrow triangles the apical angle is 9° 34′, and the basal
+angles 85° 13′.  In the broader triangles the apical angle is 19° 10′ and
+the basal angles 80° 25′.
+
+{89a}  See his interesting work, ‘Souvenirs entomologiques,’ 1879, pp.
+168–177.
+
+{89b}  Möbius, ‘Die Bewegungen der Thiere,’ &c., 1873, p. 111.
+
+{90}  ‘Annals and Mag. of N. History,’ series ii. vol. ix. 1852, p. 333.
+
+{93}  ‘Archives de Zoolog. expér.’ tom. iii. 1874, p. 405.
+
+{97}  I state this on the authority of Semper, ‘Reisen im Archipel der
+Philippinen,’ Th. ii. 1877, p. 30.
+
+{101}  Dr. King gave me some worms collected near Nice, which, as he
+believes, had constructed these castings.  They were sent to M. Perrier,
+who with great kindness examined and named them for me: they consisted of
+_Perichæta affinis_, a native of Cochin China and of the Philippines; _P.
+Luzonica_, a native of Luzon in the Philippines; and _P. Houlleti_, which
+lives near Calcutta.  M. Perrier informs me that species of Perichæta
+have been naturalized in the gardens near Montpellier and in Algiers.
+Before I had any reason to suspect that the tower-like castings from Nice
+had been formed by worms not endemic in the country, I was greatly
+surprised to see how closely they resembled castings sent to me from near
+Calcutta, where it is known that species of Perichæta abound.
+
+{102}  ‘Zeitschrift für wissenschaft.  Zoolog.’  B. xxviii. 1877, p. 364.
+
+{108}  ‘Zeitschrift für wissenschaft.  Zoolog.’ B. xxviii. 1877, p. 356.
+
+{113}  Perrier, ‘Archives de Zoolog. expér.’ tom. 3, p. 378, 1874.
+
+{126}  This case is given in a postscript to my paper in the ‘Transact.
+Geolog. Soc.’  (Vol. v. p. 505), and contains a serious error, as in the
+account received I mistook the figure 30 for 80.  The tenant, moreover,
+formerly said that he had marled the field thirty years before, but was
+now positive that this was done in 1809, that is twenty-eight years
+before the first examination of the field by my friend.  The error, as
+far as the figure 80 is concerned, was corrected in an article by me, in
+the ‘Gardeners’ Chronicle,’ 1844, p. 218.
+
+{128}  These pits or pipes are still in process of formation.  During the
+last forty years I have seen or heard of five cases, in which a circular
+space, several feet in diameter, suddenly fell in, leaving on the field
+an open hole with perpendicular sides, some feet in depth.  This occurred
+in one of my own fields, whilst it was being rolled, and the hinder
+quarters of the shaft horse fell in; two or three cart-loads of rubbish
+were required to fill up the hole.  The subsidence occurred where there
+was a broad depression, as if the surface had fallen in at several former
+periods.  I heard of a hole which must have been suddenly formed at the
+bottom of a small shallow pool, where sheep had been washed during many
+years, and into which a man thus occupied fell to his great terror.  The
+rain-water over this whole district sinks perpendicularly into the
+ground, but the chalk is more porous in certain places than in others.
+Thus the drainage from the overlying clay is directed to certain points,
+where a greater amount of calcareous matter is dissolved than elsewhere.
+Even narrow open channels are sometimes formed in the solid chalk.  As
+the chalk is slowly dissolved over the whole country, but more in some
+parts than in others, the undissolved residue—that is the overlying mass
+of red clay with flints,—likewise sinks slowly down, and tends to fill up
+the pipes or cavities.  But the upper part of the red clay holds
+together, aided probably by the roots of plants, for a longer time than
+the lower parts, and thus forms a roof, which sooner or later falls in,
+as in the above mentioned five cases.  The downward movement of the clay
+may be compared with that of a glacier, but is incomparably slower; and
+this movement accounts for a singular fact, namely, that the much
+elongated flints which are embedded in the chalk in a nearly horizontal
+position, are commonly found standing nearly or quite upright in the red
+clay.  This fact is so common that the workmen assured me that this was
+their natural position.  I roughly measured one which stood vertically,
+and it was of the same length and of the same relative thickness as one
+of my arms.  These elongated flints must get placed in their upright
+position, on the same principle that a trunk of a tree left on a glacier
+assumes a position parallel to the line of motion.  The flints in the
+clay which form almost half its bulk, are very often broken, though not
+rolled or abraded; and this may be accounted for by their mutual
+pressure, whilst the whole mass is subsiding.  I may add that the chalk
+here appears to have been originally covered in parts by a thin bed of
+fine sand with some perfectly rounded flint pebbles, probably of Tertiary
+age; for such sand often partly fills up the deeper pits or cavities in
+the chalk.
+
+{131}  S. W. Johnson, ‘How Crops Feed,’ 1870, p. 139.
+
+{136a}  ‘Nature,’ November 1877, p. 28.
+
+{136b}  ‘Proc. Phil. Soc.’ of Manchester, 1877, p. 247.
+
+{138a}  ‘Trans. of the New Zealand Institute,’ vol. xii., 1880, p. 152.
+
+{138b}  Mr. Lindsay Carnagie, in a letter (June 1838) to Sir C. Lyell,
+remarks that Scotch farmers are afraid of putting lime on ploughed land
+until just before it is laid down for pasture, from a belief that it has
+some tendency to sink.  He adds: “Some years since, in autumn, I laid
+lime on an oat-stubble and ploughed it down; thus bringing it into
+immediate contact with the dead vegetable matter, and securing its
+thorough mixture through the means of all the subsequent operations of
+fallow.  In consequence of the above prejudice, I was considered to have
+committed a great fault; but the result was eminently successful, and the
+practice was _partially_ followed.  By means of Mr. Darwin’s
+observations, I think the prejudice will be removed.”
+
+{139}  This conclusion, which, as we shall immediately see, is fully
+justified, is of some little importance, as the so-called bench-stones,
+which surveyors fix in the ground as a record of their levels, may in
+time become false standards.  My son Horace intends at some future period
+to ascertain how far this has occurred.
+
+{147}  Mr. R. Mallet remarks (‘Quarterly Journal of Geolog. Soc.’ vol.
+xxxiii., 1877, p. 745) that “the extent to which the ground beneath the
+foundations of ponderous architectural structures, such as cathedral
+towers, has been known to become compressed, is as remarkable as it is
+instructive and curious.  The amount of depression in some cases may be
+measured by feet.”  He instances the Tower of Pisa, but adds that it was
+founded on “dense clay.”
+
+{148}  ‘Zeitschrift für wissensch. Zoolog.’ Bd. xxviii., 1877, p. 360.
+
+{149}  See Mr. Dancer’s paper in ‘Proc. Phil. Soc. of Manchester,’ 1877,
+p. 248.
+
+{166a}  ‘Leçons de Géologie pratique,’ 1845, p. 142.
+
+{166b}  A short account of this discovery was published in ‘The Times’ of
+January 2, 1878; and a fuller account in ‘The Builder,’ January 5, 1878.
+
+{183}  Several accounts of these ruins have been published; the best is
+by Mr. James Farrer in ‘Proc. Soc. of Antiquaries of Scotland,’ vol. vi.,
+Part II., 1867, p. 278.  Also J. W. Grover, ‘Journal of the British Arch.
+Assoc.’ June 1866.  Professor Buckman has likewise published a pamphlet,
+‘Notes on the Roman Villa at Chedworth,’ 2nd edit. 1873 Cirencester.
+
+{187}  These details are taken from the ‘Penny Cyclopædia,’ article
+Hampshire.
+
+{210}  “On the denudation of South Wales,” &c., ‘Memoirs of the
+Geological Survey of Great Britain,’ vol. 1., p. 297, 1846.
+
+{211}  ‘Geological Magazine,’ October and November, 1867, vol. iv. pp.
+447 and 483.  Copious references on the subject are given in this
+remarkable memoir.
+
+{212}  A. Tylor “On changes of the sea-level,” &c., ‘ Philosophical Mag.’
+(Ser. 4th) vol. v., 1853, p. 258.  Archibald Geikie, Transactions Geolog.
+Soc. of Glasgow, vol. iii., p. 153 (read March, 1868).  Croll “On
+Geological Time,” ‘Philosophical Mag.,’ May, August, and November, 1868.
+See also Croll, ‘Climate and Time,’ 1875, Chap. XX.  For some recent
+information on the amount of sediment brought down by rivers, see
+‘Nature,’ Sept.  23rd, 1880.  Mr. T. Mellard Reade has published some
+interesting articles on the astonishing amount of matter brought down in
+solution by rivers.  See Address, Geolog. Soc., Liverpool, 1876–77.
+
+{213}  “An account of the fine dust which often falls on Vessels in the
+Atlantic Ocean,” Proc. Geolog. Soc. of London, June 4th, 1845.
+
+{215}  For La Plata, see my ‘Journal of Researches,’ during the voyage of
+the _Beagle_, 1845, p. 133.  Élie de Beaumont has given (‘Leçons de
+Géolog. pratique,’ tom. I. 1845, p. 183) an excellent account of the
+enormous quantity of dust which is transported in some countries.  I
+cannot but think that Mr. Proctor has somewhat exaggerated (‘Pleasant
+Ways in Science,’ 1879, p. 379) the agency of dust in a humid country
+like Great Britain.  James Geikie has given (‘Prehistoric Europe,’ 1880,
+p. 165) a full abstract of Richthofen’s views, which, however, he
+disputes.
+
+{217a}  These statements are taken from Hensen in ‘Zeitschrift für
+wissenschaft. Zoologie.’ Bd. xxviii., 1877, p. 360.  Those with respect
+to peat are taken from Mr. A. A. Julien in ‘Proc. American Assoc.
+Science,’ 1879, p. 354.
+
+{217b}  I have given some facts on the climate necessary or favourable
+for the formation of peat, in my ‘Journal of Researches,’ 1845, p. 287.
+
+{220}  A. A. Julien “On the Geological action of the Humus-acids,” ‘Proc.
+American Assoc. Science,’ vol. xxviii., 1879, p. 311.  Also on “Chemical
+erosion on Mountain Summits;” ‘New York Academy of Sciences,’ Oct. 14,
+1878, as quoted in the ‘American Naturalist.’  See also, on this subject,
+S. W. Johnson, ‘How Crops Feed,’ 1870, p. 138.
+
+{222}  See, for references on this subject, S. W. Johnson, ‘How Crops
+Feed,’ 1870, p. 326.
+
+{223}  This statement is taken from Mr. Julien, ‘Proc. American Assoc.
+Science,’ vol.  xxviii., 1879, p. 330.
+
+{224a}  The preservative power of a layer of mould and turf is often
+shown by the perfect state of the glacial scratches on rocks when first
+uncovered.  Mr. J. Geikie maintains, in his last very interesting work
+(‘Prehistoric Europe,’ 1881), that the more perfect scratches are
+probably due to the last access of cold and increase of ice, during the
+long-continued, intermittent glacial period.
+
+{224b}  Many geologists have felt much surprise at the complete
+disappearance of flints over wide and nearly level areas, from which the
+chalk has been removed by subaerial denudation.  But the surface of every
+flint is coated by an opaque modified layer, which will just yield to a
+steel point, whilst the freshly fractured, translucent surface will not
+thus yield.  The removal by atmospheric agencies of the outer modified
+surfaces of freely exposed flints, though no doubt excessively slow,
+together with the modification travelling inwards, will, as may be
+suspected, ultimately lead to their complete disintegration,
+notwithstanding that they appear to be so extremely durable.
+
+{225a}  ‘Archives de Zoolog. expér.’ tom. iii. 1874, p. 409.
+
+{225b}  ‘Nouvelles Archives du Muséum,’ tom. viii. 1872, pp.  95, 131.
+
+{226}  Morren, in speaking of the earth in the alimentary canals of
+worms, says, “præsepè cum lapillis commixtam vidi:” ‘De Lumbrici
+terrestris Hist. Nat.’ &c., 1829, p. 16.
+
+{227}  Perrier, ‘Archives de Zoolog. expér.’ tom. iii. 1874, p. 419.
+
+{228a}  Morren, ‘De Lumbrici terrestris Hist. Nat.’ &c., p. 16.
+
+{228b}  ‘Archives de Zoolog. expér.’ tom. iii. 1874, p. 418.
+
+{234}  This conclusion reminds me of the vast amount of extremely fine
+chalky mud which is found within the lagoons of many atolls, where the
+sea is tranquil and waves cannot triturate the blocks of coral.  This mud
+must, as I believe (‘The Structure and Distribution of Coral-Reefs,’ 2nd
+edit. 1874, p. 19), be attributed to the innumerable annelids and other
+animals which burrow into the dead coral, and to the fishes,
+Holothurians, &c., which browse on the living corals.
+
+{236}  Anniversary Address: ‘The Quarterly Journal of the Geological
+Soc.’ May 1880, p. 59.
+
+{244}  Mr. James Wallace has pointed out that it is necessary to take
+into consideration the possibility of burrows being made at right angles
+to the surface instead of vertically down, in which case the lateral
+displacement of the soil would be increased.
+
+{259}  ‘Elements of Geology,’ 1865, p. 20.
+
+{265}  ‘Leçons de Géologie pratique, 1845; cinquième Leçon.  All Élie de
+Beaumont’s arguments are admirably controverted by Prof. A. Geikie in his
+essay in Transact. Geolog. Soc. of Glasgow, vol. iii. p. 153, 1868.
+
+{266}  ‘Illustrations of the Huttonian Theory of the Earth,’ p. 107.
+
+{269}  Mr. E. Tylor in his Presidential address (‘Journal of the
+Anthropological Institute,’ May 1880, p. 451) remarks: “It appears from
+several papers of the Berlin Society as to the German ‘high-fields’ or
+‘heathen-fields’ (Hochäcker, and Heidenäcker) that they correspond much
+in their situation on hills and wastes with the ‘elf-furrows’ of
+Scotland, which popular mythology accounts for by the story of the fields
+having been put under a Papal interdict, so that people took to
+cultivating the hills.  There seems reason to suppose that, like the
+tilled plots in the Swedish forest which tradition ascribes to the old
+‘hackers,’ the German heathen-fields represent tillage by an ancient and
+barbaric population.”
+
+{284}  White of Selborne has some good remarks on the service performed
+by worms in loosening, &c., the soil.  Edit, by L. Jenyns, 1843, p. 281.
+
+{285}  ‘Zeitschrift für wissenschaft. Zoolog.’ B. xxviii. 1877, p. 360.
+
+
+
+
+*** END OF THE PROJECT GUTENBERG EBOOK THE FORMATION OF VEGETABLE MOULD ***
+
+Updated editions will replace the previous one--the old editions will
+be renamed.
+
+Creating the works from print editions not protected by U.S. copyright
+law means that no one owns a United States copyright in these works,
+so the Foundation (and you!) can copy and distribute it in the
+United States without permission and without paying copyright
+royalties. Special rules, set forth in the General Terms of Use part
+of this license, apply to copying and distributing Project
+Gutenberg-tm electronic works to protect the PROJECT GUTENBERG-tm
+concept and trademark. Project Gutenberg is a registered trademark,
+and may not be used if you charge for an eBook, except by following
+the terms of the trademark license, including paying royalties for use
+of the Project Gutenberg trademark. If you do not charge anything for
+copies of this eBook, complying with the trademark license is very
+easy. You may use this eBook for nearly any purpose such as creation
+of derivative works, reports, performances and research. Project
+Gutenberg eBooks may be modified and printed and given away--you may
+do practically ANYTHING in the United States with eBooks not protected
+by U.S. copyright law. Redistribution is subject to the trademark
+license, especially commercial redistribution.
+
+START: FULL LICENSE
+
+THE FULL PROJECT GUTENBERG LICENSE
+PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK
+
+To protect the Project Gutenberg-tm mission of promoting the free
+distribution of electronic works, by using or distributing this work
+(or any other work associated in any way with the phrase "Project
+Gutenberg"), you agree to comply with all the terms of the Full
+Project Gutenberg-tm License available with this file or online at
+www.gutenberg.org/license.
+
+Section 1. General Terms of Use and Redistributing Project
+Gutenberg-tm electronic works
+
+1.A. By reading or using any part of this Project Gutenberg-tm
+electronic work, you indicate that you have read, understand, agree to
+and accept all the terms of this license and intellectual property
+(trademark/copyright) agreement. If you do not agree to abide by all
+the terms of this agreement, you must cease using and return or
+destroy all copies of Project Gutenberg-tm electronic works in your
+possession. If you paid a fee for obtaining a copy of or access to a
+Project Gutenberg-tm electronic work and you do not agree to be bound
+by the terms of this agreement, you may obtain a refund from the
+person or entity to whom you paid the fee as set forth in paragraph
+1.E.8.
+
+1.B. "Project Gutenberg" is a registered trademark. It may only be
+used on or associated in any way with an electronic work by people who
+agree to be bound by the terms of this agreement. There are a few
+things that you can do with most Project Gutenberg-tm electronic works
+even without complying with the full terms of this agreement. See
+paragraph 1.C below. There are a lot of things you can do with Project
+Gutenberg-tm electronic works if you follow the terms of this
+agreement and help preserve free future access to Project Gutenberg-tm
+electronic works. See paragraph 1.E below.
+
+1.C. The Project Gutenberg Literary Archive Foundation ("the
+Foundation" or PGLAF), owns a compilation copyright in the collection
+of Project Gutenberg-tm electronic works. Nearly all the individual
+works in the collection are in the public domain in the United
+States. If an individual work is unprotected by copyright law in the
+United States and you are located in the United States, we do not
+claim a right to prevent you from copying, distributing, performing,
+displaying or creating derivative works based on the work as long as
+all references to Project Gutenberg are removed. Of course, we hope
+that you will support the Project Gutenberg-tm mission of promoting
+free access to electronic works by freely sharing Project Gutenberg-tm
+works in compliance with the terms of this agreement for keeping the
+Project Gutenberg-tm name associated with the work. You can easily
+comply with the terms of this agreement by keeping this work in the
+same format with its attached full Project Gutenberg-tm License when
+you share it without charge with others.
+
+1.D. The copyright laws of the place where you are located also govern
+what you can do with this work. Copyright laws in most countries are
+in a constant state of change. If you are outside the United States,
+check the laws of your country in addition to the terms of this
+agreement before downloading, copying, displaying, performing,
+distributing or creating derivative works based on this work or any
+other Project Gutenberg-tm work. The Foundation makes no
+representations concerning the copyright status of any work in any
+country other than the United States.
+
+1.E. Unless you have removed all references to Project Gutenberg:
+
+1.E.1. The following sentence, with active links to, or other
+immediate access to, the full Project Gutenberg-tm License must appear
+prominently whenever any copy of a Project Gutenberg-tm work (any work
+on which the phrase "Project Gutenberg" appears, or with which the
+phrase "Project Gutenberg" is associated) is accessed, displayed,
+performed, viewed, copied or distributed:
+
+  This eBook is for the use of anyone anywhere in the United States and
+  most other parts of the world at no cost and with almost no
+  restrictions whatsoever. You may copy it, give it away or re-use it
+  under the terms of the Project Gutenberg License included with this
+  eBook or online at www.gutenberg.org. If you are not located in the
+  United States, you will have to check the laws of the country where
+  you are located before using this eBook.
+
+1.E.2. If an individual Project Gutenberg-tm electronic work is
+derived from texts not protected by U.S. copyright law (does not
+contain a notice indicating that it is posted with permission of the
+copyright holder), the work can be copied and distributed to anyone in
+the United States without paying any fees or charges. If you are
+redistributing or providing access to a work with the phrase "Project
+Gutenberg" associated with or appearing on the work, you must comply
+either with the requirements of paragraphs 1.E.1 through 1.E.7 or
+obtain permission for the use of the work and the Project Gutenberg-tm
+trademark as set forth in paragraphs 1.E.8 or 1.E.9.
+
+1.E.3. If an individual Project Gutenberg-tm electronic work is posted
+with the permission of the copyright holder, your use and distribution
+must comply with both paragraphs 1.E.1 through 1.E.7 and any
+additional terms imposed by the copyright holder. Additional terms
+will be linked to the Project Gutenberg-tm License for all works
+posted with the permission of the copyright holder found at the
+beginning of this work.
+
+1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm
+License terms from this work, or any files containing a part of this
+work or any other work associated with Project Gutenberg-tm.
+
+1.E.5. Do not copy, display, perform, distribute or redistribute this
+electronic work, or any part of this electronic work, without
+prominently displaying the sentence set forth in paragraph 1.E.1 with
+active links or immediate access to the full terms of the Project
+Gutenberg-tm License.
+
+1.E.6. You may convert to and distribute this work in any binary,
+compressed, marked up, nonproprietary or proprietary form, including
+any word processing or hypertext form. However, if you provide access
+to or distribute copies of a Project Gutenberg-tm work in a format
+other than "Plain Vanilla ASCII" or other format used in the official
+version posted on the official Project Gutenberg-tm website
+(www.gutenberg.org), you must, at no additional cost, fee or expense
+to the user, provide a copy, a means of exporting a copy, or a means
+of obtaining a copy upon request, of the work in its original "Plain
+Vanilla ASCII" or other form. Any alternate format must include the
+full Project Gutenberg-tm License as specified in paragraph 1.E.1.
+
+1.E.7. Do not charge a fee for access to, viewing, displaying,
+performing, copying or distributing any Project Gutenberg-tm works
+unless you comply with paragraph 1.E.8 or 1.E.9.
+
+1.E.8. You may charge a reasonable fee for copies of or providing
+access to or distributing Project Gutenberg-tm electronic works
+provided that:
+
+* You pay a royalty fee of 20% of the gross profits you derive from
+  the use of Project Gutenberg-tm works calculated using the method
+  you already use to calculate your applicable taxes. The fee is owed
+  to the owner of the Project Gutenberg-tm trademark, but he has
+  agreed to donate royalties under this paragraph to the Project
+  Gutenberg Literary Archive Foundation. Royalty payments must be paid
+  within 60 days following each date on which you prepare (or are
+  legally required to prepare) your periodic tax returns. Royalty
+  payments should be clearly marked as such and sent to the Project
+  Gutenberg Literary Archive Foundation at the address specified in
+  Section 4, "Information about donations to the Project Gutenberg
+  Literary Archive Foundation."
+
+* You provide a full refund of any money paid by a user who notifies
+  you in writing (or by e-mail) within 30 days of receipt that s/he
+  does not agree to the terms of the full Project Gutenberg-tm
+  License. You must require such a user to return or destroy all
+  copies of the works possessed in a physical medium and discontinue
+  all use of and all access to other copies of Project Gutenberg-tm
+  works.
+
+* You provide, in accordance with paragraph 1.F.3, a full refund of
+  any money paid for a work or a replacement copy, if a defect in the
+  electronic work is discovered and reported to you within 90 days of
+  receipt of the work.
+
+* You comply with all other terms of this agreement for free
+  distribution of Project Gutenberg-tm works.
+
+1.E.9. If you wish to charge a fee or distribute a Project
+Gutenberg-tm electronic work or group of works on different terms than
+are set forth in this agreement, you must obtain permission in writing
+from the Project Gutenberg Literary Archive Foundation, the manager of
+the Project Gutenberg-tm trademark. Contact the Foundation as set
+forth in Section 3 below.
+
+1.F.
+
+1.F.1. Project Gutenberg volunteers and employees expend considerable
+effort to identify, do copyright research on, transcribe and proofread
+works not protected by U.S. copyright law in creating the Project
+Gutenberg-tm collection. Despite these efforts, Project Gutenberg-tm
+electronic works, and the medium on which they may be stored, may
+contain "Defects," such as, but not limited to, incomplete, inaccurate
+or corrupt data, transcription errors, a copyright or other
+intellectual property infringement, a defective or damaged disk or
+other medium, a computer virus, or computer codes that damage or
+cannot be read by your equipment.
+
+1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right
+of Replacement or Refund" described in paragraph 1.F.3, the Project
+Gutenberg Literary Archive Foundation, the owner of the Project
+Gutenberg-tm trademark, and any other party distributing a Project
+Gutenberg-tm electronic work under this agreement, disclaim all
+liability to you for damages, costs and expenses, including legal
+fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT
+LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE
+PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE
+TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE
+LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR
+INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH
+DAMAGE.
+
+1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a
+defect in this electronic work within 90 days of receiving it, you can
+receive a refund of the money (if any) you paid for it by sending a
+written explanation to the person you received the work from. If you
+received the work on a physical medium, you must return the medium
+with your written explanation. The person or entity that provided you
+with the defective work may elect to provide a replacement copy in
+lieu of a refund. If you received the work electronically, the person
+or entity providing it to you may choose to give you a second
+opportunity to receive the work electronically in lieu of a refund. If
+the second copy is also defective, you may demand a refund in writing
+without further opportunities to fix the problem.
+
+1.F.4. Except for the limited right of replacement or refund set forth
+in paragraph 1.F.3, this work is provided to you 'AS-IS', WITH NO
+OTHER WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
+LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE.
+
+1.F.5. Some states do not allow disclaimers of certain implied
+warranties or the exclusion or limitation of certain types of
+damages. If any disclaimer or limitation set forth in this agreement
+violates the law of the state applicable to this agreement, the
+agreement shall be interpreted to make the maximum disclaimer or
+limitation permitted by the applicable state law. The invalidity or
+unenforceability of any provision of this agreement shall not void the
+remaining provisions.
+
+1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the
+trademark owner, any agent or employee of the Foundation, anyone
+providing copies of Project Gutenberg-tm electronic works in
+accordance with this agreement, and any volunteers associated with the
+production, promotion and distribution of Project Gutenberg-tm
+electronic works, harmless from all liability, costs and expenses,
+including legal fees, that arise directly or indirectly from any of
+the following which you do or cause to occur: (a) distribution of this
+or any Project Gutenberg-tm work, (b) alteration, modification, or
+additions or deletions to any Project Gutenberg-tm work, and (c) any
+Defect you cause.
+
+Section 2. Information about the Mission of Project Gutenberg-tm
+
+Project Gutenberg-tm is synonymous with the free distribution of
+electronic works in formats readable by the widest variety of
+computers including obsolete, old, middle-aged and new computers. It
+exists because of the efforts of hundreds of volunteers and donations
+from people in all walks of life.
+
+Volunteers and financial support to provide volunteers with the
+assistance they need are critical to reaching Project Gutenberg-tm's
+goals and ensuring that the Project Gutenberg-tm collection will
+remain freely available for generations to come. In 2001, the Project
+Gutenberg Literary Archive Foundation was created to provide a secure
+and permanent future for Project Gutenberg-tm and future
+generations. To learn more about the Project Gutenberg Literary
+Archive Foundation and how your efforts and donations can help, see
+Sections 3 and 4 and the Foundation information page at
+www.gutenberg.org
+
+Section 3. Information about the Project Gutenberg Literary
+Archive Foundation
+
+The Project Gutenberg Literary Archive Foundation is a non-profit
+501(c)(3) educational corporation organized under the laws of the
+state of Mississippi and granted tax exempt status by the Internal
+Revenue Service. The Foundation's EIN or federal tax identification
+number is 64-6221541. Contributions to the Project Gutenberg Literary
+Archive Foundation are tax deductible to the full extent permitted by
+U.S. federal laws and your state's laws.
+
+The Foundation's business office is located at 809 North 1500 West,
+Salt Lake City, UT 84116, (801) 596-1887. Email contact links and up
+to date contact information can be found at the Foundation's website
+and official page at www.gutenberg.org/contact
+
+Section 4. Information about Donations to the Project Gutenberg
+Literary Archive Foundation
+
+Project Gutenberg-tm depends upon and cannot survive without
+widespread public support and donations to carry out its mission of
+increasing the number of public domain and licensed works that can be
+freely distributed in machine-readable form accessible by the widest
+array of equipment including outdated equipment. Many small donations
+($1 to $5,000) are particularly important to maintaining tax exempt
+status with the IRS.
+
+The Foundation is committed to complying with the laws regulating
+charities and charitable donations in all 50 states of the United
+States. Compliance requirements are not uniform and it takes a
+considerable effort, much paperwork and many fees to meet and keep up
+with these requirements. We do not solicit donations in locations
+where we have not received written confirmation of compliance. To SEND
+DONATIONS or determine the status of compliance for any particular
+state visit www.gutenberg.org/donate
+
+While we cannot and do not solicit contributions from states where we
+have not met the solicitation requirements, we know of no prohibition
+against accepting unsolicited donations from donors in such states who
+approach us with offers to donate.
+
+International donations are gratefully accepted, but we cannot make
+any statements concerning tax treatment of donations received from
+outside the United States. U.S. laws alone swamp our small staff.
+
+Please check the Project Gutenberg web pages for current donation
+methods and addresses. Donations are accepted in a number of other
+ways including checks, online payments and credit card donations. To
+donate, please visit: www.gutenberg.org/donate
+
+Section 5. General Information About Project Gutenberg-tm electronic works
+
+Professor Michael S. Hart was the originator of the Project
+Gutenberg-tm concept of a library of electronic works that could be
+freely shared with anyone. For forty years, he produced and
+distributed Project Gutenberg-tm eBooks with only a loose network of
+volunteer support.
+
+Project Gutenberg-tm eBooks are often created from several printed
+editions, all of which are confirmed as not protected by copyright in
+the U.S. unless a copyright notice is included. Thus, we do not
+necessarily keep eBooks in compliance with any particular paper
+edition.
+
+Most people start at our website which has the main PG search
+facility: www.gutenberg.org
+
+This website includes information about Project Gutenberg-tm,
+including how to make donations to the Project Gutenberg Literary
+Archive Foundation, how to help produce our new eBooks, and how to
+subscribe to our email newsletter to hear about new eBooks.
+
+
diff --git a/2355-0.zip b/2355-0.zip
new file mode 100644
index 0000000..9581338
--- /dev/null
+++ b/2355-0.zip
diff --git a/2355-h.zip b/2355-h.zip
new file mode 100644
index 0000000..b143213
--- /dev/null
+++ b/2355-h.zip
diff --git a/2355-h/2355-h.htm b/2355-h/2355-h.htm
new file mode 100644
index 0000000..4a12268
--- /dev/null
+++ b/2355-h/2355-h.htm
@@ -0,0 +1,7731 @@
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
+"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
+<head>
+<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
+<meta http-equiv="Content-Style-Type" content="text/css" />
+<title>The Project Gutenberg eBook of The Formation of Vegetable Mould, by Charles Darwin</title>
+<link rel="coverpage" href="images/cover.jpg" />
+<style type="text/css">
+
+    body {margin-left: 10%;
+         margin-right: 10%;
+        }
+
+    p {  margin-top: .75em;
+         margin-bottom: .75em;
+         }
+    P.gutsumm { margin-left: 5%;}
+    .GutSmall { font-size: 0.7em; }
+    H1, H2 {
+         text-align: center;
+		margin-top: 2em;
+		margin-bottom: 2em;
+         }
+    H3, H4, H5 {
+	text-align: center;
+	margin-top: 1em;
+	margin-bottom: 1em;
+	}
+ table { border-collapse: collapse; }
+table {margin-left:auto; margin-right:auto;}
+    td { vertical-align: top; border: 1px solid black;}
+    td p { margin: 0.2em; }
+
+    .smcap    {font-variant: small-caps;}
+
+    .pagenum {position: absolute;
+               left: 92%;
+               font-size: small;
+               text-align: right;
+               font-weight: normal;
+               color: gray;
+               }
+    img { border: none; }
+    div.gapspace { height: 0.8em; }
+    .citation {vertical-align: super;
+               font-size: .8em;
+               text-decoration: none;}
+
+div.fig { display:block;
+          margin:0 auto;
+          text-align:center;
+          margin-top: 1em;
+          margin-bottom: 1em;}
+
+    </style>
+</head>
+<body>
+
+<div style='text-align:center; font-size:1.2em; font-weight:bold'>The Project Gutenberg eBook of The Formation of Vegetable Mould, by Charles Darwin</div>
+<div style='display:block; margin:1em 0'>
+This eBook is for the use of anyone anywhere in the United States and
+most other parts of the world at no cost and with almost no restrictions
+whatsoever. You may copy it, give it away or re-use it under the terms
+of the Project Gutenberg License included with this eBook or online
+at <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you
+are not located in the United States, you will have to check the laws of the
+country where you are located before using this eBook.
+</div>
+<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Title: The Formation of Vegetable Mould<br />
+  through the action of worms with observations on their habits</div>
+<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Author: Charles Darwin</div>
+<div style='display:block; margin:1em 0'>Release Date: December 1, 1999 [eBook #2355]<br />
+[Most recently updated: February 20, 2021]</div>
+<div style='display:block; margin:1em 0'>Language: English</div>
+<div style='display:block; margin:1em 0'>Character set encoding: UTF-8</div>
+<div style='display:block; margin-left:2em; text-indent:-2em'>Produced by: David Price</div>
+<div style='margin-top:2em; margin-bottom:4em'>*** START OF THE PROJECT GUTENBERG EBOOK THE FORMATION OF VEGETABLE MOULD ***</div>
+
+<div class="fig" style="width:100%;">
+<img src="images/cover.jpg" width="374" height="600" alt="[cover]" />
+</div>
+
+<h1>THE FORMATION OF<br />
+VEGETABLE MOULD<br />
+<span class="GutSmall">THROUGH THE ACTION OF WORMS</span><br />
+<span class="GutSmall">WITH OBSERVATIONS ON THEIR
+HABITS.</span></h1>
+<p style="text-align: center">BY CHARLES DARWIN, LL.D.,
+F.R.S.</p>
+<p style="text-align: center"><span class="GutSmall">THIRTEENTH
+THOUSAND</span><br />
+<span class="GutSmall">WITH ILLUSTRATIONS</span></p>
+
+<div class="gapspace">&nbsp;</div>
+<p style="text-align: center">LONDON<br />
+JOHN MURRAY, ALBEMARLE STREET<br />
+<span class="GutSmall">1904</span></p>
+
+<div class="gapspace">&nbsp;</div>
+<p style="text-align: center"><span class="GutSmall">PRINTED
+BY</span><br />
+<span class="GutSmall">WILLIAM CLOWES AND SONS,
+LIMITED,</span><br />
+<span class="GutSmall">LONDON AND BECCLES.</span></p>
+
+<div class="gapspace">&nbsp;</div>
+<h2>CONTENTS.</h2>
+<table>
+<tr>
+<td><p><span class="smcap">Introduction</span></p>
+</td>
+<td><p style="text-align: right">Page <span
+class="indexpageno"><a href="#page1">1</a></span>&ndash;6</p>
+</td>
+</tr>
+<tr>
+<td colspan="2"><p style="text-align: center">CHAPTER I.<br />
+<span class="GutSmall">HABITS OF WORMS.</span></p>
+</td>
+</tr>
+<tr>
+<td><p>Nature of the sites inhabited&mdash;Can live long under
+water&mdash;Nocturnal&mdash;Wander about at night&mdash;Often lie
+close to the mouths of their burrows, and are thus destroyed in
+large numbers by birds&mdash;Structure&mdash;Do not possess eyes,
+but can distinguish between light and darkness&mdash;Retreat
+rapidly when brightly illuminated, not by a reflex
+action&mdash;Power of attention&mdash;Sensitive to heat and
+cold&mdash;Completely deaf&mdash;Sensitive to vibrations and to
+touch&mdash;Feeble power of smell&mdash;Taste&mdash;Mental
+qualities&mdash;Nature of
+food&mdash;Omnivorous&mdash;Digestion&mdash;Leaves before being
+swallowed, moistened with a fluid of the nature of the pancreatic
+secretion&mdash;Extra-stomachal digestion&mdash;Calciferous
+glands, structure of&mdash;Calcareous concretions formed in the
+anterior pair of glands&mdash;The calcareous matter primarily an
+excretion, but secondarily serves to neutralise the acids
+generated during the digestive process.</p>
+</td>
+<td><p style="text-align: right"><span class="indexpageno"><a
+href="#page7">7</a></span>&ndash;15</p>
+</td>
+</tr>
+<tr>
+<td colspan="2"><p style="text-align: center">CHAPTER II.<br />
+<span class="GutSmall">HABITS OF WORMS&mdash;</span><span
+class="GutSmall"><i>continued</i></span><span
+class="GutSmall">.</span></p>
+</td>
+</tr>
+<tr>
+<td><p>Manner in which worms seize objects&mdash;Their power of
+suction&mdash;The instinct of plugging up the mouths of their
+burrows&mdash;Stones piled over the burrows&mdash;The advantages
+thus gained&mdash;Intelligence shown by worms in their manner of
+plugging up their burrows&mdash;Various kinds of leaves and other
+objects thus used&mdash;Triangles of paper&mdash;Summary of
+reasons for believing that worms exhibit some
+intelligence&mdash;Means by which they excavate their burrows, by
+pushing away the earth and swallowing it&mdash;Earth also
+swallowed for the nutritious matter which it contains&mdash;Depth
+to which worms burrow, and the construction of their
+burrows&mdash;Burrows lined with castings, and in the upper part
+with leaves&mdash;The lowest part paved with little stones or
+seeds&mdash;Manner in which the castings are ejected&mdash;The
+collapse of old burrows&mdash;Distribution of
+worms&mdash;Tower-like castings in Bengal&mdash;Gigantic castings
+on the Nilgiri Mountains&mdash;Castings ejected in all
+countries.</p>
+</td>
+<td><p style="text-align: right"><span class="indexpageno"><a
+href="#page52">52</a></span>&ndash;120</p>
+</td>
+</tr>
+<tr>
+<td colspan="2"><p style="text-align: center">CHAPTER III.<br />
+<span class="GutSmall">THE AMOUNT OF FINE EARTH BROUGHT UP BY
+WORMS TO THE SURFACE.</span></p>
+</td>
+</tr>
+<tr>
+<td><p>Rate at which various objects strewed on the surface of
+grass-fields are covered up by the castings of worms&mdash;The
+burial of a paved path&mdash;The slow subsidence of great stones
+left on the surface&mdash;The number of worms which live within a
+given space&mdash;The weight of earth ejected from a burrow, and
+from all the burrows within a given space&mdash;The thickness of
+the layer of mould which the castings on a given space would form
+within a given time if uniformly spread out&mdash;The slow rate
+at which mould can increase to a great
+thickness&mdash;Conclusion.</p>
+</td>
+<td><p style="text-align: right"><span class="indexpageno"><a
+href="#page121">121</a></span>&ndash;163</p>
+</td>
+</tr>
+<tr>
+<td colspan="2"><p style="text-align: center">CHAPTER IV.<br />
+<span class="GutSmall">THE PART WHICH WORMS HAVE PLAYED IN THE
+BURIAL OF ANCIENT BUILDINGS.</span></p>
+</td>
+</tr>
+<tr>
+<td><p>The accumulation of rubbish on the sites of great cities
+independent of the action of worms&mdash;The burial of a Roman
+villa at Abinger&mdash;The floors and walls penetrated by
+worms&mdash;Subsidence of a modern pavement&mdash;The buried
+pavement at Beaulieu Abbey&mdash;Roman villas at Chedworth and
+Brading&mdash;The remains of the Roman town at
+Silchester&mdash;The nature of the débris by which the
+remains are covered&mdash;The penetration of the tesselated
+floors and walls by worms&mdash;Subsidence of the
+floors&mdash;Thickness of the mould&mdash;The old Roman city of
+Wroxeter&mdash;Thickness of the mould&mdash;Depth of the
+foundations of some of the Buildings&mdash;Conclusion.</p>
+</td>
+<td><p style="text-align: right"><span class="indexpageno"><a
+href="#page164">164</a></span>&ndash;208</p>
+</td>
+</tr>
+<tr>
+<td colspan="2"><p style="text-align: center">CHAPTER V.<br />
+<span class="GutSmall">THE ACTION OF WORMS IN THE DENUDATION OF
+THE LAND.</span></p>
+</td>
+</tr>
+<tr>
+<td><p>Evidence of the amount of denudation which the land has
+undergone&mdash;Sub-aerial denudation&mdash;The deposition of
+dust&mdash;Vegetable mould, its dark colour and fine texture
+largely due to the action of worms&mdash;The disintegration of
+rocks by the humus-acids&mdash;Similar acids apparently generated
+within the bodies of worms&mdash;The action of these acids
+facilitated by the continued movement of the particles of
+earth&mdash;A thick bed of mould checks the disintegration of the
+underlying soil and rocks. Particles of stone worn or
+triturated in the gizzards of worms&mdash;Swallowed stones serve
+as mill-stones&mdash;The levigated state of the
+castings&mdash;Fragments of brick in the castings over ancient
+buildings well rounded. The triturating power of worms not
+quite insignificant under a geological point of view.</p>
+</td>
+<td><p style="text-align: right"><span class="indexpageno"><a
+href="#page209">209</a></span>&ndash;236</p>
+</td>
+</tr>
+<tr>
+<td colspan="2"><p style="text-align: center">CHAPTER VI.<br />
+<span class="GutSmall">THE DENUDATION OF THE
+LAND&mdash;</span><span
+class="GutSmall"><i>continued</i></span><span
+class="GutSmall">.</span></p>
+</td>
+</tr>
+<tr>
+<td><p>Denudation aided by recently ejected castings flowing down
+inclined grass-covered surfaces&mdash;The amount of earth which
+annually flows downwards&mdash;The effect of tropical rain on
+worm castings&mdash;The finest particles of earth washed
+completely away from castings&mdash;The disintegration of dried
+castings into pellets, and their rolling down inclined
+surfaces&mdash;The formation of little ledges on hill-sides, in
+part due to the accumulation of disintegrated
+castings&mdash;Castings blown to leeward over level land&mdash;An
+attempt to estimate the amount thus blown&mdash;The degradation
+of ancient encampments and tumuli&mdash;The preservation of the
+crowns and furrows on land anciently ploughed&mdash;The formation
+and amount of mould over the Chalk formation.</p>
+</td>
+<td><p style="text-align: right"><span class="indexpageno"><a
+href="#page237">237</a></span>&ndash;279</p>
+</td>
+</tr>
+<tr>
+<td colspan="2"><p style="text-align: center">CHAPTER VII.<br />
+<span class="GutSmall">CONCLUSION.</span></p>
+</td>
+</tr>
+<tr>
+<td><p>Summary of the part which worms have played in the history
+of the world&mdash;Their aid in the disintegration of
+rocks&mdash;In the denudation of the land&mdash;In the
+preservation of ancient remains&mdash;In the preparation of the
+soil for the growth of plants&mdash;Mental powers of
+worms&mdash;Conclusion.</p>
+</td>
+<td><p style="text-align: right"><span class="indexpageno"><a
+href="#page280">280</a></span>&ndash;288</p>
+</td>
+</tr>
+</table>
+<h2><a name="page1"></a><span class="pagenum">p.
+1</span>INTRODUCTION.</h2>
+<p><span class="smcap">The</span> share which worms have taken in
+the formation of the layer of vegetable mould, which covers the
+whole surface of the land in every moderately humid country, is
+the subject of the present volume. This mould is generally
+of a blackish colour and a few inches in thickness. In
+different districts it differs but little in appearance, although
+it may rest on various subsoils. The uniform fineness of
+the particles of which it is composed is one of its chief
+characteristic features; and this may be well observed in any
+gravelly country, where a recently-ploughed field immediately
+adjoins one which has long remained undisturbed for pasture, and
+where the vegetable mould is exposed on the sides of a ditch or
+hole. The subject may appear an insignificant one, but we
+shall see that it possesses some interest; and the maxim
+&ldquo;de minimis non curat lex,&rdquo; does not apply to
+science. Even Élie de Beaumont, who generally
+undervalues small agencies and their accumulated effects,
+remarks: <a name="citation2"></a><a href="#footnote2"
+class="citation">[2]</a> &ldquo;La couche très-mince de la
+terre végétale est un monument d&rsquo;une haute
+antiquité, et, par le fait de sa permanence, un objet
+digne d&rsquo;occuper le géologue, et capable de lui
+fournir des remarques intéressantes.&rdquo; Although
+the superficial layer of vegetable mould as a whole no doubt is
+of the highest antiquity, yet in regard to its permanence, we
+shall hereafter see reason to believe that its component
+particles are in most cases removed at not a very slow rate, and
+are replaced by others due to the disintegration of the
+underlying materials.</p>
+
+<p>As I was led to keep in my study during many months worms in
+pots filled with earth, I became interested in them, and wished
+to learn how far they acted consciously, and how much mental
+power they displayed. I was the more desirous to learn
+something on this head, as few observations of this kind have
+been made, as far as I know, on animals so low in the scale of
+organization and so poorly provided with sense-organs, as are
+earth-worms.</p>
+
+<p>In the year 1837, a short paper was read by me before the
+Geological Society of London, <a name="citation3"></a><a
+href="#footnote3" class="citation">[3]</a> &ldquo;On the
+Formation of Mould,&rdquo; in which it was shown that small
+fragments of burnt marl, cinders, &amp;c., which had been thickly
+strewed over the surface of several meadows, were found after a
+few years lying at the depth of some inches beneath the turf, but
+still forming a layer. This apparent sinking of superficial
+bodies is due, as was first suggested to me by Mr. Wedgwood of
+Maer Hall in Staffordshire, to the large quantity of fine earth
+continually brought up to the surface by worms in the form of
+castings. These castings are sooner or later spread out and
+cover up any object left on the surface. I was thus led to
+conclude that all the vegetable mould over the whole country has
+passed many times through, and will again pass many times
+through, the intestinal canals of worms. Hence the term
+&ldquo;animal mould&rdquo; would be in some respects more
+appropriate than that commonly used of &ldquo;vegetable
+mould.&rdquo;</p>
+
+<p>Ten years after the publication of my paper, M.
+D&rsquo;Archiac, evidently influenced by the doctrines of
+Élie de Beaumont, wrote about my &ldquo;singulière
+théorie,&rdquo; and objected that it could apply only to
+&ldquo;les prairies basses et humides;&rdquo; and that &ldquo;les
+terres labourées, les bois, les prairies
+élevées, n&rsquo;apportent aucune preuve à
+l&rsquo;appui de cette manière de voir.&rdquo; <a
+name="citation4a"></a><a href="#footnote4a"
+class="citation">[4a]</a> But M. D&rsquo;Archiac must have
+thus argued from inner consciousness and not from observation,
+for worms abound to an extraordinary degree in kitchen gardens
+where the soil is continually worked, though in such loose soil
+they generally deposit their castings in any open cavities or
+within their old burrows instead of on the surface. Hensen
+estimates that there are about twice as many worms in gardens as
+in corn-fields. <a name="citation4b"></a><a href="#footnote4b"
+class="citation">[4b]</a> With respect to &ldquo;prairies
+élevées,&rdquo; I do not know how it may be in
+France, but nowhere in England have I seen the ground so thickly
+covered with castings as on commons, at a height of several
+hundred feet above the sea. In woods again, if the loose
+leaves in autumn are removed, the whole surface will be found
+strewed with castings. Dr. King, the superintendent of the
+Botanic Garden in Calcutta, to whose kindness I am indebted for
+many observations on earth-worms, informs me that he found, near
+Nancy in France, the bottom of the State forests covered over
+many acres with a spongy layer, composed of dead leaves and
+innumerable worm-castings. He there heard the Professor of
+&ldquo;Aménagement des Forêts&rdquo; lecturing to
+his pupils, and pointing out this case as a &ldquo;beautiful
+example of the natural cultivation of the soil; for year after
+year the thrown-up castings cover the dead leaves; the result
+being a rich humus of great thickness.&rdquo;</p>
+
+<p>In the year 1869, Mr. Fish <a name="citation5"></a><a
+href="#footnote5" class="citation">[5]</a> rejected my
+conclusions with respect to the part which worms have played in
+the formation of vegetable mould, merely on account of their
+assumed incapacity to do so much work. He remarks that
+&ldquo;considering their weakness and their size, the work they
+are represented to have accomplished is stupendous.&rdquo;
+Here we have an instance of that inability to sum up the effects
+of a continually recurrent cause, which has often retarded the
+progress of science, as formerly in the case of geology, and more
+recently in that of the principle of evolution.</p>
+
+<p>Although these several objections seemed to me to have no
+weight, yet I resolved to make more observations of the same kind
+as those published, and to attack the problem on another side;
+namely, to weigh all the castings thrown up within a given time
+in a measured space, instead of ascertaining the rate at which
+objects left on the surface were buried by worms. But some
+of my observations have been rendered almost superfluous by an
+admirable paper by Hensen, already alluded to, which appeared in
+1877. <a name="citation6"></a><a href="#footnote6"
+class="citation">[6]</a> Before entering on details with
+respect to the castings, it will be advisable to give some
+account of the habits of worms from my own observations and from
+those of other naturalists.</p>
+
+<p>[<span class="smcap">First Edition</span>,<br />
+
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+<i>October</i> 10<i>th</i>, 1881.]</p>
+<h2><a name="page7"></a><span class="pagenum">p. 7</span>CHAPTER
+I.<br />
+<span class="GutSmall">HABITS OF WORMS.</span></h2>
+<p class="gutsumm">Nature of the sites inhabited&mdash;Can live
+long under water&mdash;Nocturnal&mdash;Wander about at
+night&mdash;Often lie close to the mouths of their burrows, and
+are thus destroyed in large numbers by
+birds&mdash;Structure&mdash;Do not possess eyes, but can
+distinguish between light and darkness&mdash;Retreat rapidly when
+brightly illuminated, not by a reflex action&mdash;Power of
+attention&mdash;Sensitive to heat and cold&mdash;Completely
+deaf&mdash;Sensitive to vibrations and to touch&mdash;Feeble
+power of smell&mdash;Taste&mdash;Mental qualities&mdash;Nature of
+food&mdash;Omnivorous&mdash;Digestion&mdash;Leaves before being
+swallowed, moistened with a fluid of the nature of the pancreatic
+secretion&mdash;Extra-stomachal digestion&mdash;Calciferous
+glands, structure of&mdash;Calcareous concretions formed in the
+anterior pair of glands&mdash;The calcareous matter primarily an
+excretion, but secondarily serves to neutralise the acids
+generated during the digestive process.</p>
+
+<p><span class="smcap">Earth-worms</span> are distributed
+throughout the world under the form of a few genera, which
+externally are closely similar to one another. The British
+species of Lumbricus have never been carefully monographed; but
+we may judge of their probable number from those inhabiting
+neighbouring countries. In Scandinavia there are eight
+species, according to Eisen; <a name="citation8a"></a><a
+href="#footnote8a" class="citation">[8a]</a> but two of these
+rarely burrow in the ground, and one inhabits very wet places or
+even lives under the water. We are here concerned only with
+the kinds which bring up earth to the surface in the form of
+castings. Hoffmeister says that the species in Germany are
+not well known, but gives the same number as Eisen, together with
+some strongly marked varieties. <a name="citation8b"></a><a
+href="#footnote8b" class="citation">[8b]</a></p>
+
+<p>Earth-worms abound in England in many different
+stations. Their castings may be seen in extraordinary
+numbers on commons and chalk-downs, so as almost to cover the
+whole surface, where the soil is poor and the grass short and
+thin. But they are almost or quite as numerous in some of
+the London parks, where the grass grows well and the soil appears
+rich. Even on the same field worms are much more frequent
+in some places than in others, without any visible difference in
+the nature of the soil. They abound in paved court-yards
+close to houses; and an instance will be given in which they had
+burrowed through the floor of a very damp cellar. I have
+seen worms in black peat in a boggy field; but they are extremely
+rare, or quite absent in the drier, brown, fibrous peat, which is
+so much valued by gardeners. On dry, sandy or gravelly
+tracks, where heath with some gorse, ferns, coarse grass, moss
+and lichens alone grow, hardly any worms can be found. But
+in many parts of England, wherever a path crosses a heath, its
+surface becomes covered with a fine short sward. Whether
+this change of vegetation is due to the taller plants being
+killed by the occasional trampling of man and animals, or to the
+soil being occasionally manured by the droppings from animals, I
+do not know. <a name="citation9b"></a><a href="#footnote9b"
+class="citation">[9b]</a> On such grassy paths
+worm-castings may often be seen. On a heath in Surrey,
+which was carefully examined, there were only a few castings on
+these paths, where they were much inclined; but on the more level
+parts, where a bed of fine earth had been washed down from the
+steeper parts and had accumulated to a thickness of a few inches,
+worm-castings abounded. These spots seemed to be
+overstocked with worms, so that they had been compelled to spread
+to a distance of a few feet from the grassy paths, and here their
+castings had been thrown up among the heath; but beyond this
+limit, not a single casting could be found. A layer, though
+a thin one, of fine earth, which probably long retains some
+moisture, is in all cases, as I believe, necessary for their
+existence; and the mere compression of the soil appears to be in
+some degree favourable to them, for they often abound in old
+gravel walks, and in foot-paths across fields.</p>
+
+<p>Beneath large trees few castings can be found during certain
+seasons of the year, and this is apparently due to the moisture
+having been sucked out of the ground by the innumerable roots of
+the trees; for such places may be seen covered with castings
+after the heavy autumnal rains. Although most coppices and
+woods support many worms, yet in a forest of tall and ancient
+beech-trees in Knole Park, where the ground beneath was bare of
+all vegetation, not a single casting could be found over wide
+spaces, even during the autumn. Nevertheless, castings were
+abundant on some grass-covered glades and indentations which
+penetrated this forest. On the mountains of North Wales and
+on the Alps, worms, as I have been informed, are in most places
+rare; and this may perhaps be due to the close proximity of the
+subjacent rocks, into which worms cannot burrow during the winter
+so as to escape being frozen. Dr. McIntosh, however, found
+worm-castings at a height of 1500 feet on Schiehallion in
+Scotland. They are numerous on some hills near Turin at
+from 2000 to 3000 feet above the sea, and at a great altitude on
+the Nilgiri Mountains in South India and on the Himalaya.</p>
+
+<p>Earth-worms must be considered as terrestrial animals, though
+they are still in one sense semi-aquatic, like the other members
+of the great class of annelids to which they belong. M.
+Perrier found that their exposure to the dry air of a room for
+only a single night was fatal to them. On the other hand he
+kept several large worms alive for nearly four months, completely
+submerged in water. <a name="citation11"></a><a
+href="#footnote11" class="citation">[11]</a> During the
+summer when the ground is dry, they penetrate to a considerable
+depth and cease to work, as they do during the winter when the
+ground is frozen. Worms are nocturnal in their habits, and
+at night may be seen crawling about in large numbers, but usually
+with their tails still inserted in their burrows. By the
+expansion of this part of their bodies, and with the help of the
+short, slightly reflexed bristles, with which their bodies are
+armed, they hold so fast that they can seldom be dragged out of
+the ground without being torn into pieces. <a
+name="citation12"></a><a href="#footnote12"
+class="citation">[12]</a> During the day they remain in
+their burrows, except at the pairing season, when those which
+inhabit adjoining burrows expose the greater part of their bodies
+for an hour or two in the early morning. Sick individuals,
+which are generally affected by the parasitic larvæ of a
+fly, must also be excepted, as they wander about during the day
+and die on the surface. After heavy rain succeeding dry
+weather, an astonishing number of dead worms may sometimes be
+seen lying on the ground. Mr. Galton informs me that on one
+such occasion (March, 1881), the dead worms averaged one for
+every two and a half paces in length on a walk in Hyde Park, four
+paces in width. He counted no less than 45 dead worms in
+one place in a length of sixteen paces. From the facts
+above given, it is not probable that these worms could have been
+drowned, and if they had been drowned they would have perished in
+their burrows. I believe that they were already sick, and
+that their deaths were merely hastened by the ground being
+flooded.</p>
+
+<p>It has often been said that under ordinary circumstances
+healthy worms never, or very rarely, completely leave their
+burrows at night; but this is an error, as White of Selborne long
+ago knew. In the morning, after there has been heavy rain,
+the film of mud or of very fine sand over gravel-walks is often
+plainly marked with their tracks. I have noticed this from
+August to May, both months included, and it probably occurs
+during the two remaining months of the year when they are
+wet. On these occasions, very few dead worms could anywhere
+be seen. On January 31, 1881, after a long-continued and
+unusually severe frost with much snow, as soon as a thaw set in,
+the walks were marked with innumerable tracks. On one
+occasion, five tracks were counted crossing a space of only an
+inch square. They could sometimes be traced either to or
+from the mouths of the burrows in the gravel-walks, for distances
+between 2 or 3 up to 15 yards. I have never seen two tracks
+leading to the same burrow; nor is it likely, from what we shall
+presently see of their sense-organs, that a worm could find its
+way back to its burrow after having once left it. They
+apparently leave their burrows on a voyage of discovery, and thus
+they find new sites to inhabit.</p>
+
+<p>Morren states <a name="citation14"></a><a href="#footnote14"
+class="citation">[14]</a> that worms often lie for hours almost
+motionless close beneath the mouths of their burrows. I
+have occasionally noticed the same fact with worms kept in pots
+in the house; so that by looking down into their burrows, their
+heads could just be seen. If the ejected earth or rubbish
+over the burrows be suddenly removed, the end of the worm&rsquo;s
+body may very often be seen rapidly retreating. This habit
+of lying near the surface leads to their destruction to an
+immense extent. Every morning during certain seasons of the
+year, the thrushes and blackbirds on all the lawns throughout the
+country draw out of their holes an astonishing number of worms,
+and this they could not do, unless they lay close to the
+surface. It is not probable that worms behave in this
+manner for the sake of breathing fresh air, for we have seen that
+they can live for a long time under water. I believe that
+they lie near the surface for the sake of warmth, especially in
+the morning; and we shall hereafter find that they often coat the
+mouths of their burrows with leaves, apparently to prevent their
+bodies from coming into close contact with the cold damp
+earth. It is said that they completely close their burrows
+during the winter.</p>
+
+<p><i>Structure</i>.&mdash;A few remarks must be made on this
+subject. The body of a large worm consists of from 100 to
+200 almost cylindrical rings or segments, each furnished with
+minute bristles. The muscular system is well
+developed. Worms can crawl backwards as well as forwards,
+and by the aid of their affixed tails can retreat with
+extraordinary rapidity into their burrows. The mouth is
+situated at the anterior end of the body, and is provided with a
+little projection (lobe or lip, as it has been variously called)
+which is used for prehension. Internally, behind the mouth,
+there is a strong pharynx, shown in the accompanying diagram
+(Fig. 1) which is pushed forwards when the animal eats, and this
+part corresponds, according to Perrier, with the protrudable
+trunk or proboscis of other annelids. The pharynx leads
+into the œsophagus, on each side of which in the lower part
+there are three pairs of large glands, which secrete a surprising
+amount of carbonate of lime. These calciferous glands are
+highly remarkable, for nothing like them is known in any other
+animal. Their use will be discussed when we treat of the
+digestive process. In most of the species, the
+œsophagus is enlarged into a crop in front of the
+gizzard. This latter organ is lined with a smooth thick
+chitinous membrane, and is surrounded by weak longitudinal, but
+powerful transverse muscles. Perrier saw these muscles in
+energetic action; and, as he remarks, the trituration of the food
+must be chiefly effected by this organ, for worms possess no jaws
+or teeth of any kind. Grains of sand and small stones, from
+the 1/20 to a little more than the 1/10 inch in diameter, may
+generally be found in their gizzards and intestines. As it
+is certain that worms swallow many little stones, independently
+of those swallowed while excavating their burrows, it is probable
+that they serve, like mill-stones, to triturate their food.
+The gizzard opens into the intestine, which runs in a straight
+course to the vent at the posterior end of the body. The
+intestine presents a remarkable structure, the typhlosolis, or,
+as the old anatomists called it, an intestine within an
+intestine; and Claparède <a name="citation17"></a><a
+href="#footnote17" class="citation">[17]</a> has shown that this
+consists of a deep longitudinal involution of the walls of the
+intestine, by which means an extensive absorbent surface is
+gained.</p>
+<p style="text-align: center">
+<a href="images/p17b.jpg">
+<img alt=
+"Fig. 1: Diagram of the alimentary canal of an earth-worm.  Fig.
+2: Tower-like casting from near Nice"
+title=
+"Fig. 1: Diagram of the alimentary canal of an earth-worm.  Fig.
+2: Tower-like casting from near Nice"
+ src="images/p17s.jpg" />
+</a></p>
+
+<p>The circulatory system is well developed. Worms breathe
+by their skin, as they do not possess any special respiratory
+organs. The two sexes are united in the same individual,
+but two individuals pair together. The nervous system is
+fairly well developed; and the two almost confluent cerebral
+ganglia are situated very near to the anterior end of the
+body.</p>
+
+<p><i>Senses</i>.&mdash;Worms are destitute of eyes, and at first
+I thought that they were quite insensible to light; for those
+kept in confinement were repeatedly observed by the aid of a
+candle, and others out of doors by the aid of a lantern, yet they
+were rarely alarmed, although extremely timid animals.
+Other persons have found no difficulty in observing worms at
+night by the same means. <a name="citation18a"></a><a
+href="#footnote18a" class="citation">[18a]</a></p>
+
+<p>Hoffmeister, however, states <a name="citation18b"></a><a
+href="#footnote18b" class="citation">[18b]</a> that worms, with
+the exception of a few individuals, are extremely sensitive to
+light; but he admits that in most cases a certain time is
+requisite for its action. These statements led me to watch
+on many successive nights worms kept in pots, which were
+protected from currents of air by means of glass plates.
+The pots were approached very gently, in order that no vibration
+of the floor should be caused. When under these
+circumstances worms were illuminated by a bull&rsquo;s-eye
+lantern having slides of dark red and blue glass, which
+intercepted so much light that they could be seen only with some
+difficulty, they were not at all affected by this amount of
+light, however long they were exposed to it. The light, as
+far as I could judge, was brighter than that from the full
+moon. Its colour apparently made no difference in the
+result. When they were illuminated by a candle, or even by
+a bright paraffin lamp, they were not usually affected at
+first. Nor were they when the light was alternately
+admitted and shut off. Sometimes, however, they behaved
+very differently, for as soon as the light fell on them, they
+withdrew into their burrows with almost instantaneous
+rapidity. This occurred perhaps once out of a dozen
+times. When they did not withdraw instantly, they often
+raised the anterior tapering ends of their bodies from the
+ground, as if their attention was aroused or as if surprise was
+felt; or they moved their bodies from side to side as if feeling
+for some object. They appeared distressed by the light; but
+I doubt whether this was really the case, for on two occasions
+after withdrawing slowly, they remained for a long time with
+their anterior extremities protruding a little from the mouths of
+their burrows, in which position they were ready for instant and
+complete withdrawal.</p>
+
+<p>When the light from a candle was concentrated by means of a
+large lens on the anterior extremity, they generally withdrew
+instantly; but this concentrated light failed to act perhaps once
+out of half a dozen trials. The light was on one occasion
+concentrated on a worm lying beneath water in a saucer, and it
+instantly withdrew into its burrow. In all cases the
+duration of the light, unless extremely feeble, made a great
+difference in the result; for worms left exposed before a
+paraffin lamp or a candle invariably retreated into their burrows
+within from five to fifteen minutes; and if in the evening the
+pots were illuminated before the worms had come out of their
+burrows, they failed to appear.</p>
+
+<p>From the foregoing facts it is evident that light affects
+worms by its intensity and by its duration. It is only the
+anterior extremity of the body, where the cerebral ganglia lie,
+which is affected by light, as Hoffmeister asserts, and as I
+observed on many occasions. If this part is shaded, other
+parts of the body may be fully illuminated, and no effect will be
+produced. As these animals have no eyes, we must suppose
+that the light passes through their skins, and in some manner
+excites their cerebral ganglia. It appeared at first
+probable that the different manner in which they were affected on
+different occasions might be explained, either by the degree of
+extension of their skin and its consequent transparency, or by
+some particular incident of the light; but I could discover no
+such relation. One thing was manifest, namely, that when
+worms were employed in dragging leaves into their burrows or in
+eating them, and even during the short intervals whilst they
+rested from their work, they either did not perceive the light or
+were regardless of it; and this occurred even when the light was
+concentrated on them through a large lens. So, again,
+whilst they are paired, they will remain for an hour or two out
+of their burrows, fully exposed to the morning light; but it
+appears from what Hoffmeister says that a light will occasionally
+cause paired individuals to separate.</p>
+
+<p>When a worm is suddenly illuminated and dashes like a rabbit
+into its burrow&mdash;to use the expression employed by a
+friend&mdash;we are at first led to look at the action as a
+reflex one. The irritation of the cerebral ganglia appears
+to cause certain muscles to contract in an inevitable manner,
+independently of the will or consciousness of the animal, as if
+it were an automaton. But the different effect which a
+light produced on different occasions, and especially the fact
+that a worm when in any way employed and in the intervals of such
+employment, whatever set of muscles and ganglia may then have
+been brought into play, is often regardless of light, are opposed
+to the view of the sudden withdrawal being a simple reflex
+action. With the higher animals, when close attention to
+some object leads to the disregard of the impressions which other
+objects must be producing on them, we attribute this to their
+attention being then absorbed; and attention implies the presence
+of a mind. Every sportsman knows that he can approach
+animals whilst they are grazing, fighting or courting, much more
+easily than at other times. The state, also, of the nervous
+system of the higher animals differs much at different times, for
+instance, a horse is much more readily startled at one time than
+at another. The comparison here implied between the actions
+of one of the higher animals and of one so low in the scale as an
+earth-worm, may appear far-fetched; for we thus attribute to the
+worm attention and some mental power, nevertheless I can see no
+reason to doubt the justice of the comparison.</p>
+
+<p>Although worms cannot be said to possess the power of vision,
+their sensitiveness to light enables them to distinguish between
+day and night; and they thus escape extreme danger from the many
+diurnal animals which prey on them. Their withdrawal into
+their burrows during the day appears, however, to have become an
+habitual action; for worms kept in pots covered by glass plates,
+over which sheets of black paper were spread, and placed before a
+north-east window, remained during the day-time in their burrows
+and came out every night; and they continued thus to act for a
+week. No doubt a little light may have entered between the
+sheets of glass and the blackened paper; but we know from the
+trials with coloured glass, that worms are indifferent to a small
+amount of light.</p>
+
+<p>Worms appear to be less sensitive to moderate radiant heat
+than to a bright light. I judge of this from having held at
+different times a poker heated to dull redness near some worms,
+at a distance which caused a very sensible degree of warmth in my
+hand. One of them took no notice; a second withdrew into
+its burrow, but not quickly; the third and fourth much more
+quickly, and the fifth as quickly as possible. The light
+from a candle, concentrated by a lens and passing through a sheet
+of glass which would intercept most of the heat-rays, generally
+caused a much more rapid retreat than did the heated poker.
+Worms are sensitive to a low temperature, as may be inferred from
+their not coming out of their burrows during a frost.</p>
+
+<p>Worms do not possess any sense of hearing. They took not
+the least notice of the shrill notes from a metal whistle, which
+was repeatedly sounded near them; nor did they of the deepest and
+loudest tones of a bassoon. They were indifferent to
+shouts, if care was taken that the breath did not strike
+them. When placed on a table close to the keys of a piano,
+which was played as loudly as possible, they remained perfectly
+quiet.</p>
+
+<p>Although they are indifferent to undulations in the air
+audible by us, they are extremely sensitive to vibrations in any
+solid object. When the pots containing two worms which had
+remained quite indifferent to the sound of the piano, were placed
+on this instrument, and the note C in the bass clef was struck,
+both instantly retreated into their burrows. After a time
+they emerged, and when G above the line in the treble clef was
+struck they again retreated. Under similar circumstances on
+another night one worm dashed into its burrow on a very high note
+being struck only once, and the other worm when C in the treble
+clef was struck. On these occasions the worms were not
+touching the sides of the pots, which stood in saucers; so that
+the vibrations, before reaching their bodies, had to pass from
+the sounding board of the piano, through the saucer, the bottom
+of the pot and the damp, not very compact earth on which they lay
+with their tails in their burrows. They often showed their
+sensitiveness when the pot in which they lived, or the table on
+which the pot stood, was accidentally and lightly struck; but
+they appeared less sensitive to such jars than to the vibrations
+of the piano; and their sensitiveness to jars varied much at
+different times.</p>
+
+<p>It has often been said that if the ground is beaten or
+otherwise made to tremble, worms believe that they are pursued by
+a mole and leave their burrows. From one account that I
+have received, I have no doubt that this is often the case; but a
+gentleman informs me that he lately saw eight or ten worms leave
+their burrows and crawl about the grass on some boggy land on
+which two men had just trampled while setting a trap; and this
+occurred in a part of Ireland where there were no moles. I
+have been assured by a Volunteer that he has often seen many
+large earth-worms crawling quickly about the grass, a few minutes
+after his company had fired a volley with blank cartridges.
+The Peewit (<i>Tringa vanellus</i>, Linn.) seems to know
+instinctively that worms will emerge if the ground is made to
+tremble; for Bishop Stanley states (as I hear from Mr. Moorhouse)
+that a young peewit kept in confinement used to stand on one leg
+and beat the turf with the other leg until the worms crawled out
+of their burrows, when they were instantly devoured.
+Nevertheless, worms do not invariably leave their burrows when
+the ground is made to tremble, as I know by having beaten it with
+a spade, but perhaps it was beaten too violently.</p>
+
+<p>The whole body of a worm is sensitive to contact. A
+slight puff of air from the mouth causes an instant
+retreat. The glass plates placed over the pots did not fit
+closely, and blowing through the very narrow chinks thus left,
+often sufficed to cause a rapid retreat. They sometimes
+perceived the eddies in the air caused by quickly removing the
+glass plates. When a worm first comes out of its burrow, it
+generally moves the much extended anterior extremity of its body
+from side to side in all directions, apparently as an organ of
+touch; and there is some reason to believe, as we shall see in
+the next chapter, that they are thus enabled to gain a general
+notion of the form of an object. Of all their senses that
+of touch, including in this term the perception of a vibration,
+seems much the most highly developed.</p>
+
+<p>In worms the sense of smell apparently is confined to the
+perception of certain odours, and is feeble. They were
+quite indifferent to my breath, as long as I breathed on them
+very gently. This was tried, because it appeared possible
+that they might thus be warned of the approach of an enemy.
+They exhibited the same indifference to my breath whilst I chewed
+some tobacco, and while a pellet of cotton-wool with a few drops
+of millefleurs perfume or of acetic acid was kept in my
+mouth. Pellets of cotton-wool soaked in tobacco juice, in
+millefleurs perfume, and in paraffin, were held with pincers and
+were waved about within two or three inches of several worms, but
+they took no notice. On one or two occasions, however, when
+acetic acid had been placed on the pellets, the worms appeared a
+little uneasy, and this was probably due to the irritation of
+their skins. The perception of such unnatural odours would
+be of no service to worms; and as such timid creatures would
+almost certainly exhibit some signs of any new impression, we may
+conclude that they did not perceive these odours.</p>
+
+<p>The result was different when cabbage-leaves and pieces of
+onion were employed, both of which are devoured with much relish
+by worms. Small square pieces of fresh and half-decayed
+cabbage-leaves and of onion bulbs were on nine occasions buried
+in my pots, beneath about &frac14; of an inch of common garden
+soil; and they were always discovered by the worms. One bit
+of cabbage was discovered and removed in the course of two hours;
+three were removed by the next morning, that is, after a single
+night; two others after two nights; and the seventh bit after
+three nights. Two pieces of onion were discovered and
+removed after three nights. Bits of fresh raw meat, of
+which worms are very fond, were buried, and were not discovered
+within forty-eight hours, during which time they had not become
+putrid. The earth above the various buried objects was
+generally pressed down only slightly, so as not to prevent the
+emission of any odour. On two occasions, however, the
+surface was well watered, and was thus rendered somewhat
+compact. After the bits of cabbage and onion had been
+removed, I looked beneath them to see whether the worms had
+accidentally come up from below, but there was no sign of a
+burrow; and twice the buried objects were laid on pieces of
+tin-foil which were not in the least displaced. It is of
+course possible that the worms whilst moving about on the surface
+of the ground, with their tails affixed within their burrows, may
+have poked their heads into the places where the above objects
+were buried; but I have never seen worms acting in this
+manner. Some pieces of cabbage-leaf and of onion were twice
+buried beneath very fine ferruginous sand, which was slightly
+pressed down and well watered, so as to be rendered very compact,
+and these pieces were never discovered. On a third occasion
+the same kind of sand was neither pressed down nor watered, and
+the pieces of cabbage were discovered and removed after the
+second night. These several facts indicate that worms
+possess some power of smell; and that they discover by this means
+odoriferous and much-coveted kinds of food.</p>
+
+<p>It may be presumed that all animals which feed on various
+substances possess the sense of taste, and this is certainly the
+case with worms. Cabbage-leaves are much liked by worms;
+and it appears that they can distinguish between different
+varieties; but this may perhaps be owing to differences in their
+texture. On eleven occasions pieces of the fresh leaves of
+a common green variety and of the red variety used for pickling
+were given them, and they preferred the green, the red being
+either wholly neglected or much less gnawed. On two other
+occasions, however, they seemed to prefer the red.
+Half-decayed leaves of the red variety and fresh leaves of the
+green were attacked about equally. When leaves of the
+cabbage, horse-radish (a favourite food) and of the onion were
+given together, the latter were always, and manifestly
+preferred. Leaves of the cabbage, lime-tree, Ampelopsis,
+parsnip (Pastinaca), and celery (Apium) were likewise given
+together; and those of the celery were first eaten. But
+when leaves of cabbage, turnip, beet, celery, wild cherry and
+carrots were given together, the two latter kinds, especially
+those of the carrot, were preferred to all the others, including
+those of celery. It was also manifest after many trials
+that wild cherry leaves were greatly preferred to those of the
+lime-tree and hazel (Corylus). According to Mr. Bridgman
+the half-decayed leaves of <i>Phlox verna</i> are particularly
+liked by worms. <a name="citation31"></a><a href="#footnote31"
+class="citation">[31]</a></p>
+
+<p>Pieces of the leaves of cabbage, turnip, horse-radish and
+onion were left on the pots during 22 days, and were all attacked
+and had to be renewed; but during the whole of this time leaves
+of an Artemisia and of the culinary sage, thyme and mint, mingled
+with the above leaves, were quite neglected excepting those of
+the mint, which were occasionally and very slightly
+nibbled. These latter four kinds of leaves do not differ in
+texture in a manner which could make them disagreeable to worms;
+they all have a strong taste, but so have the four first
+mentioned kinds of leaves; and the wide difference in the result
+must be attributed to a preference by the worms for one taste
+over another.</p>
+
+<p><i>Mental Qualities</i>.&mdash;There is little to be said on
+this head. We have seen that worms are timid. It may
+be doubted whether they suffer as much pain when injured, as they
+seem to express by their contortions. Judging by their
+eagerness for certain kinds of food, they must enjoy the pleasure
+of eating. Their sexual passion is strong enough to
+overcome for a time their dread of light. They perhaps have
+a trace of social feeling, for they are not disturbed by crawling
+over each other&rsquo;s bodies, and they sometimes lie in
+contact. According to Hoffmeister they pass the winter
+either singly or rolled up with others into a ball at the bottom
+of their burrows. <a name="citation32"></a><a href="#footnote32"
+class="citation">[32]</a> Although worms are so remarkably
+deficient in the several sense-organs, this does not necessarily
+preclude intelligence, as we know from such cases as those of
+Laura Bridgman; and we have seen that when their attention is
+engaged, they neglect impressions to which they would otherwise
+have attended; and attention indicates the presence of a mind of
+some kind. They are also much more easily excited at
+certain times than at others. They perform a few actions
+instinctively, that is, all the individuals, including the young,
+perform such actions in nearly the same fashion. This is
+shown by the manner in which the species of Perichæta eject
+their castings, so as to construct towers; also by the manner in
+which the burrows of the common earth-worm are smoothly lined
+with fine earth and often with little stones, and the mouths of
+their burrows with leaves. One of their strongest instincts
+is the plugging up the mouths of their burrows with various
+objects; and very young worms act in this manner. But some
+degree of intelligence appears, as we shall see in the next
+chapter, to be exhibited in this work,&mdash;a result which has
+surprised me more than anything else in regard to worms.</p>
+
+<p><i>Food and Digestion</i>.&mdash;Worms are omnivorous.
+They swallow an enormous quantity of earth, out of which they
+extract any digestible matter which it may contain; but to this
+subject I must recur. They also consume a large number of
+half-decayed leaves of all kinds, excepting a few which have an
+unpleasant taste or are too tough for them; likewise petioles,
+peduncles, and decayed flowers. But they will also consume
+fresh leaves, as I have found by repeated trials. According
+to Morren <a name="citation33"></a><a href="#footnote33"
+class="citation">[33]</a> they will eat particles of sugar and
+liquorice; and the worms which I kept drew many bits of dry
+starch into their burrows, and a large bit had its angles well
+rounded by the fluid poured out of their mouths. But as
+they often drag particles of soft stone, such as of chalk, into
+their burrows, I feel some doubt whether the starch was used as
+food. Pieces of raw and roasted meat were fixed several
+times by long pins to the surface of the soil in my pots, and
+night after night the worms could be seen tugging at them, with
+the edges of the pieces engulfed in their mouths, so that much
+was consumed. Raw fat seems to be preferred even to raw
+meat or to any other substance which was given them, and much was
+consumed. They are cannibals, for the two halves of a dead
+worm placed in two of the pots were dragged into the burrows and
+gnawed; but as far as I could judge, they prefer fresh to putrid
+meat, and in so far I differ from Hoffmeister.</p>
+
+<p>Léon Fredericq states <a name="citation34"></a><a
+href="#footnote34" class="citation">[34]</a> that the digestive
+fluid of worms is of the same nature as the pancreatic secretion
+of the higher animals; and this conclusion agrees perfectly with
+the kinds of food which worms consume. Pancreatic juice
+emulsifies fat, and we have just seen how greedily worms devour
+fat; it dissolves fibrin, and worms eat raw meat; it converts
+starch into grape-sugar with wonderful rapidity, and we shall
+presently show that the digestive fluid of worms acts on starch.
+<a name="citation35a"></a><a href="#footnote35a"
+class="citation">[35a]</a> But they live chiefly on
+half-decayed leaves; and these would be useless to them unless
+they could digest the cellulose forming the cell-walls; for it is
+well known that all other nutritious substances are almost
+completely withdrawn from leaves, shortly before they fall
+off. It has, however, now been ascertained that some forms
+of cellulose, though very little or not at all attacked by the
+gastric secretion of the higher animals, are acted on by that
+from the pancreas. <a name="citation35b"></a><a
+href="#footnote35b" class="citation">[35b]</a></p>
+
+<p>The half-decayed or fresh leaves which worms intend to devour,
+are dragged into the mouths of their burrows to a depth of from
+one to three inches, and are then moistened with a secreted
+fluid. It has been assumed that this fluid serves to hasten
+their decay; but a large number of leaves were twice pulled out
+of the burrows of worms and kept for many weeks in a very moist
+atmosphere under a bell-glass in my study; and the parts which
+had been moistened by the worms did not decay more quickly in any
+plain manner than the other parts. When fresh leaves were
+given in the evening to worms kept in confinement and examined
+early on the next morning, therefore not many hours after they
+had been dragged into the burrows, the fluid with which they were
+moistened, when tested with neutral litmus paper, showed an
+alkaline reaction. This was repeatedly found to be the case
+with celery, cabbage and turnip leaves. Parts of the same
+leaves which had not been moistened by the worms, were pounded
+with a few drops of distilled water, and the juice thus extracted
+was not alkaline. Some leaves, however, which had been
+drawn into burrows out of doors, at an unknown antecedent period,
+were tried, and though still moist, they rarely exhibited even a
+trace of alkaline reaction.</p>
+
+<p>The fluid, with which the leaves are bathed, acts on them
+whilst they are fresh or nearly fresh, in a remarkable manner;
+for it quickly kills and discolours them. Thus the ends of
+a fresh carrot-leaf, which had been dragged into a burrow, were
+found after twelve hours of a dark brown tint. Leaves of
+celery, turnip, maple, elm, lime, thin leaves of ivy, and,
+occasionally those of the cabbage were similarly acted on.
+The end of a leaf of <i>Triticum repens</i>, still attached to a
+growing plant, had been drawn into a burrow, and this part was
+dark brown and dead, whilst the rest of the leaf was fresh and
+green. Several leaves of lime and elm removed from burrows
+out of doors were found affected in different degrees. The
+first change appears to be that the veins become of a dull
+reddish-orange. The cells with chlorophyll next lose more
+or less completely their green colour, and their contents finally
+become brown. The parts thus affected often appeared almost
+black by reflected light; but when viewed as a transparent object
+under the microscope, minute specks of light were transmitted,
+and this was not the case with the unaffected parts of the same
+leaves. These effects, however, merely show that the
+secreted fluid is highly injurious or poisonous to leaves; for
+nearly the same effects were produced in from one to two days on
+various kinds of young leaves, not only by artificial pancreatic
+fluid, prepared with or without thymol, but quickly by a solution
+of thymol by itself. On one occasion leaves of Corylus were
+much discoloured by being kept for eighteen hours in pancreatic
+fluid, without any thymol. With young and tender leaves
+immersion in human saliva during rather warm weather, acted in
+the same manner as the pancreatic fluid, but not so
+quickly. The leaves in all these cases often became
+infiltrated with the fluid.</p>
+
+<p>Large leaves from an ivy plant growing on a wall were so tough
+that they could not be gnawed by worms, but after four days they
+were affected in a peculiar manner by the secretion poured out of
+their mouths. The upper surfaces of the leaves, over which
+the worms had crawled, as was shown by the dirt left on them,
+were marked in sinuous lines, by either a continuous or broken
+chain of whitish and often star-shaped dots, about 2 mm. in
+diameter. The appearance thus presented was curiously like
+that of a leaf, into which the larva of some minute insect had
+burrowed. But my son Francis, after making and examining
+sections, could nowhere find that the cell-walls had been broken
+down or that the epidermis had been penetrated. When the
+section passed through the whitish dots, the grains of
+chlorophyll were seen to be more or less discoloured, and some of
+the palisade and mesophyll cells contained nothing but broken
+down granular matter. These effects must be attributed to
+the transudation of the secretion through the epidermis into the
+cells.</p>
+
+<p>The secretion with which worms moisten leaves likewise acts on
+the starch-granules within the cells. My son examined some
+leaves of the ash and many of the lime, which had fallen off the
+trees and had been partly dragged into worm-burrows. It is
+known that with fallen leaves the starch-grains are preserved in
+the guard-cells of the stomata. Now in several cases the
+starch had partially or wholly disappeared from these cells, in
+the parts which had been moistened by the secretion; while it was
+still well preserved in the other parts of the same leaves.
+Sometimes the starch was dissolved out of only one of the two
+guard-cells. The nucleus in one case had disappeared,
+together with the starch-granules. The mere burying of
+lime-leaves in damp earth for nine days did not cause the
+destruction of the starch-granules. On the other hand, the
+immersion of fresh lime and cherry leaves for eighteen hours in
+artificial pancreatic fluid, led to the dissolution of the
+starch-granules in the guard-cells as well as in the other
+cells.</p>
+
+<p>From the secretion with which the leaves are moistened being
+alkaline, and from its acting both on the starch-granules and on
+the protoplasmic contents of the cells, we may infer that it
+resembles in nature not saliva, <a name="citation40"></a><a
+href="#footnote40" class="citation">[40]</a> but pancreatic
+secretion; and we know from Fredericq that a secretion of this
+kind is found in the intestines of worms. As the leaves
+which are dragged into the burrows are often dry and shrivelled,
+it is indispensable for their disintegration by the unarmed
+mouths of worms that they should first be moistened and softened;
+and fresh leaves, however soft and tender they may be, are
+similarly treated, probably from habit. The result is that
+they are partially digested before they are taken into the
+alimentary canal. I am not aware of any other case of
+extra-stomachal digestion having been recorded. The
+boa-constrictor is said to bathe its prey with saliva, but this
+is doubtful; and it is done solely for the sake of lubricating
+its prey. Perhaps the nearest analogy may be found in such
+plants as Drosera and Dionæa; for here animal matter is
+digested and converted into peptone not within a stomach, but on
+the surfaces of the leaves.</p>
+
+<p><i>Calciferous Glands</i>.&mdash;These glands (see Fig. 1),
+judging from their size and from their rich supply of
+blood-vessels, must be of much importance to the animal.
+But almost as many theories have been advanced on their use as
+there have been observers. They consist of three pairs,
+which in the common earth-worm debouch into the alimentary canal
+in advance of the gizzard, but posteriorly to it in
+Urochæta and some other genera. <a
+name="citation41a"></a><a href="#footnote41a"
+class="citation">[41a]</a> The two posterior pairs are
+formed by lamellæ, which, according to Claparède,
+are diverticula from the œsophagus. <a
+name="citation41b"></a><a href="#footnote41b"
+class="citation">[41b]</a> These lamellæ are coated
+with a pulpy cellular layer, with the outer cells lying free in
+infinite numbers. If one of these glands is punctured and
+squeezed, a quantity of white pulpy matter exudes, consisting of
+these free cells. They are minute, and vary in diameter
+from 2 to 6 <i>&mu;</i>. They contain in their centres a
+little excessively fine granular matter; but they look so like
+oil globules that Claparède and others at first treated
+them with ether. This produces no effect; but they are
+quickly dissolved with effervescence in acetic acid, and when
+oxalate of ammonia is added to the solution a white precipitate
+is thrown down. We may therefore conclude that they contain
+carbonate of lime. If the cells are immersed in a very
+little acid, they become more transparent, look like ghosts, and
+are soon lost to view; but if much acid is added, they disappear
+instantly. After a very large number have been dissolved, a
+flocculent residue is left, which apparently consists of the
+delicate ruptured cell-walls. In the two posterior pairs of
+glands the carbonate of lime contained in the cells occasionally
+aggregates into small rhombic crystals or into concretions, which
+lie between the lamellæ; but I have seen only one case, and
+Claparède only a very few such cases.</p>
+
+<p>The two anterior glands differ a little in shape from the four
+posterior ones, by being more oval. They differ also
+conspicuously in generally containing several small, or two or
+three larger, or a single very large concretion of carbonate of
+lime, as much as 1&frac12; mm. in diameter. When a gland
+includes only a few very small concretions, or, as sometimes
+happens, none at all, it is easily overlooked. The large
+concretions are round or oval, and exteriorly almost
+smooth. One was found which filled up not only the whole
+gland, as is often the case, but its neck; so that it resembled
+an olive-oil flask in shape. These concretions when broken
+are seen to be more or less crystalline in structure. How
+they escape from the gland is a marvel; but that they do escape
+is certain, for they are often found in the gizzard, intestines,
+and in the castings of worms, both with those kept in confinement
+and those in a state of nature.</p>
+
+<p>Claparède says very little about the structure of the
+two anterior glands, and he supposes that the calcareous matter
+of which the concretions are formed is derived from the four
+posterior glands. But if an anterior gland which contains
+only small concretions is placed in acetic acid and afterwards
+dissected, or if sections are made of such a gland without being
+treated with acid, lamellæ like those in the posterior
+glands and coated with cellular matter could be plainly seen,
+together with a multitude of free calciferous cells readily
+soluble in acetic acid. When a gland is completely filled
+with a single large concretion, there are no free cells, as these
+have been all consumed in forming the concretion. But if
+such a concretion, or one of only moderately large size, is
+dissolved in acid, much membranous matter is left, which appears
+to consist of the remains of the formerly active
+lamellæ. After the formation and expulsion of a large
+concretion, new lamellæ must be developed in some
+manner. In one section made by my son, the process had
+apparently commenced, although the gland contained two rather
+large concretions, for near the walls several cylindrical and
+oval pipes were intersected, which were lined with cellular
+matter and were quite filled with free calciferous cells. A
+great enlargement in one direction of several oval pipes would
+give rise to the lamellæ.</p>
+
+<p>Besides the free calciferous cells in which no nucleus was
+visible, other and rather larger free cells were seen on three
+occasions; and these contained a distinct nucleus and
+nucleolus. They were only so far acted on by acetic acid
+that the nucleus was thus rendered more distinct. A very
+small concretion was removed from between two of the
+lamellæ within an anterior gland. It was imbedded in
+pulpy cellular matter, with many free calciferous cells, together
+with a multitude of the larger, free, nucleated cells, and these
+latter cells were not acted on by acetic acid, while the former
+were dissolved. From this and other such cases I am led to
+suspect that the calciferous cells are developed from the larger
+nucleated ones; but how this was effected was not
+ascertained.</p>
+
+<p>When an anterior gland contains several minute concretions,
+some of these are generally angular or crystalline in outline,
+while the greater number are rounded with an irregular
+mulberry-like surface. Calciferous cells adhered to many
+parts of these mulberry-like masses, and their gradual
+disappearance could be traced while they still remained
+attached. It was thus evident that the concretions are
+formed from the lime contained within the free calciferous
+cells. As the smaller concretions increase in size, they
+come into contact and unite, thus enclosing the now functionless
+lamellæ; and by such steps the formation of the largest
+concretions could be followed. Why the process regularly
+takes place in the two anterior glands, and only rarely in the
+four posterior glands, is quite unknown. Morren says that
+these glands disappear during the winter; and I have seen some
+instances of this fact, and others in which either the anterior
+or posterior glands were at this season so shrunk and empty, that
+they could be distinguished only with much difficulty.</p>
+
+<p>With respect to the function of the calciferous glands, it is
+probable that they primarily serve as organs of excretion, and
+secondarily as an aid to digestion. Worms consume many
+fallen leaves; and it is known that lime goes on accumulating in
+leaves until they drop off the parent-plant, instead of being
+re-absorbed into the stem or roots, like various other organic
+and inorganic substances. <a name="citation46"></a><a
+href="#footnote46" class="citation">[46]</a> The ashes of a
+leaf of an acacia have been known to contain as much as 72 per
+cent. of lime. Worms therefore would be liable to become
+charged with this earth, unless there were some special means for
+its excretion; and the calciferous glands are well adapted for
+this purpose. The worms which live in mould close over the
+chalk, often have their intestines filled with this substance,
+and their castings are almost white. Here it is evident
+that the supply of calcareous matter must be
+super-abundant. Nevertheless with several worms collected
+on such a site, the calciferous glands contained as many free
+calciferous cells, and fully as many and large concretions, as
+did the glands of worms which lived where there was little or no
+lime; and this indicates that the lime is an excretion, and not a
+secretion poured into the alimentary canal for some special
+purpose.</p>
+
+<p>On the other hand, the following considerations render it
+highly probable that the carbonate of lime, which is excreted by
+the glands, aids the digestive process under ordinary
+circumstances. Leaves during their decay generate an
+abundance of various kinds of acids, which have been grouped
+together under the term of humus acids. We shall have to
+recur to this subject in our fifth chapter, and I need here only
+say that these acids act strongly on carbonate of lime. The
+half-decayed leaves which are swallowed in such large quantities
+by worms would, therefore, after they have been moistened and
+triturated in the alimentary canal, be apt to produce such
+acids. And in the case of several worms, the contents of
+the alimentary canal were found to be plainly acid, as shown by
+litmus paper. This acidity cannot be attributed to the
+nature of the digestive fluid, for pancreatic fluid is alkaline;
+and we have seen that the secretion which is poured out of the
+mouths of worms for the sake of preparing the leaves for
+consumption, is likewise alkaline. The acidity can hardly
+be due to uric acid, as the contents of the upper part of the
+intestine were often acid. In one case the contents of the
+gizzard were slightly acid, those of the upper intestines being
+more plainly acid. In another case the contents of the
+pharynx were not acid, those of the gizzard doubtfully so, while
+those of the intestine were distinctly acid at a distance of 5
+cm. below the gizzard. Even with the higher herbivorous and
+omnivorous animals, the contents of the large intestine are
+acid. &ldquo;This, however, is not caused by any acid
+secretion from the mucous membrane; the reaction of the
+intestinal walls in the larger as in the small intestine is
+alkaline. It must therefore arise from acid fermentations
+going on in the contents themselves . . . In Carnivora the
+contents of the coecum are said to be alkaline, and naturally the
+amount of fermentation will depend largely on the nature of the
+food.&rdquo; <a name="citation49"></a><a href="#footnote49"
+class="citation">[49]</a></p>
+
+<p>With worms not only the contents of the intestines, but their
+ejected matter or the castings, are generally acid. Thirty
+castings from different places were tested, and with three or
+four exceptions were found to be acid; and the exceptions may
+have been due to such castings not having been recently ejected;
+for some which were at first acid, were on the following morning,
+after being dried and again moistened, no longer acid; and this
+probably resulted from the humus acids being, as is known to be
+the case, easily decomposed. Five fresh castings from worms
+which lived in mould close over the chalk, were of a whitish
+colour and abounded with calcareous matter; and these were not in
+the least acid. This shows how effectually carbonate of
+lime neutralises the intestinal acids. When worms were kept
+in pots filled with fine ferruginous sand, it was manifest that
+the oxide of iron, with which the grains of silex were coated,
+had been dissolved and removed from them in the castings.</p>
+
+<p>The digestive fluid of worms resembles in its action, as
+already stated, the pancreatic secretion of the higher animals;
+and in these latter, &ldquo;pancreatic digestion is essentially
+alkaline; the action will not take place unless some alkali be
+present; and the activity of an alkaline juice is arrested by
+acidification, and hindered by neutralization.&rdquo; <a
+name="citation50"></a><a href="#footnote50"
+class="citation">[50]</a> Therefore it seems highly
+probable that the innumerable calciferous cells, which are poured
+from the four posterior glands into the alimentary canal of
+worms, serve to neutralise more or less completely the acids
+there generated by the half-decayed leaves. We have seen
+that these cells are instantly dissolved by a small quantity of
+acetic acid, and as they do not always suffice to neutralise the
+contents of even the upper part of the alimentary canal, the lime
+is perhaps aggregated into concretions in the anterior pair of
+glands, in order that some may be carried down to the posterior
+parts of the intestine, where these concretions would be rolled
+about amongst the acid contents. The concretions found in
+the intestines and in the castings often have a worn appearance,
+but whether this is due to some amount of attrition or of
+chemical corrosion could not be told. Claparède
+believes that they are formed for the sake of acting as
+mill-stones, and of thus aiding in the trituration of the
+food. They may give some aid in this way; but I fully agree
+with Perrier that this must be of quite subordinate importance,
+seeing that the object is already attained by stones being
+generally present in the gizzards and intestines of worms.</p>
+<h2><a name="page52"></a><span class="pagenum">p.
+52</span>CHAPTER II.<br />
+<span class="GutSmall">HABITS OF WORMS&mdash;</span><span
+class="GutSmall"><i>continued</i></span><span
+class="GutSmall">.</span></h2>
+<p class="gutsumm">Manner in which worms seize
+objects&mdash;Their power of suction&mdash;The instinct of
+plugging up the mouths of their burrows&mdash;Stones piled over
+the burrows&mdash;The advantages thus gained&mdash;Intelligence
+shown by worms in their manner of plugging up their
+burrows&mdash;Various kinds of leaves and other objects thus
+used&mdash;Triangles of paper&mdash;Summary of reasons for
+believing that worms exhibit some intelligence&mdash;Means by
+which they excavate their burrows, by pushing away the earth and
+swallowing it&mdash;Earth also swallowed for the nutritious
+matter which it contains&mdash;Depth to which worms burrow, and
+the construction of their burrows&mdash;Burrows lined with
+castings, and in the upper part with leaves&mdash;The lowest part
+paved with little stones or seeds&mdash;Manner in which the
+castings are ejected&mdash;The collapse of old
+burrows&mdash;Distribution of worms&mdash;Tower-like castings in
+Bengal&mdash;Gigantic castings on the Nilgiri
+Mountains&mdash;Castings ejected in all countries.</p>
+
+<p><span class="smcap">In</span> the pots in which worms were
+kept, leaves were pinned down to the soil, and at night the
+manner in which they were seized could be observed. The
+worms always endeavoured to drag the leaves towards their
+burrows; and they tore or sucked off small fragments, whenever
+the leaves were sufficiently tender. They generally seized
+the thin edge of a leaf with their mouths, between the projecting
+upper and lower lip; the thick and strong pharynx being at the
+same time, as Perrier remarks, pushed forward within their
+bodies, so as to afford a point of resistance for the upper
+lip. In the case of broad flat objects they acted in a
+wholly different manner. The pointed anterior extremity of
+the body, after being brought into contact with an object of this
+kind, was drawn within the adjoining rings, so that it appeared
+truncated and became as thick as the rest of the body. This
+part could then be seen to swell a little; and this, I believe,
+is due to the pharynx being pushed a little forwards. Then
+by a slight withdrawal of the pharynx or by its expansion, a
+vacuum was produced beneath the truncated slimy end of the body
+whilst in contact with the object; and by this means the two
+adhered firmly together. <a name="citation53"></a><a
+href="#footnote53" class="citation">[53]</a> That under
+these circumstances a vacuum was produced was plainly seen on one
+occasion, when a large worm lying beneath a flaccid cabbage leaf
+tried to drag it away; for the surface of the leaf directly over
+the end of the worm&rsquo;s body became deeply pitted. On
+another occasion a worm suddenly lost its hold on a flat leaf;
+and the anterior end of the body was momentarily seen to be
+cup-formed. Worms can attach themselves to an object
+beneath water in the same manner; and I saw one thus dragging
+away a submerged slice of an onion-bulb.</p>
+
+<p>The edges of fresh or nearly fresh leaves affixed to the
+ground were often nibbled by the worms; and sometimes the
+epidermis and all the parenchyma on one side was gnawed
+completely away over a considerable space; the epidermis alone on
+the opposite side being left quite clean. The veins were
+never touched, and leaves were thus sometimes partly converted
+into skeletons. As worms have no teeth and as their mouths
+consist of very soft tissue, it may be presumed that they consume
+by means of suction the edges and the parenchyma of fresh leaves,
+after they have been softened by the digestive fluid. They
+cannot attack such strong leaves as those of sea-kale or large
+and thick leaves of ivy; though one of the latter after it had
+become rotten was reduced in parts to the state of a
+skeleton.</p>
+
+<p>Worms seize leaves and other objects, not only to serve as
+food, but for plugging up the mouths of their burrows; and this
+is one of their strongest instincts. They sometimes work so
+energetically that Mr. D. F. Simpson, who has a small walled
+garden where worms abound in Bayswater, informs me that on a calm
+damp evening he there heard so extraordinary a rustling noise
+from under a tree from which many leaves had fallen, that he went
+out with a light and discovered that the noise was caused by many
+worms dragging the dry leaves and squeezing them into the
+burrows. Not only leaves, but petioles of many kinds, some
+flower-peduncles, often decayed twigs of trees, bits of paper,
+feathers, tufts of wool and horse-hairs are dragged into their
+burrows for this purpose. I have seen as many as seventeen
+petioles of a Clematis projecting from the mouth of one burrow,
+and ten from the mouth of another. Some of these objects,
+such as the petioles just named, feathers, &amp;c., are never
+gnawed by worms. In a gravel-walk in my garden I found many
+hundred leaves of a pine-tree (<i>P. austriaca</i> or
+<i>nigricans</i>) drawn by their bases into burrows. The
+surfaces by which these leaves are articulated to the branches
+are shaped in as peculiar a manner as is the joint between the
+leg-bones of a quadruped; and if these surfaces had been in the
+least gnawed, the fact would have been immediately visible, but
+there was no trace of gnawing. Of ordinary dicotyledonous
+leaves, all those which are dragged into burrows are not
+gnawed. I have seen as many as nine leaves of the lime-tree
+drawn into the same burrow, and not nearly all of them had been
+gnawed; but such leaves may serve as a store for future
+consumption. Where fallen leaves are abundant, many more
+are sometimes collected over the mouth of a burrow than can be
+used, so that a small pile of unused leaves is left like a roof
+over those which have been partly dragged in.</p>
+
+<p>A leaf in being dragged a little way into a cylindrical burrow
+is necessarily much folded or crumpled. When another leaf
+is drawn in, this is done exteriorly to the first one, and so on
+with the succeeding leaves; and finally all become closely folded
+and pressed together. Sometimes the worm enlarges the mouth
+of its burrow, or makes a fresh one close by, so as to draw in a
+still larger number of leaves. They often or generally fill
+up the interstices between the drawn-in leaves with moist viscid
+earth ejected from their bodies; and thus the mouths of the
+burrows are securely plugged. Hundreds of such plugged
+burrows may be seen in many places, especially during the
+autumnal and early winter months. But, as will hereafter be
+shown, leaves are dragged into the burrows not only for plugging
+them up and for food, but for the sake of lining the upper part
+or mouth.</p>
+
+<p>When worms cannot obtain leaves, petioles, sticks, &amp;c.,
+with which to plug up the mouths of their burrows, they often
+protect them by little heaps of stones; and such heaps of smooth
+rounded pebbles may frequently be seen on gravel-walks.
+Here there can be no question about food. A lady, who was
+interested in the habits of worms, removed the little heaps of
+stones from the mouths of several burrows and cleared the surface
+of the ground for some inches all round. She went out on
+the following night with a lantern, and saw the worms with their
+tails fixed in their burrows, dragging the stones inwards by the
+aid of their mouths, no doubt by suction. &ldquo;After two
+nights some of the holes had 8 or 9 small stones over them; after
+four nights one had about 30, and another 34 stones.&rdquo; <a
+name="citation58"></a><a href="#footnote58"
+class="citation">[58]</a> One stone&mdash;which had been
+dragged over the gravel-walk to the mouth of a burrow weighed two
+ounces; and this proves how strong worms are. But they show
+greater strength in sometimes displacing stones in a well-trodden
+gravel-walk; that they do so, may be inferred from the cavities
+left by the displaced stones being exactly filled by those lying
+over the mouths of adjoining burrows, as I have myself
+observed.</p>
+
+<p>Work of this kind is usually performed during the night; but I
+have occasionally known objects to be drawn into the burrows
+during the day. What advantage the worms derive from
+plugging up the mouths of their burrows with leaves, &amp;c., or
+from piling stones over them, is doubtful. They do not act
+in this manner at the times when they eject much earth from their
+burrows; for their castings then serve to cover the mouths.
+When gardeners wish to kill worms on a lawn, it is necessary
+first to brush or rake away the castings from the surface, in
+order that the lime-water may enter the burrows. <a
+name="citation59a"></a><a href="#footnote59a"
+class="citation">[59a]</a> It might be inferred from this
+fact that the mouths are plugged up with leaves, &amp;c., to
+prevent the entrance of water during heavy rain; but it may be
+urged against this view that a few, loose, well-rounded stones
+are ill-adapted to keep out water. I have moreover seen
+many burrows in the perpendicularly cut turf-edgings to
+gravel-walks, into which water could hardly flow, as well plugged
+as burrows on a level surface. It is not probable that the
+plugs or piles of stones serve to conceal the burrows from
+scolopendras, which, according to Hoffmeister, <a
+name="citation59b"></a><a href="#footnote59b"
+class="citation">[59b]</a> are the bitterest enemies of worms, or
+from the larger species of Carabus and Staphylinus which attack
+them ferociously, for these animals are nocturnal, and the
+burrows are opened at night. May not worms when the mouth
+of the burrow is protected be able to remain with safety with
+their heads close to it, which we know that they like to do, but
+which costs so many of them their lives? Or may not the
+plugs check the free ingress of the lowest stratum of air, when
+chilled by radiation at night, from the surrounding ground and
+herbage? I am inclined to believe in this latter view:
+firstly, because when worms were kept in pots in a room with a
+fire, in which case cold air could not enter the burrows, they
+plugged them up in a slovenly manner; and secondarily, because
+they often coat the upper part of their burrows with leaves,
+apparently to prevent their bodies from coming into close contact
+with the cold damp earth. Mr. E. Parfitt has suggested to
+me that the mouths of the burrows are closed in order that the
+air within them may be kept thoroughly damp, and this seems the
+most probable explanation of the habit. But the plugging-up
+process may serve for all the above purposes.</p>
+
+<p>Whatever the motive may be, it appears that worms much dislike
+leaving the mouths of their burrows open. Nevertheless they
+will reopen them at night, whether or not they can afterwards
+close them. Numerous open burrows may be seen on
+recently-dug ground, for in this case the worms eject their
+castings in cavities left in the ground, or in the old burrows
+instead of piling them over the mouths of their burrows, and they
+cannot collect objects on the surface by which the mouths might
+be protected. So again on a recently disinterred pavement
+of a Roman villa at Abinger (hereafter to be described) the worms
+pertinaciously opened their burrows almost every night, when
+these had been closed by being trampled on, although they were
+rarely able to find a few minute stones wherewith to protect
+them.</p>
+
+<p><i>Intelligence shown by worms in their manner of plugging up
+their burrows</i>.&mdash;If a man had to plug up a small
+cylindrical hole, with such objects as leaves, petioles or twigs,
+he would drag or push them in by their pointed ends; but if these
+objects were very thin relatively to the size of the hole, he
+would probably insert some by their thicker or broader
+ends. The guide in his case would be intelligence. It
+seemed therefore worth while to observe carefully how worms
+dragged leaves into their burrows; whether by their tips or bases
+or middle parts. It seemed more especially desirable to do
+this in the case of plants not natives to our country; for
+although the habit of dragging leaves into their burrows is
+undoubtedly instinctive with worms, yet instinct could not tell
+them how to act in the case of leaves about which their
+progenitors knew nothing. If, moreover, worms acted solely
+through instinct or an unvarying inherited impulse, they would
+draw all kinds of leaves into their burrows in the same
+manner. If they have no such definite instinct, we might
+expect that chance would determine whether the tip, base or
+middle was seized. If both these alternatives are excluded,
+intelligence alone is left; unless the worm in each case first
+tries many different methods, and follows that alone which proves
+possible or the most easy; but to act in this manner and to try
+different methods makes a near approach to intelligence.</p>
+
+<p>In the first place 227 withered leaves of various kinds,
+mostly of English plants, were pulled out of worm-burrows in
+several places. Of these, 181 had been drawn into the
+burrows by or near their tips, so that the foot-stalk projected
+nearly upright from the mouth of the burrow; 20 had been drawn in
+by their bases, and in this case the tips projected from the
+burrows; and 26 had been seized near the middle, so that these
+had been drawn in transversely and were much crumpled.
+Therefore 80 per cent. (always using the nearest whole number)
+had been drawn in by the tip, 9 per cent. by the base or
+foot-stalk, and 11 per cent. transversely or by the middle.
+This alone is almost sufficient to show that chance does not
+determine the manner in which leaves are dragged into the
+burrows.</p>
+
+<p>Of the above 227 leaves, 70 consisted of the fallen leaves of
+the common lime-tree, which is almost certainly not a native of
+England. These leaves are much acuminated towards the tip,
+and are very broad at the base with a well-developed
+foot-stalk. They are thin and quite flexible when
+half-withered. Of the 70, 79 per cent. had been drawn in by
+or near the tip; 4 per cent. by or near the base; and 17 per
+cent. transversely or by the middle. These proportions
+agree very closely, as far as the tip is concerned, with those
+before given. But the percentage drawn in by the base is
+smaller, which may be attributed to the breadth of the basal part
+of the blade. We here, also, see that the presence of a
+foot-stalk, which it might have been expected would have tempted
+the worms as a convenient handle, has little or no influence in
+determining the manner in which lime leaves are dragged into the
+burrows. The considerable proportion, viz., 17 per cent.,
+drawn in more or less transversely depends no doubt on the
+flexibility of these half-decayed leaves. The fact of so
+many having been drawn in by the middle, and of some few having
+been drawn in by the base, renders it improbable that the worms
+first tried to draw in most of the leaves by one or both of these
+methods, and that they afterwards drew in 79 per cent. by their
+tips; for it is clear that they would not have failed in drawing
+them in by the base or middle.</p>
+
+<p>The leaves of a foreign plant were next searched for, the
+blades of which were not more pointed towards the apex than
+towards the base. This proved to be the case with those of
+a laburnum (a hybrid between <i>Cytisus alpinus</i> and
+<i>laburnum</i>) for on doubling the terminal over the basal
+half, they generally fitted exactly; and when there was any
+difference, the basal half was a little the narrower. It
+might, therefore, have been expected that an almost equal number
+of these leaves would have been drawn in by the tip and base, or
+a slight excess in favour of the latter. But of 73 leaves
+(not included in the first lot of 227) pulled out of
+worm-burrows, 63 per cent. had been drawn in by the tip; 27 per
+cent. by the base, and 10 per cent. transversely. We here
+see that a far larger proportion, viz., 27 per cent. were drawn
+in by the base than in the case of lime leaves, the blades of
+which are very broad at the base, and of which only 4 per cent.
+had thus been drawn in. We may perhaps account for the fact
+of a still larger proportion of the laburnum leaves not having
+been drawn in by the base, by worms having acquired the habit of
+generally drawing in leaves by their tips and thus avoiding the
+foot-stalk. For the basal margin of the blade in many kinds
+of leaves forms a large angle with the foot-stalk; and if such a
+leaf were drawn in by the foot-stalk, the basal margin would come
+abruptly into contact with the ground on each side of the burrow,
+and would render the drawing in of the leaf very difficult.</p>
+
+<p>Nevertheless worms break through their habit of avoiding the
+foot-stalk, if this part offers them the most convenient means
+for drawing leaves into their burrows. The leaves of the
+endless hybridised varieties of the Rhododendron vary much in
+shape; some are narrowest towards the base and others towards the
+apex. After they have fallen off, the blade on each side of
+the midrib often becomes curled up while drying, sometimes along
+the whole length, sometimes chiefly at the base, sometimes
+towards the apex. Out of 28 fallen leaves on one bed of
+peat in my garden, no less than 23 were narrower in the basal
+quarter than in the terminal quarter of their length; and this
+narrowness was chiefly due to the curling in of the
+margins. Out of 36 fallen leaves on another bed, in which
+different varieties of the Rhododendron grew, only 17 were
+narrower towards the base than towards the apex. My son
+William, who first called my attention to this case, picked up
+237 fallen leaves in his garden (where the Rhododendron grows in
+the natural soil) and of these 65 per cent. could have been drawn
+by worms into their burrows more easily by the base or foot-stalk
+than by the tip; and this was partly due to the shape of the leaf
+and in a less degree to the curling in of the margins: 27 per
+cent. could have been drawn in more easily by the tip than by the
+base: and 8 per cent. with about equal ease by either end.
+The shape of a fallen leaf ought to be judged of before one end
+has been drawn into a burrow, for after this has happened, the
+free end, whether it be the base or apex, will dry more quickly
+than the end imbedded in the damp ground; and the exposed margins
+of the free end will consequently tend to become more curled
+inwards than they were when the leaf was first seized by the
+worm. My son found 91 leaves which had been dragged by
+worms into their burrows, though not to a great depth; of these
+66 per cent. had been drawn in by the base or foot-stalk; and 34
+per cent. by the tip. In this case, therefore, the worms
+judged with a considerable degree of correctness how best to draw
+the withered leaves of this foreign plant into their burrows;
+notwithstanding that they had to depart from their usual habit of
+avoiding the foot-stalk.</p>
+
+<p>On the gravel-walks in my garden a very large number of leaves
+of three species of Pinus (<i>P. austriaca</i>, <i>nigricans</i>
+and <i>sylvestris</i>) are regularly drawn into the mouths of
+worm burrows. These leaves consist of two so-called
+needles, which are of considerable length in the two first and
+short in the last named species, and are united to a common base;
+and it is by this part that they are almost invariably drawn into
+the burrows. I have seen only two or at most three
+exceptions to this rule with worms in a state of nature. As
+the sharply pointed needles diverge a little, and as several
+leaves are drawn into the same burrow, each tuft forms a perfect
+<i>chevaux de frise</i>. On two occasions many of these
+tufts were pulled up in the evening, but by the following morning
+fresh leaves had been pulled in, and the burrows were again well
+protected. These leaves could not be dragged into the
+burrows to any depth, except by their bases, as a worm cannot
+seize hold of the two needles at the same time, and if one alone
+were seized by the apex, the other would be pressed against the
+ground and would resist the entry of the seized one. This
+was manifest in the above mentioned two or three exceptional
+cases. In order, therefore, that worms should do their work
+well, they must drag pine-leaves into their burrows by their
+bases, where the two needles are conjoined. But how they
+are guided in this work is a perplexing question.</p>
+
+<p>This difficulty led my son Francis and myself to observe worms
+in confinement during several nights by the aid of a dim light,
+while they dragged the leaves of the above named pines into their
+burrows. They moved the anterior extremities of their
+bodies about the leaves, and on several occasions when they
+touched the sharp end of a needle they withdrew suddenly as if
+pricked. But I doubt whether they were hurt, for they are
+indifferent to very sharp objects, and will swallow even
+rose-thorns and small splinters of glass. It may also be
+doubted, whether the sharp ends of the needles serve to tell them
+that this is the wrong end to seize; for the points were cut off
+many leaves for a length of about one inch, and fifty-seven of
+them thus treated were drawn into the burrows by their bases, and
+not one by the cut-off ends. The worms in confinement often
+seized the needles near the middle and drew them towards the
+mouths of their burrows; and one worm tried in a senseless manner
+to drag them into the burrow by bending them. They
+sometimes collected many more leaves over the mouths of their
+burrows (as in the case formerly mentioned of lime-leaves) than
+could enter them. On other occasions, however, they behaved
+very differently; for as soon as they touched the base of a
+pine-leaf, this was seized, being sometimes completely engulfed
+in their mouths, or a point very near the base was seized, and
+the leaf was then quickly dragged or rather jerked into their
+burrows. It appeared both to my son and myself as if the
+worms instantly perceived as soon as they had seized a leaf in
+the proper manner. Nine such cases were observed, but in
+one of them the worm failed to drag the leaf into its burrow, as
+it was entangled by other leaves lying near. In another
+case a leaf stood nearly upright with the points of the needles
+partly inserted into a burrow, but how placed there was not seen;
+and then the worm reared itself up and seized the base, which was
+dragged into the mouth of the burrow by bowing the whole
+leaf. On the other hand, after a worm had seized the base
+of a leaf, this was on two occasions relinquished from some
+unknown motive.</p>
+
+<p>As already remarked, the habit of plugging up the mouths of
+the burrows with various objects, is no doubt instinctive in
+worms; and a very young one, born in one of my pots, dragged for
+some little distance a Scotch-fir leaf, one needle of which was
+as long and almost as thick as its own body. No species of
+pine is endemic in this part of England, it is therefore
+incredible that the proper manner of dragging pine-leaves into
+the burrows can be instinctive with our worms. But as the
+worms on which the above observations were made, were dug up
+beneath or near some pines, which had been planted there about
+forty years, it was desirable to prove that their actions were
+not instinctive. Accordingly, pine-leaves were scattered on
+the ground in places far removed from any pine-tree, and 90 of
+them were drawn into the burrows by their bases. Only two
+were drawn in by the tips of the needles, and these were not real
+exceptions, as one was drawn in for a very short distance, and
+the two needles of the other cohered. Other pine-leaves
+were given to worms kept in pots in a warm room, and here the
+result was different; for out of 42 leaves drawn into the
+burrows, no less than 16 were drawn in by the tips of the
+needles. These worms, however, worked in a careless or
+slovenly manner; for the leaves were often drawn in to only a
+small depth; sometimes they were merely heaped over the mouths of
+the burrows, and sometimes none were drawn in. I believe
+that this carelessness may be accounted for either by the warmth
+of the air, or by its dampness, as the pots were covered by glass
+plates; the worms consequently did not care about plugging up
+their holes effectually. Pots tenanted by worms and covered
+with a net which allowed the free entrance of air, were left out
+of doors for several nights, and now 72 leaves were all properly
+drawn in by their bases.</p>
+
+<p>It might perhaps be inferred from the facts as yet given, that
+worms somehow gain a general notion of the shape or structure of
+pine-leaves, and perceive that it is necessary for them to seize
+the base where the two needles are conjoined. But the
+following cases make this more than doubtful. The tips of a
+large number of needles of <i>P. austriaca</i> were cemented
+together with shell-lac dissolved in alcohol, and were kept for
+some days, until, as I believe, all odour or taste had been lost;
+and they were then scattered on the ground where no pine-trees
+grew, near burrows from which the plugging had been
+removed. Such leaves could have been drawn into the burrows
+with equal ease by either end; and judging from analogy and more
+especially from the case presently to be given of the petioles of
+<i>Clematis montana</i>, I expected that the apex would have been
+preferred. But the result was that out of 121 leaves with
+the tips cemented, which were drawn into burrows, 108 were drawn
+in by their bases, and only 13 by their tips. Thinking that
+the worms might possibly perceive and dislike the smell or taste
+of the shell-lac, though this was very improbable, especially
+after the leaves had been left out during several nights, the
+tips of the needles of many leaves were tied together with fine
+thread. Of leaves thus treated 150 were drawn into
+burrows&mdash;123 by the base and 27 by the tied tips; so that
+between four and five times as many were drawn in by the base as
+by the tip. It is possible that the short cut-off ends of
+the thread with which they were tied, may have tempted the worms
+to drag in a larger proportional number by the tips than when
+cement was used. Of the leaves with tied and cemented tips
+taken together (271 in number) 85 per cent. were drawn in by the
+base and 15 per cent. by the tips. We may therefore infer
+that it is not the divergence of the two needles which leads
+worms in a state of nature almost invariably to drag pine-leaves
+into their burrows by the base. Nor can it be the sharpness
+of the points of the needles which determines them; for, as we
+have seen, many leaves with the points cut off were drawn in by
+their bases. We are thus led to conclude, that with
+pine-leaves there must be something attractive to worms in the
+base, notwithstanding that few ordinary leaves are drawn in by
+the base or foot-stalk.</p>
+
+<p><i>Petioles</i>.&mdash;We will now turn to the petioles or
+foot-stalks of compound leaves, after the leaflets have fallen
+off. Those from <i>Clematis montana</i>, which grew over a
+verandah, were dragged early in January in large numbers into the
+burrows on an adjoining gravel-walk, lawn, and flower-bed.
+These petioles vary from 2&frac12; to 4&frac12; inches in length,
+are rigid and of nearly uniform thickness, except close to the
+base where they thicken rather abruptly, being here about twice
+as thick as in any other part. The apex is somewhat
+pointed, but soon withers and is then easily broken off. Of
+these petioles, 314 were pulled out of burrows in the above
+specified sites; and it was found that 76 per cent. had been
+drawn in by their tips, and 24 per cent by their bases; so that
+those drawn in by the tip were a little more than thrice as many
+as those drawn in by the base. Some of those extracted from
+the well-beaten gravel-walk were kept separate from the others;
+and of these (59 in number) nearly five times as many had been
+drawn in by the tip as by the base; whereas of those extracted
+from the lawn and flower-bed, where from the soil yielding more
+easily, less care would be necessary in plugging up the burrows,
+the proportion of those drawn in by the tip (130) to those drawn
+in by the base (48) was rather less than three to one. That
+these petioles had been dragged into the burrows for plugging
+them up, and not for food, was manifest, as neither end, as far
+as I could see, had been gnawed. As several petioles are
+used to plug up the same burrow, in one case as many as 10, and
+in another case as many as 15, the worms may perhaps at first
+draw in a few by the thicker end so as to save labour; but
+afterwards a large majority are drawn in by the pointed end, in
+order to plug up the hole securely.</p>
+
+<p>The fallen petioles of our native ash-tree were next observed,
+and the rule with most objects, viz., that a large majority are
+dragged into the burrows by the more pointed end, had not here
+been followed; and this fact much surprised me at first.
+These petioles vary in length from 5 to 8&frac12; inches; they
+are thick and fleshy towards the base, whence they taper gently
+towards the apex, which is a little enlarged and truncated where
+the terminal leaflet had been originally attached. Under
+some ash-trees growing in a grass-field, 229 petioles were pulled
+out of worm burrows early in January, and of these 51.5 per cent.
+had been drawn in by the base, and 48.5 per cent. by the
+apex. This anomaly was however readily explained as soon as
+the thick basal part was examined; for in 78 out of 103 petioles,
+this part had been gnawed by worms, just above the horse-shoe
+shaped articulation. In most cases there could be no
+mistake about the gnawing; for ungnawed petioles which were
+examined after being exposed to the weather for eight additional
+weeks had not become more disintegrated or decayed near the base
+than elsewhere. It is thus evident that the thick basal end
+of the petiole is drawn in not solely for the sake of plugging up
+the mouths of the burrows, but as food. Even the narrow
+truncated tips of some few petioles had been gnawed; and this was
+the case in 6 out of 37 which were examined for this
+purpose. Worms, after having drawn in and gnawed the basal
+end, often push the petioles out of their burrows; and then drag
+in fresh ones, either by the base for food, or by the apex for
+plugging up the mouth more effectually. Thus, out of 37
+petioles inserted by their tips, 5 had been previously drawn in
+by the base, for this part had been gnawed. Again, I
+collected a handful of petioles lying loose on the ground close
+to some plugged-up burrows, where the surface was thickly strewed
+with other petioles which apparently had never been touched by
+worms; and 14 out of 47 (<i>i.e.</i> nearly one-third), after
+having had their bases gnawed had been pushed out of the burrows
+and were now lying on the ground. From these several facts
+we may conclude that worms draw in some petioles of the ash by
+the base to serve as food, and others by the tip to plug up the
+mouths of their burrows in the most efficient manner.</p>
+
+<p>The petioles of <i>Robinia pseudo-acacia</i> vary from 4 or 5
+to nearly 12 inches in length; they are thick close to the base
+before the softer parts have rotted off, and taper much towards
+the upper end. They are so flexible that I have seen some
+few doubled up and thus drawn into the burrows of worms.
+Unfortunately these petioles were not examined until February, by
+which time the softer parts had completely rotted off, so that it
+was impossible to ascertain whether worms had gnawed the bases,
+though this is in itself probable. Out of 121 petioles
+extracted from burrows early in February, 68 were imbedded by the
+base, and 53 by the apex. On February 5 all the petioles
+which had been drawn into the burrows beneath a Robinia, were
+pulled up; and after an interval of eleven days, 35 petioles had
+been again dragged in, 19 by the base, and 16 by the apex.
+Taking these two lots together, 56 per cent. were drawn in by the
+base, and 44 per cent. by the apex. As all the softer parts
+had long ago rotted off, we may feel sure, especially in the
+latter case, that none had been drawn in as food. At this
+season, therefore, worms drag these petioles into their burrows
+indifferently by either end, a slight preference being given to
+the base. This latter fact may be accounted for by the
+difficulty of plugging up a burrow with objects so extremely thin
+as are the upper ends. In support of this view, it may be
+stated that out of the 16 petioles which had been drawn in by
+their upper ends, the more attenuated terminal portion of 7 had
+been previously broken off by some accident.</p>
+
+<p><i>Triangles of paper</i>.&mdash;Elongated triangles were cut
+out of moderately stiff writing-paper, which was rubbed with raw
+fat on both sides, so as to prevent their becoming excessively
+limp when exposed at night to rain and dew. The sides of
+all the triangles were three inches in length, with the bases of
+120 one inch, and of the other 183 half an inch in length.
+These latter triangles were very narrow or much acuminated. <a
+name="citation79"></a><a href="#footnote79"
+class="citation">[79]</a> As a check on the observations
+presently to be given, similar triangles in a damp state were
+seized by a very narrow pair of pincers at different points and
+at all inclinations with reference to the margins, and were then
+drawn into a short tube of the diameter of a worm-burrow.
+If seized by the apex, the triangle was drawn straight into the
+tube, with its margins infolded; if seized at some little
+distance from the apex, for instance at half an inch, this much
+was doubled back within the tube. So it was with the base
+and basal angles, though in this case the triangles offered, as
+might have been expected, much more resistance to being drawn
+in. If seized near the middle the triangle was doubled up,
+with the apex and base left sticking out of the tube. As
+the sides of the triangles were three inches in length, the
+result of their being drawn into a tube or into a burrow in
+different ways, may be conveniently divided into three groups:
+those drawn in by the apex or within an inch of it; those drawn
+in by the base or within an inch of it; and those drawn in by any
+point in the middle inch.</p>
+
+<p>In order to see how the triangles would be seized by worms,
+some in a damp state were given to worms kept in
+confinement. They were seized in three different manners in
+the case of both the narrow and broad triangles: viz., by the
+margin; by one of the three angles, which was often completely
+engulfed in their mouths; and lastly, by suction applied to any
+part of the flat surface. If lines parallel to the base and
+an inch apart, are drawn across a triangle with the sides three
+inches in length, it will be divided into three parts of equal
+length. Now if worms seized indifferently by chance any
+part, they would assuredly seize on the basal part or division
+far oftener than on either of the two other divisions. For
+the area of the basal to the apical part is as 5 to 1, so that
+the chance of the former being drawn into a burrow by suction,
+will be as 5 to 1, compared with the apical part. The base
+offers two angles and the apex only one, so that the former would
+have twice as good a chance (independently of the size of the
+angles) of being engulfed in a worm&rsquo;s mouth, as would the
+apex. It should, however, be stated that the apical angle
+is not often seized by worms; the margin at a little distance on
+either side being preferred. I judge of this from having
+found in 40 out of 46 cases in which triangles had been drawn
+into burrows by their apical ends, that the tip had been doubled
+back within the burrow for a length of between 1/20 of an inch
+and 1 inch. Lastly, the proportion between the margins of
+the basal and apical parts is as 3 to 2 for the broad, and
+2&frac12; to 2 for the narrow triangles. From these several
+considerations it might certainly have been expected, supposing
+that worms seized hold of the triangles by chance, that a
+considerably larger proportion would have been dragged into the
+burrows by the basal than by the apical part; but we shall
+immediately see how different was the result.</p>
+
+<p>Triangles of the above specified sizes were scattered on the
+ground in many places and on many successive nights near
+worm-burrows, from which the leaves, petioles, twigs, &amp;c.,
+with which they had been plugged, were removed. Altogether
+303 triangles were drawn by worms into their burrows: 12 others
+were drawn in by both ends, but as it was impossible to judge by
+which end they had been first seized, these are excluded.
+Of the 303, 62 per cent. had been drawn in by the apex (using
+this term for all drawn in by the apical part, one inch in
+length); 15 per cent. by the middle; and 23 per cent. by the
+basal part. If they had been drawn indifferently by any
+point, the proportion for the apical, middle and basal parts
+would have been 33.3 per cent. for each; but, as we have just
+seen, it might have been expected that a much larger proportion
+would have been drawn in by the basal than by any other
+part. As the case stands, nearly three times as many were
+drawn in by the apex as by the base. If we consider the
+broad triangles by themselves, 59 per cent. were drawn in by the
+apex, 25 per cent. by the middle, and 16 per cent. by the
+base. Of the narrow triangles, 65 per cent. were drawn in
+by the apex, 14 per cent, by the middle, and 21 per cent. by the
+base; so that here those drawn in by the apex were more than 3
+times as many as those drawn in by the base. We may
+therefore conclude that the manner in which the triangles are
+drawn into the burrows is not a matter of chance.</p>
+
+<p>In eight cases, two triangles had been drawn into the same
+burrow, and in seven of these cases, one had been drawn in by the
+apex and the other by the base. This again indicates that
+the result is not determined by chance. Worms appear
+sometimes to revolve in the act of drawing in the triangles, for
+five out of the whole lot had been wound into an irregular spire
+round the inside of the burrow. Worms kept in a warm room
+drew 63 triangles into their burrows; but, as in the case of the
+pine-leaves, they worked in a rather careless manner, for only 44
+per cent. were drawn in by the apex, 22 per cent. by the middle,
+and 33 per cent. by the base. In five cases, two triangles
+were drawn into the same burrow.</p>
+
+<p>It may be suggested with much apparent probability that so
+large a proportion of the triangles were drawn in by the apex,
+not from the worms having selected this end as the most
+convenient for the purpose, but from having first tried in other
+ways and failed. This notion was countenanced by the manner
+in which worms in confinement were seen to drag about and drop
+the triangles; but then they were working carelessly. I did
+not at first perceive the importance of this subject, but merely
+noticed that the bases of those triangles which had been drawn in
+by the apex, were generally clean and not crumpled. The
+subject was afterwards attended to carefully. In the first
+place several triangles which had been drawn in by the basal
+angles, or by the base, or a little above the base, and which
+were thus much crumpled and dirtied, were left for some hours in
+water and were then well shaken while immersed; but neither the
+dirt nor the creases were thus removed. Only slight creases
+could be obliterated, even by pulling the wet triangles several
+times through my fingers. Owing to the slime from the
+worms&rsquo; bodies, the dirt was not easily washed off. We
+may therefore conclude that if a triangle, before being dragged
+in by the apex, had been dragged into a burrow by its base with
+even a slight degree of force, the basal part would long retain
+its creases and remain dirty. The condition of 89 triangles
+(65 narrow and 24 broad ones), which had been drawn in by the
+apex, was observed; and the bases of only 7 of them were at all
+creased, being at the same time generally dirty. Of the 82
+uncreased triangles, 14 were dirty at the base; but it does not
+follow from this fact that these had first been dragged towards
+the burrows by their bases; for the worms sometimes covered large
+portions of the triangles with slime, and these when dragged by
+the apex over the ground would be dirtied; and during rainy
+weather, the triangles were often dirtied over one whole side or
+over both sides. If the worms had dragged the triangles to
+the mouths of their burrows by their bases, as often as by their
+apices, and had then perceived, without actually trying to draw
+them into the burrow, that the broader end was not well adapted
+for this purpose&mdash;even in this case a large proportion would
+probably have had their basal ends dirtied. We may
+therefore infer&mdash;improbable as is the inference&mdash;that
+worms are able by some means to judge which is the best end by
+which to draw triangles of paper into their burrows.</p>
+
+<p>The percentage results of the foregoing observations on the
+manner in which worms draw various kinds of objects into the
+mouths of their burrows may be abridged as follows:&mdash;</p>
+<table>
+<tr>
+<td><p style="text-align: center">Nature of Object.</p>
+</td>
+<td><p style="text-align: center">Drawn into the burrows, by or
+near the apex.</p>
+</td>
+<td><p style="text-align: center">Drawn in, by or near the
+middle.</p>
+</td>
+<td><p style="text-align: center">Drawn in, by or near the
+base.</p>
+</td>
+</tr>
+<tr>
+<td><p>Leaves of various kinds</p>
+</td>
+<td><p style="text-align: right">80</p>
+</td>
+<td><p style="text-align: right">11</p>
+</td>
+<td><p style="text-align: right">9</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of the Lime, basal margin of blade broad, apex
+acuminated</p>
+</td>
+<td><p style="text-align: right">79</p>
+</td>
+<td><p style="text-align: right">17</p>
+</td>
+<td><p style="text-align: right">4</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of a Laburnum, basal part of blade as narrow as, or
+sometimes little narrower than the apical part</p>
+</td>
+<td><p style="text-align: right">63</p>
+</td>
+<td><p style="text-align: right">10</p>
+</td>
+<td><p style="text-align: right">27</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of the Rhododendron, basal part of blade often
+narrower than the apical part</p>
+</td>
+<td><p style="text-align: right">34</p>
+</td>
+<td><p style="text-align: center">...</p>
+</td>
+<td><p style="text-align: right">66</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of Pine-trees, consisting of two needles arising
+from a common base</p>
+</td>
+<td><p style="text-align: center">...</p>
+</td>
+<td><p style="text-align: center">...</p>
+</td>
+<td><p style="text-align: right">100</p>
+</td>
+</tr>
+<tr>
+<td><p>Petioles of a Clematis, somewhat pointed at the apex, and
+blunt at the base</p>
+</td>
+<td><p style="text-align: right">76</p>
+</td>
+<td><p style="text-align: center">...</p>
+</td>
+<td><p style="text-align: right">24</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of the Ash, the thick basal end often drawn in to
+serve as food</p>
+</td>
+<td><p style="text-align: right">48.5</p>
+</td>
+<td><p style="text-align: center">...</p>
+</td>
+<td><p style="text-align: right">51.5</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of Robinia, extremely thin, especially towards the
+apex, so as to be ill-fitted for plugging up the burrows</p>
+</td>
+<td><p style="text-align: right">44</p>
+</td>
+<td><p style="text-align: center">...</p>
+</td>
+<td><p style="text-align: right">56</p>
+</td>
+</tr>
+<tr>
+<td><p>Triangles of paper, of the two sizes</p>
+</td>
+<td><p style="text-align: right">62</p>
+</td>
+<td><p style="text-align: right">15</p>
+</td>
+<td><p style="text-align: right">23</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of the broad ones alone</p>
+</td>
+<td><p style="text-align: right">59</p>
+</td>
+<td><p style="text-align: right">25</p>
+</td>
+<td><p style="text-align: right">16</p>
+</td>
+</tr>
+<tr>
+<td><p>&mdash;of the narrow ones alone</p>
+</td>
+<td><p style="text-align: right">65</p>
+</td>
+<td><p style="text-align: right">14</p>
+</td>
+<td><p style="text-align: right">21</p>
+</td>
+</tr>
+</table>
+<p>If we consider these several cases, we can hardly escape from
+the conclusion that worms show some degree of intelligence in
+their manner of plugging up their burrows. Each particular
+object is seized in too uniform a manner, and from causes which
+we can generally understand, for the result to be attributed to
+mere chance. That every object has not been drawn in by its
+pointed end, may be accounted for by labour having been saved
+through some being inserted by their broader or thicker
+ends. No doubt worms are led by instinct to plug up their
+burrows; and it might have been expected that they would have
+been led by instinct how best to act in each particular case,
+independently of intelligence. We see how difficult it is
+to judge whether intelligence comes into play, for even plants
+might sometimes be thought to be thus directed; for instance when
+displaced leaves re-direct their upper surfaces towards the light
+by extremely complicated movements and by the shortest
+course. With animals, actions appearing due to intelligence
+may be performed through inherited habit without any
+intelligence, although aboriginally thus acquired. Or the
+habit may have been acquired through the preservation and
+inheritance of beneficial variations of some other habit; and in
+this case the new habit will have been acquired independently of
+intelligence throughout the whole course of its
+development. There is no <i>à priori</i>
+improbability in worms having acquired special instincts through
+either of these two latter means. Nevertheless it is
+incredible that instincts should have been developed in reference
+to objects, such as the leaves of petioles of foreign plants,
+wholly unknown to the progenitors of the worms which act in the
+described manner. Nor are their actions so unvarying or
+inevitable as are most true instincts.</p>
+
+<p>As worms are not guided by special instincts in each
+particular case, though possessing a general instinct to plug up
+their burrows, and as chance is excluded, the next most probable
+conclusion seems to be that they try in many different ways to
+draw in objects, and at last succeed in some one way. But
+it is surprising that an animal so low in the scale as a worm
+should have the capacity for acting in this manner, as many
+higher animals have no such capacity. For instance, ants
+may be seen vainly trying to drag an object transversely to their
+course, which could be easily drawn longitudinally; though after
+a time they generally act in a wiser manner, M. Fabre states <a
+name="citation89a"></a><a href="#footnote89a"
+class="citation">[89a]</a> that a Sphex&mdash;an insect belonging
+to the same highly-endowed order with ants&mdash;stocks its nest
+with paralysed grass-hoppers, which are invariably dragged into
+the burrow by their antennæ. When these were cut off
+close to the head, the Sphex seized the palpi; but when these
+were likewise cut off, the attempt to drag its prey into the
+burrow was given up in despair. The Sphex had not
+intelligence enough to seize one of the six legs or the
+ovipositor of the grasshopper, which, as M. Fabre remarks, would
+have served equally well. So again, if the paralysed prey
+with an egg attached to it be taken out of the cell, the Sphex
+after entering and finding the cell empty, nevertheless closes it
+up in the usual elaborate manner. Bees will try to escape
+and go on buzzing for hours on a window, one half of which has
+been left open. Even a pike continued during three months
+to dash and bruise itself against the glass sides of an aquarium,
+in the vain attempt to seize minnows on the opposite side. <a
+name="citation89b"></a><a href="#footnote89b"
+class="citation">[89b]</a> A cobra-snake was seen by Mr.
+Layard <a name="citation90"></a><a href="#footnote90"
+class="citation">[90]</a> to act much more wisely than either the
+pike or the Sphex; it had swallowed a toad lying within a hole,
+and could not withdraw its head; the toad was disgorged, and
+began to crawl away; it was again swallowed and again disgorged;
+and now the snake had learnt by experience, for it seized the
+toad by one of its legs and drew it out of the hole. The
+instincts of even the higher animals are often followed in a
+senseless or purposeless manner: the weaver-bird will
+perseveringly wind threads through the bars of its cage, as if
+building a nest: a squirrel will pat nuts on a wooden floor, as
+if he had just buried them in the ground: a beaver will cut up
+logs of wood and drag them about, though there is no water to dam
+up; and so in many other cases.</p>
+
+<p>Mr. Romanes, who has specially studied the minds of animals,
+believes that we can safely infer intelligence, only when we see
+an individual profiting by its own experience. By this test
+the cobra showed some intelligence; but this would have been much
+plainer if on a second occasion he had drawn a toad out of a hole
+by its leg. The Sphex failed signally in this
+respect. Now if worms try to drag objects into their
+burrows first in one way and then in another, until they at last
+succeed, they profit, at least in each particular instance, by
+experience.</p>
+
+<p>But evidence has been advanced showing that worms do not
+habitually try to draw objects into their burrows in many
+different ways. Thus half-decayed lime-leaves from their
+flexibility could have been drawn in by their middle or basal
+parts, and were thus drawn into the burrows in considerable
+numbers; yet a large majority were drawn in by or near the
+apex. The petioles of the Clematis could certainly have
+been drawn in with equal ease by the base and apex; yet three
+times and in certain cases five times as many were drawn in by
+the apex as by the base. It might have been thought that
+the foot-stalks of leaves would have tempted the worms as a
+convenient handle; yet they are not largely used, except when the
+base of the blade is narrower than the apex. A large number
+of the petioles of the ash are drawn in by the base; but this
+part serves the worms as food. In the case of pine-leaves
+worms plainly show that they at least do not seize the leaf by
+chance; but their choice does not appear to be determined by the
+divergence of the two needles, and the consequent advantage or
+necessity of drawing them into their burrows by the base.
+With respect to the triangles of paper, those which had been
+drawn in by the apex rarely had their bases creased or dirty; and
+this shows that the worms had not often first tried to drag them
+in by this end.</p>
+
+<p>If worms are able to judge, either before drawing or after
+having drawn an object close to the mouths of their burrows, how
+best to drag it in, they must acquire some notion of its general
+shape. This they probably acquire by touching it in many
+places with the anterior extremity of their bodies, which serves
+as a tactile organ. It may be well to remember how perfect
+the sense of touch becomes in a man when born blind and deaf, as
+are worms. If worms have the power of acquiring some
+notion, however rude, of the shape of an object and of their
+burrows, as seems to be the case, they deserve to be called
+intelligent; for they then act in nearly the same manner as would
+a man under similar circumstances.</p>
+
+<p>To sum up, as chance does not determine the manner in which
+objects are drawn into the burrows, and as the existence of
+specialized instincts for each particular case cannot be
+admitted, the first and most natural supposition is that worms
+try all methods until they at last succeed; but many appearances
+are opposed to such a supposition. One alternative alone is
+left, namely, that worms, although standing low in the scale of
+organization, possess some degree of intelligence. This
+will strike every one as very improbable; but it may be doubted
+whether we know enough about the nervous system of the lower
+animals to justify our natural distrust of such a
+conclusion. With respect to the small size of the cerebral
+ganglia, we should remember what a mass of inherited knowledge,
+with some power of adapting means to an end, is crowded into the
+minute brain of a worker-ant.</p>
+
+<p><i>Means by which worms excavate their burrows</i>.&mdash;This
+is effected in two ways; by pushing away the earth on all sides,
+and by swallowing it. In the former case, the worm inserts
+the stretched out and attenuated anterior extremity of its body
+into any little crevice, or hole; and then, as Perrier remarks,
+<a name="citation93"></a><a href="#footnote93"
+class="citation">[93]</a> the pharynx is pushed forwards into
+this part, which consequently swells and pushes away the earth on
+all sides. The anterior extremity thus serves as a
+wedge. It also serves, as we have before seen, for
+prehension and suction, and as a tactile organ. A worm was
+placed on loose mould, and it buried itself in between two and
+three minutes. On another occasion four worms disappeared
+in 15 minutes between the sides of the pot and the earth, which
+had been moderately pressed down. On a third occasion three
+large worms and a small one were placed on loose mould well mixed
+with fine sand and firmly pressed down, and they all disappeared,
+except the tail of one, in 35 minutes. On a fourth occasion
+six large worms were placed on argillaceous mud mixed with sand
+firmly pressed down, and they disappeared, except the extreme
+tips of the tails of two of them, in 40 minutes. In none of
+these cases, did the worms swallow, as far as could be seen, any
+earth. They generally entered the ground close to the sides
+of the pot.</p>
+
+<p>A pot was next filled with very fine ferruginous sand, which
+was pressed down, well watered, and thus rendered extremely
+compact. A large worm left on the surface did not succeed
+in penetrating it for some hours, and did not bury itself
+completely until 25 hrs. 40 min. had elapsed. This was
+effected by the sand being swallowed, as was evident by the large
+quantity ejected from the vent, long before the whole body had
+disappeared. Castings of a similar nature continued to be
+ejected from the burrow during the whole of the following
+day.</p>
+
+<p>As doubts have been expressed by some writers whether worms
+ever swallow earth solely for the sake of making their burrows,
+some additional cases may be given. A mass of fine reddish
+sand, 23 inches in thickness, left on the ground for nearly two
+years, had been penetrated in many places by worms; and their
+castings consisted partly of the reddish sand and partly of black
+earth brought up from beneath the mass. This sand had been
+dug up from a considerable depth, and was of so poor a nature
+that weeds could not grow on it. It is therefore highly
+improbable that it should have been swallowed by the worms as
+food. Again in a field near my house the castings
+frequently consist of almost pure chalk, which lies at only a
+little depth beneath the surface; and here again it is very
+improbable that the chalk should have been swallowed for the sake
+of the very little organic matter which could have percolated
+into it from the poor overlying pasture. Lastly, a casting
+thrown up through the concrete and decayed mortar between the
+tiles, with which the now ruined aisle of Beaulieu Abbey had
+formerly been paved, was washed, so that the coarser matter alone
+was left. This consisted of grains of quartz, micaceous
+slate, other rocks, and bricks or tiles, many of them from 1/20
+to 1/10 inch in diameter. No one will suppose that these
+grains were swallowed as food, yet they formed more than half of
+the casting, for they weighed 19 grains, the whole casting having
+weighed 33 grains. Whenever a worm burrows to a depth of
+some feet in undisturbed compact ground, it must form its passage
+by swallowing the earth; for it is incredible that the ground
+could yield on all sides to the pressure of the pharynx when
+pushed forwards within the worm&rsquo;s body.</p>
+
+<p>That worms swallow a larger quantity of earth for the sake of
+extracting any nutritious matter which it may contain than for
+making their burrows, appears to me certain. But as this
+old belief has been doubted by so high an authority as
+Claparède, evidence in its favour must be given in some
+detail. There is no <i>à priori</i> improbability in
+such a belief, for besides other annelids, especially the
+<i>Arenicola marina</i>, which throws up such a profusion of
+castings on our tidal sands, and which it is believed thus
+subsists, there are animals belonging to the most distinct
+classes, which do not burrow, but habitually swallow large
+quantities of sand; namely, the molluscan Onchidium and many
+Echinoderms. <a name="citation97"></a><a href="#footnote97"
+class="citation">[97]</a></p>
+
+<p>If earth were swallowed only when worms deepened their burrows
+or made new ones, castings would be thrown up only occasionally;
+but in many places fresh castings may be seen every morning, and
+the amount of earth ejected from the same burrow on successive
+days is large. Yet worms do not burrow to a great depth,
+except when the weather is very dry or intensely cold. On
+my lawn the black vegetable mould or humus is only about 5 inches
+in thickness, and overlies light-coloured or reddish clayey soil:
+now when castings are thrown up in the greatest profusion, only a
+small proportion are light coloured, and it is incredible that
+the worms should daily make fresh burrows in every direction in
+the thin superficial layer of dark-coloured mould, unless they
+obtained nutriment of some kind from it. I have observed a
+strictly analogous case in a field near my house where bright red
+clay lay close beneath the surface. Again on one part of
+the Downs near Winchester the vegetable mould overlying the chalk
+was found to be only from 3 to 4 inches in thickness; and the
+many castings here ejected were as black as ink and did not
+effervesce with acids; so that the worms must have confined
+themselves to this thin superficial layer of mould, of which
+large quantities were daily swallowed. In another place at
+no great distance the castings were white; and why the worms
+should have burrowed into the chalk in some places and not in
+others, I am unable to conjecture.</p>
+
+<p>Two great piles of leaves had been left to decay in my
+grounds, and months after their removal, the bare surface,
+several yards in diameter, was so thickly covered during several
+months with castings that they formed an almost continuous layer;
+and the large number of worms which lived here must have
+subsisted during these months on nutritious matter contained in
+the black earth.</p>
+
+<p>The lowest layer from another pile of decayed leaves mixed
+with some earth was examined under a high power, and the number
+of spores of various shapes and sizes which it contained was
+astonishingly great; and these crushed in the gizzards of worms
+may largely aid in supporting them. Whenever castings are
+thrown up in the greatest number, few or no leaves are drawn into
+the burrows; for instance the turf along a hedgerow, about 200
+yards in length, was daily observed in the autumn during several
+weeks, and every morning many fresh castings were seen; but not a
+single leaf was drawn into these burrows. These castings
+from their blackness and from the nature of the subsoil could not
+have been brought up from a greater depth than 6 or 8
+inches. On what could these worms have subsisted during
+this whole time, if not on matter contained in the black
+earth? On the other hand, whenever a large number of leaves
+are drawn into the burrows, the worms seem to subsist chiefly on
+them, for few earth-castings are then ejected on the
+surface. This difference in the behaviour of worms at
+different times, perhaps explains a statement by
+Claparède, namely, that triturated leaves and earth are
+always found in distinct parts of their intestines.</p>
+
+<p>Worms sometimes abound in places where they can rarely or
+never obtain dead or living leaves; for instance, beneath the
+pavement in well-swept courtyards, into which leaves are only
+occasionally blown. My son Horace examined a house, one
+corner of which had subsided; and he found here in the cellar,
+which was extremely damp, many small worm-castings thrown up
+between the stones with which the cellar was paved; and in this
+case it is improbable that the worms could ever have obtained
+leaves. Mr. A. C. Horner confirms this account, as he has
+seen castings in the cellars of his house, which is an old one at
+Tonbridge.</p>
+
+<p>But the best evidence, known to me, of worms subsisting for at
+least considerable periods of time solely on the organic matter
+contained in earth, is afforded by some facts communicated to me
+by Dr. King. Near Nice large castings abound in
+extraordinary numbers, so that 5 or 6 were often found within the
+space of a square foot. They consist of fine, pale-coloured
+earth, containing calcareous matter, which after having passed
+through the bodies of worms and being dried, coheres with
+considerable force. I have reason to believe that these
+castings had been formed by species of Perichæta, which
+have been naturalized here from the East. <a
+name="citation101"></a><a href="#footnote101"
+class="citation">[101]</a> They rise like towers, with
+their summits often a little broader than their bases, sometimes
+to a height of above 3 and often to a height of 2&frac12;
+inches. The tallest of those which were measured was 3.3
+inches in height and 1 inch in diameter. A small
+cylindrical passage runs up the centre of each tower, through
+which the worm ascends to eject the earth which it has swallowed,
+and thus to add to its height. A structure of this kind
+would not allow leaves being easily dragged from the surrounding
+ground into the burrows; and Dr. King, who looked carefully,
+never saw even a fragment of a leaf thus drawn in. Nor
+could any trace be discovered of the worms having crawled down
+the exterior surfaces of the towers in search of leaves; and had
+they done so, tracks would almost certainly have been left on the
+upper part whilst it remained soft. It does not, however,
+follow that these worms do not draw leaves into their burrows
+during some other season of the year, at which time they would
+not build up their towers.</p>
+
+<p>From the several foregoing cases, it can hardly be doubted
+that worms swallow earth, not only for the sake of making their
+burrows, but for obtaining food. Hensen, however, concludes
+from his analyses of mould that worms probably could not live on
+ordinary vegetable mould, though he admits that they might be
+nourished to some extent by leaf-mould. <a
+name="citation102"></a><a href="#footnote102"
+class="citation">[102]</a> But we have seen that worms
+eagerly devour raw meat, fat, and dead worms; and ordinary mould
+can hardly fail to contain many ova, larvæ, and small
+living or dead creatures, spores of cryptogamic plants, and
+micrococci, such as those which give rise to saltpetre.
+These various organisms, together with some cellulose from any
+leaves and roots not utterly decayed, might well account for such
+large quantities of mould being swallowed by worms. It may
+be worth while here to recall the fact that certain species of
+Utricularia, which grow in damp places in the tropics, possess
+bladders beautifully constructed for catching minute subterranean
+animals; and these traps would not have been developed unless
+many small animals inhabited such soil.</p>
+
+<p><i>The depth to which worms penetrate</i>, <i>and the
+construction of their burrows</i>.&mdash;Although worms usually
+live near the surface, yet they burrow to a considerable depth
+during long-continued dry weather and severe cold. In
+Scandinavia, according to Eisen, and in Scotland, according to
+Mr. Lindsay Carnagie, the burrows run down to a depth of from 7
+to 8 feet; in North Germany, according to Hoffmeister, from 6 to
+8 feet, but Hensen says, from 3 to 6 feet. This latter
+observer has seen worms frozen at a depth of 1&frac12; feet
+beneath the surface. I have not myself had many
+opportunities for observation, but I have often met with worms at
+depths of 3 to 4 feet. In a bed of fine sand overlying the
+chalk, which had never been disturbed, a worm was cut into two at
+55 inches, and another was found here at Down in December at the
+bottom of its burrow, at 61 inches beneath the surface.
+Lastly, in earth near an old Roman Villa, which had not been
+disturbed for many centuries, a worm was met with at a depth of
+66 inches; and this was in the middle of August.</p>
+
+<p>The burrows run down perpendicularly, or more commonly a
+little obliquely. They are said sometimes to branch, but as
+far as I have seen this does not occur, except in recently dug
+ground and near the surface. They are generally, or as I
+believe invariably, lined with a thin layer of fine,
+dark-coloured earth voided by the worms; so that they must at
+first be made a little wider than their ultimate diameter.
+I have seen several burrows in undisturbed sand thus lined at a
+depth of 4 ft. 6 in.; and others close to the surface thus lined
+in recently dug ground. The walls of fresh burrows are
+often dotted with little globular pellets of voided earth, still
+soft and viscid; and these, as it appears, are spread out on all
+sides by the worm as it travels up or down its burrow. The
+lining thus formed becomes very compact and smooth when nearly
+dry, and closely fits the worm&rsquo;s body. The minute
+reflexed bristles which project in rows on all sides from the
+body, thus have excellent points of support; and the burrow is
+rendered well adapted for the rapid movement of the animal.
+The lining appears also to strengthen the walls, and perhaps
+saves the worm&rsquo;s body from being scratched. I think
+so because several burrows which passed through a layer of sifted
+coal-cinders, spread over turf to a thickness of 1&frac12; inch,
+had been thus lined to an unusual thickness. In this case
+the worms, judging from the castings, had pushed the cinders away
+on all sides and had not swallowed any of them. In another
+place, burrows similarly lined, passed through a layer of coarse
+coal-cinders, 3&frac12; inches in thickness. We thus see
+that the burrows are not mere excavations, but may rather be
+compared with tunnels lined with cement.</p>
+
+<p>The mouths of the burrow are in addition often lined with
+leaves; and this is an instinct distinct from that of plugging
+them up, and does not appear to have been hitherto noticed.
+Many leaves of the Scotch-fir or pine (<i>Pinus sylvestris</i>)
+were given to worms kept in confinement in two pots; and when
+after several weeks the earth was carefully broken up, the upper
+parts of three oblique burrows were found surrounded for lengths
+of 7, 4, and 3&frac12; inches with pine-leaves, together with
+fragments of other leaves which had been given the worms as
+food. Glass beads and bits of tile, which had been strewed
+on the surface of the soil, were stuck into the interstices
+between the pine-leaves; and these interstices were likewise
+plastered with the viscid castings voided by the worms. The
+structures thus formed cohered so well, that I succeeded in
+removing one with only a little earth adhering to it. It
+consisted of a slightly curved cylindrical case, the interior of
+which could be seen through holes in the sides and at either
+end. The pine-leaves had all been drawn in by their bases;
+and the sharp points of the needles had been pressed into the
+lining of voided earth. Had this not been effectually done,
+the sharp points would have prevented the retreat of the worms
+into their burrows; and these structures would have resembled
+traps armed with converging points of wire, rendering the ingress
+of an animal easy and its egress difficult or impossible.
+The skill shown by these worms is noteworthy and is the more
+remarkable, as the Scotch pine is not a native of this
+district.</p>
+
+<p>After having examined these burrows made by worms in
+confinement, I looked at those in a flower-bed near some Scotch
+pines. These had all been plugged up in the ordinary manner
+with the leaves of this tree, drawn in for a length of from 1 to
+1&frac12; inch; but the mouths of many of them were likewise
+lined with them, mingled with fragments of other kinds of leaves,
+drawn in to a depth of 4 or 5 inches. Worms often remain,
+as formerly stated, for a long time close to the mouths of their
+burrows, apparently for warmth; and the basket-like structures
+formed of leaves would keep their bodies from coming into close
+contact with the cold damp earth. That they habitually
+rested on the pine-leaves, was rendered probable by their clean
+and almost polished surfaces.</p>
+
+<p>The burrows which run far down into the ground, generally, or
+at least often, terminate in a little enlargement or
+chamber. Here, according to Hoffmeister, one or several
+worms pass the winter rolled up into a ball. Mr. Lindsay
+Carnagie informed me (1838) that he had examined many burrows
+over a stone-quarry in Scotland, where the overlying boulder-clay
+and mould had recently been cleared away, and a little vertical
+cliff thus left. In several cases the same burrow was a
+little enlarged at two or three points one beneath the other; and
+all the burrows terminated in a rather large chamber, at a depth
+of 7 or 8 feet from the surface. These chambers contained
+many small sharp bits of stone and husks of flax-seeds.
+They must also have contained living seeds, for on the following
+spring Mr. Carnagie saw grass-plants sprouting out of some of the
+intersected chambers. I found at Abinger in Surrey two
+burrows terminating in similar chambers at a depth of 36 and 41
+inches, and these were lined or paved with little pebbles, about
+as large as mustard seeds; and in one of the chambers there was a
+decayed oat-grain, with its husk. Hensen likewise states
+that the bottoms of the burrows are lined with little stones; and
+where these could not be procured, seeds, apparently of the pear,
+had been used, as many as fifteen having been carried down into a
+single burrow, one of which had germinated. <a
+name="citation108"></a><a href="#footnote108"
+class="citation">[108]</a> We thus see how easily a
+botanist might be deceived who wished to learn how long deeply
+buried seeds remained alive, if he were to collect earth from a
+considerable depth, on the supposition that it could contain only
+seeds which had long lain buried. It is probable that the
+little stones, as well as the seeds, are carried down from the
+surface by being swallowed; for a surprising number of glass
+beads, bits of tile and of glass were certainly thus carried down
+by worms kept in pots; but some may have been carried down within
+their mouths. The sole conjecture which I can form why
+worms line their winter-quarters with little stones and seeds, is
+to prevent their closely coiled-up bodies from coming into close
+contact with the surrounding cold soil; and such contact would
+perhaps interfere with their respiration which is effected by the
+skin alone.</p>
+
+<p>A worm after swallowing earth, whether for making its burrow
+or for food, soon comes to the surface to empty its body.
+The ejected earth is thoroughly mingled with the intestinal
+secretions, and is thus rendered viscid. After being dried
+it sets hard. I have watched worms during the act of
+ejection, and when the earth was in a very liquid state it was
+ejected in little spurts, and by a slow peristaltic movement when
+not so liquid. It is not cast indifferently on any side,
+but with some care, first on one and then on another side; the
+tail being used almost like a trowel. When a worm comes to
+the surface to eject earth, the tail protrudes, but when it
+collects leaves its head must protrude. Worms therefore
+must have the power of turning round in their closely-fitting
+burrows; and this, as it appears to us, would be a difficult
+feat. As soon as a little heap has been formed, the worm
+apparently avoids, for the sake of safety, protruding its tail;
+and the earthy matter is forced up through the previously
+deposited soft mass. The mouth of the same burrow is used
+for this purpose for a considerable time. In the case of
+the tower-like castings (see Fig. 2) near Nice, and of the
+similar but still taller towers from Bengal (hereafter to be
+described and figured), a considerable degree of skill is
+exhibited in their construction. Dr. King also observed
+that the passage up these towers hardly ever ran in the same
+exact line with the underlying burrow, so that a thin cylindrical
+object such as a haulm of grass, could not be passed down the
+tower into the burrow; and this change of direction probably
+serves in some manner as a protection.</p>
+
+<p>Worms do not always eject their castings on the surface of the
+ground. When they can find any cavity, as when burrowing in
+newly turned-up earth, or between the stems of banked-up plants,
+they deposit their castings in such places. So again any
+hollow beneath a large stone lying on the surface of the ground,
+is soon filled up with their castings. According to Hensen,
+old burrows are habitually used for this purpose; but as far as
+my experience serves, this is not the case, excepting with those
+near the surface in recently dug ground. I think that
+Hensen may have been deceived by the walls of old burrows, lined
+with black earth, having sunk in or collapsed; for black streaks
+are thus left, and these are conspicuous when passing through
+light-coloured soil, and might be mistaken for completely
+filled-up burrows.</p>
+
+<p>It is certain that old burrows collapse in the course of time;
+for as we shall see in the next chapter, the fine earth voided by
+worms, if spread out uniformly, would form in many places in the
+course of a year a layer 0.2 of an inch in thickness; so that at
+any rate this large amount is not deposited within the old unused
+burrows. If the burrows did not collapse, the whole ground
+would be first thickly riddled with holes to a depth of about ten
+inches, and in fifty years a hollow unsupported space, ten inches
+in depth, would be left. The holes left by the decay of
+successively formed roots of trees and plants must likewise
+collapse in the course of time.</p>
+
+<p>The burrows of worms run down perpendicularly or a little
+obliquely, and where the soil is at all argillaceous, there is no
+difficulty in believing that the walls would slowly flow or slide
+inwards during very wet weather. When, however, the soil is
+sandy or mingled with many small stones, it can hardly be viscous
+enough to flow inwards during even the wettest weather; but
+another agency may here come into play. After much rain the
+ground swells, and as it cannot expand laterally, the surface
+rises; during dry weather it sinks again. For instance, a
+large flat stone laid on the surface of a field sank 3.33 mm.
+whilst the weather was dry between May 9th and June 13th, and
+rose 1.91 mm, between September 7th and 19th of the same year,
+much rain having fallen during the latter part of this
+time. During frosts and thaws the movements were twice as
+great. These observations were made by my son Horace, who
+will hereafter publish an account of the movements of this stone
+during successive wet and dry seasons, and of the effects of its
+being undermined by worms. Now when the ground swells, if
+it be penetrated by cylindrical holes, such as worm-burrows,
+their walls will tend to yield and be pressed inwards; and the
+yielding will be greater in the deeper parts (supposing the whole
+to be equally moistened) from the greater weight of the
+superincumbent soil which has to be raised, than in the parts
+near the surface. When the ground dries, the walls will
+shrink a little and the burrows will be a little enlarged.
+Their enlargement, however, through the lateral contraction of
+the ground, will not be favoured, but rather opposed, by the
+weight of the superincumbent soil.</p>
+
+<p><i>Distribution of Worms</i>.&mdash;Earth-worms are found in
+all parts of the world, and some of the genera have an enormous
+range. <a name="citation113"></a><a href="#footnote113"
+class="citation">[113]</a> They inhabit the most isolated
+islands; they abound in Iceland, and are known to exist in the
+West Indies, St. Helena, Madagascar, New Caledonia and
+Tahiti. In the Antarctic regions, worms from Kerguelen Land
+have been described by Ray Lankester; and I found them in the
+Falkland Islands. How they reach such isolated islands is
+at present quite unknown. They are easily killed by
+salt-water, and it does not appear probable that young worms or
+their egg-capsules could be carried in earth adhering to the feet
+or beaks of land-birds. Moreover Kerguelen Land is not now
+inhabited by any land-bird.</p>
+
+<p>In this volume we are chiefly concerned with the earth cast up
+by worms, and I have gleaned a few facts on this subject with
+respect to distant lands. Worms throw up plenty of castings
+in the United States. In Venezuela, castings, probably
+ejected by species of Urochæta, are common in the gardens
+and fields, but not in the forests, as I hear from Dr. Ernst of
+Caracas. He collected 156 castings from the court-yard of
+his house, having an area of 200 square yards. They varied
+in bulk from half a cubic centimeter to five cubic centimeters,
+and were on an average three cubic centimeters. They were,
+therefore, of small size in comparison with those often found in
+England; for six large castings from a field near my house
+averaged 16 cubic centimeters. Several species of
+earth-worms are common in St. Catharina in South Brazil, and
+Fritz M&uuml;ller informs me &ldquo;that in most parts of the
+forests and pasture-lands, the whole soil, to a depth of a
+quarter of a metre, looks as if it had passed repeatedly through
+the intestines of earth-worms, even where hardly any castings are
+to be seen on the surface.&rdquo; A gigantic but very rare
+species is found there, the burrows of which are sometimes even
+two centimeters or nearly 0.8 of an inch in diameter, and which
+apparently penetrate the ground to a great depth.</p>
+
+<p>In the dry climate of New South Wales, I hardly expected that
+worms would be common; but Dr. G. Krefft of Sydney, to whom I
+applied, after making inquiries from gardeners and others, and
+from his own observations, informs me that their castings
+abound. He sent me some collected after heavy rain, and
+they consisted of little pellets, about 0.15 inch in diameter;
+and the blackened sandy earth of which they were formed still
+cohered with considerable tenacity.</p>
+
+<p>The late Mr. John Scott of the Botanic Gardens near Calcutta
+made many observations for me on worms living under the hot and
+humid climate of Bengal. The castings abound almost
+everywhere, in jungles and in the open ground, to a greater
+degree, as he thinks, than in England. After the water has
+subsided from the flooded rice-fields, the whole surface very
+soon becomes studded with castings&mdash;a fact which much
+surprised Mr. Scott, as he did not know how long worms could
+survive beneath water. They cause much trouble in the
+Botanic garden, &ldquo;for some of the finest of our lawns can be
+kept in anything like order only by being almost daily rolled; if
+left undisturbed for a few days they become studded with large
+castings.&rdquo; These closely resemble those described as
+abounding near Nice; and they are probably the work of a species
+of Perichæta. They stand up like towers, with an open
+passage in the centre.</p>
+<p style="text-align: center">
+<a href="images/p116b.jpg">
+<img alt=
+"Fig. 3: A tower-like casting.  Fig. 4: A casting from the
+Nilgiri Mountains"
+title=
+"Fig. 3: A tower-like casting.  Fig. 4: A casting from the
+Nilgiri Mountains"
+ src="images/p116s.jpg" />
+</a></p>
+
+<p>A figure of one of these castings from a photograph is here
+given (Fig. 3). The largest received by me was 3&frac12;
+inches in height and 1.35 inch in diameter; another was only
+&frac34; inch in diameter and 2&frac34; in height. In the
+following year, Mr. Scott measured several of the largest; one
+was 6 inches in height and nearly 1&frac12; in diameter: two
+others were 5 inches in height and respectively 2 and rather more
+than 2&frac12; inches in diameter. The average weight of
+the 22 castings sent to me was 35 grammes (1&frac14; oz.); and
+one of them weighed 44.8 grammes (or 2 oz.). All these castings
+were thrown up either in one night or in two. Where the
+ground in Bengal is dry, as under large trees, castings of a
+different kind are found in vast numbers: these consist of little
+oval or conical bodies, from about the 1/20 to rather above 1/10
+of an inch in length. They are obviously voided by a
+distinct species of worms.</p>
+
+<p>The period during which worms near Calcutta display such
+extraordinary activity lasts for only a little over two months,
+namely, during the cool season after the rains. At this
+time they are generally found within about 10 inches beneath the
+surface. During the hot season they burrow to a greater
+depth, and are then found coiled up and apparently
+hybernating. Mr. Scott has never seen them at a greater
+depth than 2&frac12; feet, but has heard of their having been
+found at 4 feet. Within the forests, fresh castings may be
+found even during the hot season. The worms in the Botanic
+garden, during the cool and dry season, draw many leaves and
+little sticks into the mouths of their burrows, like our English
+worms; but they rarely act in this manner during the rainy
+season.</p>
+
+<p>Mr. Scott saw worm-castings on the lofty mountains of Sikkim
+in North India. In South India Dr. King found in one place,
+on the plateau of the Nilgiris, at an elevation of 7000 feet,
+&ldquo;a good many castings,&rdquo; which are interesting for
+their great size. The worms which eject them are seen only
+during the wet season, and are reported to be from 12 to 15
+inches in length, and as thick as a man&rsquo;s little
+finger. These castings were collected by Dr. King after a
+period of 110 days without any rain; and they must have been
+ejected either during the north-east or more probably during the
+previous south-west monsoon; for their surfaces had suffered some
+disintegration and they were penetrated by many fine roots.
+A drawing is here given (Fig. 4) of one which seems to have best
+retained its original size and appearance. Notwithstanding
+some loss from disintegration, five of the largest of these
+castings (after having been well sun-dried) weighed each on an
+average 89.5 grammes, or above 3 oz.; and the largest weighed
+123.14 grammes, or 4&#8531; oz.,&mdash;that is, above a quarter
+of a pound! The largest convolutions were rather more than
+one inch in diameter; but it is probable that they had subsided a
+little whilst soft, and that their diameters had thus been
+increased. Some had flowed so much that they now consisted
+of a pile of almost flat confluent cakes. All were formed
+of fine, rather light-coloured earth, and were surprisingly hard
+and compact, owing no doubt to the animal matter by which the
+particles of earth had been cemented together. They did not
+disintegrate, even when left for some hours in water.
+Although they had been cast up on the surface of gravelly soil,
+they contained extremely few bits of rock, the largest of which
+was only 0.15 inch in diameter.</p>
+
+<p>Dr. King saw in Ceylon a worm about 2 feet in length and
+&frac12; inch in diameter; and he was told that it was a very
+common species during the wet season. These worms must
+throw up castings at least as large as those on the Nilgiri
+Mountains; but Dr. King saw none during his short visit to
+Ceylon.</p>
+
+<p>Sufficient facts have now been given, showing that worms do
+much work in bringing up fine earth to the surface in most or all
+parts of the world, and under the most different climates.</p>
+<h2><a name="page121"></a><span class="pagenum">p.
+121</span>CHAPTER III.<br />
+<span class="GutSmall">THE AMOUNT OF FINE EARTH BROUGHT UP BY
+WORMS TO THE SURFACE.</span></h2>
+<p class="gutsumm">Rate at which various objects strewed on the
+surface of grass-fields are covered up by the castings of
+worms&mdash;The burial of a paved path&mdash;The slow subsidence
+of great stones left on the surface&mdash;The number of worms
+which live within a given space&mdash;The weight of earth ejected
+from a burrow, and from all the burrows within a given
+space&mdash;The thickness of the layer of mould which the
+castings on a given space would form within a given time if
+uniformly spread out&mdash;The slow rate at which mould can
+increase to a great thickness&mdash;Conclusion.</p>
+
+<p><span class="smcap">We</span> now come to the more immediate
+subject of this volume, namely, the amount of earth which is
+brought up by worms from beneath the surface, and is afterwards
+spread out more or less completely by the rain and wind.
+The amount can be judged of by two methods,&mdash;by the rate at
+which objects left on the surface are buried, and more accurately
+by weighing the quantity brought up within a given time. We
+will begin with the first method, as it was first followed.</p>
+
+<p>Near Mael Hall in Staffordshire, quick-lime had been spread
+about the year 1827 thickly over a field of good pasture-land,
+which had not since been ploughed. Some square holes were
+dug in this field in the beginning of October 1837; and the
+sections showed a layer of turf, formed by the matted roots of
+the grasses, &frac12; inch in thickness, beneath which, at a
+depth of 2&frac12; inches (or 3 inches from the surface), a layer
+of the lime in powder or in small lumps could be distinctly seen
+running all round the vertical sides of the holes. The soil
+beneath the layer of lime was either gravelly or of a coarse
+sandy nature, and differed considerably in appearance from the
+overlying dark-coloured fine mould. Coal-cinders had been
+spread over a part of this same field either in the year 1833 or
+1834; and when the above holes were dug, that is after an
+interval of 3 or 4 years, the cinders formed a line of black
+spots round the holes, at a depth of 1 inch beneath the surface,
+parallel to and above the white layer of lime. Over another
+part of this field cinders had been strewed, only about
+half-a-year before, and these either still lay on the surface or
+were entangled among the roots of the grasses; and I here saw the
+commencement of the burying process, for worm-castings had been
+heaped on several of the smaller fragments. After an
+interval of 4&frac34; years this field was re-examined, and now
+the two layers of lime and cinders were found almost everywhere
+at a greater depth than before by nearly 1 inch, we will say by
+&frac34; of an inch. Therefore mould to an average
+thickness of 0.22 of an inch had been annually brought up by the
+worms, and had been spread over the surface of this field.</p>
+
+<p>Coal-cinders had been strewed over another field, at a date
+which could not be positively ascertained, so thickly that they
+formed (October, 1837) a layer, 1 inch in thickness at a depth of
+about 3 inches from the surface. The layer was so
+continuous that the over-lying dark vegetable mould was connected
+with the sub-soil of red clay only by the roots of the grasses;
+and when these were broken, the mould and the red clay fell
+apart. In a third field, on which coal-cinders and burnt
+marl had been strewed several times at unknown dates, holes were
+dug in 1842; and a layer of cinders could be traced at a depth of
+3&frac12; inches, beneath which at a depth of 9&frac12; inches
+from the surface there was a line of cinders together with burnt
+marl. On the sides of one hole there were two layers of
+cinders, at 2 and 3&frac12; inches beneath the surface; and below
+them at a depth in parts of 9&frac12;, and in other parts of
+10&frac12; inches there were fragments of burnt marl. In a
+fourth field two layers of lime, one above the other, could be
+distinctly traced, and beneath them a layer of cinders and burnt
+marl at a depth of from 10 to 12 inches below the surface.</p>
+<p style="text-align: center">
+<a href="images/p124b.jpg">
+<img alt=
+"Fig. 5: Section of the vegetable mould in a field.  Fig. 6:
+Traverse section across a large stone"
+title=
+"Fig. 5: Section of the vegetable mould in a field.  Fig. 6:
+Traverse section across a large stone"
+ src="images/p124s.jpg" />
+</a></p>
+
+<p>A piece of waste, swampy land was enclosed, drained, ploughed,
+harrowed and thickly covered in the year 1822 with burnt marl and
+cinders. It was sowed with grass seeds, and now supports a
+tolerably good but coarse pasture. Holes were dug in this
+field in 1837, or 15 years after its reclamation, and we see in
+the accompanying diagram (Fig. 5), reduced to half of the natural
+scale, that the turf was &frac12; inch thick, beneath which there
+was a layer of vegetable mould 2&frac12; inches thick. This
+layer did not contain fragments of any kind; but beneath it there
+was a layer of mould, 1&frac12; inch in thickness, full of
+fragments of burnt marl, conspicuous from their red colour, one
+of which near the bottom was an inch in length; and other
+fragments of coal-cinders together with a few white quartz
+pebbles. Beneath this layer and at a depth of 4&frac12;
+inches from the surface, the original black, peaty, sandy soil
+with a few quartz pebbles was encountered. Here therefore
+the fragments of burnt marl and cinders had been covered in the
+course of 15 years by a layer of fine vegetable mould, only
+2&frac12; inches in thickness, excluding the turf. Six and
+a half years subsequently this field was re-examined, and the
+fragments were now found at from 4 to 5 inches beneath the
+surface. So that in this interval of 6&frac12; years, about
+1&frac12; inch of mould had been added to the superficial
+layer. I am surprised that a greater quantity had not been
+brought up during the whole 21&frac12; years, for in the closely
+underlying black, peaty soil there were many worms. It is,
+however, probable that formerly, whilst the land remained poor,
+worms were scanty; and the mould would then have accumulated
+slowly. The average annual increase of thickness for the
+whole period is 0.19 of an inch.</p>
+
+<p>Two other cases are worth recording. In the spring of
+1835, a field, which had long existed as poor pasture and was so
+swampy that it trembled slightly when stamped on, was thickly
+covered with red sand so that the whole surface appeared at first
+bright red. When holes were dug in this field after an
+interval of about 2&frac12; years, the sand formed a layer at a
+depth of &frac34; in. beneath the surface. In 1842 (i.e., 7
+years after the sand had been laid on) fresh holes were dug, and
+now the red sand formed a distinct layer, 2 inches beneath the
+surface, or 1&frac12; inch beneath the turf; so that on an
+average, 0.21 inch of mould had been annually brought to the
+surface. Immediately beneath the layer of red sand, the
+original substratum of black sandy peat extended.</p>
+
+<p>A grass field, likewise not far from Maer Hall, had formerly
+been thickly covered with marl, and was then left for several
+years as pasture; it was afterwards ploughed. A friend had
+three trenches dug in this field 28 years after the application
+of the marl, <a name="citation126"></a><a href="#footnote126"
+class="citation">[126]</a> and a layer of the marl fragments
+could be traced at a depth, carefully measured, of 12 inches in
+some parts, and of 14 inches in other parts. This
+difference in depth depended on the layer being horizontal,
+whilst the surface consisted of ridges and furrows from the field
+having been ploughed. The tenant assured me that it had
+never been turned up to a greater depth than from 6 to 8 inches;
+and as the fragments formed an unbroken horizontal layer from 12
+to 14 inches beneath the surface, these must have been buried by
+the worms whilst the land was in pasture before it was ploughed,
+for otherwise they would have been indiscriminately scattered by
+the plough throughout the whole thickness of the soil.
+Four-and-a-half years afterwards I had three holes dug in this
+field, in which potatoes had been lately planted, and the layer
+of marl-fragments was now found 13 inches beneath the bottoms of
+the furrows, and therefore probably 15 inches beneath the general
+level of the field. It should, however, be observed that
+the thickness of the blackish sandy soil, which had been thrown
+up by the worms above the marl-fragments in the course of
+32&frac12; years, would have measured less than 15 inches, if the
+field had always remained as pasture, for the soil would in this
+case have been much more compact. The fragments of marl
+almost rested on an undisturbed substratum of white sand with
+quartz pebbles; and as this would be little attractive to worms,
+the mould would hereafter be very slowly increased by their
+action.</p>
+
+<p>We will now give some cases of the action of worms, on land
+differing widely from the dry sandy or the swampy pastures just
+described. The chalk formation extends all round my house
+in Kent; and its surface, from having been exposed during an
+immense period to the dissolving action of rain-water, is
+extremely irregular, being abruptly festooned and penetrated by
+many deep well-like cavities. <a name="citation128"></a><a
+href="#footnote128" class="citation">[128]</a> During the
+dissolution of the chalk, the insoluble matter, including a vast
+number of unrolled flints of all sizes, has been left on the
+surface and forms a bed of stiff red clay, full of flints, and
+generally from 6 to 14 feet in thickness. Over the red
+clay, wherever the land has long remained as pasture, there is a
+layer a few inches in thickness, of dark-coloured vegetable
+mould.</p>
+
+<p>A quantity of broken chalk was spread, on December 20, 1842,
+over a part of a field near my house, which had existed as
+pasture certainly for 30, probably for twice or thrice as many
+years. The chalk was laid on the land for the sake of
+observing at some future period to what depth it would become
+buried. At the end of November, 1871, that is after an
+interval of 29 years, a trench was dug across this part of the
+field; and a line of white nodules could be traced on both sides
+of the trench, at a depth of 7 inches from the surface. The
+mould, therefore, (excluding the turf) had here been thrown up at
+an average rate of 0.22 inch per year. Beneath the line of
+chalk nodules there was in parts hardly any fine earth free of
+flints, while in other parts there was a layer, 2&frac14; inches
+in thickness. In this latter case the mould was altogether
+9&frac14; inches thick; and in one such spot a nodule of chalk
+and a smooth flint pebble, both of which must have been left at
+some former time on the surface, were found at this depth.
+At from 11 to 12 inches beneath the surface, the undisturbed
+reddish clay, full of flints, extended. The appearance of
+the above nodules of chalk surprised me, much at first, as they
+closely resembled water-worn pebbles, whereas the freshly-broken
+fragments had been angular. But on examining the nodules
+with a lens, they no longer appeared water-worn, for their
+surfaces were pitted through unequal corrosion, and minute, sharp
+points, formed of broken fossil shells, projected from
+them. It was evident that the corners of the original
+fragments of chalk had been wholly dissolved, from presenting a
+large surface to the carbonic acid dissolved in the rain-water
+and to that generated in soil containing vegetable matter, as
+well as to the humus-acids. <a name="citation131"></a><a
+href="#footnote131" class="citation">[131]</a> The
+projecting corners would also, relatively to the other parts,
+have been embraced by a larger number of living rootlets; and
+these have the power of even attacking marble, as Sachs has
+shown. Thus, in the course of 29 years, buried angular
+fragments of chalk had been converted into well-rounded
+nodules.</p>
+
+<p>Another part of this same field was mossy, and as it was
+thought that sifted coal-cinders would improve the pasture, a
+thick layer was spread over this part either in 1842 or 1843, and
+another layer some years afterwards. In 1871 a trench was
+here dug, and many cinders lay in a line at a depth of 7 inches
+beneath the surface, with another line at a depth of 5&frac12;
+inches parallel to the one beneath. In another part of this
+field, which had formerly existed as a separate one, and which it
+was believed had been pasture-land for more than a century,
+trenches were dug to see how thick the vegetable mould was.
+By chance the first trench was made at a spot where at some
+former period, certainly more than forty years before, a large
+hole had been filled up with coarse red clay, flints, fragments
+of chalk, and gravel; and here the fine vegetable mould was only
+from 4&#8539; to 4&#8540; inches in thickness. In another
+and undisturbed place, the mould varied much in thickness,
+namely, from 6&frac12; to 8&frac12; inches; beneath which a few
+small fragments of brick were found in one place. From
+these several cases, it would appear that during the last 29
+years mould has been heaped on the surface at an average annual
+rate of from 0.2 to 0.22 of an inch. But in this district
+when a ploughed field is first laid down in grass, the mould
+accumulates at a much slower rate. The rate, also, must
+become very much slower after a bed of mould, several inches in
+thickness, has been formed; for the worms then live chiefly near
+the surface, and burrow down to a greater depth so as to bring up
+fresh earth from below, only during the winter when the weather
+is very cold (at which time worms were found in this field at a
+depth of 26 inches) and during summer, when the weather is very
+dry.</p>
+
+<p>A field, which adjoins the one just described, slopes in one
+part rather steeply (viz., at from 10&deg; to 15&deg;); this part
+was last ploughed in 1841, was then harrowed and left to become
+pasture-land. For several years it was clothed with an
+extremely scant vegetation, and was so thickly covered with small
+and large flints (some of them half as large as a child&rsquo;s
+head) that the field was always called by my sons &ldquo;the
+stony field.&rdquo; When they ran down the slope the stones
+clattered together, I remember doubting whether I should live to
+see these larger flints covered with vegetable mould and
+turf. But the smaller stones disappeared before many years
+had elapsed, as did every one of the larger ones after a time; so
+that after thirty years (1871) a horse could gallop over the
+compact turf from one end of the field to the other, and not
+strike a single stone with his shoes. To anyone who
+remembered the appearance of the field in 1842, the
+transformation was wonderful. This was certainly the work
+of the worms, for though castings were not frequent for several
+years, yet some were thrown up month after month, and these
+gradually increased in numbers as the pasture improved. In
+the year 1871 a trench was dug on the above slope, and the blades
+of grass were cut off close to the roots, so that the thickness
+of the turf and of the vegetable mould could be measured
+accurately. The turf was rather less than half an inch, and
+the mould, which did not contain any stones, 2&frac12; inches in
+thickness. Beneath this lay coarse clayey earth full of
+flints, like that in any of the neighbouring ploughed
+fields. This coarse earth easily fell apart from the
+overlying mould when a spit was lifted up. The average rate
+of accumulation of the mould during the whole thirty years was
+only .083 inch per year (i.e., nearly one inch in twelve years);
+but the rate must have been much slower at first, and afterwards
+considerably quicker.</p>
+
+<p>The transformation in the appearance of this field, which had
+been effected beneath my eyes, was afterwards rendered the more
+striking, when I examined in Knole Park a dense forest of lofty
+beech-trees, beneath which nothing grew. Here the ground
+was thickly strewed with large naked stones, and worm-castings
+were almost wholly absent. Obscure lines and irregularities
+on the surface indicated that the land had been cultivated some
+centuries ago. It is probable that a thick wood of young
+beech-trees sprung up so quickly, that time enough was not
+allowed for worms to cover up the stones with their castings,
+before the site became unfitted for their existence. Anyhow
+the contrast between the state of the now miscalled &ldquo;stony
+field,&rdquo; well stocked with worms, and the present state of
+the ground beneath the old beech-trees in Knole Park, where worms
+appeared to be absent, was striking.</p>
+
+<p>A narrow path running across part of my lawn was paved in 1843
+with small flagstones, set edgeways; but worms threw up many
+castings and weeds grew thickly between them. During
+several years the path was weeded and swept; but ultimately the
+weeds and worms prevailed, and the gardener ceased to sweep,
+merely mowing off the weeds, as often as the lawn was
+mowed. The path soon became almost covered up, and after
+several years no trace of it was left. On removing, in
+1877, the thin overlying layer of turf, the small flag-stones,
+all in their proper places, were found covered by an inch of fine
+mould.</p>
+
+<p>Two recently published accounts of substances strewed on the
+surface of pasture-land, having become buried through the action
+of worms, may be here noticed. The Rev. H. C. Key had a
+ditch cut in a field, over which coal-ashes had been spread, as
+it was believed, eighteen years before; and on the clean-cut
+perpendicular sides of the ditch, at a depth of at least seven
+inches, there could be seen, for a length of 60 yards, &ldquo;a
+distinct, very even, narrow line of coal-ashes, mixed with small
+coal, perfectly parallel with the top-sward.&rdquo; <a
+name="citation136a"></a><a href="#footnote136a"
+class="citation">[136a]</a> This parallelism and the length
+of the section give interest to the case. Secondly, Mr.
+Dancer states <a name="citation136b"></a><a href="#footnote136b"
+class="citation">[136b]</a> that crushed bones had been thickly
+strewed over a field; and &ldquo;some years afterwards&rdquo;
+these were found &ldquo;several inches below the surface, at a
+uniform depth.&rdquo;</p>
+
+<p>The Rev. Mr. Zincke informs me that he has lately had an
+orchard dug to the unusual depth of 4 feet. The upper 18
+inches consisted of dark-coloured vegetable mould, and the next
+18 inches of sandy loam, containing in the lower part many rolled
+pieces of sandstone, with some bits of brick and tile, probably
+of Roman origin, as remains of this period have been found close
+by. The sandy loam rested on an indurated ferruginous pan
+of yellow clay, on the surface of which two perfect celts were
+found. If, as seems probable, the celts were originally
+left on the surface of the land, they have since been covered up
+with earth 3 feet in thickness, all of which has probably passed
+through the bodies of worms, excepting the stones which may have
+been scattered on the surface at different times, together with
+manure or by other means. It is difficult otherwise to
+understand the source of the 18 inches of sandy loam, which
+differed from the overlying dark vegetable mould, after both had
+been burnt, only in being of a brighter red colour, and in not
+being quite so fine-grained. But on this view we must
+suppose that the carbon in vegetable mould, when it lies at some
+little depth beneath the surface and does not continually receive
+decaying vegetable matter from above, loses its dark colour in
+the course of centuries; but whether this is probable I do not
+know.</p>
+
+<p>Worms appear to act in the same manner in New Zealand as in
+Europe; for Professor J. von Haast has described <a
+name="citation138a"></a><a href="#footnote138a"
+class="citation">[138a]</a> a section near the coast, consisting
+of mica-schist, &ldquo;covered by 5 or 6 feet of loess, above
+which about 12 inches of vegetable soil had
+accumulated.&rdquo; Between the loess and the mould there
+was a layer from 3 to 6 inches in thickness, consisting of
+&ldquo;cores, implements, flakes, and chips, all manufactured
+from hard basaltic rock.&rdquo; It is therefore probable
+that the aborigines, at some former period, had left these
+objects on the surface, and that they had afterwards been slowly
+covered up by the castings of worms.</p>
+
+<p>Farmers in England are well aware that objects of all kinds,
+left on the surface of pasture-land, after a time disappear, or,
+as they say, work themselves downwards. How powdered lime,
+cinders, and heavy stones, can work down, and at the same rate,
+through the matted roots of a grass-covered surface, is a
+question which has probably never occurred to them. <a
+name="citation138b"></a><a href="#footnote138b"
+class="citation">[138b]</a></p>
+
+<p><i>The Sinking of great Stones through the Action of
+Worms</i>.&mdash;When a stone of large size and of irregular
+shape is left on the surface of the ground, it rests, of course,
+on the more protuberant parts; but worms soon fill up with their
+castings all the hollow spaces on the lower side; for, as Hensen
+remarks, they like the shelter of stones. As soon as the
+hollows are filled up, the worms eject the earth which they have
+swallowed beyond the circumference of the stones; and thus the
+surface of the ground is raised all round the stone. As the
+burrows excavated directly beneath the stone after a time
+collapse, the stone sinks a little. <a name="citation139"></a><a
+href="#footnote139" class="citation">[139]</a> Hence it is,
+that boulders which at some ancient period have rolled down from
+a rocky mountain or cliff on to a meadow at its base, are always
+somewhat imbedded in the soil; and, when removed, leave an exact
+impression of their lower surfaces in the underlying fine
+mould. If, however, a boulder is of such huge dimensions,
+that the earth beneath is kept dry, such earth will not be
+inhabited by worms, and the boulder will not sink into the
+ground.</p>
+
+<p>A lime-kiln formerly stood in a grass-field near Leith Hill
+Place in Surrey, and was pulled down 35 years before my visit;
+all the loose rubbish had been carted away, excepting three large
+stones of quartzose sandstone, which it was thought might
+hereafter be of some use. An old workman remembered that
+they had been left on a bare surface of broken bricks and mortar,
+close to the foundations of the kiln; but the whole surrounding
+surface is now covered with turf and mould. The two largest
+of these stones had never since been moved; nor could this easily
+have been done, as, when I had them removed, it was the work of
+two men with levers. One of these stones, and not the
+largest, was 64 inches long, 17 inches broad, and from 9 to 10
+inches in thickness. Its lower surface was somewhat
+protuberant in the middle; and this part still rested on broken
+bricks and mortar, showing the truth of the old workman&rsquo;s
+account. Beneath the brick rubbish the natural sandy soil,
+full of fragments of sandstone was found; and this could have
+yielded very little, if at all, to the weight of the stone, as
+might have been expected if the sub-soil had been clay. The
+surface of the field, for a distance of about 9 inches round the
+stone, gradually sloped up to it, and close to the stone stood in
+most places about 4 inches above the surrounding ground.
+The base of the stone was buried from 1 to 2 inches beneath the
+general level, and the upper surface projected about 8 inches
+above this level, or about 4 inches above the sloping border of
+turf. After the removal of the stone it became evident that
+one of its pointed ends must at first have stood clear above the
+ground by some inches, but its upper surface was now on a level
+with the surrounding turf. When the stone was removed, an
+exact cast of its lower side, forming a shallow crateriform
+hollow, was left, the inner surface of which consisted of fine
+black mould, excepting where the more protuberant parts rested on
+the brick-rubbish. A transverse section of this stone,
+together with its bed, drawn from measurements made after it had
+been displaced, is here given on a scale of &frac12; inch to a
+foot (Fig. 6). The turf-covered border which sloped up to
+the stone, consisted of fine vegetable mould, in one part 7
+inches in thickness. This evidently consisted of
+worm-castings, several of which had been recently ejected.
+The whole stone had sunk in the thirty-five years, as far as I
+could judge, about 1&frac12; inch; and this must have been due to
+the brick-rubbish beneath the more protuberant parts having been
+undermined by worms. At this rate the upper surface of the
+stone, if it had been left undisturbed, would have sunk to the
+general level of the field in 247 years; but before this could
+have occurred, some earth would have been washed down by heavy
+rain from the castings on the raised border of turf over the
+upper surface of the stone.</p>
+
+<p>The second stone was larger that the one just described, viz.,
+67 inches in length, 39 in breadth, and 15 in thickness.
+The lower surface was nearly flat, so that the worms must soon
+have been compelled to eject their castings beyond its
+circumference. The stone as a whole had sunk about 2 inches
+into the ground. At this rate it would have required 262
+years for its upper surface to have sunk to the general level of
+the field. The upwardly sloping, turf-covered border round
+the stone was broader than in the last case, viz., from 14 to 16
+inches; and why this should be so, I could see no reason.
+In most parts this border was not so high as in the last case,
+viz., from 2 to 2&frac12; inches, but in one place it was as much
+as 5&frac12;. Its average height close to the stone was
+probably about 3 inches, and it thinned out to nothing. If
+so, a layer of fine earth, 15 inches in breadth and 1&frac12;
+inch in average thickness, of sufficient length to surround the
+whole of the much elongated slab, must have been brought up by
+the worms in chief part from beneath the stone in the course of
+35 years. This amount would be amply sufficient to account
+for its having sunk about 2 inches into the ground; more
+especially if we bear in mind that a good deal of the finest
+earth would have been washed by heavy rain from the castings
+ejected on the sloping border down to the level of the
+field. Some fresh castings were seen close to the
+stone. Nevertheless, on digging a large hole to a depth of
+18 inches where the stone had lain, only two worms and a few
+burrows were seen, although the soil was damp and seemed
+favourable for worms. There were some large colonies of
+ants beneath the stone, and possibly since their establishment
+the worms had decreased in number.</p>
+
+<p>The third stone was only about half as large as the others;
+and two strong boys could together have rolled it over. I
+have no doubt that it had been rolled over at a moderately recent
+time, for it now lay at some distance from the two other stones
+at the bottom of a little adjoining slope. It rested also
+on fine earth, instead of partly on brick-rubbish. In
+agreement with this conclusion, the raised surrounding border of
+turf was only 1 inch high in some parts, and 2 inches in other
+parts. There were no colonies of ants beneath this stone,
+and on digging a hole where it had lain, several burrows and
+worms were found.</p>
+
+<p>At Stonehenge, some of the outer Druidical stones are now
+prostrate, having fallen at a remote but unknown period; and
+these have become buried to a moderate depth in the ground.
+They are surrounded by sloping borders of turf, on which recent
+castings were seen. Close to one of these fallen stones,
+which was 17 ft long, 6 ft. broad, and 28&frac12; inches thick, a
+hole was dug; and here the vegetable mould was at least 9&frac12;
+inches in thickness. At this depth a flint was found, and a
+little higher up on one side of the hole a fragment of
+glass. The base of the stone lay about 9&frac12; inches
+beneath the level of the surrounding ground, and its upper
+surface 19 inches above the ground.</p>
+
+<p>A hole was also dug close to a second huge stone, which in
+falling had broken into two pieces; and this must have happened
+long ago, judging from the weathered aspect of the fractured
+ends. The base was buried to a depth of 10 inches, as was
+ascertained by driving an iron skewer horizontally into the
+ground beneath it. The vegetable mould forming the
+turf-covered sloping border round the stone, on which many
+castings had recently been ejected, was 10 inches in thickness;
+and most of this mould must have been brought up by worms from
+beneath its base. At a distance of 8 yards from the stone,
+the mould was only 5&frac12; inches in thickness (with a piece of
+tobacco pipe at a depth of 4 inches), and this rested on broken
+flint and chalk which could not have easily yielded to the
+pressure or weight of the stone.</p>
+
+<p>A straight rod was fixed horizontally (by the aid of a
+spirit-level) across a third fallen stone, which was 7 feet 9
+inches long; and the contour of the projecting parts and of the
+adjoining ground, which was not quite level, was thus
+ascertained, as shown in the accompanying diagram (Fig. 7) on a
+scale of &frac12; inch to a foot. The turf-covered border
+sloped up to the stone on one side to a height of 4 inches, and
+on the opposite side to only 2&frac12; inches above the general
+level. A hole was dug on the eastern side, and the base of
+the stone was here found to lie at a depth of 4 inches beneath
+the general level of the ground, and of 8 inches beneath the top
+of the sloping turf-covered border.</p>
+
+<div class="gapspace">&nbsp;</div>
+<p>Sufficient evidence has now been given showing that small
+objects left on the surface of the land where worms abound soon
+get buried, and that large stones sink slowly downwards through
+the same means. Every step of the process could be
+followed, from the accidental deposition of a single casting on a
+small object lying loose on the surface, to its being entangled
+amidst the matted roots of the turf, and lastly to its being
+embedded in the mould at various depths beneath the
+surface. When the same field was re-examined after the
+interval of a few years, such objects were found at a greater
+depth than before. The straightness and regularity of the
+lines formed by the imbedded objects, and their parallelism with
+the surface of the land, are the most striking features of the
+case; for this parallelism shows how equably the worms must have
+worked; the result being, however, partly the effect of the
+washing down of the fresh castings by rain. The specific
+gravity of the objects does not affect their rate of sinking, as
+could be seen by porous cinders, burnt marl, chalk and quartz
+pebbles, having all sunk to the same depth within the same
+time. Considering the nature of the substratum, which at
+Leith Hill Place was sandy soil including many bits of rock, and
+at Stonehenge, chalk-rubble with broken flints; considering,
+also, the presence of the turf-covered sloping border of mould
+round the great fragments of stone at both these places, their
+sinking does not appear to have been sensibly aided by their
+weight, though this was considerable. <a
+name="citation147"></a><a href="#footnote147"
+class="citation">[147]</a></p>
+
+<p><i>On the number of worms which live within a given
+space</i>.&mdash;We will now show, firstly, what a vast number of
+worms live unseen by us beneath our feet, and, secondly, the
+actual weight of the earth which they bring up to the surface
+within a given space and within a given time. Hensen, who
+has published so full and interesting an account of the habits of
+worms, <a name="citation148"></a><a href="#footnote148"
+class="citation">[148]</a> calculates, from the number which he
+found in a measured space, that there must exist 133,000 living
+worms in a hectare of land, or 53,767 in an acre. This
+latter number of worms would weigh 356 pounds, taking
+Hensen&rsquo;s standard of the weight of a single worm, namely,
+three grams. It should, however, be noted that this
+calculation is founded on the numbers found in a garden, and
+Hensen believes that worms are here twice as numerous as in
+corn-fields. The above result, astonishing though it be,
+seems to me credible, judging from the number of worms which I
+have sometimes seen, and from the number daily destroyed by birds
+without the species being exterminated. Some barrels of bad
+ale were left on Mr. Miller&rsquo;s land, <a
+name="citation149"></a><a href="#footnote149"
+class="citation">[149]</a> in the hope of making vinegar, but the
+vinegar proved bad, and the barrels were upset. It should
+be premised that acetic acid is so deadly a poison to worms that
+Perrier found that a glass rod dipped into this acid and then
+into a considerable body of water in which worms were immersed,
+invariably killed them quickly. On the morning after the
+barrels had been upset, &ldquo;the heaps of worms which lay dead
+on the ground were so amazing, that if Mr. Miller had not seen
+them, he could not have thought it possible for such numbers to
+have existed in the space.&rdquo; As further evidence of
+the large number of worms which live in the ground, Hensen states
+that he found in a garden sixty-four open burrows in a space of
+14&frac12; square feet, that is, nine in 2 square feet. But
+the burrows are sometimes much more numerous, for when digging in
+a grass-field near Maer Hall, I found a cake of dry earth, as
+large as my two open hands, which was penetrated by seven
+burrows, as large as goose-quills.</p>
+
+<p><i>Weight of the earth ejected from a single burrow</i>,
+<i>and from all the burrows within a given space</i>.&mdash;With
+respect to the weight of the earth daily ejected by worms, Hensen
+found that it amounted, in the case of some worms which he kept
+in confinement, and which he appears to have fed with leaves, to
+only 0.5 gram, or less than 8 grains per diem. But a very
+much larger amount must be ejected by worms in their natural
+state, at the periods when they consume earth as food instead of
+leaves, and when they are making deep burrows. This is
+rendered almost certain by the following weights of the castings
+thrown up at the mouths of single burrows; the whole of which
+appeared to have been ejected within no long time, as was
+certainly the case in several instances. The castings were
+dried (excepting in one specified instance) by exposure during
+many days to the sun or before a hot fire.</p>
+<table>
+<tr>
+<td colspan="2"><p style="text-align: center"><span
+class="smcap">Weight of the Castings accumulated at the mouth of
+a single Burrow</span>.</p>
+</td>
+</tr>
+<tr>
+<td><p>(1.) Down, Kent (sub-soil red clay, full of flints,
+over-lying the chalk). The largest casting which I could
+find on the flanks of a steep valley, the sub-soil being here
+shallow. In this one case, the casting was not well
+dried</p>
+</td>
+<td><p style="text-align: right">3.98</p>
+</td>
+</tr>
+<tr>
+<td><p>(2.) Down.&mdash;Largest casting which I could find
+(consisting chiefly of calcareous matter), on extremely poor
+pasture land at the bottom of the valley mentioned under (1.)</p>
+</td>
+<td><p style="text-align: right">3.87</p>
+</td>
+</tr>
+<tr>
+<td><p>(3.) Down.&mdash;A large casting, but not of unusual
+size, from a nearly level field, poor pasture, laid down in a
+grass about 35 years before</p>
+</td>
+<td><p style="text-align: right">1.22</p>
+</td>
+</tr>
+<tr>
+<td><p>(4.) Down. Average weight of 11 not large
+castings ejected on a sloping surface on my lawn, after they had
+suffered some loss of weight from being exposed during a
+considerable length of time to rain</p>
+</td>
+<td><p style="text-align: right">0.7</p>
+</td>
+</tr>
+<tr>
+<td><p>(5.) Near Nice in France.&mdash;Average weight of 12
+castings of ordinary dimensions, collected by Dr. King on land
+which had not been mown for a long time and where worms abounded,
+viz., a lawn protected by shrubberies near the sea; soil sandy
+and calcareous; these castings had been exposed for some time to
+rain, before being collected, and must have lost some weight by
+disintegration, but they still retained their form</p>
+</td>
+<td><p style="text-align: right">1.37</p>
+</td>
+</tr>
+<tr>
+<td><p>(6.) The heaviest of the above twelve castings</p>
+</td>
+<td><p style="text-align: right">1.76</p>
+</td>
+</tr>
+<tr>
+<td><p>(7.)&nbsp; Lower Bengal.&mdash;Average weight of 22
+castings, collected by Mr. J. Scott, and stated by him to have
+been thrown up in the course of one or two nights</p>
+</td>
+<td><p style="text-align: right">1.24</p>
+</td>
+</tr>
+<tr>
+<td><p>(8.) The heaviest of the above 22 castings</p>
+</td>
+<td><p style="text-align: right">2.09</p>
+</td>
+</tr>
+<tr>
+<td><p>(9.) Nilgiri Mountains, S. India; average weight of
+the 5 largest castings collected by Dr. King. They had been
+exposed to the rain of the last monsoon, and must have lost some
+weight</p>
+</td>
+<td><p style="text-align: right">3.15</p>
+</td>
+</tr>
+<tr>
+<td><p>(10.) The heaviest of the above 5 castings</p>
+</td>
+<td><p style="text-align: right">4.34</p>
+</td>
+</tr>
+</table>
+<p>In this table we see that castings which had been ejected at
+the mouth of the same burrow, and which in most cases appeared
+fresh and always retained their vermiform configuration,
+generally exceeded an ounce in weight after being dried, and
+sometimes nearly equalled a quarter of a pound. On the
+Nilgiri mountains one casting even exceeded this latter
+weight. The largest castings in England were found on
+extremely poor pasture-land; and these, as far as I have seen,
+are generally larger than those on land producing a rich
+vegetation. It would appear that worms have to swallow a
+greater amount of earth on poor than on rich land, in order to
+obtain sufficient nutriment.</p>
+
+<p>With respect to the tower-like castings near Nice (Nos. 5 and
+6 in the above table), Dr. King often found five or six of them
+on a square foot of surface; and these, judging from their
+average weight, would have weighed together 7&frac12; ounces; so
+that the weight of those on a square yard would have been 4 lb.
+3&frac12; oz. Dr. King collected, near the close of the
+year 1872, all the castings which still retained their vermiform
+shape, whether broken down or not, from a square foot, in a place
+abounding with worms, on the summit of a bank, where no castings
+could have rolled down from above. These castings must have
+been ejected, as he judged from their appearance in reference to
+the rainy and dry periods near Nice, within the previous five or
+six months; they weighed 9&frac12; oz., or 5 lb. 5&frac12; oz.
+per square yard. After an interval of four months, Dr. King
+collected all the castings subsequently ejected on the same
+square foot of surface, and they weighed 2&frac12; oz., or 1 lb.
+6&frac12; oz. per square yard. Therefore within about ten
+months, or we will say for safety&rsquo;s sake within a year, 12
+oz. of castings were thrown up on this one square foot, or 6.75
+pounds on the square yard; and this would give 14.58 tons per
+acre.</p>
+
+<p>In a field at the bottom of a valley in the chalk (see No. 2
+in the foregoing table), a square yard was measured at a spot
+where very large castings abounded; they appeared, however,
+almost equally numerous in a few other places. These
+castings, which retained perfectly their vermiform shape, were
+collected; and they weighed when partially dried, 1 lb.
+13&frac12; oz. This field had been rolled with a heavy
+agricultural roller fifty-two days before, and this would
+certainly have flattened every single casting on the land.
+The weather had been very dry for two or three weeks before the
+day of collection, so that not one casting appeared fresh or had
+been recently ejected. We may therefore assume that those
+which were weighed had been ejected within, we will say, forty
+days from the time when the field was rolled,&mdash;that is,
+twelve days short of the whole intervening period. I had
+examined the same part of the field shortly before it was rolled,
+and it then abounded with fresh castings. Worms do not work
+in dry weather during the summer, or in winter during severe
+frosts. If we assume that they work for only half the
+year&mdash;though this is too low an estimate&mdash;then the
+worms in this field would eject during the year, 8.387 pounds per
+square yard; or 18.12 tons per acre, assuming the whole surface
+to be equally productive in castings.</p>
+
+<p>In the foregoing cases some of the necessary data had to be
+estimated, but in the two following cases the results are much
+more trustworthy. A lady, on whose accuracy I can
+implicitly rely, offered to collect during a year all the
+castings thrown up on two separate square yards, near Leith Hill
+Place, in Surrey. The amount collected was, however,
+somewhat less than that originally ejected by the worms; for, as
+I have repeatedly observed, a good deal of the finest earth is
+washed away, whenever castings are thrown up during or shortly
+before heavy rain. Small portions also adhered to the
+surrounding blades of grass, and it required too much time to
+detach every one of them.</p>
+
+<p>On sandy soil, as in the present instance, castings are liable
+to crumble after dry weather, and particles were thus often
+lost. The lady also occasionally left home for a week or
+two, and at such times the castings must have suffered still
+greater loss from exposure to the weather. These losses
+were, however, compensated to some extent by the collections
+having been made on one of the squares for four days, and on the
+other square for two days more than the year.</p>
+
+<p>A space was selected (October 9th, 1870) for one of the
+squares on a broad, grass-covered terrace, which had been mowed
+and swept during many years. It faced the south, but was
+shaded during part of the day by trees. It had been formed
+at least a century ago by a great accumulation of small and large
+fragments of sandstone, together with some sandy earth, rammed
+down level. It is probable that it was at first protected
+by being covered with turf. This terrace, judging from the
+number of castings on it, was rather unfavourable for the
+existence of worms, in comparison with the neighbouring fields
+and an upper terrace. It was indeed surprising that as many
+worms could live here as were seen; for on digging a hole in this
+terrace, the black vegetable mould together with the turf was
+only four inches in thickness, beneath which lay the level
+surface of light-coloured sandy soil, with many fragments of
+sandstone. Before any castings were collected all the
+previously existing ones were carefully removed. The last
+day&rsquo;s collection was on October 14th, 1871. The
+castings were then well dried before a fire; and they weighed
+exactly 3&frac12; lbs. This would give for an acre of
+similar land 7.56 tons of dry earth annually ejected by
+worms.</p>
+
+<p>The second square was marked on unenclosed common land, at a
+height of about 700 ft. above the sea, at some little distance
+from Leith Hill Tower. The surface was clothed with short,
+fine turf, and had never been disturbed by the hand of man.
+The spot selected appeared neither particularly favourable nor
+the reverse for worms; but I have often noticed that castings are
+especially abundant on common land, and this may, perhaps, be
+attributed to the poorness of the soil. The vegetable mould
+was here between three and four inches in thickness. As
+this spot was at some distance from the house where the lady
+lived, the castings were not collected at such short intervals of
+time as those on the terrace; consequently the loss of fine earth
+during rainy weather must have been greater in this than in the
+last case. The castings moreover were more sandy, and in
+collecting them during dry weather they sometimes crumbled into
+dust, and much was thus lost. Therefore it is certain that
+the worms brought up to the surface considerably more earth than
+that which was collected. The last collection was made on
+October 27th, 1871; i.e., 367 days after the square had been
+marked out and the surface cleared of all pre-existing
+castings. The collected castings, after being well dried,
+weighed 7.453 pounds; and this would give, for an acre of the
+same kind of land, 16.1 tons of annually ejected dry earth.</p>
+<table>
+<tr>
+<td><p style="text-align: center"><span class="smcap">Summary of
+the four foregoing cases</span>.</p>
+</td>
+</tr>
+<tr>
+<td><p>(1.) Castings ejected near Nice within about a year,
+collected by Dr. King on a square foot of surface, calculated to
+yield per acre 14.58 tons.</p>
+</td>
+</tr>
+<tr>
+<td><p>(2.) Castings ejected during about 40 days on a
+square yard, in a field of poor pasture at the bottom of a large
+valley in the Chalk, calculated to yield annually per acre 18.12
+tons.</p>
+</td>
+</tr>
+<tr>
+<td><p>(3.) Castings collected from a square yard on an old
+terrace at Leith Hill Place, during 369 days, calculated to yield
+annually per acre 7.56 tons.</p>
+</td>
+</tr>
+<tr>
+<td><p>(4.) Castings collected from a square yard on Leith
+Hill Common during 367 days, calculated to yield annually per
+acre 16.1 tons.</p>
+</td>
+</tr>
+</table>
+<p><i>The thickness of the layer of mould</i>, <i>which castings
+ejected during a year would form if uniformly spread
+out</i>.&mdash;As we know, from the two last cases in the above
+summary, the weight of the dried castings ejected by worms during
+a year on a square yard of surface, I wished to learn how thick a
+layer of ordinary mould this amount would form if spread
+uniformly over a square yard. The dry castings were
+therefore broken into small particles, and whilst being placed in
+a measure were well shaken and pressed down. Those
+collected on the Terrace amounted to 124.77 cubic inches; and
+this amount, if spread out over a square yard, would make a layer
+0.9627 inch in thickness. Those collected on the Common
+amounted to 197.56 cubic inches, and would make a similar layer
+0.1524 inch in thickness.</p>
+
+<p>These thicknesses must, however, be corrected, for the
+triturated castings, after being well shaken down and pressed,
+did not make nearly so compact a mass as vegetable mould, though
+each separate particle was very compact. Yet mould is far
+from being compact, as is shown by the number of air-bubbles
+which rise up when the surface is flooded with water. It is
+moreover penetrated by many fine roots. To ascertain
+approximately by how much ordinary vegetable mould would be
+increased in bulk by being broken up into small particles and
+then dried, a thin oblong block of somewhat argillaceous mould
+(with the turf pared off) was measured before being broken up,
+was well dried and again measured. The drying caused it to
+shrink by 1/7 of its original bulk, judging from exterior
+measurements alone. It was then triturated and partly
+reduced to powder, in the same manner as the castings had been
+treated, and its bulk now exceeded (notwithstanding shrinkage
+from drying) by 1/16 that of the original block of damp
+mould. Therefore the above calculated thickness of the
+layer, formed by the castings from the Terrace, after being
+damped and spread over a square yard, would have to be reduced by
+1/16; and this will reduce the layer to 0.09 of an inch, so that
+a layer 0.9 inch in thickness would be formed in the course of
+ten years. On the same principle the castings from the
+Common would make in the course of a single year a layer 0.1429
+inch, or in the course of 10 years 1.429 inch, in
+thickness. We may say in round numbers that the thickness
+in the former case would amount to nearly 1 inch, and in the
+second case to nearly 1&frac12; inch in 10 years.</p>
+
+<p>In order to compare these results with those deduced from the
+rates at which small objects left on the surfaces of grass-fields
+become buried (as described in the early part of this chapter),
+we will give the following summary:&mdash;</p>
+<table>
+<tr>
+<td><p style="text-align: center"><span class="smcap">Summary of
+the thickness of the Mould accumulated over Objects left strewed
+on the Surface, in the course of ten years</span>.</p>
+</td>
+</tr>
+<tr>
+<td><p>The accumulation of mould during 14&frac34; years on the
+surface of a dry, sandy, grass-field near Maer Hall, amounted to
+2.2 inches in 10 years.</p>
+</td>
+</tr>
+<tr>
+<td><p>The accumulation during 21&frac12; years on a swampy field
+near Maer Hall, amounted to nearly 1.9 inch in 10 years.</p>
+</td>
+</tr>
+<tr>
+<td><p>The accumulation during 7 years on a very swampy field
+near Maer Hall amounted to 2.1 inches in 10 years.</p>
+</td>
+</tr>
+<tr>
+<td><p>The accumulation during 29 years, on good, argillaceous
+pasture-land over the Chalk at Down, amounted to 2.2 inches in 10
+years.</p>
+</td>
+</tr>
+<tr>
+<td><p>The accumulation during 30 years on the side of a valley
+over the Chalk at Down, the soil being argillaceous, very poor,
+and only just converted into pasture (so that it was for some
+years unfavourable for worms), amounted to 0.83 inch in 10
+years.</p>
+</td>
+</tr>
+</table>
+<p>In these cases (excepting the last) it may be seen that the
+amount of earth brought to the surface during 10 years is
+somewhat greater than that calculated from the castings which
+were actually weighed. This excess may be partly accounted
+for by the loss which the weighed castings had previously
+undergone through being washed by rain, by the adhesion of
+particles to the blades of the surrounding grass, and by their
+crumbling when dry. Nor must we overlook other agencies
+which in all ordinary cases add to the amount of mould, and which
+would not be included in the castings that were collected,
+namely, the fine earth brought up to the surface by burrowing
+larvæ and insects, especially by ants. The earth
+brought up by moles generally has a somewhat different appearance
+from vegetable mould; but after a time would not be
+distinguishable from it. In dry countries, moreover, the
+wind plays an important part in carrying dust from one place to
+another, and even in England it must add to the mould on fields
+near great roads. But in our country these latter several
+agencies appear to be of quite subordinate importance in
+comparison with the action of worms.</p>
+
+<p>We have no means of judging how great a weight of earth a
+single full-sized worm ejects during a year. Hensen
+estimates that 53,767 worms exist in an acre of land; but this is
+founded on the number found in gardens, and he believes that only
+about half as many live in corn-fields. How many live in
+old pasture land is unknown; but if we assume that half the above
+number, or 26,886 worms live on such land, then taking from the
+previous summary 15 tons as the weight of the castings annually
+thrown up on an acre of land, each worm must annually eject 20
+ounces. A full-sized casting at the mouth of a single
+burrow often exceeds, as we have seen, an ounce in weight; and it
+is probable that worms eject more than 20 full-sized castings
+during a year. If they eject annually more than 20 ounces,
+we may infer that the worms which live in an acre of pasture land
+must be less than 26,886 in number.</p>
+
+<p>Worms live chiefly in the superficial mould, which is usually
+from 4 or 5 to 10 and even 12 inches in thickness; and it is this
+mould which passes over and over again through their bodies and
+is brought to the surface. But worms occasionally burrow
+into the subsoil to a much greater depth, and on such occasions
+they bring up earth from this greater depth; and this process has
+gone on for countless ages. Therefore the superficial layer
+of mould would ultimately attain, though at a slower and slower
+rate, a thickness equal to the depth to which worms ever burrow,
+were there not other opposing agencies at work which carry away
+to a lower level some of the finest earth which is continually
+being brought to the surface by worms. How great a
+thickness vegetable mould ever attains, I have not had good
+opportunities for observing; but in the next chapter, when we
+consider the burial of ancient buildings, some facts will be
+given on this head. In the two last chapters we shall see
+that the soil is actually increased, though only to a small
+degree, through the agency of worms; but their chief work is to
+sift the finer from the coarser particles, to mingle the whole
+with vegetable débris, and to saturate it with their
+intestinal secretions.</p>
+
+<p>Finally, no one who considers the facts given in this
+chapter&mdash;on the burying of small objects and on the sinking
+of great stones left on the surface&mdash;on the vast number of
+worms which live within a moderate extent of ground on the weight
+of the castings ejected from the mouth of the same
+burrow&mdash;on the weight of all the castings ejected within a
+known time on a measured space&mdash;will hereafter, as I
+believe, doubt that worms play an important part in nature.</p>
+<h2><a name="page164"></a><span class="pagenum">p.
+164</span>CHAPTER IV.<br />
+<span class="GutSmall">THE PART WHICH WORMS HAVE PLAYED IN THE
+BURIAL OF ANCIENT BUILDINGS.</span></h2>
+<p class="gutsumm">The accumulation of rubbish on the sites of
+great cities independent of the action of worms&mdash;The burial
+of a Roman villa at Abinger&mdash;The floors and walls penetrated
+by worms&mdash;Subsidence of a modern pavement&mdash;The buried
+pavement at Beaulieu Abbey&mdash;Roman villas at Chedworth and
+Brading&mdash;The remains of the Roman town at
+Silchester&mdash;The nature of the débris by which the
+remains are covered&mdash;The penetration of the tesselated
+floors and walls by worms&mdash;Subsidence of the
+floors&mdash;Thickness of the mould&mdash;The old Roman city of
+Wroxeter&mdash;Thickness of the mould&mdash;Depth of the
+foundations of some of the Buildings&mdash;Conclusion.</p>
+
+<p><span class="smcap">Archæologists</span> are probably
+not aware how much they owe to worms for the preservation of many
+ancient objects. Coins, gold ornaments, stone implements,
+&amp;c., if dropped on the surface of the ground, will infallibly
+be buried by the castings of worms in a few years, and will thus
+be safely preserved, until the land at some future time is turned
+up. For instance, many years ago a grass-field was ploughed
+on the northern side of the Severn, not far from Shrewsbury; and
+a surprising number of iron arrow-heads were found at the bottom
+of the furrows, which, as Mr. Blakeway, a local antiquary,
+believed, were relics of the battle of Shrewsbury in the year
+1403, and no doubt had been originally left strewed on the
+battle-field. In the present chapter I shall show that not
+only implements, &amp;c., are thus preserved, but that the floors
+and the remains of many ancient buildings in England have been
+buried so effectually, in large part through the action of worms,
+that they have been discovered in recent times solely through
+various accidents. The enormous beds of rubbish, several
+yards in thickness, which underlie many cities, such as Rome,
+Paris, and London, the lower ones being of great antiquity, are
+not here referred to, as they have not been in any way acted on
+by worms. When we consider how much matter is daily brought
+into a great city for building, fuel, clothing and food, and that
+in old times when the roads were bad and the work of the
+scavenger was neglected, a comparatively small amount was carried
+away, we may agree with Élie de Beaumont, who, in
+discussing this subject, says, &ldquo;pour une voiture de
+matériaux qui en sort, on y en fait entrer cent.&rdquo; <a
+name="citation166a"></a><a href="#footnote166a"
+class="citation">[166a]</a> Nor should we overlook the
+effects of fires, the demolition of old buildings, and the
+removal of rubbish to the nearest vacant space.</p>
+
+<p><i>Abinger</i>, <i>Surrey</i>.&mdash;Late in the autumn of
+1876, the ground in an old farm-yard at this place was dug to a
+depth of 2 to 2&frac12; feet, and the workmen found various
+ancient remains. This led Mr. T. H. Farrer of Abinger Hall
+to have an adjoining ploughed field searched. On a trench
+being dug, a layer of concrete, still partly covered with
+tesseræ (small red tiles), and surrounded on two sides by
+broken-down walls, was soon discovered. It is believed, <a
+name="citation166b"></a><a href="#footnote166b"
+class="citation">[166b]</a> that this room formed part of the
+atrium or reception-room of a Roman villa. The walls of two
+or three other small rooms were afterwards discovered. Many
+fragments of pottery, other objects, and coins of several Roman
+emperors, dating from 133 to 361, and perhaps to 375 <span
+class="GutSmall">A.D.</span>, were likewise found. Also a
+half-penny of George I., 1715. The presence of this latter
+coin seems an anomaly; but no doubt it was dropped on the ground
+during the last century, and since then there has been ample time
+for its burial under a considerable depth of the castings of
+worms. From the different dates of the Roman coins we may
+infer that the building was long inhabited. It was probably
+ruined and deserted 1400 or 1500 years ago.</p>
+
+<p>I was present during the commencement of the excavations
+(August 20, 1877) and Mr. Farrer had two deep trenches dug at
+opposite ends of the atrium, so that I might examine the nature
+of the soil near the remains. The field sloped from east to
+west at an angle of about 7&deg;; and one of the two trenches,
+shown in the accompanying section (Fig. 8) was at the upper or
+eastern end. The diagram is on a scale of 1/20 of an inch
+to an inch; but the trench, which was between 4 and 5 feet broad,
+and in parts above 5 feet deep, has necessarily been reduced out
+of all proportion. The fine mould over the floor of the
+atrium varied in thickness from 11 to 16 inches; and on the side
+of the trench in the section was a little over 13 inches.
+After the mould had been removed, the floor appeared as a whole
+moderately level; but it sloped in parts at an angle of 1&deg;,
+and in one place near the outside at as much as 8&deg;
+30&prime;. The wall surrounding the pavement was built of
+rough stones, and was 23 inches in thickness where the trench was
+dug. Its broken summit was here 13 inches, but in another
+part 15 inches, beneath the surface of the field, being covered
+by this thickness of mould. In one spot, however, it rose
+to within 6 inches of the surface. On two sides of the
+room, where the junction of the concrete floor with the bounding
+walls could be carefully examined, there was no crack or
+separation. This trench afterwards proved to have been dug
+within an adjoining room (11 ft. by 11 ft. 6 in. in size), the
+existence of which was not even suspected whilst I was
+present.</p>
+<p style="text-align: center">
+<a href="images/p168b.jpg">
+<img alt=
+"Fig. 8: Section through the foundations of a buried Roman villa"
+title=
+"Fig. 8: Section through the foundations of a buried Roman villa"
+ src="images/p168s.jpg" />
+</a></p>
+
+<p>On the side of the trench farthest from the buried wall (W),
+the mould varied from 9 to 14 inches in thickness; it rested on a
+mass (B) 23 inches thick of blackish earth, including many large
+stones. Beneath this was a thin bed of very black mould
+(C), then a layer of earth full of fragments of mortar (D), and
+then another thin bed (about 3 inches thick) (E) of very black
+mould, which rested on the undisturbed subsoil (F) of firm,
+yellowish, argillaceous sand. The 23-inch bed (B) was
+probably made ground, as this would have brought up the floor of
+the room to a level with that of the atrium. The two thin
+beds of black mould at the bottom of the trench evidently marked
+two former land-surfaces. Outside the walls of the northern
+room, many bones, ashes, oyster-shells, broken pottery and an
+entire pot were subsequently found at a depth of 16 inches
+beneath the surface.</p>
+
+<p>The second trench was dug on the western or lower side of the
+villa: the mould was here only 6&frac12; inches in thickness, and
+it rested on a mass of fine earth full of stones, broken tiles
+and fragments of mortar, 34 inches in thickness, beneath which
+was the undisturbed sand. Most of this earth had probably
+been washed down from the upper part of the field, and the
+fragments of stones, tiles, &amp;c., must have come from the
+immediately adjoining ruins.</p>
+
+<p>It appears at first sight a surprising fact that this field of
+light sandy soil should have been cultivated and ploughed during
+many years, and that not a vestige of these buildings should have
+been discovered. No one even suspected that the remains of
+a Roman villa lay hidden close beneath the surface. But the
+fact is less surprising when it is known that the field, as the
+bailiff believed, had never been ploughed to a greater depth than
+4 inches. It is certain that when the land was first
+ploughed, the pavement and the surrounding broken walls must have
+been covered by at least 4 inches of soil, for otherwise the
+rotten concrete floor would have been scored by the ploughshare,
+the tesseræ torn up, and the tops of the old walls knocked
+down.</p>
+
+<p>When the concrete and tesseræ were first cleared over a
+space of 14 by 9 ft., the floor which was coated with
+trodden-down earth exhibited no signs of having been penetrated
+by worms; and although the overlying fine mould closely resembled
+that which in many places has certainly been accumulated by
+worms, yet it seemed hardly possible that this mould could have
+been brought up by worms from beneath the apparently sound
+floor. It seemed also extremely improbable that the thick
+walls, surrounding the room and still united to the concrete, had
+been undermined by worms, and had thus been caused to sink, being
+afterwards covered up by their castings. I therefore at
+first concluded that all the fine mould above the ruins had been
+washed down from the upper parts of the field; but we shall soon
+see that this conclusion was certainly erroneous, though much
+fine earth is known to be washed down from the upper part of the
+field in its present ploughed state during heavy rains.</p>
+
+<p>Although the concrete floor did not at first appear to have
+been anywhere penetrated by worms, yet by the next morning little
+cakes of the trodden-down earth had been lifted up by worms over
+the mouths of seven burrows, which passed through the softer
+parts of the naked concrete, or between the interstices of the
+tesseræ. On the third morning twenty-five burrows
+were counted; and by suddenly lifting up the little cakes of
+earth, four worms were seen in the act of quickly
+retreating. Two castings were thrown up during the third
+night on the floor, and these were of large size. The
+season was not favourable for the full activity of worms, and the
+weather had lately been hot and dry, so that most of the worms
+now lived at a considerable depth. In digging the two
+trenches many open burrows and some worms were encountered at
+between 30 and 40 inches beneath the surface; but at a greater
+depth they became rare. One worm, however, was cut through
+at 48&frac12;, and another at 51&frac12; inches beneath the
+surface. A fresh humus-lined burrow was also met with at a
+depth of 57 and another at 65&frac12; inches. At greater
+depths than this, neither burrows nor worms were seen.</p>
+
+<p>As I wished to learn how many worms lived beneath the floor of
+the atrium&mdash;a space of about 14 by 9 feet&mdash;Mr. Farrer
+was so kind as to make observations for me, during the next seven
+weeks, by which time the worms in the surrounding country were in
+full activity, and were working near the surface. It is
+very improbable that worms should have migrated from the
+adjoining field into the small space of the atrium, after the
+superficial mould in which they prefer to live, had been
+removed. We may therefore conclude that the burrows and the
+castings which were seen here during the ensuing seven weeks were
+the work of the former inhabitants of the space. I will now
+give a few extracts from Mr. Farrer&rsquo;s notes.</p>
+
+<p>Aug. 26th, 1877; that is, five days after the floor had been
+cleared. On the previous night there had been some heavy
+rain, which washed the surface clean, and now the mouths of forty
+burrows were counted. Parts of the concrete were seen to be
+solid, and had never been penetrated by worms, and here the
+rain-water lodged.</p>
+
+<p>Sept. 5th.&mdash;Tracks of worms, made during the previous
+night, could be seen on the surface of the floor, and five or six
+vermiform castings had been thrown up. These were
+defaced.</p>
+
+<p>Sept. 12th.&mdash;During the last six days, the worms have not
+been active, though many castings have been ejected in the
+neighbouring fields; but on this day the earth was a little
+raised over the mouths of the burrows, or castings were ejected,
+at ten fresh points. These were defaced. It should be
+understood that when a fresh burrow is spoken of, this generally
+means only that an old burrow has been re-opened. Mr.
+Farrer was repeatedly struck with the pertinacity with which the
+worms re-opened their old burrows, even when no earth was ejected
+from them. I have often observed the same fact, and
+generally the mouths of the burrows are protected by an
+accumulation of pebbles, sticks or leaves. Mr. Farrer
+likewise observed that the worms living beneath the floor of the
+atrium often collected coarse grains of sand, and such little
+stones as they could find, round the mouths of their burrows.</p>
+
+<p>Sept. 13th; soft wet weather. The mouths of the burrows
+were re-opened, or castings were ejected, at 31 points; these
+were all defaced.</p>
+
+<p>Sept. 14th; 34 fresh holes or castings; all defaced.</p>
+
+<p>Sept. 15th; 44 fresh holes, only 5 castings; all defaced.</p>
+
+<p>Sept. 18th; 43 fresh holes, 8 castings; all defaced.</p>
+
+<p>The number of castings on the surrounding fields was now very
+large.</p>
+
+<p>Sept. 19th; 40 holes, 8 castings; all defaced.</p>
+
+<p>Sept. 22nd; 43 holes, only a few fresh castings; all
+defaced.</p>
+
+<p>Sept. 23rd; 44 holes, 8 castings.</p>
+
+<p>Sept. 25th; 50 holes, no record of the number of castings.</p>
+
+<p>Oct. 13th; 61 holes, no record of the number of
+castings.</p>
+
+<p>After an interval of three years, Mr. Farrer, at my request,
+again looked at the concrete floor, and found the worms still at
+work.</p>
+
+<p>Knowing what great muscular power worms possess, and seeing
+how soft the concrete was in many parts, I was not surprised at
+its having been penetrated by their burrows; but it is a more
+surprising fact that the mortar between the rough stones of the
+thick walls, surrounding the rooms, was found by Mr. Farrer to
+have been penetrated by worms. On August 26th, that is,
+five days after the ruins had been exposed, he observed four open
+burrows on the broken summit of the eastern wall (W in Fig. 8);
+and, on September 15th, other burrows similarly situated were
+seen. It should also be noted that in the perpendicular
+side of the trench (which was much deeper than is represented in
+Fig. 8) three recent burrows were seen, which ran obliquely far
+down beneath the base of the old wall.</p>
+
+<p>We thus see that many worms lived beneath the floor and the
+walls of the atrium at the time when the excavations were made;
+and that they afterwards almost daily brought up earth to the
+surface from a considerable depth. There is not the
+slightest reason to doubt that worms have acted in this manner
+ever since the period when the concrete was sufficiently decayed
+to allow them to penetrate it; and even before that period they
+would have lived beneath the floor, as soon as it became pervious
+to rain, so that the soil beneath was kept damp. The floor
+and the walls must therefore have been continually undermined;
+and fine earth must have been heaped on them during many
+centuries, perhaps for a thousand years. If the burrows
+beneath the floor and walls, which it is probable were formerly
+as numerous as they now are, had not collapsed in the course of
+time in the manner formerly explained, the underlying earth would
+have been riddled with passages like a sponge; and as this was
+not the case, we may feel sure that they have collapsed.
+The inevitable result of such collapsing during successive
+centuries, will have been the slow subsidence of the floor and of
+the walls, and their burial beneath the accumulated
+worm-castings. The subsidence of a floor, whilst it still
+remains nearly horizontal, may at first appear improbable; but
+the case presents no more real difficulty than that of loose
+objects strewed on the surface of a field, which, as we have
+seen, become buried several inches beneath the surface in the
+course of a few years, though still forming a horizontal layer
+parallel to the surface. The burial of the paved and level
+path on my lawn, which took place under my own observation, is an
+analogous case. Even those parts of the concrete floor
+which the worms could not penetrate would almost certainly have
+been undermined, and would have sunk, like the great stones at
+Leith Hill Place and Stonehenge, for the soil would have been
+damp beneath them. But the rate of sinking of the different
+parts would not have been quite equal, and the floor was not
+quite level. The foundations of the boundary walls lie, as
+shown in the section, at a very small depth beneath the surface;
+they would therefore have tended to subside at nearly the same
+rate as the floor. But this would not have occurred if the
+foundations had been deep, as in the case of some other Roman
+ruins presently to be described.</p>
+
+<p>Finally, we may infer that a large part of the fine vegetable
+mould, which covered the floor and the broken-down walls of this
+villa, in some places to a thickness of 16 inches, was brought up
+from below by worms. From facts hereafter to be given there
+can be no doubt that some of the finest earth thus brought up
+will have been washed down the sloping surface of the field
+during every heavy shower of rain. If this had not occurred
+a greater amount of mould would have accumulated over the ruins
+than that now present. But beside the castings of worms and
+some earth brought up by insects, and some accumulation of dust,
+much fine earth will have been washed over the ruins from the
+upper parts of the field, since it has been under cultivation;
+and from over the ruins to the lower parts of the slope; the
+present thickness of the mould being the resultant of these
+several agencies.</p>
+
+<div class="gapspace">&nbsp;</div>
+<p>I may here append a modern instance of the sinking of a
+pavement, communicated to me in 1871 by Mr. Ramsay, Director of
+the Geological Survey of England. A passage without a roof,
+7 feet in length by 3 feet 2 inches in width, led from his house
+into the garden, and was paved with slabs of Portland
+stone. Several of these slabs were 16 inches square, others
+larger, and some a little smaller. This pavement had
+subsided about 3 inches along the middle of the passage, and two
+inches on each side, as could be seen by the lines of cement by
+which the slabs had been originally joined to the walls.
+The pavement had thus become slightly concave along the middle;
+but there was no subsidence at the end close to the house.
+Mr. Ramsay could not account for this sinking, until he observed
+that castings of black mould were frequently ejected along the
+lines of junction between the slabs; and these castings were
+regularly swept away. The several lines of junction,
+including those with the lateral walls, were altogether 39 feet 2
+inches in length. The pavement did not present the
+appearance of ever having been renewed, and the house was
+believed to have been built about eighty-seven years ago.
+Considering all these circumstances, Mr. Ramsay does not doubt
+that the earth brought up by the worms since the pavement was
+first laid down, or rather since the decay of the mortar allowed
+the worms to burrow through it, and therefore within a much
+shorter time than the eighty-seven years, has sufficed to cause
+the sinking of the pavement to the above amount, except close to
+the house, where the ground beneath would have been kept nearly
+dry.</p>
+
+<p>Beaulieu Abbey, Hampshire.&mdash;This abbey was destroyed by
+Henry VIII., and there now remains only a portion of the southern
+aisle-wall. It is believed that the king had most of the
+stones carried away for building a castle; and it is certain that
+they have been removed. The positions of the nave and
+transepts were ascertained not long ago by the foundations having
+been found; and the place is now marked by stones let into the
+ground. Where the abbey formerly stood, there now extends a
+smooth grass-covered surface, which resembles in all respects the
+rest of the field. The guardian, a very old man, said the
+surface had never been levelled in his time. In the year
+1853, the Duke of Buccleuch had three holes dug in the turf
+within a few yards of one another, at the western end of the
+nave; and the old tesselated pavement of the abbey was thus
+discovered. These holes were afterwards surrounded by
+brickwork, and protected by trap-doors, so that the pavement
+might be readily inspected and preserved. When my son
+William examined the place on January 5, 1872, he found that the
+pavement in the three holes lay at depths of 6&frac34;, 10 and
+11&frac12; inches beneath the surrounding turf-covered
+surface. The old guardian asserted that he was often forced
+to remove worm-castings from the pavement; and that he had done
+so about six months before. My son collected all from one
+of the holes, the area of which was 5.32 square feet, and they
+weighed 7.97 ounces. Assuming that this amount had
+accumulated in six months, the accumulation during a year on a
+square yard would be 1.68 pounds, which, though a large amount,
+is very small compared with what, as we have seen, is often
+ejected on fields and commons. When I visited the abbey on
+June 22, 1877, the old man said that he had cleared out the holes
+about a month before, but a good many castings had since been
+ejected. I suspect that he imagined that he swept the
+pavements oftener than he really did, for the conditions were in
+several respects very unfavourable for the accumulation of even a
+moderate amount of castings. The tiles are rather large,
+viz., about 5&frac12; inches square, and the mortar between them
+was in most places sound, so that the worms were able to bring up
+earth from below only at certain points. The tiles rested
+on a bed of concrete, and the castings in consequence consisted
+in large part (viz., in the proportion of 19 to 33) of particles
+of mortar, grains of sand, little fragments of rock, bricks or
+tile; and such substances could hardly be agreeable, and
+certainly not nutritious, to worms.</p>
+
+<p>My son dug holes in several places within the former walls of
+the abbey, at a distance of several yards from the above
+described bricked squares. He did not find any tiles,
+though these are known to occur in some other parts, but he came
+in one spot to concrete on which tiles had once rested. The
+fine mould beneath the turf on the sides of the several holes,
+varied in thickness from only 2 to 2&frac34; inches, and this
+rested on a layer from 8&frac34; to above 11 inches in thickness,
+consisting of fragments of mortar and stone-rubbish with the
+interstices compactly filled up with black mould. In the
+surrounding field, at a distance of 20 yards from the abbey, the
+fine vegetable mould was 11 inches thick.</p>
+
+<p>We may conclude from these facts that when the abbey was
+destroyed and the stones removed, a layer of rubbish was left
+over the whole surface, and that as soon as the worms were able
+to penetrate the decayed concrete and the joints between the
+tiles, they slowly filled up the interstices in the overlying
+rubbish with their castings, which were afterwards accumulated to
+a thickness of nearly three inches over the whole surface.
+If we add to this latter amount the mould between the fragments
+of stones, some five or six inches of mould must have been
+brought up from beneath the concrete or tiles. The concrete
+or tiles will consequently have subsided to nearly this
+amount. The bases of the columns of the aisles are now
+buried beneath mould and turf. It is not probable that they
+can have been undermined by worms, for their foundations would no
+doubt have been laid at a considerable depth. If they have
+not subsided, the stones of which the columns were constructed
+must have been removed from beneath the former level of the
+floor.</p>
+
+<p><i>Chedworth</i>, <i>Gloucestershire</i>.&mdash;The remains of
+a large Roman villa were discovered here in 1866, on ground which
+had been covered with wood from time immemorial. No
+suspicion seems ever to have been entertained that ancient
+buildings lay buried here, until a gamekeeper, in digging for
+rabbits, encountered some remains. <a name="citation183"></a><a
+href="#footnote183" class="citation">[183]</a> But
+subsequently the tops of some stone walls were detected in parts
+of the wood, projecting a little above the surface of the
+ground. Most of the coins found here belonged to Constans
+(who died 350 <span class="GutSmall">A.D.</span>) and the
+Constantine family. My sons Francis and Horace visited the
+place in November 1877, for the sake of ascertaining what part
+worms may have played in the burial of these extensive
+remains. But the circumstances were not favourable for this
+object, as the ruins are surrounded on three sides by rather
+steep banks, down which earth is washed during rainy
+weather. Moreover most of the old rooms have been covered
+with roofs, for the protection of the elegant tesselated
+pavements.</p>
+
+<p>A few facts may, however, be given on the thickness of the
+soil over these ruins. Close outside the northern rooms
+there is a broken wall, the summit of which was covered by 5
+inches of black mould; and in a hole dug on the outer side of
+this wall, where the ground had never before been disturbed,
+black mould, full of stones, 26 inches in thickness, was found,
+resting on the undisturbed sub-soil of yellow clay. At a
+depth of 22 inches from the surface a pig&rsquo;s jaw and a
+fragment of a tile were found. When the excavations were
+first made, some large trees grew over the ruins; and the stump
+of one has been left directly over a party-wall near the
+bath-room, for the sake of showing the thickness of the
+superincumbent soil, which was here 38 inches. In one small
+room, which, after being cleared out, had not been roofed over,
+my sons observed the hole of a worm passing through the rotten
+concrete, and a living worm was found within the concrete.
+In another open room worm-castings were seen on the floor, over
+which some earth had by this means been deposited, and here grass
+now grew.</p>
+
+<p><i>Brading</i>, <i>Isle of Wight</i>.&mdash;A fine Roman villa
+was discovered here in 1880; and by the end of October no less
+than 18 chambers had been more or less cleared. A coin
+dated 337 <span class="GutSmall">A.D.</span> was found. My
+son William visited the place before the excavations were
+completed; and he informs me that most of the floors were at
+first covered with much rubbish and fallen stones, having their
+interstices completely filled up with mould, abounding, as the
+workmen said, with worms, above which there was mould without any
+stones. The whole mass was in most places from 3 to above 4
+ft. in thickness. In one very large room the overlying
+earth was only 2 ft. 6 in. thick; and after this had been
+removed, so many castings were thrown up between the tiles that
+the surface had to be almost daily swept. Most of the
+floors were fairly level. The tops of the broken-down walls
+were covered in some places by only 4 or 5 inches of soil, so
+that they were occasionally struck by the plough, but in other
+places they were covered by from 13 to 18 inches of soil.
+It is not probable that these walls could have been undermined by
+worms and subsided, as they rested on a foundation of very hard
+red sand, into which worms could hardly burrow. The mortar,
+however, between the stones of the walls of a hypocaust was found
+by my son to have been penetrated by many worm-burrows. The
+remains of this villa stand on land which slopes at an angle of
+about 3&deg;; and the land appears to have been long
+cultivated. Therefore no doubt a considerable quantity of
+fine earth has been washed down from the upper parts of the
+field, and has largely aided in the burial of these remains.</p>
+
+<p><i>Silchester</i>, <i>Hampshire</i>.&mdash;The ruins of this
+small Roman town have been better preserved than any other
+remains of the kind in England. A broken wall, in most
+parts from 15 to 18 feet in height and about 1&frac12; mile in
+compass, now surrounds a space of about 100 acres of cultivated
+land, on which a farm-house and a church stand. <a
+name="citation187"></a><a href="#footnote187"
+class="citation">[187]</a> Formerly, when the weather was
+dry, the lines of the buried walls could be traced by the
+appearance of the crops; and recently very extensive excavations
+have been undertaken by the Duke of Wellington, under the
+superintendence of the late Rev. J. G. Joyce, by which means many
+large buildings have been discovered. Mr. Joyce made
+careful coloured sections, and measured the thickness of each bed
+of rubbish, whilst the excavations were in progress; and he has
+had the kindness to send me copies of several of them. When
+my sons Francis and Horace visited these ruins, he accompanied
+them, and added his notes to theirs.</p>
+
+<p>Mr. Joyce estimates that the town was inhabited by the Romans
+for about three centuries; and no doubt much matter must have
+accumulated within the walls during this long period. It
+appears to have been destroyed by fire, and most of the stones
+used in the buildings have since been carried away. These
+circumstances are unfavourable for ascertaining the part which
+worms have played in the burial of the ruins; but as careful
+sections of the rubbish overlying an ancient town have seldom or
+never before been made in England, I will give copies of the most
+characteristic portions of some of those made by Mr. Joyce.
+They are of too great length to be here introduced entire.</p>
+
+<p>An east and west section, 30 ft. in length, was made across a
+room in the Basilica, now called the Hall of the Merchants (Fig.
+9). The hard concrete floor, still covered here and there
+with tesseræ, was found at 3 ft. beneath the surface of the
+field, which was here level. On the floor there were two
+large piles of charred wood, one alone of which is shown in the
+part of the section here given. This pile was covered by a
+thin white layer of decayed stucco or plaster, above which was a
+mass, presenting a singularly disturbed appearance, of broken
+tiles, mortar, rubbish and fine gravel, together 27 inches in
+thickness. Mr. Joyce believes that the gravel was used in
+making the mortar or concrete, which has since decayed, some of
+the lime probably having been dissolved. The disturbed
+state of the rubbish may have been due to its having been
+searched for building stones. This bed was capped by fine
+vegetable mould, 9 inches in thickness. From these facts we
+may conclude that the Hall was burnt down, and that much rubbish
+fell on the floor, through and from which the worms slowly
+brought up the mould, now forming the surface of the level
+field.</p>
+<p style="text-align: center">
+<a href="images/p186b.jpg">
+<img alt=
+"Fig. 7: Section through one of the fallen Druidical stones at
+Stonehenge.  Fig. 9: Section within a room in the Basilica at
+Silchester"
+title=
+"Fig. 7: Section through one of the fallen Druidical stones at
+Stonehenge.  Fig. 9: Section within a room in the Basilica at
+Silchester"
+ src="images/p186s.jpg" />
+</a></p>
+
+<p>A section across the middle of another hall in the Basilica,
+32 feet 6 inches in length, called the &AElig;rarium, is shown in
+Fig. 10. It appears that we have here evidence of two
+fires, separated by an interval of time, during which the 6
+inches of &ldquo;mortar and concrete with broken tiles&rdquo; was
+accumulated. Beneath one of the layers of charred wood, a
+valuable relic, a bronze eagle, was found; and this shows that
+the soldiers must have deserted the place in a panic. Owing
+to the death of Mr. Joyce, I have not been able to ascertain
+beneath which of the two layers the eagle was found. The
+bed of rubble overlying the undisturbed gravel originally formed,
+as I suppose, the floor, for it stands on a level with that of a
+corridor, outside the walls of the Hall; but the corridor is not
+shown in the section as here given. The vegetable mould was
+16 inches thick in the thickest part; and the depth from the
+surface of the field, clothed with herbage, to the undisturbed
+gravel, was 40 inches.</p>
+<p style="text-align: center">
+<a href="images/p188b.jpg">
+<img alt=
+"Fig. 10: Section within a hall in the Basilica of Silchester"
+title=
+"Fig. 10: Section within a hall in the Basilica of Silchester"
+ src="images/p188s.jpg" />
+</a></p>
+
+<p>The section shown in Fig. 11 represents an excavation made in
+the middle of the town, and is here introduced because the bed of
+&ldquo;rich mould&rdquo; attained, according to Mr. Joyce, the
+unusual thickness of 20 inches. Gravel lay at the depth of
+48 inches from the surface; but it was not ascertained whether
+this was in its natural state, or had been brought here and had
+been rammed down, as occurs in some other places.</p>
+<p style="text-align: center">
+<a href="images/p190b.jpg">
+<img alt=
+"Fig. 11: Section in a block of buildings in the middle of the
+town of Silchester"
+title=
+"Fig. 11: Section in a block of buildings in the middle of the
+town of Silchester"
+ src="images/p190s.jpg" />
+</a></p>
+
+<p>The section shown in Fig. 12 was taken in the centre of the
+Basilica, and though it was 5 feet in depth, the natural sub-soil
+was not reached. The bed marked &ldquo;concrete&rdquo; was
+probably at one time a floor; and the beds beneath seem to be the
+remnants of more ancient buildings. The vegetable mould was
+here only 9 inches thick. In some other sections, not
+copied, we likewise have evidence of buildings having been
+erected over the ruins of older ones. In one case there was
+a layer of yellow clay of very unequal thickness between two beds
+of débris, the lower one of which rested on a floor with
+tesseræ. The ancient broken walls appear to have been
+sometimes roughly cut down to a uniform level, so as to serve as
+the foundations for a temporary building; and Mr. Joyce suspects
+that some of these buildings were wattled sheds, plastered with
+clay, which would account for the above-mentioned layer of
+clay.</p>
+<p style="text-align: center">
+<a href="images/p192b.jpg">
+<img alt=
+"Fig. 12: Section in the centre of the Basilica at Silchester"
+title=
+"Fig. 12: Section in the centre of the Basilica at Silchester"
+ src="images/p192s.jpg" />
+</a></p>
+
+<p>Turning now to the points which more immediately concern
+us. Worm-castings were observed on the floors of several of
+the rooms, in one of which the tesselation was unusually
+perfect. The tesseræ here consisted of little cubes
+of hard sandstone of about 1 inch, several of which were loose or
+projected slightly above the general level. One or
+occasionally two open worm-burrows were found beneath all the
+loose tesseræ. Worms have also penetrated the old
+walls of these ruins. A wall, which had just been exposed
+to view during the excavations then in progress, was examined; it
+was built of large flints, and was 18 inches in thickness.
+It appeared sound, but when the soil was removed from beneath,
+the mortar in the lower part was found to be so much decayed that
+the flints fell apart from their own weight. Here, in the
+middle of the wall, at a depth of 29 inches beneath the old floor
+and of 49&frac12; inches beneath the surface of the field, a
+living worm was found, and the mortar was penetrated by several
+burrows.</p>
+
+<p>A second wall was exposed to view for the first time, and an
+open burrow was seen on its broken summit. By separating
+the flints this burrow was traced far down in the interior of the
+wall; but as some of the flints cohered firmly, the whole mass
+was disturbed in pulling down the wall, and the burrow could not
+be traced to the bottom. The foundations of a third wall,
+which appeared quite sound, lay at a depth of 4 feet beneath one
+of the floors, and of course at a considerably greater depth
+beneath the level of the ground. A large flint was wrenched
+out of the wall at about a foot from the base, and this required
+much force, as the mortar was sound; but behind the flint in the
+middle of the wall, the mortar was friable, and here there were
+worm-burrows. Mr. Joyce and my sons were surprised at the
+blackness of the mortar in this and in several other cases, and
+at the presence of mould in the interior of the walls. Some
+may have been placed there by the old builders instead of mortar;
+but we should remember that worms line their burrows with black
+humus. Moreover open spaces would almost certainly have
+been occasionally left between the large irregular flints; and
+these spaces, we may feel sure, would be filled up by the worms
+with their castings, as soon as they were able to penetrate the
+wall. Rain-water, oozing down the burrows would also carry
+fine dark-coloured particles into every crevice. Mr. Joyce
+was at first very sceptical about the amount of work which I
+attributed to worms; but he ends his notes with reference to the
+last-mentioned wall by saying, &ldquo;This case caused me more
+surprise and brought more conviction to me than any other.
+I should have said, and did say, that it was quite impossible
+such a wall could have been penetrated by earth-worms.&rdquo;</p>
+
+<p>In almost all the rooms the pavement has sunk considerably,
+especially towards the middle; and this is shown in the three
+following sections. The measurements were made by
+stretching a string tightly and horizontally over the
+floor. The section, Fig. 13, was taken from north to south
+across a room, 18 feet 4 inches in length, with a nearly perfect
+pavement, next to the &ldquo;Red Wooden Hut.&rdquo; In the
+northern half, the subsidence amounted to 5&frac34; inches
+beneath the level of the floor as it now stands close to the
+walls; and it was greater in the northern than in the southern
+half; but, according to Mr. Joyce, the entire pavement has
+obviously subsided. In several places, the tesseræ
+appeared as if drawn a little away from the walls; whilst in
+other places they were still in close contact with them.</p>
+<p style="text-align: center">
+<a href="images/p194b.jpg">
+<img alt=
+"Fig. 14: A north and south section through the subsided floor of
+a corridor"
+title=
+"Fig. 14: A north and south section through the subsided floor of
+a corridor"
+ src="images/p194s.jpg" />
+</a></p>
+
+<p>In Fig. 14, we see a section across the paved floor of the
+southern corridor or ambulatory of a quadrangle, in an excavation
+made near &ldquo;The Spring.&rdquo; The floor is 7 feet 9
+inches wide, and the broken-down walls now project only &frac34;
+of an inch above its level. The field, which was in
+pasture, here sloped from north to south, at an angle of 30&deg;,
+40&prime;. The nature of the ground at some little distance
+on each side of the corridor is shown in the section. It
+consisted of earth full of stones and other débris, capped
+with dark vegetable mould which was thicker on the lower or
+southern than on the northern side. The pavement was nearly
+level along lines parallel to the side-walls, but had sunk in the
+middle as much as 7&frac34; inches.</p>
+
+<p>A small room at no great distance from that represented in
+Fig. 13, had been enlarged by the Roman occupier on the southern
+side, by an addition of 5 feet 4 inches in breadth. For
+this purpose the southern wall of the house had been pulled down,
+but the foundations of the old wall had been left buried at a
+little depth beneath the pavement of the enlarged room. Mr.
+Joyce believes that this buried wall must have been built before
+the reign of Claudius II., who died 270 <span
+class="GutSmall">A.D.</span> We see in the accompanying
+section, Fig. 15, that the tesselated pavement has subsided to a
+less degree over the buried wall than elsewhere; so that a slight
+convexity or protuberance here stretched in a straight line
+across the room. This led to a hole being dug, and the
+buried wall was thus discovered.</p>
+<p style="text-align: center">
+<a href="images/p196b.jpg">
+<img alt=
+"Fig. 15: Section through the subsided floor"
+title=
+"Fig. 15: Section through the subsided floor"
+ src="images/p196s.jpg" />
+</a></p>
+
+<p>We see in these three sections, and in several others not
+given, that the old pavements have sunk or sagged
+considerably. Mr. Joyce formerly attributed this sinking
+solely to the slow settling of the ground. That there has
+been some settling is highly probable, and it may be seen in Fig.
+15 that the pavement for a width of 5 feet over the southern
+enlargement of the room, which must have been built on fresh
+ground, has sunk a little more than on the old northern
+side. But this sinking may possibly have had no connection
+with the enlargement of the room; for in Fig. 13 one half of the
+pavement has subsided more than the other half without any
+assignable cause. In a bricked passage to Mr. Joyce&rsquo;s
+own house, laid down only about six years ago, the same kind of
+sinking has occurred as in the ancient buildings.
+Nevertheless it does not appear probable that the whole amount of
+sinking can be thus accounted for. The Roman builders
+excavated the ground to an unusual depth for the foundations of
+their walls, which were thick and solid; it is therefore hardly
+credible that they should have been careless about the solidity
+of the bed on which their tesselated and often ornamented
+pavements were laid. The sinking must, as it appears to me,
+be attributed in chief part to the pavement having been
+undermined by worms, which we know are still at work. Even
+Mr. Joyce at last admitted that this could not have failed to
+have produced a considerable effect. Thus also the large
+quantity of fine mould overlying the pavements can be accounted
+for, the presence of which would otherwise be inexplicable.
+My sons noticed that in one room in which the pavement had sagged
+very little, there was an unusually small amount of overlying
+mould.</p>
+
+<p>As the foundations of the walls generally lie at a
+considerable depth, they will either have not subsided at all
+through the undermining action of worms, or they will have
+subsided much less than the floor. This latter result would
+follow from worms not often working deep down beneath the
+foundations; but more especially from the walls not yielding when
+penetrated by worms, whereas the successively formed burrows in a
+mass of earth, equal to one of the walls in depth and thickness,
+would have collapsed many times since the desertion of the ruins,
+and would consequently have shrunk or subsided. As the
+walls cannot have sunk much or at all, the immediately adjoining
+pavement from adhering to them will have been prevented from
+subsiding; and thus the present curvature of the pavement is
+intelligible.</p>
+
+<p>The circumstance which has surprised me most with respect to
+Silchester is that during the many centuries which have elapsed
+since the old buildings were deserted, the vegetable mould has
+not accumulated over them to a greater thickness than that here
+observed. In most places it is only about 9 inches in
+thickness, but in some places 12 or even more inches. In
+Fig. 11, it is given as 20 inches, but this section was drawn by
+Mr. Joyce before his attention was particularly called to this
+subject. The land enclosed within the old walls is
+described as sloping slightly to the south; but there are parts
+which, according to Mr. Joyce, are nearly level, and it appears
+that the mould is here generally thicker than elsewhere.
+The surface slopes in other parts from west to east, and Mr.
+Joyce describes one floor as covered at the western end by
+rubbish and mould to a thickness of 28&frac12; inches, and at the
+eastern end by a thickness of only 11&frac12; inches. A
+very slight slope suffices to cause recent castings to flow
+downwards during heavy rain, and thus much earth will ultimately
+reach the neighbouring rills and streams and be carried
+away. By this means, the absence of very thick beds of
+mould over these ancient ruins may, as I believe, be
+explained. Moreover most of the land here has long been
+ploughed, and this would greatly aid the washing away of the
+finer earth during rainy weather.</p>
+
+<p>The nature of the beds immediately beneath the vegetable mould
+in some of the sections is rather perplexing. We see, for
+instance, in the section of an excavation in a grass meadow (Fig.
+14), which sloped from north to south at an angle of 3&deg;
+40&prime;, that the mould on the upper side is only six inches
+and on the lower side nine inches in thickness. But this
+mould lies on a mass (25&frac12; inches in thickness on the upper
+side) &ldquo;of dark brown mould,&rdquo; as described by Mr.
+Joyce, &ldquo;thickly interspersed with small pebbles and bits of
+tiles, which present a corroded or worn appearance.&rdquo;
+The state of this dark-coloured earth is like that of a field
+which has long been ploughed, for the earth thus becomes
+intermingled with stones and fragments of all kinds which have
+been much exposed to the weather. If during the course of
+many centuries this grass meadow and the other now cultivated
+fields have been at times ploughed, and at other times left as
+pasture, the nature of the ground in the above section is
+rendered intelligible. For worms will continually have
+brought up fine earth from below, which will have been stirred up
+by the plough whenever the land was cultivated. But after a
+time a greater thickness of fine earth will thus have been
+accumulated than could be reached by the plough; and a bed like
+the 25&frac12;-inch mass, in Fig. 14, will have been formed
+beneath the superficial mould, which latter will have been
+brought to the surface within more recent times, and have been
+well sifted by the worms.</p>
+
+<p><i>Wroxeter</i>, <i>Shropshire</i>.&mdash;The old Roman city
+of Uriconium was founded in the early part of the second century,
+if not before this date; and it was destroyed, according to Mr.
+Wright, probably between the middle of the fourth and fifth
+century. The inhabitants were massacred, and skeletons of
+women were found in the hypocausts. Before the year 1859,
+the sole remnant of the city above ground, was a portion of a
+massive wall about 20 ft. in height. The surrounding land
+undulates slightly, and has long been under cultivation. It
+had been noticed that the corn-crops ripened prematurely in
+certain narrow lines, and that the snow remained unmelted in
+certain places longer than in others. These appearances
+led, as I was informed, to extensive excavations being
+undertaken. The foundations of many large buildings and
+several streets have thus been exposed to view. The space
+enclosed within the old walls is an irregular oval, about
+1&frac34; mile in length. Many of the stones or bricks used
+in the buildings must have been carried away; but the hypocausts,
+baths, and other underground buildings were found tolerably
+perfect, being filled with stones, broken tiles, rubbish and
+soil. The old floors of various rooms were covered with
+rubble. As I was anxious to know how thick the mantle of
+mould and rubbish was, which had so long concealed these ruins, I
+applied to Dr. H. Johnson, who had superintended the excavations;
+and he, with the greatest kindness, twice visited the place to
+examine it in reference to my questions, and had many trenches
+dug in four fields which had hitherto been undisturbed. The
+results of his observations are given in the following
+Table. He also sent me specimens of the mould, and
+answered, as far as he could, all my questions.</p>
+<h3><span class="smcap">Measurements by Dr. H. Johnson of the
+thickness of the vegetable mould over the Roman ruins at
+Wroxeter</span>.</h3>
+<p style="text-align: center">Trenches dug in a field called
+&ldquo;Old Works.&rdquo;</p>
+<table>
+<tr>
+<td><p>&nbsp;</p>
+</td>
+<td><p>Thickness of mould in inches.</p>
+</td>
+</tr>
+<tr>
+<td><p>1. At a depth of 36 inches undisturbed sand was
+reached</p>
+</td>
+<td><p style="text-align: right">20</p>
+</td>
+</tr>
+<tr>
+<td><p>2. At a depth of 33 inches concrete was reached</p>
+</td>
+<td><p style="text-align: right">21</p>
+</td>
+</tr>
+<tr>
+<td><p>3. At a depth of 9 inches concrete was reached</p>
+</td>
+<td><p style="text-align: right">9</p>
+</td>
+</tr>
+</table>
+<p>Trenches dug in a field called &ldquo;Shop Leasows;&rdquo;
+this is the highest field within the old walls, and slopes down
+from a sub-central point on all sides at about an angle of
+2&deg;.</p>
+<table>
+<tr>
+<td><p>&nbsp;</p>
+</td>
+<td><p>Thickness of mould in inches.</p>
+</td>
+</tr>
+<tr>
+<td><p>4. Summit of field, trench 45 inches deep</p>
+</td>
+<td><p style="text-align: right">40</p>
+</td>
+</tr>
+<tr>
+<td><p>5. Close to summit of field, trench 36 inches
+deep</p>
+</td>
+<td><p style="text-align: right">26</p>
+</td>
+</tr>
+<tr>
+<td><p>6. Close to summit of field, trench 28 inches
+deep</p>
+</td>
+<td><p style="text-align: right">28</p>
+</td>
+</tr>
+<tr>
+<td><p>7. Near summit of field, trench 36 inches deep</p>
+</td>
+<td><p style="text-align: right">24</p>
+</td>
+</tr>
+<tr>
+<td><p>8. Near summit of field, trench at one end 39 inches
+deep; the mould here graduated into the underlying undisturbed
+sand, and its thickness (24 inches) is somewhat arbitrary.
+At the other end of the trench, a causeway was encountered at a
+depth of only 7 inches, and the mould was here only 7 inches
+thick</p>
+</td>
+<td><p style="text-align: right">24</p>
+</td>
+</tr>
+<tr>
+<td><p>9. Trench close to the last, 28 inches in depth</p>
+</td>
+<td><p style="text-align: right">24</p>
+</td>
+</tr>
+<tr>
+<td><p>10. Lower part of same field, trench 30 inches
+deep</p>
+</td>
+<td><p style="text-align: right">15</p>
+</td>
+</tr>
+<tr>
+<td><p>11. Lower part of same field, trench 31 inches
+deep</p>
+</td>
+<td><p style="text-align: right">17</p>
+</td>
+</tr>
+<tr>
+<td><p>12. Lower part of same field, trench 36 inches deep,
+at which depth undisturbed sand was reached</p>
+</td>
+<td><p style="text-align: right">28</p>
+</td>
+</tr>
+<tr>
+<td><p>13. In another part of same field, trench 9&frac12;
+inches deep stopped by concrete</p>
+</td>
+<td><p style="text-align: right">9&frac12;</p>
+</td>
+</tr>
+<tr>
+<td><p>14. In another part of same field, trench 9 inches
+deep, stopped by concrete</p>
+</td>
+<td><p style="text-align: right">9</p>
+</td>
+</tr>
+<tr>
+<td><p>15. In another part of the same field, trench 24
+inches deep, when sand was reached</p>
+</td>
+<td><p style="text-align: right">16</p>
+</td>
+</tr>
+<tr>
+<td><p>16. In another part of same field, trench 30 inches
+deep, when stones were reached; at one end of the trench mould 12
+inches, at the other end 14 inches thick</p>
+</td>
+<td><p style="text-align: right">13</p>
+</td>
+</tr>
+</table>
+<p>Small field between &ldquo;Old Works&rdquo; and &ldquo;Shop
+Leasows,&rdquo; I believe nearly as high as the upper part of the
+latter field.</p>
+<table>
+<tr>
+<td><p>&nbsp;</p>
+</td>
+<td><p>Thickness of mould in inches.</p>
+</td>
+</tr>
+<tr>
+<td><p>17. Trench 26 inches deep</p>
+</td>
+<td><p style="text-align: right">24</p>
+</td>
+</tr>
+<tr>
+<td><p>18. Trench 10 inches deep, and then came upon a
+causeway</p>
+</td>
+<td><p style="text-align: right">10</p>
+</td>
+</tr>
+<tr>
+<td><p>19. Trench 34 inches deep</p>
+</td>
+<td><p style="text-align: right">30</p>
+</td>
+</tr>
+<tr>
+<td><p>20. Trench 31 inches deep</p>
+</td>
+<td><p style="text-align: right">31</p>
+</td>
+</tr>
+</table>
+<p>Field on the western side of the space enclosed within the old
+walls.</p>
+<table>
+<tr>
+<td><p>&nbsp;</p>
+</td>
+<td><p>Thickness of mould in inches.</p>
+</td>
+</tr>
+<tr>
+<td><p>21. Trench 28 inches deep, when undisturbed sand was
+reached</p>
+</td>
+<td><p style="text-align: right">16</p>
+</td>
+</tr>
+<tr>
+<td><p>22. Trench 29 inches deep, when undisturbed sand was
+reached</p>
+</td>
+<td><p style="text-align: right">15</p>
+</td>
+</tr>
+<tr>
+<td><p>23. Trench 14 inches deep, and then came upon a
+building</p>
+</td>
+<td><p style="text-align: right">14</p>
+</td>
+</tr>
+</table>
+<p>Dr. Johnson distinguished as mould the earth which differed,
+more or less abruptly, in its dark colour and in its texture from
+the underlying sand or rubble. In the specimens sent to me,
+the mould resembled that which lies immediately beneath the turf
+in old pasture-land, excepting that it often contained small
+stones, too large to have passed through the bodies of
+worms. But the trenches above described were dug in fields,
+none of which were in pasture, and all had been long
+cultivated. Bearing in mind the remarks made in reference
+to Silchester on the effects of long-continued culture, combined
+with the action of worms in bringing up the finer particles to
+the surface, the mould, as so designated by Dr. Johnson, seems
+fairly well to deserve its name. Its thickness, where there
+was no causeway, floor or walls beneath, was greater than has
+been elsewhere observed, namely, in many places above 2 ft., and
+in one spot above 3 ft. The mould was thickest on and close
+to the nearly level summit of the field called &ldquo;Shop
+Leasows,&rdquo; and in a small adjoining field, which, as I
+believe, is of nearly the same height. One side of the
+former field slopes at an angle of rather above 2&deg;, and I
+should have expected that the mould, from being washed down
+during heavy rain, would have been thicker in the lower than in
+the upper part; but this was not the case in two out of the three
+trenches here dug.</p>
+
+<p>In many places, where streets ran beneath the surface, or
+where old buildings stood, the mould was only 8 inches in
+thickness; and Dr. Johnson was surprised that in ploughing the
+land, the ruins had never been struck by the plough as far as he
+had heard. He thinks that when the land was first
+cultivated the old walls were perhaps intentionally pulled down,
+and that hollow places were filled up. This may have been
+the case; but if after the desertion of the city the land was
+left for many centuries uncultivated, worms would have brought up
+enough fine earth to have covered the ruins completely; that is
+if they had subsided from having been undermined. The
+foundations of some of the walls, for instance those of the
+portion still standing about 20 feet above the ground, and those
+of the marketplace, lie at the extraordinary depth of 14 feet;
+but it is highly improbable that the foundations were generally
+so deep. The mortar employed in the buildings must have
+been excellent, for it is still in parts extremely hard.
+Wherever walls of any height have been exposed to view, they are,
+as Dr. Johnson believes, still perpendicular. The walls
+with such deep foundations cannot have been undermined by worms,
+and therefore cannot have subsided, as appears to have occurred
+at Abinger and Silchester. Hence it is very difficult to
+account for their being now completely covered with earth; but
+how much of this covering consists of vegetable mould and how
+much of rubble I do not know. The market-place, with the
+foundations at a depth of 14 feet, was covered up, as Dr. Johnson
+believes, by between 6 and 24 inches of earth. The tops of
+the broken-down walls of a caldarium or bath, 9 feet in depth,
+were likewise covered up with nearly 2 feet of earth. The
+summit of an arch, leading into an ash-pit 7 feet in depth, was
+covered up with not more than 8 inches of earth. Whenever a
+building which has not subsided is covered with earth, we must
+suppose, either that the upper layers of stone have been at some
+time carried away by man, or that earth has since been washed
+down during heavy rain, or blown down during storms, from the
+adjoining land; and this would be especially apt to occur where
+the land has long been cultivated. In the above cases the
+adjoining land is somewhat higher than the three specified sites,
+as far as I can judge by maps and from information given me by
+Dr. Johnson. If; however, a great pile of broken stones,
+mortar, plaster, timber and ashes fell over the remains of any
+building, their disintegration in the course of time, and the
+sifting action of worms, would ultimately conceal the whole
+beneath fine earth.</p>
+
+<div class="gapspace">&nbsp;</div>
+<p><i>Conclusion</i>.&mdash;The cases given in this chapter show
+that worms have played a considerable part in the burial and
+concealment of several Roman and other old buildings in England;
+but no doubt the washing down of soil from the neighbouring
+higher lands, and the deposition of dust, have together aided
+largely in the work of concealment. Dust would be apt to
+accumulate wherever old broken-down walls projected a little
+above the then existing surface and thus afforded some
+shelter. The floors of the old rooms, halls and passages
+have generally sunk, partly from the settling of the ground, but
+chiefly from having been undermined by worms; and the sinking has
+commonly been greater in the middle than near the walls.
+The walls themselves, whenever their foundations do not lie at a
+great depth, have been penetrated and undermined by worms, and
+have consequently subsided. The unequal subsidence thus
+caused, probably explains the great cracks which may be seen in
+many ancient walls, as well as their inclination from the
+perpendicular.</p>
+<h2><a name="page209"></a><span class="pagenum">p.
+209</span>CHAPTER V.<br />
+<span class="GutSmall">THE ACTION OF WORMS IN THE DENUDATION OF
+THE LAND.</span></h2>
+<p class="gutsumm">Evidence of the amount of denudation which the
+land has undergone&mdash;Sub-aerial denudation&mdash;The
+deposition of dust&mdash;Vegetable mould, its dark colour and
+fine texture largely due to the action of worms&mdash;The
+disintegration of rocks by the humus-acids&mdash;Similar acids
+apparently generated within the bodies of worms&mdash;The action
+of these acids facilitated by the continued movement of the
+particles of earth&mdash;A thick bed of mould checks the
+disintegration of the underlying soil and rocks. Particles
+of stone worn or triturated in the gizzards of
+worms&mdash;Swallowed stones serve as mill-stones&mdash;The
+levigated state of the castings&mdash;Fragments of brick in the
+castings over ancient buildings well rounded. The
+triturating power of worms not quite insignificant under a
+geological point of view.</p>
+
+<p><span class="smcap">No</span> one doubts that our world at one
+time consisted of crystalline rocks, and that it is to their
+disintegration through the action of air, water, changes of
+temperature, rivers, waves of the sea, earthquakes and volcanic
+outbursts, that we owe our sedimentary formations. These
+after being consolidated and sometimes recrystallized, have often
+been again disintegrated. Denudation means the removal of
+such disintegrated matter to a lower level. Of the many
+striking results due to the modern progress of geology there are
+hardly any more striking than those which relate to
+denudation. It was long ago seen that there must have been
+an immense amount of denudation; but until the successive
+formations were carefully mapped and measured, no one fully
+realised how great was the amount. One of the first and
+most remarkable memoirs ever published on this subject was that
+by Ramsay, <a name="citation210"></a><a href="#footnote210"
+class="citation">[210]</a> who in 1846 showed that in Wales from
+9000 to 11,000 feet in thickness of solid rock had been stripped
+off large tracks of country. Perhaps the plainest evidence
+of great denudation is afforded by faults or cracks, which extend
+for many miles across certain districts, with the strata on one
+side raised even ten thousand feet above the corresponding strata
+on the opposite side; and yet there is not a vestige of this
+gigantic displacement visible on the surface of the land. A
+huge pile of rock has been planed away on one side and not a
+remnant left.</p>
+
+<p>Until the last twenty or thirty years, most geologists thought
+that the waves of the sea were the chief agents in the work of
+denudation; but we may now feel sure that air and rain, aided by
+streams and rivers, are much more powerful agents,&mdash;that is
+if we consider the whole area of the land. The long lines
+of escarpment which stretch across several parts of England were
+formerly considered to be undoubtedly ancient coast-lines; but we
+now know that they stand up above the general surface merely from
+resisting air, rain and frost better than the adjoining
+formations. It has rarely been the good fortune of a
+geologist to bring conviction to the minds of his fellow-workers
+on a disputed point by a single memoir; but Mr. Whitaker, of the
+Geological Survey of England, was so fortunate when, in 1867, he
+published his paper &ldquo;On sub-aerial Denudation, and on
+Cliffs and Escarpments of the Chalk.&rdquo; <a
+name="citation211"></a><a href="#footnote211"
+class="citation">[211]</a> Before this paper appeared, Mr.
+A. Tylor had adduced important evidence on sub-aerial denudation,
+by showing that the amount of matter brought down by rivers must
+infallibly lower the level of their drainage basins by many feet
+in no immense lapse of time. This line of argument has
+since been followed up in the most interesting manner by
+Archibald Geikie, Croll and others, in a series of valuable
+memoirs. <a name="citation212"></a><a href="#footnote212"
+class="citation">[212]</a> For the sake of those who have
+never attended to this subject, a single instance may be here
+given, namely, that of the Mississippi, which is chosen because
+the amount of sediment brought down by this great river has been
+investigated with especial care by order of the United States
+Government. The result is, as Mr. Croll shows, that the
+mean level of its enormous area of drainage must be lowered
+1/4566 of a foot annually, or 1 foot in 4566 years.
+Consequently, taking the best estimate of the mean height of the
+North American continent, viz. 748 feet, and looking to the
+future, the whole of the great Mississippi basin will be washed
+away, and &ldquo;brought down to the sea-level in less than
+4,500,000 years, if no elevation of the land takes
+place.&rdquo; Some rivers carry down much more sediment
+relatively to their size, and some much less than the
+Mississippi.</p>
+
+<p>Disintegrated matter is carried away by the wind as well as by
+running water. During volcanic outbursts much rock is
+triturated and is thus widely dispersed; and in all arid
+countries the wind plays an important part in the removal of such
+matter. Wind-driven sand also wears down the hardest
+rocks. I have shown <a name="citation213"></a><a
+href="#footnote213" class="citation">[213]</a> that during four
+months of the year a large quantity of dust is blown from the
+north-western shores of Africa, and falls on the Atlantic over a
+space of 1600 miles in latitude, and for a distance of from 300
+to 600 miles from the coast. But dust has been seen to fall
+at a distance of 1030 miles from the shores of Africa.
+During a stay of three weeks at St. Jago in the Cape Verde
+Archipelago, the atmosphere was almost always hazy, and extremely
+fine dust coming from Africa was continually falling. In
+some of this dust which fell in the open ocean at a distance of
+between 330 and 380 miles from the African coast, there were many
+particles of stone, about 1/1000 of an inch square. Nearer
+to the coast the water has been seen to be so much discoloured by
+the falling dust, that a sailing vessel left a track behind
+her. In countries, like the Cape Verde Archipelago, where
+it seldom rains and there are no frosts, the solid rock
+nevertheless disintegrates; and in conformity with the views
+lately advanced by a distinguished Belgian geologist, De Koninck,
+such disintegration may be attributed in chief part to the action
+of the carbonic and nitric acids, together with the nitrates and
+nitrites of ammonia, dissolved in the dew.</p>
+
+<p>In all humid, even moderately humid, countries, worms aid in
+the work of denudation in several ways. The vegetable mould
+which covers, as with a mantle, the surface of the land, has all
+passed many times through their bodies. Mould differs in
+appearance from the subsoil only in its dark colour, and in the
+absence of fragments or particles of stone (when such are present
+in the subsoil), larger than those which can pass through the
+alimentary canal of a worm. This sifting of the soil is
+aided, as has already been remarked, by burrowing animals of many
+kinds, especially by ants. In countries where the summer is
+long and dry, the mould in protected places must be largely
+increased by dust blown from other and more exposed places.
+For instance, the quantity of dust sometimes blown over the
+plains of La Plata, where there are no solid rocks, is so great,
+that during the &ldquo;gran seco,&rdquo; 1827 to 1830, the
+appearance of the land, which is here unenclosed, was so
+completely changed that the inhabitants could not recognise the
+limits of their own estates, and endless lawsuits arose.
+Immense quantities of dust are likewise blown about in Egypt and
+in the south of France. In China, as Richthofen maintains,
+beds appearing like fine sediment, several hundred feet in
+thickness and extending over an enormous area, owe their origin
+to dust blown from the high lands of central Asia. <a
+name="citation215"></a><a href="#footnote215"
+class="citation">[215]</a> In humid countries like Great
+Britain, as long as the land remains in its natural state clothed
+with vegetation, the mould in any one place can hardly be much
+increased by dust; but in its present condition, the fields near
+high roads, where there is much traffic, must receive a
+considerable amount of dust, and when fields are harrowed during
+dry and windy weather, clouds of dust may be seen to be blown
+away. But in all these cases the surface-soil is merely
+transported from one place to another. The dust which falls
+so thickly within our houses consists largely of organic matter,
+and if spread over the land would in time decay and disappear
+almost entirely. It appears, however, from recent
+observations on the snow-fields of the Arctic regions, that some
+little meteoric dust of extra mundane origin is continually
+falling.</p>
+
+<p>The dark colour of ordinary mould is obviously due to the
+presence of decaying organic matter, which, however, is present
+in but small quantities. The loss of weight which mould
+suffers when heated to redness seems to be in large part due to
+water in combination being dispelled. In one sample of
+fertile mould the amount of organic matter was ascertained to be
+only 1.76 per cent.; in some artificially prepared soil it was as
+much as 5.5 per cent., and in the famous black soil of Russia
+from 5 to even 12 per cent. <a name="citation217a"></a><a
+href="#footnote217a" class="citation">[217a]</a> In
+leaf-mould formed exclusively by the decay of leaves the amount
+is much greater, and in peat the carbon alone sometimes amounts
+to 64 per cent.; but with these latter cases we are not here
+concerned. The carbon in the soil tends gradually to
+oxidise and to disappear, except where water accumulates and the
+climate is cool; <a name="citation217b"></a><a
+href="#footnote217b" class="citation">[217b]</a> so that in the
+oldest pasture-land there is no great excess of organic matter,
+notwithstanding the continued decay of the roots and the
+underground stems of plants, and the occasional addition of
+manure. The disappearance of the organic matter from mould
+is probably much aided by its being brought again and again to
+the surface in the castings of worms.</p>
+
+<p>Worms, on the other hand, add largely to the organic matter in
+the soil by the astonishing number of half-decayed leaves which
+they draw into their burrows to a depth of 2 or 3 inches.
+They do this chiefly for obtaining food, but partly for closing
+the mouths of their burrows and for lining the upper part.
+The leaves which they consume are moistened, torn into small
+shreds, partially digested, and intimately commingled with earth;
+and it is this process which gives to vegetable mould its uniform
+dark tint. It is known that various kinds of acids are
+generated by the decay of vegetable matter; and from the contents
+of the intestines of worms and from their castings being acid, it
+seems probable that the process of digestion induces an analogous
+chemical change in the swallowed, triturated, and half-decayed
+leaves. The large quantity of carbonate of lime secreted by
+the calciferous glands apparently serves to neutralise the acids
+thus generated; for the digestive fluid of worms will not act
+unless it be alkaline. As the contents of the upper part of
+their intestines are acid, the acidity can hardly be due to the
+presence of uric acid. We may therefore conclude that the
+acids in the alimentary canal of worms are formed during the
+digestive process; and that probably they are nearly of the same
+nature as those in ordinary mould or humus. The latter are
+well known to have the power of de-oxidising or dissolving
+per-oxide of iron, as may be seen wherever peat overlies red
+sand, or where a rotten root penetrates such sand. Now I
+kept some worms in a pot filled with very fine reddish sand,
+consisting of minute particles of silex coated with the red oxide
+of iron; and the burrows, which the worms made through this sand,
+were lined or coated in the usual manner with their castings,
+formed of the sand mingled with their intestinal secretions and
+the refuse of the digested leaves; and this sand had almost
+wholly lost its red colour. When small portions of it were
+placed under the microscope, most of the grains were seen to be
+transparent and colourless, owing to the dissolution of the
+oxide; whilst almost all the grains taken from other parts of the
+pot were coated with the oxide. Acetic acid produced hardly
+any effect on his sand; and even hydrochloric, nitric and
+sulphuric acids, diluted as in the Pharmacopoeia, produced less
+effect than did the acids in the intestines of the worms.</p>
+
+<p>Mr. A. A. Julien has lately collected all the extant
+information about the acids generated in humus, which, according
+to some chemists, amount to more than a dozen different
+kinds. These acids, as well as their acid salts (i.e., in
+combination with potash, soda, and ammonia), act energetically on
+carbonate of lime and on the oxides of iron. It is also
+known that some of these acids, which were called long ago by
+Thénard azohumic, are enabled to dissolve colloid silica
+in proportion to the nitrogen which they contain. <a
+name="citation220"></a><a href="#footnote220"
+class="citation">[220]</a> In the formation of these latter
+acids worms probably afford some aid, for Dr. H. Johnson informs
+me that by Nessler&rsquo;s test he found 0.018 per cent. of
+ammonia in their castings.</p>
+
+<p>It may be here added that I have recently been informed by Dr.
+Gilbert &ldquo;that several square yards on his lawn were swept
+clean, and after two or three weeks all the worm-castings on the
+space were collected and dried. These were found to contain
+0.35 of nitrogen. This is from two to three times as much
+as we find in our ordinary arable surface-soil; more than in our
+ordinary pasture surface-soil; but less than in rich
+kitchen-garden mould. Supposing a quantity of castings
+equal to 10 tons in the dry state were annually deposited on an
+acre, this would represent a manuring of 78 lbs. of nitrogen per
+acre per annum; and this is very much more than the amount of
+nitrogen in the annual yield of hay per acre, if raised without
+any nitrogenous manure. Obviously, so far as the nitrogen
+in the castings is derived from surface-growth or from
+surface-soil, it is not a gain to the latter; but so far as it is
+derived from below, it is a gain.&rdquo;</p>
+
+<p>The several humus-acids, which appear, as we have just seen,
+to be generated within the bodies of worms during the digestive
+process, and their acid salts, play a highly important part,
+according to the recent observations of Mr. Julien, in the
+disintegration of various kinds of rocks. It has long been
+known that the carbonic acid, and no doubt nitric and nitrous
+acids, which are present in rain-water, act in like manner.
+There is, also, a great excess of carbonic acid in all soils,
+especially in rich soils, and this is dissolved by the water in
+the ground. The living roots of plants, moreover, as Sachs
+and others have shown, quickly corrode and leave their
+impressions on polished slabs of marble, dolomite and phosphate
+of lime. They will attack even basalt and sandstone. <a
+name="citation222"></a><a href="#footnote222"
+class="citation">[222]</a> But we are not here concerned
+with agencies which are wholly independent of the action of
+worms.</p>
+
+<p>The combination of any acid with a base is much facilitated by
+agitation, as fresh surfaces are thus continually brought into
+contact. This will be thoroughly effected with the
+particles of stone and earth in the intestines of worms, during
+the digestive process; and it should be remembered that the
+entire mass of the mould over every field, passes, in the course
+of a few years, through their alimentary canals. Moreover
+as the old burrows slowly collapse, and as fresh castings are
+continually brought to the surface, the whole superficial layer
+of mould slowly revolves or circulates; and the friction of the
+particles one with another will rub off the finest films of
+disintegrated matter as soon as they are formed. Through
+these several means, minute fragments of rocks of many kinds and
+mere particles in the soil will be continually exposed to
+chemical decomposition; and thus the amount of soil will tend to
+increase.</p>
+
+<p>As worms line their burrows with their castings, and as the
+burrows penetrate to a depth of 5 or 6, or even more feet, some
+small amount of the humus-acids will be carried far down, and
+will there act on the underlying rocks and fragments of
+rock. Thus the thickness of the soil, if none be removed
+from the surface, will steadily though slowly tend to increase;
+but the accumulation will after a time delay the disintegration
+of the underlying rocks and of the more deeply seated
+particles. For the humus-acids which are generated chiefly
+in the upper layer of vegetable mould, are extremely unstable
+compounds, and are liable to decomposition before they reach any
+considerable depth. <a name="citation223"></a><a
+href="#footnote223" class="citation">[223]</a> A thick bed
+of overlying soil will also check the downward extension of great
+fluctuations of temperature, and in cold countries will check the
+powerful action of frost. The free access of air will
+likewise be excluded. From these several causes
+disintegration would be almost arrested, if the overlying mould
+were to increase much in thickness, owing to none or little being
+removed from the surface. <a name="citation224a"></a><a
+href="#footnote224a" class="citation">[224a]</a> In my own
+immediate neighbourhood we have a curious proof how effectually a
+few feet of clay checks some change which goes on in flints,
+lying freely exposed; for the large ones which have lain for some
+time on the surface of ploughed fields cannot be used for
+building; they will not cleave properly, and are said by the
+workmen to be rotten. <a name="citation224b"></a><a
+href="#footnote224b" class="citation">[224b]</a> It is
+therefore necessary to obtain flints for building purposes from
+the bed of red clay overlying the chalk (the residue of its
+dissolution by rain-water) or from the chalk itself.</p>
+
+<p>Not only do worms aid directly in the chemical disintegration
+of rocks, but there is good reason to believe that they likewise
+act in a direct and mechanical manner on the smaller
+particles. All the species which swallow earth are
+furnished with gizzards; and these are lined with so thick a
+chitinous membrane, that Perrier speaks of it, <a
+name="citation225a"></a><a href="#footnote225a"
+class="citation">[225a]</a> as &ldquo;une véritable
+armature.&rdquo; The gizzard is surrounded by powerful
+transverse muscles, which, according to Claparède, are
+about ten times as thick as the longitudinal ones; and Perrier
+saw them contracting energetically. Worms belonging to one
+genus, Digaster, have two distinct but quite similar gizzards;
+and in another genus, Moniligaster, the second gizzard consists
+of four pouches, one succeeding the other, so that it may almost
+be said to have five gizzards. <a name="citation225b"></a><a
+href="#footnote225b" class="citation">[225b]</a> In the
+same manner as gallinaceous and struthious birds swallow stones
+to aid in the trituration of their food, so it appears to be with
+terricolous worms. The gizzards of thirty-eight of our
+common worms were opened, and in twenty-five of them small stones
+or grains of sand, sometimes together with the hard calcareous
+concretions formed within the anterior calciferous glands, were
+found, and in two others concretions alone. In the gizzards
+of the remaining worms there were no stones; but some of these
+were not real exceptions, as the gizzards were opened late in the
+autumn, when the worms had ceased to feed and their gizzards were
+quite empty. <a name="citation226"></a><a href="#footnote226"
+class="citation">[226]</a></p>
+
+<p>When worms make their burrows through earth abounding with
+little stones, no doubt many will be unavoidably swallowed; but
+it must not be supposed that this fact accounts for the frequency
+with which stones and sand are found in their gizzards. For
+beads of glass and fragments of brick and of hard tiles were
+scattered over the surface of the earth, in pots in which worms
+were kept and had already made their burrows; and very many of
+these beads and fragments were picked up and swallowed by the
+worms, for they were found in their castings, intestines, and
+gizzards. They even swallowed the coarse red dust, formed
+by the pounding of the tiles. Nor can it be supposed that
+they mistook the beads and fragments for food; for we have seen
+that their taste is delicate enough to distinguish between
+different kinds of leaves. It is therefore manifest that
+they swallow hard objects, such as bits of stone, beads of glass
+and angular fragments of bricks or tiles for some special
+purpose; and it can hardly be doubted that this is to aid their
+gizzards in crushing and grinding the earth, which they so
+largely consume. That such hard objects are not necessary
+for crushing leaves, may be inferred from the fact that certain
+species, which live in mud or water and feed on dead or living
+vegetable matter, but which do not swallow earth, are not
+provided with gizzards, <a name="citation227"></a><a
+href="#footnote227" class="citation">[227]</a> and therefore
+cannot have the power of utilising stones.</p>
+
+<p>During the grinding process, the particles of earth must be
+rubbed against one another, and between the stones and the tough
+lining membrane of the gizzard. The softer particles will
+thus suffer some attrition, and will perhaps even be
+crushed. This conclusion is supported by the appearance of
+freshly ejected castings, for these often reminded me of the
+appearance of paint which has just been ground by a workman
+between two flat stones. Morren remarks that the intestinal
+canal is &ldquo;impleta tenuissim&acirc; terr&acirc;, veluti in
+pulverem redact&acirc;.&rdquo; <a name="citation228a"></a><a
+href="#footnote228a" class="citation">[228a]</a> Perrier
+also speaks of &ldquo;l&rsquo;état de p&acirc;te
+excessivement fine à laquelle est réduite la terre
+qu&rsquo;ils rejettent,&rdquo; &amp;c. <a
+name="citation228b"></a><a href="#footnote228b"
+class="citation">[228b]</a></p>
+
+<p>As the amount of trituration which the particles of earth
+undergo in the gizzards of worms possesses some interest (as we
+shall hereafter see), I endeavoured to obtain evidence on this
+head by carefully examining many of the fragments which had
+passed through their alimentary canals. With worms living
+in a state of nature, it is of course impossible to know how much
+the fragments may have been worn before they were
+swallowed. It is, however, clear that worms do not
+habitually select already rounded particles, for sharply angular
+bits of flint and of other hard rocks were often found in their
+gizzards or intestines. On three occasions sharp spines
+from the stems of rose-bushes were thus found. Worms kept
+in confinement repeatedly swallowed angular fragments of hard
+tile, coal, cinders, and even the sharpest fragments of
+glass. Gallinaceous and struthious birds retain the same
+stones in their gizzards for a long time, which thus become well
+rounded; but this does not appear to be the case with worms,
+judging from the large number of the fragments of tiles, glass
+beads, stones, &amp;c., commonly found in their castings and
+intestines. So that unless the same fragments were to pass
+repeatedly through their gizzards, visible signs of attrition in
+the fragments could hardly be expected, except perhaps in the
+case of very soft stones.</p>
+
+<p>I will now give such evidence of attrition as I have been able
+to collect. In the gizzards of some worms dug out of a thin
+bed of mould over the chalk, there were many well-rounded small
+fragments of chalk, and two fragments of the shells of a
+land-mollusc (as ascertained by their microscopical structure),
+which latter were not only rounded but somewhat polished.
+The calcareous concretions formed in the calciferous glands,
+which are often found in their gizzards, intestines, and
+occasionally in their castings, when of large size, sometimes
+appeared to have been rounded; but with all calcareous bodies the
+rounded appearance may be partly or wholly due to their corrosion
+by carbonic acid and the humus-acids. In the gizzards of
+several worms collected in my kitchen garden near a hothouse,
+eight little fragments of cinders were found, and of these, six
+appeared more or less rounded, as were two bits of brick; but
+some other bits were not at all rounded. A farm-road near
+Abinger Hall had been covered seven years before with
+brick-rubbish to the depth of about 6 inches; turf had grown over
+this rubbish on both sides of the road for a width of 18 inches,
+and on this turf there were innumerable castings. Some of
+them were coloured of a uniform red owing to the presence of much
+brick-dust, and they contained many particles of brick and of
+hard mortar from 1 to 3 mm. in diameter, most of which were
+plainly rounded; but all these particles may have been rounded
+before they were protected by the turf and were swallowed, like
+those on the bare parts of the road which were much worn. A
+hole in a pasture-field had been filled up with brick-rubbish at
+the same time, viz., seven years ago, and was now covered with
+turf; and here the castings contained very many particles of
+brick, all more or less rounded; and this brick-rubbish, after
+being shot into the hole, could not have undergone any
+attrition. Again, old bricks very little broken, together
+with fragments of mortar, were laid down to form walks, and were
+then covered with from 4 to 6 inches of gravel; six little
+fragments of brick were extracted from castings collected on
+these walks, three of which were plainly worn. There were
+also very many particles of hard mortar, about half of which were
+well rounded; and it is not credible that these could have
+suffered so much corrosion from the action of carbonic acid in
+the course of only seven years.</p>
+
+<p>Much better evidence of the attrition of hard objects in the
+gizzards of worms, is afforded by the state of the small
+fragments of tiles or bricks, and of concrete in the castings
+thrown up where ancient buildings once stood. As all the
+mould covering a field passes every few years through the bodies
+of worms, the same small fragments will probably be swallowed and
+brought to the surface many times in the course of
+centuries. It should be premised that in the several
+following cases, the finer matter was first washed away from the
+castings, and then <i>all</i> the particles of bricks, tiles and
+concrete were collected without any selection, and were
+afterwards examined. Now in the castings ejected between
+the tesseræ on one of the buried floors of the Roman villa
+at Abinger, there were many particles (from &frac12; to 2 mm. in
+diameter) of tiles and concrete, which it was impossible to look
+at with the naked eye or through a strong lens, and doubt for a
+moment that they had almost all undergone much attrition. I
+speak thus after having examined small water-worn pebbles, formed
+from Roman bricks, which M. Henri de Saussure had the kindness to
+send me, and which he had extracted from sand and gravel beds,
+deposited on the shores of the Lake of Geneva, at a former period
+when the water stood at about two metres above its present
+level. The smallest of these water-worn pebbles of brick
+from Geneva resembled closely many of those extracted from the
+gizzards of worms, but the larger ones were somewhat
+smoother.</p>
+
+<p>Four castings found on the recently uncovered, tesselated
+floor of the great room in the Roman villa at Brading, contained
+many particles of tile or brick, of mortar, and of hard white
+cement; and the majority of these appeared plainly worn.
+The particles of mortar, however, seemed to have suffered more
+corrosion than attrition, for grains of silex often projected
+from their surfaces. Castings from within the nave of
+Beaulieu Abbey, which was destroyed by Henry VIII., were
+collected from a level expanse of turf, overlying the buried
+tesselated pavement, through which worm-burrows passed; and these
+castings contained innumerable particles of tiles and bricks, of
+concrete and cement, the majority of which had manifestly
+undergone some or much attrition. There were also many
+minute flakes of a micaceous slate, the points of which were
+rounded. If the above supposition, that in all these cases
+the same minute fragments have passed several times through the
+gizzards of worms, be rejected, notwithstanding its inherent
+probability, we must then assume that in all the above cases the
+many rounded fragments found in the castings had all accidentally
+undergone much attrition before they were swallowed; and this is
+highly improbable.</p>
+
+<p>On the other hand it must be stated that fragments of
+ornamental tiles, somewhat harder than common tiles or bricks,
+which had been swallowed only once by worms kept in confinement,
+were with the doubtful exception of one or two of the smallest
+grains, not at all rounded. Nevertheless some of them
+appeared a little worn, though not rounded. Notwithstanding
+these cases, if we consider the evidence above given, there can
+be little doubt that the fragments, which serve as millstones in
+the gizzards of worms, suffer, when of a not very hard texture,
+some amount of attrition; and that the smaller particles in the
+earth, which is habitually swallowed in such astonishingly large
+quantities by worms, are ground together and are thus
+levigated. If this be the case, the &ldquo;terra
+tenuissima,&rdquo;&mdash;the &ldquo;p&acirc;te excessivement
+fine,&rdquo;&mdash;of which the castings largely consist, is in
+part due to the mechanical action of the gizzard; <a
+name="citation234"></a><a href="#footnote234"
+class="citation">[234]</a> and this fine matter, as we shall see
+in the next chapter, is that which is chiefly washed away from
+the innumerable castings on every field during each heavy shower
+of rain. If the softer stones yield at all, the harder ones
+will suffer some slight amount of wear and tear.</p>
+
+<p>The trituration of small particles of stone in the gizzards of
+worms is of more importance under a geological point of view than
+may at first appear to be the case; for Mr. Sorby has clearly
+shown that the ordinary means of disintegration, namely, running
+water and the waves of the sea, act with less and less power on
+fragments of rock the smaller they are.
+&ldquo;Hence,&rdquo; as he remarks, &ldquo;even making no
+allowance for the extra buoying up of very minute particles by a
+current of water, depending on surface cohesion, the effects of
+wearing on the form of the grains must vary directly as their
+diameter or thereabouts. If so, a grain of 1/10 an inch in
+diameter would be worn ten times as much as one of an inch in
+diameter, and at least a hundred times as much as one of 1/100 an
+inch in diameter. Perhaps, then, we may conclude that a
+grain 1/10 of an inch in diameter would be worn as much or more
+in drifting a mile as a grain 1/1000 of an inch in being drifted
+100 miles. On the same principle a pebble one inch in
+diameter would be worn relatively more by being drifted only a
+few hundred yards.&rdquo; <a name="citation236"></a><a
+href="#footnote236" class="citation">[236]</a> Nor should
+we forget, in considering the power which worms exert in
+triturating particles of rock, that there is good evidence that
+on each acre of land, which is sufficiently damp and not too
+sandy, gravelly or rocky for worms to inhabit, a weight of more
+than ten tons of earth annually passes through their bodies and
+is brought to the surface. The result for a country of the
+size of Great Britain, within a period not very long in a
+geological sense, such as a million years, cannot be
+insignificant; for the ten tons of earth has to be multiplied
+first by the above number of years, and then by the number of
+acres fully stocked with worms; and in England, together with
+Scotland, the land which is cultivated and is well fitted for
+these animals, has been estimated at above 32 million
+acres. The product is 320 million million tons of
+earth.</p>
+<h3><a name="page237"></a><span class="pagenum">p.
+237</span>CHAPTER VI.<br />
+<span class="GutSmall">THE DENUDATION OF THE
+LAND&mdash;</span><span
+class="GutSmall"><i>continued</i></span><span
+class="GutSmall">.</span></h3>
+<p class="gutsumm">Denudation aided by recently ejected castings
+flowing down inclined grass-covered surfaces&mdash;The amount of
+earth which annually flows downwards&mdash;The effect of tropical
+rain on worm castings&mdash;The finest particles of earth washed
+completely away from castings&mdash;The disintegration of dried
+castings into pellets, and their rolling down inclined
+surfaces&mdash;The formation of little ledges on hill-sides, in
+part due to the accumulation of disintegrated
+castings&mdash;Castings blown to leeward over level land&mdash;An
+attempt to estimate the amount thus blown&mdash;The degradation
+of ancient encampments and tumuli&mdash;The preservation of the
+crowns and furrows on land anciently ploughed&mdash;The formation
+and amount of mould over the Chalk formation.</p>
+
+<p><span class="smcap">We</span> are now prepared to consider the
+more direct part which worms take in the denudation of the
+land. When reflecting on sub-aerial denudation, it formerly
+appeared to me, as it has to others, that a nearly level or very
+gently inclined surface, covered with turf, could suffer no loss
+during even a long lapse of time. It may, however, be urged
+that at long intervals, debacles of rain or water-spouts would
+remove all the mould from a very gentle slope; but when examining
+the steep, turf-covered slopes in Glen Roy, I was struck with the
+fact how rarely any such event could have happened since the
+Glacial period, as was plain from the well-preserved state of the
+three successive &ldquo;roads&rdquo; or lake-margins. But
+the difficulty in believing that earth in any appreciable
+quantity can be removed from a gently inclined surface, covered
+with vegetation and matted with roots, is removed through the
+agency of worms. For the many castings which are thrown up
+during rain, and those thrown up some little time before heavy
+rain, flow for a short distance down an inclined surface.
+Moreover much of the finest levigated earth is washed completely
+away from the castings. During dry weather castings often
+disintegrate into small rounded pellets, and these from their
+weight often roll down any slope. This is more especially
+apt to occur when they are started by the wind, and probably when
+started by the touch of an animal, however small. We shall
+also see that a strong wind blows all the castings, even on a
+level field, to leeward, whilst they are soft; and in like manner
+the pellets when they are dry. If the wind blows in nearly
+the direction of an inclined surface, the flowing down of the
+castings is much aided.</p>
+
+<p>The observations on which these several statements are founded
+must now be given in some detail. Castings when first
+ejected are viscid and soft; during rain, at which time worms
+apparently prefer to eject them, they are still softer; so that I
+have sometimes thought that worms must swallow much water at such
+times. However this may be, rain, even when not very heavy,
+if long continued, renders recently-ejected castings semi-fluid;
+and on level ground they then spread out into thin, circular,
+flat discs, exactly as would so much honey or very soft mortar,
+with all traces of their vermiform structure lost. This
+latter fact was sometimes made evident, when a worm had
+subsequently bored through a flat circular disc of this kind, and
+heaped up a fresh vermiform mass in the centre. These flat
+subsided discs have been repeatedly seen by me after heavy rain,
+in many places on land of all kinds.</p>
+
+<p><i>On the flowing of wet castings</i>, <i>and the rolling of
+dry disintegrated castings down inclined surfaces</i>.&mdash;When
+castings are ejected on an inclined surface during or shortly
+before heavy rain, they cannot fail to flow a little down the
+slope. Thus, on some steep slopes in Knole Park, which were
+covered with coarse grass and had apparently existed in this
+state from time immemorial, I found (Oct. 22, 1872) after several
+wet days that almost all the many castings were considerably
+elongated in the line of the slope; and that they now consisted
+of smooth, only slightly conical masses. Whenever the
+mouths of the burrows could be found from which the earth had
+been ejected, there was more earth below than above them.
+After some heavy storms of rain (Jan. 25, 1872) two rather
+steeply inclined fields near Down, which had formerly been
+ploughed and were now rather sparsely clothed with poor grass,
+were visited, and many castings extended down the slopes for a
+length of 5 inches, which was twice or thrice the usual diameter
+of the castings thrown up on the level parts of these same
+fields. On some fine grassy slopes in Holwood Park,
+inclined at angles between 8&deg; and 11&deg; 30&prime; with the
+horizon, where the surface apparently had never been disturbed by
+the hand of man, castings abounded in extraordinary numbers: and
+a space 16 inches in length transversely to the slope and 6
+inches in the line of the slope, was completely coated, between
+the blades of grass, with a uniform sheet of confluent and
+subsided castings. Here also in many places the castings
+had flowed down the slope, and now formed smooth narrow patches
+of earth, 6, 7, and 7&frac12; inches in length. Some of
+these consisted of two castings, one above the other, which had
+become so completely confluent that they could hardly be
+distinguished. On my lawn, clothed with very fine grass,
+most of the castings are black, but some are yellowish from earth
+having been brought up from a greater depth than usual, and the
+flowing-down of these yellow castings after heavy rain, could be
+clearly seen where the slope was 5&deg;; and where it was less
+than 1&deg; some evidence of their flowing down could still be
+detected. On another occasion, after rain which was never
+heavy, but which lasted for 18 hours, all the castings on this
+same gently inclined lawn had lost their vermiform structure; and
+they had flowed, so that fully two-thirds of the ejected earth
+lay below the mouths of the burrows.</p>
+
+<p>These observations led me to make others with more care.
+Eight castings were found on my lawn, where the grass-blades are
+fine and close together, and three others on a field with coarse
+grass. The inclination of the surface at the eleven places
+where these castings were collected varied between 4&deg;
+30&prime; and 17&deg; 30&prime;; the mean of the eleven
+inclinations being 9&deg; 26&prime;. The length of the
+castings in the direction of the slope was first measured with as
+much accuracy as their irregularities would permit. It was
+found possible to make these measurements within about ⅛ of an
+inch, but one of the castings was too irregular to admit of
+measurement. The average length in the direction of the
+slope of the remaining ten castings was 2.03 inches. The
+castings were then divided with a knife into two parts along a
+horizontal line passing through the mouth of the burrow, which
+was discovered by slicing off the turf; and all the ejected earth
+was separately collected, namely, the part above the hole and the
+part below. Afterwards these two parts were weighed.
+In every case there was much more earth below than above; the
+mean weight of that above being 103 grains, and of that below 205
+grains; so that the latter was very nearly double the
+former. As on level ground castings are commonly thrown up
+almost equally round the mouths of the burrows, this difference
+in weight indicates the amount of ejected earth which had flowed
+down the slope. But very many more observations would be
+requisite to arrive at any general result; for the nature of the
+vegetation and other accidental circumstances, such as the
+heaviness of the rain, the direction and force of the wind,
+&amp;c., appear to be more important in determining the quantity
+of the earth which flows down a slope than its angle. Thus
+with four castings on my lawn (included in the above eleven)
+where the mean slope was 7&deg; 19&prime;, the difference in the
+amount of earth above and below the burrows was greater than with
+three other castings on the same lawn where the mean slope was
+12&deg; 5&prime;.</p>
+
+<p>We may, however, take the above eleven cases, which are
+accurate as far as they go, and calculate the weight of the
+ejected earth which annually flows down a slope having a mean
+inclination of 9&deg; 26&prime;. This was done by my son
+George. It has been shown that almost exactly two-thirds of
+the ejected earth is found below the mouth of the burrow and
+one-third above it. Now if the two-thirds which is below
+the hole be divided into two equal parts, the upper half of this
+two-thirds exactly counterbalances the one-third which is above
+the hole, so that as far as regards the one-third above and the
+upper half of the two-thirds below, there is no flow of earth
+down the hill-side. The earth constituting the lower half
+of the two-thirds is, however, displaced through distances which
+are different for every part of it, but which may be represented
+by the distance between the middle point of the lower half of the
+two-thirds and the hole. So that the average distance of
+displacement is a half of the whole length of the
+worm-casting. Now the average length of ten out of the
+above eleven castings was 2.03 inches, and half of this we may
+take as being 1 inch. It may therefore be concluded that
+one-third of the whole earth brought to the surface was in these
+cases carried down the slope through 1 inch. <a
+name="citation244"></a><a href="#footnote244"
+class="citation">[244]</a></p>
+
+<p>It was shown in the third chapter that on Leith Hill Common,
+dry earth weighing at least 7.453 lbs. was brought up by worms to
+the surface on a square yard in the course of a year. If a
+square yard be drawn on a hillside with two of its sides
+horizontal, then it is clear that only 1/36 part of the earth
+brought up on that square yard would be near enough to its lower
+side to cross it, supposing the displacement of the earth to be
+through one inch. But it appears that only &#8531; of the
+earth brought up can be considered to flow downwards; hence
+&#8531; of 1/36 or 1/108 of 7.453 lbs. will cross the lower side
+of our square yard in a year. Now 1/108 of 7.453 lbs. is
+1.1 oz. Therefore 1.1 oz. of dry earth will annually cross
+each linear yard running horizontally along a slope having the
+above inclination; or very nearly 7 lbs. will annually cross a
+horizontal line, 100 yards in length, on a hill-side having this
+inclination.</p>
+
+<p>A more accurate, though still very rough, calculation can be
+made of the bulk of earth, which in its natural damp state
+annually flows down the same slope over a yard-line drawn
+horizontally across it. From the several cases given in the
+third chapter, it is known that the castings annually brought to
+the surface on a square yard, if uniformly spread out would form
+a layer 0.2 of an inch in thickness: it therefore follows by a
+calculation similar to the one already given, that &#8531; of 0.2
+&times; 36, or 2.4 cubic inches of damp earth will annually cross
+a horizontal line one yard in length on a hillside with the above
+inclination. This bulk of damp castings was found to weigh
+1.85 oz. Therefore 11.56 lbs. of damp earth, instead of 7
+lbs. of dry earth as by the former calculation, would annually
+cross a line 100 yards in length on our inclined surface.</p>
+
+<p>In these calculations it has been assumed that the castings
+flow a short distance downwards during the whole year, but this
+occurs only with those ejected during or shortly before rain; so
+that the above results are thus far exaggerated. On the
+other hand, during rain much of the finest earth is washed to a
+considerable distance from the castings, even where the slope is
+an extremely gentle one, and is thus wholly lost as far as the
+above calculations are concerned. Castings ejected during
+dry weather and which have set hard, lose in the same manner a
+considerable quantity of fine earth. Dried castings,
+moreover, are apt to disintegrate into little pellets, which
+often roll or are blown down any inclined surface.
+Therefore the above result, namely, that 24 cubic inches of earth
+(weighing 1.85 oz. whilst damp) annually crosses a yard-line of
+the specified kind, is probably not much if at all
+exaggerated.</p>
+
+<p>This amount is small; but we should bear in mind how many
+branching valleys intersect most countries, the whole length of
+which must be very great; and that earth is steadily travelling
+down both turf-covered sides of each valley. For every 100
+yards in length in a valley with sides sloping as in the
+foregoing cases, 480 cubic inches of damp earth, weighing above
+23 pounds, will annually reach the bottom. Here a thick bed
+of alluvium will accumulate, ready to be washed away in the
+course of centuries, as the stream in the middle meanders from
+side to side.</p>
+
+<p>If it could be shown that worms generally excavate their
+burrows at right angles to an inclined surface, and this would be
+their shortest course for bringing up earth from beneath, then as
+the old burrows collapsed from the weight of the superincumbent
+soil, the collapsing would inevitably cause the whole bed of
+vegetable mould to sink or slide slowly down the inclined
+surface. But to ascertain the direction of many burrows was
+found too difficult and troublesome. A straight piece of
+wire was, however, pushed into twenty-five burrows on several
+sloping fields, and in eight cases the burrows were nearly at
+right angles to the slope; whilst in the remaining cases they
+were indifferently directed at various angles, either upwards or
+downwards with respect to the slope.</p>
+
+<p>In countries where the rain is very heavy, as in the tropics,
+the castings appear, as might have been expected, to be washed
+down in a greater degree than in England. Mr. Scott informs
+me that near Calcutta the tall columnar castings (previously
+described), the diameter of which is usually between 1 and
+1&frac12; inch, subside on a level surface, after heavy rain,
+into almost circular, thin, flat discs, between 3 and 4 and
+sometimes 5 inches in diameter. Three fresh castings, which
+had been ejected in the Botanic Gardens &ldquo;on a slightly
+inclined, grass-covered, artificial bank of loamy clay,&rdquo;
+were carefully measured, and had a mean height of 2.17, and a
+mean diameter of 1.43 inches; these after heavy rain, formed
+elongated patches of earth, with a mean length in the direction
+of the slope of 5.83 inches. As the earth had spread very
+little up the slope, a large part, judging from the original
+diameter of these castings, must have flowed bodily downwards
+about 4 inches. Moreover some of the finest earth of which
+they were composed must have been washed completely away to a
+still greater distance. In drier sites near Calcutta, a
+species of worm ejects its castings, not in vermiform masses, but
+in little pellets of varying sizes: these are very numerous in
+some places, and Mr. Scott says that they &ldquo;are washed away
+by every shower.&rdquo;</p>
+
+<p>I was led to believe that a considerable quantity of fine
+earth is washed quite away from castings during rain, from the
+surfaces of old ones being often studded with coarse
+particles. Accordingly a little fine precipitated chalk,
+moistened with saliva or gum-water, so as to be slightly viscid
+and of the same consistence as a fresh casting, was placed on the
+summits of several castings and gently mixed with them.
+These castings were then watered through a very fine rose, the
+drops from which were closer together than those of rain, but not
+nearly so large as those in a thunderstorm; nor did they strike
+the ground with nearly so much force as drops during heavy
+rain. A casting thus treated subsided with surprising
+slowness, owing as I suppose to its viscidity. It did not
+flow bodily down the grass-covered surface of the lawn, which was
+here inclined at an angle of 16&deg; 20&prime;; nevertheless many
+particles of the chalk were found three inches below the
+casting. The experiment was repeated on three other
+castings on different parts of the lawn, which sloped at 2&deg;
+30&prime;, 3&deg; and 6&deg;; and particles of chalk could be
+seen between 4 and 5 inches below the casting; and after the
+surface had become dry, particles were found in two cases at a
+distance of 5 and 6 inches. Several other castings with
+precipitated chalk placed on their summits were left to the
+natural action of the rain. In one case, after rain which
+was not heavy, the casting was longitudinally streaked with
+white. In two other cases the surface of the ground was
+rendered somewhat white for a distance of one inch from the
+casting; and some soil collected at a distance of 2&frac12;
+inches, where the slope was 7&deg;, effervesced slightly when
+placed in acid. After one or two weeks, the chalk was
+wholly or almost wholly washed away from all the castings on
+which it had been placed, and these had recovered their natural
+colour.</p>
+
+<p>It may be here remarked that after very heavy rain shallow
+pools may be seen on level or nearly level fields, where the soil
+is not very porous, and the water in them is often slightly
+muddy; when such little pools have dried, the leaves and blades
+of grass at their bottoms are generally coated with a thin layer
+of mud. This mud I believe is derived in large part from
+recently ejected castings.</p>
+
+<p>Dr. King informs me that the majority of the before described
+gigantic castings, which he found on a fully exposed, bare,
+gravelly knoll on the Nilgiri Mountains in India, had been more
+or less weathered by the previous north-east monsoon; and most of
+them presented a subsided appearance. The worms here eject
+their castings only during the rainy season; and at the time of
+Dr. King&rsquo;s visit no rain had fallen for 110 days. He
+carefully examined the ground between the place where these huge
+castings lay, and a little watercourse at the base of the knoll,
+and nowhere was there any accumulation of fine earth, such as
+would necessarily have been left by the disintegration of the
+castings if they had not been wholly removed. He therefore
+has no hesitation in asserting that the whole of these huge
+castings are annually washed during the two monsoons (when about
+100 inches of rain fall) into the little water-course, and thence
+into the plains lying below at a depth of 3000 or 4000 feet.</p>
+
+<p>Castings ejected before or during dry weather become hard,
+sometimes surprisingly hard, from the particles of earth having
+been cemented together by the intestinal secretions. Frost
+seems to be less effective in their disintegration than might
+have been expected. Nevertheless they readily disintegrate
+into small pellets, after being alternately moistened with rain
+and again dried. Those which have flowed during rain down a
+slope, disintegrate in the same manner. Such pellets often
+roll a little down any sloping surface; their descent being
+sometimes much aided by the wind. The whole bottom of a
+broad dry ditch in my grounds, where there were very few fresh
+castings, was completely covered with these pellets or
+disintegrated castings, which had rolled down the steep sides,
+inclined at an angle of 27&deg;.</p>
+
+<p>Near Nice, in places where the great cylindrical castings,
+previously described, abound, the soil consists of very fine
+arenaceo-calcareous loam; and Dr. King informs me that these
+castings are extremely liable to crumble during dry weather into
+small fragments, which are soon acted on by rain, and then sink
+down so as to be no longer distinguishable from the surrounding
+soil. He sent me a mass of such disintegrated castings,
+collected on the top of a bank, where none could have rolled down
+from above. They must have been ejected within the previous
+five or six months, but they now consisted of more or less
+rounded fragments of all sizes, from &frac34; of an inch in
+diameter to minute grains and mere dust. Dr. King witnessed
+the crumbling process whilst drying some perfect castings, which
+he afterwards sent me. Mr. Scott also remarks on the
+crumbling of the castings near Calcutta and on the mountains of
+Sikkim during the hot and dry season.</p>
+
+<p>When the castings near Nice had been ejected on an inclined
+surface, the disintegrated fragments rolled downwards, without
+losing their distinctive shape; and in some places could
+&ldquo;be collected in basketfuls.&rdquo; Dr. King observed
+a striking instance of this fact on the Corniche road, where a
+drain, about 2&frac12; feet wide and 9 inches deep, had been made
+to catch the surface drainage from the adjoining hill-side.
+The bottom of this drain was covered for a distance of several
+hundred yards, to a depth of from 1&frac12; to 3 inches, by a
+layer of broken castings, still retaining their characteristic
+shape. Nearly all these innumerable fragments had rolled
+down from above, for extremely few castings had been ejected in
+the drain itself. The hill-side was steep, but varied much
+in inclination, which Dr. King estimated at from 30&deg; to
+60&deg; with the horizon. He climbed up the slope, and
+&ldquo;found every here and there little embankments, formed by
+fragments of the castings that had been arrested in their
+downward progress by irregularities of the surface, by stones,
+twigs, &amp;c. One little group of plants of <i>Anemone
+hortensis</i> had acted in this manner, and quite a small bank of
+soil had collected round it. Much of this soil had crumbled
+down, but a great deal of it still retained the form of
+castings.&rdquo; Dr. King dug up this plant, and was struck
+with the thickness of the soil which must have recently
+accumulated over the crown of the rhizoma, as shown by the length
+of the bleached petioles, in comparison with those of other
+plants of the same kind, where there had been no such
+accumulation. The earth thus accumulated had no doubt been
+secured (as I have everywhere seen) by the smaller roots of the
+plants. After describing this and other analogous cases,
+Dr. King concludes: &ldquo;I can have no doubt that worms help
+greatly in the process of denudation.&rdquo;</p>
+
+<p><i>Ledges of earth on steep hill-sides</i>.&mdash;Little
+horizontal ledges, one above another, have been observed on steep
+grassy slopes in many parts of the world. The formation has
+been attributed to animals travelling repeatedly along the slope
+in the same horizontal lines while grazing, and that they do thus
+move and use the ledges is certain; but Professor Henslow (a most
+careful observer) told Sir J. Hooker that he was convinced that
+this was not the sole cause of their formation. Sir J.
+Hooker saw such ledges on the Himalayan and Atlas ranges, where
+there were no domesticated animals and not many wild ones; but
+these latter would, it is probable, use the ledges at night while
+grazing like our domesticated animals. A friend observed
+for me the ledges on the Alps of Switzerland, and states that
+they ran at 3 or 4 ft. one above the other, and were about a foot
+in breadth. They had been deeply pitted by the feet of
+grazing cows. Similar ledges were observed by the same
+friend on our Chalk downs, and on an old talus of chalk-fragments
+(thrown out of a quarry) which had become clothed with turf.</p>
+
+<p>My son Francis examined a Chalk escarpment near Lewes; and
+here on a part which was very steep, sloping at 40&deg; with the
+horizon, about 30 flat ledges extended horizontally for more than
+100 yards, at an average distance of about 20 inches, one beneath
+the other. They were from 9 to 10 inches in breadth.
+When viewed from a distance they presented a striking appearance,
+owing to their parallelism; but when examined closely, they were
+seen to be somewhat sinuous, and one often ran into another,
+giving the appearance of the ledge having forked into two.
+They are formed of light-coloured earth, which on the outside,
+where thickest, was in one case 9 inches, and in another case
+between 6 and 7 inches in thickness. Above the ledges, the
+thickness of the earth over the chalk was in the former case 4
+and in the latter only 3 inches. The grass grew more
+vigorously on the outer edges of the ledges than on any other
+part of the slope, and here formed a tufted fringe. Their
+middle part was bare, but whether this had been caused by the
+trampling of sheep, which sometimes frequent the ledges, my son
+could not ascertain. Nor could he feel sure how much of the
+earth on the middle and bare parts, consisted of disintegrated
+worm-castings which had rolled down from above; but he felt
+convinced that some had thus originated; and it was manifest that
+the ledges with their grass-fringed edges would arrest any small
+object rolling down from above.</p>
+
+<p>At one end or side of the bank bearing these ledges, the
+surface consisted in parts of bare chalk, and here the ledges
+were very irregular. At the other end of the bank, the
+slope suddenly became less steep, and here the ledges ceased
+rather abruptly; but little embankments only a foot or two in
+length were still present. The slope became steeper lower
+down the hill, and the regular ledges then reappeared.
+Another of my sons observed, on the inland side of Beachy Head,
+where the surface sloped at about 25&deg;, many short little
+embankments like those just mentioned. They extended
+horizontally and were from a few inches to two or three feet in
+length. They supported tufts of grass growing
+vigorously. The average thickness of the mould of which
+they were formed, taken from nine measurements, was 4.5 inches;
+while that of the mould above and beneath them was on an average
+only 3.2 inches, and on each side, on the same level, 3.1
+inches. On the upper parts of the slope, these embankments
+showed no signs of having been trampled on by sheep, but in the
+lower parts such signs were fairly plain. No long
+continuous ledges had here been formed.</p>
+
+<p>If the little embankments above the Corniche road, which Dr.
+King saw in the act of formation by the accumulation of
+disintegrated and rolled worm-castings, were to become confluent
+along horizontal lines, ledges would be formed. Each
+embankment would tend to extend laterally by the lateral
+extension of the arrested castings; and animals grazing on a
+steep slope would almost certainly make use of every prominence
+at nearly the same level, and would indent the turf between them;
+and such intermediate indentations would again arrest the
+castings. An irregular ledge when once formed would also
+tend to become more regular and horizontal by some of the
+castings rolling laterally from the higher to the lower parts,
+which would thus be raised. Any projection beneath a ledge
+would not afterwards receive disintegrated matter from above, and
+would tend to be obliterated by rain and other atmospheric
+agencies. There is some analogy between the formation, as
+here supposed, of these ledges, and that of the ripples of
+wind-drifted sand as described by Lyell. <a
+name="citation259"></a><a href="#footnote259"
+class="citation">[259]</a></p>
+
+<p>The steep, grass-covered sides of a mountainous valley in
+Westmoreland, called Grisedale, was marked in many places with
+innumerable lines of miniature cliffs, with almost horizontal,
+little ledges at their bases. Their formation was in no way
+connected with the action of worms, for castings could not
+anywhere be seen (and their absence is an inexplicable fact),
+although the turf lay in many places over a considerable
+thickness of boulder-clay and moraine rubbish. Nor, as far
+as I could judge, was the formation of these little cliffs at all
+closely connected with the trampling of cows or sheep. It
+appeared as if the whole superficial, somewhat argillaceous
+earth, while partially held together by the roots of the grasses,
+had slided a little way down the mountain sides; and in thus
+sliding, had yielded and cracked in horizontal lines,
+transversely to the slope.</p>
+
+<p><i>Castings blown to leeward by the wind</i>.&mdash;We have
+seen that moist castings flow, and that disintegrated castings
+roll down any inclined surface; and we shall now see that
+castings, recently ejected on level grass-covered surfaces, are
+blown during gales of wind accompanied by rain to leeward.
+This has been observed by me many times on many fields during
+several successive years. After such gales, the castings
+present a gently inclined and smooth, or sometimes furrowed,
+surface to windward, while they are steeply inclined or
+precipitous to leeward, so that they resemble on a miniature
+scale glacier-ground hillocks of rock. They are often
+cavernous on the leeward side, from the upper part having curled
+over the lower part. During one unusually heavy south-west
+gale with torrents of rain, many castings were wholly blown to
+leeward, so that the mouths of the burrows were left naked and
+exposed on the windward side. Recent castings naturally
+flow down an inclined surface, but on a grassy field, which
+sloped between 10&deg; and 15&deg;, several were found after a
+heavy gale blown up the slope. This likewise occurred on
+another occasion on a part of my lawn where the slope was
+somewhat less. On a third occasion, the castings on the
+steep, grass-covered sides of a valley, down which a gale had
+blown, were directed obliquely instead of straight down the
+slope; and this was obviously due to the combined action of the
+wind and gravity. Four castings on my lawn, where the
+downward inclination was 0&deg; 45&prime;, 1&deg;, 3&deg; and
+3&deg; 30&prime; (mean 2&deg; 45&prime;) towards the north-east,
+after a heavy south-west gale with rain, were divided across the
+mouths of the burrows and weighed in the manner formerly
+described. The mean weight of the earth below the mouths of
+burrows and to leeward, was to that above the mouths and on the
+windward side as 2&frac34; to 1; whereas we have seen that with
+several castings which had flowed down slopes having a mean
+inclination of 9&deg; 26&prime;, and with three castings where
+the inclination was above 12&deg;; the proportional weight of the
+earth below to that above the burrows was as only 2 to 1.
+These several cases show how efficiently gales of wind
+accompanied by rain act in displacing recently ejected
+castings. We may therefore conclude that even a moderately
+strong wind will produce some slight effect on them.</p>
+
+<p>Dry and indurated castings, after their disintegration into
+small fragments or pellets, are sometimes, probably often, blown
+by a strong wind to leeward. This was observed on four
+occasions, but I did not sufficiently attend to this point.
+One old casting on a gently sloping bank was blown quite away by
+a strong south-west wind. Dr. King believes that the wind
+removes the greater part of the old crumbling castings near
+Nice. Several old castings on my lawn were marked with pins
+and protected from any disturbance. They were examined
+after an interval of 10 weeks, during which time the weather had
+been alternately dry and rainy. Some, which were of a
+yellowish colour had been washed almost completely away, as could
+be seen by the colour of the surrounding ground. Others had
+completely disappeared, and these no doubt had been blown
+away. Lastly, others still remained and would long remain,
+as blades of grass had grown through them. On poor
+pasture-land, which has never been rolled and has not been much
+trampled on by animals, the whole surface is sometimes dotted
+with little pimples, through and on which grass grows; and these
+pimples consist of old worm-castings.</p>
+
+<p>In all the many observed cases of soft castings blown to
+leeward, this had been effected by strong winds accompanied by
+rain. As such winds in England generally blow from the
+south and south-west, earth must on the whole tend to travel over
+our fields in a north and north-east direction. This fact
+is interesting, because it might be thought that none could be
+removed from a level, grass-covered surface by any means.
+In thick and level woods, protected from the wind, castings will
+never be removed as long as the wood lasts; and mould will here
+tend to accumulate to the depth at which worms can work. I
+tried to procure evidence as to how much mould is blown, whilst
+in the state of castings, by our wet southern gales to the
+north-east, over open and flat land, by looking to the level of
+the surface on opposite sides of old trees and hedge-rows; but I
+failed owing to the unequal growth of the roots of trees and to
+most pasture-land having been formerly ploughed.</p>
+
+<p>On an open plain near Stonehenge, there exist shallow circular
+trenches, with a low embankment outside, surrounding level spaces
+50 yards in diameter. These rings appear very ancient, and
+are believed to be contemporaneous with the Druidical
+stones. Castings ejected within these circular spaces, if
+blown to the north-east by south-west winds would form a layer of
+mould within the trench, thicker on the north-eastern than on any
+other side. But the site was not favourable for the action
+of worms, for the mould over the surrounding Chalk formation with
+flints, was only 3.37 inches in thickness, from a mean of six
+observations made at a distance of 10 yards outside the
+embankment. The thickness of the mould within two of the
+circular trenches was measured every 5 yards all round, on the
+inner sides near the bottom. My son Horace protracted these
+measurements on paper; and though the curved line representing
+the thickness of the mould was extremely irregular, yet in both
+diagrams it could be seen to be thicker on the north-eastern side
+than elsewhere. When a mean of all the measurements in both
+the trenches was laid down and the line smoothed, it was obvious
+that the mould was thickest in the quarter of the circle between
+north-west and north-east; and thinnest in the quarter between
+south-east and south-west, especially at this latter point.
+Besides the foregoing measurements, six others were taken near
+together in one of the circular trenches, on the north-east side;
+and the mould here had a mean thickness of 2.29 inches; while the
+mean of six other measurements on the south-west side was only
+1.46 inches. These observations indicate that the castings
+had been blown by the south-west winds from the circular enclosed
+space into the trench on the north-east side; but many more
+measurements in other analogous cases would be requisite for a
+trustworthy result.</p>
+
+<p>The amount of fine earth brought to the surface under the form
+of castings, and afterwards transported by the winds accompanied
+by rain, or that which flows and rolls down an inclined surface,
+no doubt is small in the course of a few scores of years; for
+otherwise all the inequalities in our pasture fields would be
+smoothed within a much shorter period than appears to be the
+case. But the amount which is thus transported in the
+course of thousands of years cannot fail to be considerable and
+deserves attention. É. de Beaumont looks at the
+vegetable mould which everywhere covers the land as a fixed line,
+from which the amount of denudation may be measured. <a
+name="citation265"></a><a href="#footnote265"
+class="citation">[265]</a> He ignores the continued
+formation of fresh mould by the disintegration of the underlying
+rocks and fragments of rock; and it is curious to find how much
+more philosophical were the views maintained long ago, by
+Playfair, who, in 1802, wrote, &ldquo;In the permanence of a coat
+of vegetable mould on the surface of the earth, we have a
+demonstrative proof of the continued destruction of the
+rocks.&rdquo; <a name="citation266"></a><a href="#footnote266"
+class="citation">[266]</a></p>
+
+<p><i>Ancient encampments and tumuli</i>.&mdash;É. de
+Beaumont adduces the present state of many ancient encampments
+and tumuli and of old ploughed fields, as evidence that the
+surface of the land undergoes hardly any degradation. But
+it does not appear that he ever examined the thickness of the
+mould over different parts of such old remains. He relies
+chiefly on indirect, but apparently trustworthy, evidence that
+the slopes of the old embankments are the same as they originally
+were; and it is obvious that he could know nothing about their
+original heights. In Knole Park a mound had been thrown up
+behind the rifle-targets, which appeared to have been formed of
+earth originally supported by square blocks of turf. The
+sides sloped, as nearly as I could estimate them, at an angle of
+45&deg; or 50&deg; with the horizon, and they were covered,
+especially on the northern side, with long coarse grass, beneath
+which many worm-castings were found. These had flowed
+bodily downwards, and others had rolled down as pellets.
+Hence it is certain that as long as a mound of this kind is
+tenanted by worms, its height will be continually lowered.
+The fine earth which flows or rolls down the sides of such a
+mound accumulates at its base in the form of a talus. A
+bed, even a very thin bed, of fine earth is eminently favourable
+for worms; so that a greater number of castings would tend to be
+ejected on a talus thus formed than elsewhere; and these would be
+partially washed away by every heavy shower and be spread over
+the adjoining level ground. The final result would be the
+lowering of the whole mound, whilst the inclination of the sides
+would not be greatly lessened. The same result would
+assuredly follow with ancient embankments and tumuli; except
+where they had been formed of gravel or of nearly pure sand, as
+such matter is unfavourable for worms. Many old
+fortifications and tumuli are believed to be at least 2000 years
+old; and we should bear in mind that in many places about one
+inch of mould is brought to the surface in 5 years or two inches
+in 10 years. Therefore in so long a period as 2000 years, a
+large amount of earth will have been repeatedly brought to the
+surface on most old embankments and tumuli, especially on the
+talus round their bases, and much of this earth will have been
+washed completely away. We may therefore conclude that all
+ancient mounds, when not formed of materials unfavourable to
+worms, will have been somewhat lowered in the course of
+centuries, although their inclinations may not have been greatly
+changed.</p>
+
+<p><i>Fields formerly ploughed</i>.&mdash;From a very remote
+period and in many countries, land has been ploughed, so that
+convex beds, called crowns or ridges, usually about 8 feet across
+and separated by furrows, have been thrown up. The furrows
+are directed so as to carry off the surface water. In my
+attempts to ascertain how long a time these crowns and furrows
+last, when ploughed land has been converted into pasture,
+obstacles of many kinds were encountered. It is rarely
+known when a field was last ploughed; and some fields which were
+thought to have been in pasture from time immemorial were
+afterwards discovered to have been ploughed only 50 or 60 years
+before. During the early part of the present century, when
+the price of corn was very high, land of all kinds seems to have
+been ploughed in Britain. There is, however, no reason to
+doubt that in many cases the old crowns and furrows have been
+preserved from a very ancient period. <a
+name="citation269"></a><a href="#footnote269"
+class="citation">[269]</a> That they should have been
+preserved for very unequal lengths of time would naturally follow
+from the crowns, when first thrown up, having differed much in
+height in different districts, as is now the case with recently
+ploughed land.</p>
+
+<p>In old pasture fields, the mould, wherever measurements were
+made, was found to be from &frac12; to 2 inches thicker in the
+furrows than on the crowns; but this would naturally follow from
+the finer earth having been washed from the crowns into the
+furrows before the land was well clothed with turf; and it is
+impossible to tell what part worms may have played in the
+work. Nevertheless from what we have seen, castings would
+certainly tend to flow and to be washed during heavy rain from
+the crowns into the furrows. But as soon as a bed of fine
+earth had by any means been accumulated in the furrows, it would
+be more favourable for worms than the other parts, and a greater
+number of castings would be thrown up here than elsewhere; and as
+the furrows on sloping land are usually directed so as to carry
+off the surface water, some of the finest earth would be washed
+from the castings which had been here ejected and be carried
+completely away. The result would be that the furrows would
+be filled up very slowly, while the crowns would be lowered
+perhaps still more slowly by the flowing and rolling of the
+castings down their gentle inclinations into the furrows.</p>
+
+<p>Nevertheless it might be expected that old furrows, especially
+those on a sloping surface, would in the course of time be filled
+up and disappear. Some careful observers, however, who
+examined fields for me in Gloucestershire and Staffordshire could
+not detect any difference in the state of the furrows in the
+upper and lower parts of sloping fields, supposed to have been
+long in pasture; and they came to the conclusion that the crowns
+and furrows would last for an almost endless number of
+centuries. On the other hand the process of obliteration
+seems to have commenced in some places. Thus in a grass
+field in North Wales, known to have been ploughed about 65 years
+ago, which sloped at an angle of 15&deg; to the north-east, the
+depth of the furrows (only 7 feet apart) was carefully measured,
+and was found to be about 4&frac12; inches in the upper part of
+the slope, and only 1 inch near the base, where they could be
+traced with difficulty. On another field sloping at about
+the same angle to the south-west, the furrows were scarcely
+perceptible in the lower part; although these same furrows when
+followed on to some adjoining level ground were from 2&frac12; to
+3&frac12; inches in depth. A third and closely similar case
+was observed. In a fourth case, the mould in a furrow in
+the upper part of a sloping field was 2&frac12; inches, and in
+the lower part 4&frac12; inches in thickness.</p>
+
+<p>On the Chalk Downs at about a mile distance from Stonehenge,
+my son William examined a grass-covered, furrowed surface,
+sloping at from 8&deg; to 10 &deg;, which an old shepherd said
+had not been ploughed within the memory of man. The depth
+of one furrow was measured at 16 points in a length of 68 paces,
+and was found to be deeper where the slope was greatest and where
+less earth would naturally tend to accumulate, and at the base it
+almost disappeared. The thickness of the mould in this
+furrow in the upper part was 2&frac12; inches, which increased to
+5 inches, a little above the steepest part of the slope; and at
+the base, in the middle of the narrow valley, at a point which
+the furrow if continued would have struck, it amounted to 7
+inches. On the opposite side of the valley, there were very
+faint, almost obliterated, traces of furrows. Another
+analogous but not so decided a case was observed at a few
+miles&rsquo; distance from Stonehenge. On the whole it
+appears that the crowns and furrows on land formerly ploughed,
+but now covered with grass, tend slowly to disappear when the
+surface is inclined; and this is probably in large part due to
+the action of worms; but that the crowns and furrows last for a
+very long time when the surface is nearly level.</p>
+
+<p><i>Formation and amount of mould over the Chalk
+Formation</i>.&mdash;Worm-castings are often ejected in
+extraordinary numbers on steep, grass-covered slopes, where the
+Chalk comes close to the surface, as my son William observed near
+Winchester and elsewhere. If such castings are largely
+washed away during heavy rains, it is difficult to understand at
+first how any mould can still remain on our Downs, as there does
+not appear any evident means for supplying the loss. There
+is, moreover, another cause of loss, namely, in the percolation
+of the finer particles of earth into the fissures in the chalk
+and into the chalk itself. These considerations led me to
+doubt for a time whether I had not exaggerated the amount of fine
+earth which flows or rolls down grass-covered slopes under the
+form of castings; and I sought for additional information.
+In some places, the castings on Chalk Downs consist largely of
+calcareous matter, and here the supply is of course
+unlimited. But in other places, for instance on a part of
+Teg Down near Winchester, the castings were all black and did not
+effervesce with acids. The mould over the chalk was here
+only from 3 to 4 inches in thickness. So again on the plain
+near Stonehenge, the mould, apparently free from calcareous
+matter, averaged rather less than 3&frac12; inches in
+thickness. Why worms should penetrate and bring up chalk in
+some places and not in others I do not know.</p>
+
+<p>In many districts where the land is nearly level, a bed
+several feet in thickness of red clay full of unworn flints
+overlies the Upper Chalk. This overlying matter, the
+surface of which has been converted into mould, consists of the
+undissolved residue from the chalk. It may be well here to
+recall the case of the fragments of chalk buried beneath
+worm-castings on one of my fields, the angles of which were so
+completely rounded in the course of 29 years that the fragments
+now resembled water-worn pebbles. This must have been
+effected by the carbonic acid in the rain and in the ground, by
+the humus-acids, and by the corroding power of living
+roots. Why a thick mass of residue has not been left on the
+Chalk, wherever the land is nearly level, may perhaps be
+accounted for by the percolation of the fine particles into the
+fissures, which are often present in the chalk and are either
+open or are filled up with impure chalk, or into the solid chalk
+itself. That such percolation occurs can hardly be
+doubted. My son collected some powdered and fragmentary
+chalk beneath the turf near Winchester; the former was found by
+Colonel Parsons, R. E., to contain 10 per cent., and the
+fragments 8 per cent. of earthy matter. On the flanks of
+the escarpment near Abinger in Surrey, some chalk close beneath a
+layer of flints, 2 inches in thickness and covered by 8 inches of
+mould, yielded a residue of 3.7 per cent. of earthy matter.
+On the other hand the Upper Chalk properly contains, as I was
+informed by the late David Forbes who had made many analyses,
+only from 1 to 2 per cent. of earthy matter; and two samples from
+pits near my house contained 1.3 and 0.6 per cent. I
+mention these latter cases because, from the thickness of the
+overlying bed of red clay with flints, I had imagined that the
+underlying chalk might here be less pure than elsewhere.
+The cause of the residue accumulating more in some places than in
+others, may be attributed to a layer of argillaceous matter
+having been left at an early period on the chalk, and this would
+check the subsequent percolation of earthy matter into it.</p>
+
+<p>From the facts now given we may conclude that castings ejected
+on our Chalk Downs suffer some loss by the percolation of their
+finer matter into the chalk. But such impure superficial
+chalk, when dissolved, would leave a larger supply of earthy
+matter to be added to the mould than in the case of pure
+chalk. Besides the loss caused by percolation, some fine
+earth is certainly washed down the sloping grass-covered surfaces
+of our Downs. The washing-down process, however, will be
+checked in the course of time; for although I do not know how
+thin a layer of mould suffices to support worms, yet a limit must
+at last be reached; and then their castings would cease to be
+ejected or would become scanty.</p>
+
+<p>The following cases show that a considerable quantity of fine
+earth is washed down. The thickness of the mould was
+measured at points 12 yards apart across a small valley in the
+Chalk near Winchester. The sides sloped gently at first;
+then became inclined at about 20&deg;; then more gently to near
+the bottom, which transversely was almost level and about 50
+yards across. In the bottom, the mean thickness of the
+mould from five measurements was 8.3 inches; whilst on the sides
+of the valley, where the inclination varied between 14&deg; and
+20&deg;, its mean thickness was rather less than 3.5
+inches. As the turf-covered bottom of the valley sloped at
+an angle of only between 2&deg; and 3&deg;, it is probable that
+most of the 8.3-inch layer of mould had been washed down from the
+flanks of the valley, and not from the upper part. But as a
+shepherd said that he had seen water flowing in this valley after
+the sudden thawing of snow, it is possible that some earth may
+have been brought down from the upper part; or, on the other
+hand, that some may have been carried further down the
+valley. Closely similar results, with respect to the
+thickness of the mould, were obtained in a neighbouring
+valley.</p>
+
+<p>St. Catherine&rsquo;s Hill, near Winchester, is 327 feet in
+height, and consists of a steep cone of chalk about &frac14; of a
+mile in diameter. The upper part was converted by the
+Romans, or, as some think, by the ancient Britons, into an
+encampment, by the excavation of a deep and broad ditch all round
+it. Most of the chalk removed during the work was thrown
+upwards, by which a projecting bank was formed; and this
+effectually prevents worm-castings (which are numerous in parts),
+stones, and other objects from being washed or rolled into the
+ditch. The mould on the upper and fortified part of the
+hill was found to be in most places only from 2&frac12; to
+3&frac12; inches in thickness; whereas it had accumulated at the
+foot of the embankment above the ditch to a thickness in most
+places of from 8 to 9&frac12; inches. On the embankment
+itself the mould was only 1 to 1&frac12; inch in thickness; and
+within the ditch at the bottom it varied from 2&frac12; to
+3&frac12;, but was in one spot 6 inches in thickness. On
+the north-west side of the hill, either no embankment had ever
+been thrown up above the ditch, or it had subsequently been
+removed; so that here there was nothing to prevent worm-castings,
+earth and stones being washed into the ditch, at the bottom of
+which the mould formed a layer from 11 to 22 inches in
+thickness. It should however be stated that here and on
+other parts of the slope, the bed of mould often contained
+fragments of chalk and flint which had obviously rolled down at
+different times from above. The interstices in the
+underlying fragmentary chalk were also filled up with mould.</p>
+
+<p>My son examined the surface of this hill to its base in a
+south-west direction. Beneath the great ditch, where the
+slope was about 24&deg;, the mould was very thin, namely, from
+1&frac12; to 2&frac12; inches; whilst near the base, where the
+slope was only 3&deg; to 4&deg;, it increased to between 8 and 9
+inches in thickness. We may therefore conclude that on this
+artificially modified hill, as well as in the natural valleys of
+the neighbouring Chalk Downs, some fine earth, probably derived
+in large part from worm-castings, is washed down, and accumulates
+in the lower parts, notwithstanding the percolation of an unknown
+quantity into the underlying chalk; a supply of fresh earthy
+matter being afforded by the dissolution of the chalk through
+atmospheric and other agencies.</p>
+<h2><a name="page280"></a><span class="pagenum">p.
+280</span>CHAPTER VII.<br />
+<span class="GutSmall">CONCLUSION.</span></h2>
+<p class="gutsumm">Summary of the part which worms have played in
+the history of the world&mdash;Their aid in the disintegration of
+rocks&mdash;In the denudation of the land&mdash;In the
+preservation of ancient remains&mdash;In the preparation of the
+soil for the growth of plants&mdash;Mental powers of
+worms&mdash;Conclusion.</p>
+
+<p><span class="smcap">Worms</span> have played a more important
+part in the history of the world than most persons would at first
+suppose. In almost all humid countries they are
+extraordinarily numerous, and for their size possess great
+muscular power. In many parts of England a weight of more
+than ten tons (10,516 kilogrammes) of dry earth annually passes
+through their bodies and is brought to the surface on each acre
+of land; so that the whole superficial bed of vegetable mould
+passes through their bodies in the course of every few
+years. From the collapsing of the old burrows the mould is
+in constant though slow movement, and the particles composing it
+are thus rubbed together. By these means fresh surfaces are
+continually exposed to the action of the carbonic acid in the
+soil, and of the humus-acids which appear to be still more
+efficient in the decomposition of rocks. The generation of
+the humus-acids is probably hastened during the digestion of the
+many half-decayed leaves which worms consume. Thus the
+particles of earth, forming the superficial mould, are subjected
+to conditions eminently favourable for their decomposition and
+disintegration. Moreover, the particles of the softer rocks
+suffer some amount of mechanical trituration in the muscular
+gizzards of worms, in which small stones serve as
+mill-stones.</p>
+
+<p>The finely levigated castings, when brought to the surface in
+a moist condition, flow during rainy weather down any moderate
+slope; and the smaller particles are washed far down even a
+gently inclined surface. Castings when dry often crumble
+into small pellets and these are apt to roll down any sloping
+surface. Where the land is quite level and is covered with
+herbage, and where the climate is humid so that much dust cannot
+be blown away, it appears at first sight impossible that there
+should be any appreciable amount of sub-aerial denudation; but
+worm-castings are blown, especially whilst moist and viscid, in
+one uniform direction by the prevalent winds which are
+accompanied by rain. By these several means the superficial
+mould is prevented from accumulating to a great thickness; and a
+thick bed of mould checks in many ways the disintegration of the
+underlying rocks and fragments of rock.</p>
+
+<p>The removal of worm-castings by the above means leads to
+results which are far from insignificant. It has been shown
+that a layer of earth, 0.2 of an inch in thickness, is in many
+places annually brought to the surface; and if a small part of
+this amount flows, or rolls, or is washed, even for a short
+distance, down every inclined surface, or is repeatedly blown in
+one direction, a great effect will be produced in the course of
+ages. It was found by measurements and calculations that on
+a surface with a mean inclination of 9&deg; 26&prime;, 2.4 cubic
+inches of earth which had been ejected by worms crossed, in the
+course of a year, a horizontal line one yard in length; so that
+240 cubic inches would cross a line 100 yards in length.
+This latter amount in a damp state would weigh 11&frac12;
+pounds. Thus a considerable weight of earth is continually
+moving down each side of every valley, and will in time reach its
+bed. Finally this earth will be transported by the streams
+flowing in the valleys into the ocean, the great receptacle for
+all matter denuded from the land. It is known from the
+amount of sediment annually delivered into the sea by the
+Mississippi, that its enormous drainage-area must on an average
+be lowered .00263 of an inch each year; and this would suffice in
+four and half million years to lower the whole drainage-area to
+the level of the sea-shore. So that, if a small fraction of
+the layer of fine earth, 0.2 of an inch in thickness, which is
+annually brought to the surface by worms, is carried away, a
+great result cannot fail to be produced within a period which no
+geologist considers extremely long.</p>
+
+<div class="gapspace">&nbsp;</div>
+<p>Archæologists ought to be grateful to worms, as they
+protect and preserve for an indefinitely long period every
+object, not liable to decay, which is dropped on the surface of
+the land, by burying it beneath their castings. Thus, also,
+many elegant and curious tesselated pavements and other ancient
+remains have been preserved; though no doubt the worms have in
+these cases been largely aided by earth washed and blown from the
+adjoining land, especially when cultivated. The old
+tesselated pavements have, however, often suffered by having
+subsided unequally from being unequally undermined by the
+worms. Even old massive walls may be undermined and
+subside; and no building is in this respect safe, unless the
+foundations lie 6 or 7 feet beneath the surface, at a depth at
+which worms cannot work. It is probable that many monoliths
+and some old walls have fallen down from having been undermined
+by worms.</p>
+
+<div class="gapspace">&nbsp;</div>
+<p>Worms prepare the ground <a name="citation284"></a><a
+href="#footnote284" class="citation">[284]</a> in an excellent
+manner for the growth of fibrous-rooted plants and for seedlings
+of all kinds. They periodically expose the mould to the
+air, and sift it so that no stones larger than the particles
+which they can swallow are left in it. They mingle the
+whole intimately together, like a gardener who prepares fine soil
+for his choicest plants. In this state it is well fitted to
+retain moisture and to absorb all soluble substances, as well as
+for the process of nitrification. The bones of dead
+animals, the harder parts of insects, the shells of
+land-molluscs, leaves, twigs, &amp;c., are before long all buried
+beneath the accumulated castings of worms, and are thus brought
+in a more or less decayed state within reach of the roots of
+plants. Worms likewise drag an infinite number of dead
+leaves and other parts of plants into their burrows, partly for
+the sake of plugging them up and partly as food.</p>
+
+<p>The leaves which are dragged into the burrows as food, after
+being torn into the finest shreds, partially digested, and
+saturated with the intestinal and urinary secretions, are
+commingled with much earth. This earth forms the dark
+coloured, rich humus which almost everywhere covers the surface
+of the land with a fairly well-defined layer or mantle.
+Hensen <a name="citation285"></a><a href="#footnote285"
+class="citation">[285]</a> placed two worms in a vessel 18 inches
+in diameter, which was filled with sand, on which fallen leaves
+were strewed; and these were soon dragged into their burrows to a
+depth of 3 inches. After about 6 weeks an almost uniform
+layer of sand, a centimeter (0.4 inch) in thickness, was
+converted into humus by having passed through the alimentary
+canals of these two worms. It is believed by some persons
+that worm-burrows, which often penetrate the ground almost
+perpendicularly to a depth of 5 or 6 feet, materially aid in its
+drainage; notwithstanding that the viscid castings piled over the
+mouths of the burrows prevent or check the rain-water directly
+entering them. They allow the air to penetrate deeply into
+the ground. They also greatly facilitate the downward
+passage of roots of moderate size; and these will be nourished by
+the humus with which the burrows are lined. Many seeds owe
+their germination to having been covered by castings; and others
+buried to a considerable depth beneath accumulated castings lie
+dormant, until at some future time they are accidentally
+uncovered and germinate.</p>
+
+<p>Worms are poorly provided with sense-organs, for they cannot
+be said to see, although they can just distinguish between light
+and darkness; they are completely deaf, and have only a feeble
+power of smell; the sense of touch alone is well developed.
+They can therefore learn but little about the outside world, and
+it is surprising that they should exhibit some skill in lining
+their burrows with their castings and with leaves, and in the
+case of some species in piling up their castings into tower-like
+constructions. But it is far more surprising that they
+should apparently exhibit some degrees of intelligence instead of
+a mere blind instinctive impulse, in their manner of plugging up
+the mouths of their burrows. They act in nearly the same
+manner as would a man, who had to close a cylindrical tube with
+different kinds of leaves, petioles, triangles of paper, &amp;c.,
+for they commonly seize such objects by their pointed ends.
+But with thin objects a certain number are drawn in by their
+broader ends. They do not act in the same unvarying manner
+in all cases, as do most of the lower animals; for instance, they
+do not drag in leaves by their foot-stalks, unless the basal part
+of the blade is as narrow as the apex, or narrower than it.</p>
+
+<div class="gapspace">&nbsp;</div>
+<p>When we behold a wide, turf-covered expanse, we should
+remember that its smoothness, on which so much of its beauty
+depends, is mainly due to all the inequalities having been slowly
+levelled by worms. It is a marvellous reflection that the
+whole of the superficial mould over any such expanse has passed,
+and will again pass, every few years through the bodies of
+worms. The plough is one of the most ancient and most
+valuable of man&rsquo;s inventions; but long before he existed
+the land was in fact regularly ploughed, and still continues to
+be thus ploughed by earth-worms. It may be doubted whether
+there are many other animals which have played so important a
+part in the history of the world, as have these lowly organized
+creatures. Some other animals, however, still more lowly
+organized, namely corals, have done far more conspicuous work in
+having constructed innumerable reefs and islands in the great
+oceans; but these are almost confined to the tropical zones.</p>
+<h2>FOOTNOTES.</h2>
+<p><a name="footnote2"></a><a href="#citation2"
+class="footnote">[2]</a> &lsquo;Le&ccedil;ons de
+Géologie Pratique,&rsquo; tom. i. 1845, p. 140.</p>
+
+<p><a name="footnote3"></a><a href="#citation3"
+class="footnote">[3]</a> &lsquo;Transactions Geolog.
+Soc.&rsquo; vol. v. p. 505. Read November 1, 1837.</p>
+
+<p><a name="footnote4a"></a><a href="#citation4a"
+class="footnote">[4a]</a> &lsquo;Histoire des
+progrès de la Géologie,&rsquo; tom. i. 1847, p.
+224.</p>
+
+<p><a name="footnote4b"></a><a href="#citation4b"
+class="footnote">[4b]</a> &lsquo;Zeitschrift f&uuml;r
+wissenschaft. Zoologie,&rsquo; B. xxviii. 1877, p. 361.</p>
+
+<p><a name="footnote5"></a><a href="#citation5"
+class="footnote">[5]</a> &lsquo;Gardeners&rsquo;
+Chronicle,&rsquo; April 17, 1869, p. 418.</p>
+
+<p><a name="footnote6"></a><a href="#citation6"
+class="footnote">[6]</a> Mr. Darwin&rsquo;s attention was
+called by Professor Hensen to P. E. M&uuml;ller&rsquo;s work on
+Humus in &lsquo;Tidsskrift for Skovbrug,&rsquo; Band iii. Heft 1
+and 2, Copenhagen, 1878. He had, however, no opportunity of
+consulting M&uuml;ller&rsquo;s work. Dr. M&uuml;ller
+published a second paper in 1884 in the same periodical&mdash;a
+Danish journal of forestry. His results have also been
+published in German, in a volume entitled &lsquo;Studien
+&uuml;ber die nat&uuml;rlichen Humusformen, unter deren
+Einwirkung auf Vegetation und Boden,&rsquo; 8vo., Berlin,
+1887.</p>
+
+<p><a name="footnote8a"></a><a href="#citation8a"
+class="footnote">[8a]</a> &lsquo;Bidrag till Skandinaviens
+Oligochætfauna,&rsquo; 1871.</p>
+
+<p><a name="footnote8b"></a><a href="#citation8b"
+class="footnote">[8b]</a> &lsquo;Die bis jetzt bekannten
+Arten aus der Familie der Regenw&uuml;rmer,&rsquo; 1845.</p>
+
+<p><a name="footnote9b"></a><a href="#citation9b"
+class="footnote">[9b]</a> There is even some reason to
+believe that pressure is actually favourable to the growth of
+grasses, for Professor Buckman, who made many observations on
+their growth in the experimental gardens of the Royal
+Agricultural College, remarks (&lsquo;Gardeners&rsquo;
+Chronicle,&rsquo; 1854, p. 619): &ldquo;Another circumstance in
+the cultivation of grasses in the separate form or small patches,
+is the impossibility of rolling or treading them firmly, without
+which no pasture can continue good.&rdquo;</p>
+
+<p><a name="footnote11"></a><a href="#citation11"
+class="footnote">[11]</a> I shall have occasion often to
+refer to M. Perrier&rsquo;s admirable memoir, &lsquo;Organisation
+des Lombriciens terrestres&rsquo; in &lsquo;Archives de Zoolog.
+expér.&rsquo; tom. iii. 1874, p. 372. C. F. Morren
+(&lsquo;De Lumbrici terrestris Hist. Nat.&rsquo; 1829, p. 14)
+found that worms endured immersion for fifteen to twenty days in
+summer, but that in winter they died when thus treated.</p>
+
+<p><a name="footnote12"></a><a href="#citation12"
+class="footnote">[12]</a> Morren, &lsquo;De Lumbrici
+terrestris Hist. Nat.&rsquo; &amp;c., 1829, p. 67.</p>
+
+<p><a name="footnote14"></a><a href="#citation14"
+class="footnote">[14]</a> &lsquo;De Lumbrici terrestris
+Hist. Nat.&rsquo; &amp;c., p. 14.</p>
+
+<p><a name="footnote17"></a><a href="#citation17"
+class="footnote">[17]</a> Histolog. Untersuchungen
+&uuml;ber die Regenw&uuml;rmer. &lsquo;Zeitschrift f&uuml;r
+wissenschaft. Zoologie,&rsquo; B. xix., 1869, p. 611.</p>
+
+<p><a name="footnote18a"></a><a href="#citation18a"
+class="footnote">[18a]</a> For instance, Mr. Bridgman and
+Mr. Newman (&lsquo;The Zoologist,&rsquo; vol. vii. 1849, p.
+2576), and some friends who observed worms for me.</p>
+
+<p><a name="footnote18b"></a><a href="#citation18b"
+class="footnote">[18b]</a> &lsquo;Familie der
+Regenw&uuml;rmer,&rsquo; 1845, p. 18.</p>
+
+<p><a name="footnote31"></a><a href="#citation31"
+class="footnote">[31]</a> &lsquo;The Zoologist,&rsquo; vol.
+vii. 1849, p. 2576.</p>
+
+<p><a name="footnote32"></a><a href="#citation32"
+class="footnote">[32]</a> &lsquo;Familie der
+Regenw&uuml;rmer,&rsquo; p. 13. Dr. Sturtevant states in
+the &lsquo;New York Weekly Tribune&rsquo; (May 19, 1880) that he
+kept three worms in a pot, which was allowed to become extremely
+dry; and these worms were found &ldquo;all entwined together,
+forming a round mass and in good condition.&rdquo;</p>
+
+<p><a name="footnote33"></a><a href="#citation33"
+class="footnote">[33]</a> &lsquo;De Lumbrici terrestris
+Hist. Nat.&rsquo; p. 19.</p>
+
+<p><a name="footnote34"></a><a href="#citation34"
+class="footnote">[34]</a> &lsquo;Archives de Zoologie
+expérimentale,&rsquo; tom. vii. 1878, p. 394. When I
+wrote the above passage, I was not aware that Krukenberg
+(&lsquo;Untersuchungen a. d. physiol. Inst. d. Univ.
+Heidelberg,&rsquo; Bd. ii. p. 37, 1877) had previously
+investigated the digestive juice of Lumbricus. He states
+that it contains a peptic, and diastatic, as well as a tryptic
+ferment.</p>
+
+<p><a name="footnote35a"></a><a href="#citation35a"
+class="footnote">[35a]</a> On the action of the pancreatic
+ferment, see &lsquo;A Text-Book of Physiology,&rsquo; by Michael
+Foster, 2nd edit. pp. 198&ndash;203. 1878.</p>
+
+<p><a name="footnote35b"></a><a href="#citation35b"
+class="footnote">[35b]</a> Schmulewitsch, &lsquo;Action des
+Sucs digestifs sur la Cellulose.&rsquo; Bull. de
+l&rsquo;Acad. Imp. de St. Pétersbourg, tom. xxv. p.
+549. 1879.</p>
+
+<p><a name="footnote40"></a><a href="#citation40"
+class="footnote">[40]</a> Claparède doubts whether
+saliva is secreted by worms: see &lsquo;Zeitschrift f&uuml;r
+wissenschaft. Zoologie,&rsquo; B. xix. 1869, p. 601.</p>
+
+<p><a name="footnote41a"></a><a href="#citation41a"
+class="footnote">[41a]</a> Perrier, &lsquo;Archives de
+Zoolog. expér.&rsquo; July, 1874, pp. 416, 419.</p>
+
+<p><a name="footnote41b"></a><a href="#citation41b"
+class="footnote">[41b]</a> &lsquo;Zeitschrift f&uuml;r
+wissenschaft. Zoologie,&rsquo; B. xix, 1869, pp.
+603&ndash;606.</p>
+
+<p><a name="footnote46"></a><a href="#citation46"
+class="footnote">[46]</a> De Vries, &lsquo;Landwirth.
+Jahrb&uuml;cher,&rsquo; 1881, p. 77.</p>
+
+<p><a name="footnote49"></a><a href="#citation49"
+class="footnote">[49]</a> M. Foster, &lsquo;A Text-Book of
+Physiology,&rsquo; 2nd edit. 1878, p. 243.</p>
+
+<p><a name="footnote50"></a><a href="#citation50"
+class="footnote">[50]</a> M. Foster, <i>ut sup.</i> p.
+200.</p>
+
+<p><a name="footnote53"></a><a href="#citation53"
+class="footnote">[53]</a> Claparède remarks
+(&lsquo;Zeitschrift f&uuml;r wisseuschaft. Zoolog.&rsquo;
+B. 19, 1869, p. 602) that the pharynx appears from its structure
+to be adapted for suction.</p>
+
+<p><a name="footnote58"></a><a href="#citation58"
+class="footnote">[58]</a> An account of her observations is
+given in the &lsquo;Gardeners&rsquo; Chronicle,&rsquo; March
+28th, 1868, p. 324.</p>
+
+<p><a name="footnote59a"></a><a href="#citation59a"
+class="footnote">[59a]</a> London&rsquo;s &lsquo;Gard.
+Mag.&rsquo; xvii. p. 216, as quoted in the &lsquo;Catalogue of
+the British Museum Worms,&rsquo; 1865, p. 327.</p>
+
+<p><a name="footnote59b"></a><a href="#citation59b"
+class="footnote">[59b]</a> &lsquo;Familie der
+Regenw&uuml;rmer,&rsquo; p. 19.</p>
+
+<p><a name="footnote79"></a><a href="#citation79"
+class="footnote">[79]</a> In these narrow triangles the
+apical angle is 9&deg; 34&prime;, and the basal angles 85&deg;
+13&prime;. In the broader triangles the apical angle is
+19&deg; 10&prime; and the basal angles 80&deg; 25&prime;.</p>
+
+<p><a name="footnote89a"></a><a href="#citation89a"
+class="footnote">[89a]</a> See his interesting work,
+&lsquo;Souvenirs entomologiques,&rsquo; 1879, pp.
+168&ndash;177.</p>
+
+<p><a name="footnote89b"></a><a href="#citation89b"
+class="footnote">[89b]</a> M&ouml;bius, &lsquo;Die
+Bewegungen der Thiere,&rsquo; &amp;c., 1873, p. 111.</p>
+
+<p><a name="footnote90"></a><a href="#citation90"
+class="footnote">[90]</a> &lsquo;Annals and Mag. of N.
+History,&rsquo; series ii. vol. ix. 1852, p. 333.</p>
+
+<p><a name="footnote93"></a><a href="#citation93"
+class="footnote">[93]</a> &lsquo;Archives de Zoolog.
+expér.&rsquo; tom. iii. 1874, p. 405.</p>
+
+<p><a name="footnote97"></a><a href="#citation97"
+class="footnote">[97]</a> I state this on the authority of
+Semper, &lsquo;Reisen im Archipel der Philippinen,&rsquo; Th. ii.
+1877, p. 30.</p>
+
+<p><a name="footnote101"></a><a href="#citation101"
+class="footnote">[101]</a> Dr. King gave me some worms
+collected near Nice, which, as he believes, had constructed these
+castings. They were sent to M. Perrier, who with great
+kindness examined and named them for me: they consisted of
+<i>Perichæta affinis</i>, a native of Cochin China and of
+the Philippines; <i>P. Luzonica</i>, a native of Luzon in the
+Philippines; and <i>P. Houlleti</i>, which lives near
+Calcutta. M. Perrier informs me that species of
+Perichæta have been naturalized in the gardens near
+Montpellier and in Algiers. Before I had any reason to
+suspect that the tower-like castings from Nice had been formed by
+worms not endemic in the country, I was greatly surprised to see
+how closely they resembled castings sent to me from near
+Calcutta, where it is known that species of Perichæta
+abound.</p>
+
+<p><a name="footnote102"></a><a href="#citation102"
+class="footnote">[102]</a> &lsquo;Zeitschrift f&uuml;r
+wissenschaft. Zoolog.&rsquo; B. xxviii. 1877, p.
+364.</p>
+
+<p><a name="footnote108"></a><a href="#citation108"
+class="footnote">[108]</a> &lsquo;Zeitschrift f&uuml;r
+wissenschaft. Zoolog.&rsquo; B. xxviii. 1877, p. 356.</p>
+
+<p><a name="footnote113"></a><a href="#citation113"
+class="footnote">[113]</a> Perrier, &lsquo;Archives de
+Zoolog. expér.&rsquo; tom. 3, p. 378, 1874.</p>
+
+<p><a name="footnote126"></a><a href="#citation126"
+class="footnote">[126]</a> This case is given in a
+postscript to my paper in the &lsquo;Transact. Geolog.
+Soc.&rsquo; (Vol. v. p. 505), and contains a serious error,
+as in the account received I mistook the figure 30 for 80.
+The tenant, moreover, formerly said that he had marled the field
+thirty years before, but was now positive that this was done in
+1809, that is twenty-eight years before the first examination of
+the field by my friend. The error, as far as the figure 80
+is concerned, was corrected in an article by me, in the
+&lsquo;Gardeners&rsquo; Chronicle,&rsquo; 1844, p. 218.</p>
+
+<p><a name="footnote128"></a><a href="#citation128"
+class="footnote">[128]</a> These pits or pipes are still in
+process of formation. During the last forty years I have
+seen or heard of five cases, in which a circular space, several
+feet in diameter, suddenly fell in, leaving on the field an open
+hole with perpendicular sides, some feet in depth. This
+occurred in one of my own fields, whilst it was being rolled, and
+the hinder quarters of the shaft horse fell in; two or three
+cart-loads of rubbish were required to fill up the hole.
+The subsidence occurred where there was a broad depression, as if
+the surface had fallen in at several former periods. I
+heard of a hole which must have been suddenly formed at the
+bottom of a small shallow pool, where sheep had been washed
+during many years, and into which a man thus occupied fell to his
+great terror. The rain-water over this whole district sinks
+perpendicularly into the ground, but the chalk is more porous in
+certain places than in others. Thus the drainage from the
+overlying clay is directed to certain points, where a greater
+amount of calcareous matter is dissolved than elsewhere.
+Even narrow open channels are sometimes formed in the solid
+chalk. As the chalk is slowly dissolved over the whole
+country, but more in some parts than in others, the undissolved
+residue&mdash;that is the overlying mass of red clay with
+flints,&mdash;likewise sinks slowly down, and tends to fill up
+the pipes or cavities. But the upper part of the red clay
+holds together, aided probably by the roots of plants, for a
+longer time than the lower parts, and thus forms a roof, which
+sooner or later falls in, as in the above mentioned five
+cases. The downward movement of the clay may be compared
+with that of a glacier, but is incomparably slower; and this
+movement accounts for a singular fact, namely, that the much
+elongated flints which are embedded in the chalk in a nearly
+horizontal position, are commonly found standing nearly or quite
+upright in the red clay. This fact is so common that the
+workmen assured me that this was their natural position. I
+roughly measured one which stood vertically, and it was of the
+same length and of the same relative thickness as one of my
+arms. These elongated flints must get placed in their
+upright position, on the same principle that a trunk of a tree
+left on a glacier assumes a position parallel to the line of
+motion. The flints in the clay which form almost half its
+bulk, are very often broken, though not rolled or abraded; and
+this may be accounted for by their mutual pressure, whilst the
+whole mass is subsiding. I may add that the chalk here
+appears to have been originally covered in parts by a thin bed of
+fine sand with some perfectly rounded flint pebbles, probably of
+Tertiary age; for such sand often partly fills up the deeper pits
+or cavities in the chalk.</p>
+
+<p><a name="footnote131"></a><a href="#citation131"
+class="footnote">[131]</a> S. W. Johnson, &lsquo;How Crops
+Feed,&rsquo; 1870, p. 139.</p>
+
+<p><a name="footnote136a"></a><a href="#citation136a"
+class="footnote">[136a]</a> &lsquo;Nature,&rsquo; November
+1877, p. 28.</p>
+
+<p><a name="footnote136b"></a><a href="#citation136b"
+class="footnote">[136b]</a> &lsquo;Proc. Phil. Soc.&rsquo;
+of Manchester, 1877, p. 247.</p>
+
+<p><a name="footnote138a"></a><a href="#citation138a"
+class="footnote">[138a]</a> &lsquo;Trans. of the New
+Zealand Institute,&rsquo; vol. xii., 1880, p. 152.</p>
+
+<p><a name="footnote138b"></a><a href="#citation138b"
+class="footnote">[138b]</a> Mr. Lindsay Carnagie, in a
+letter (June 1838) to Sir C. Lyell, remarks that Scotch farmers
+are afraid of putting lime on ploughed land until just before it
+is laid down for pasture, from a belief that it has some tendency
+to sink. He adds: &ldquo;Some years since, in autumn, I
+laid lime on an oat-stubble and ploughed it down; thus bringing
+it into immediate contact with the dead vegetable matter, and
+securing its thorough mixture through the means of all the
+subsequent operations of fallow. In consequence of the
+above prejudice, I was considered to have committed a great
+fault; but the result was eminently successful, and the practice
+was <i>partially</i> followed. By means of Mr.
+Darwin&rsquo;s observations, I think the prejudice will be
+removed.&rdquo;</p>
+
+<p><a name="footnote139"></a><a href="#citation139"
+class="footnote">[139]</a> This conclusion, which, as we
+shall immediately see, is fully justified, is of some little
+importance, as the so-called bench-stones, which surveyors fix in
+the ground as a record of their levels, may in time become false
+standards. My son Horace intends at some future period to
+ascertain how far this has occurred.</p>
+
+<p><a name="footnote147"></a><a href="#citation147"
+class="footnote">[147]</a> Mr. R. Mallet remarks
+(&lsquo;Quarterly Journal of Geolog. Soc.&rsquo; vol. xxxiii.,
+1877, p. 745) that &ldquo;the extent to which the ground beneath
+the foundations of ponderous architectural structures, such as
+cathedral towers, has been known to become compressed, is as
+remarkable as it is instructive and curious. The amount of
+depression in some cases may be measured by feet.&rdquo; He
+instances the Tower of Pisa, but adds that it was founded on
+&ldquo;dense clay.&rdquo;</p>
+
+<p><a name="footnote148"></a><a href="#citation148"
+class="footnote">[148]</a> &lsquo;Zeitschrift f&uuml;r
+wissensch. Zoolog.&rsquo; Bd. xxviii., 1877, p. 360.</p>
+
+<p><a name="footnote149"></a><a href="#citation149"
+class="footnote">[149]</a> See Mr. Dancer&rsquo;s paper in
+&lsquo;Proc. Phil. Soc. of Manchester,&rsquo; 1877, p. 248.</p>
+
+<p><a name="footnote166a"></a><a href="#citation166a"
+class="footnote">[166a]</a> &lsquo;Le&ccedil;ons de
+Géologie pratique,&rsquo; 1845, p. 142.</p>
+
+<p><a name="footnote166b"></a><a href="#citation166b"
+class="footnote">[166b]</a> A short account of this
+discovery was published in &lsquo;The Times&rsquo; of January 2,
+1878; and a fuller account in &lsquo;The Builder,&rsquo; January
+5, 1878.</p>
+
+<p><a name="footnote183"></a><a href="#citation183"
+class="footnote">[183]</a> Several accounts of these ruins
+have been published; the best is by Mr. James Farrer in
+&lsquo;Proc. Soc. of Antiquaries of Scotland,&rsquo; vol. vi.,
+Part II., 1867, p. 278. Also J. W. Grover, &lsquo;Journal
+of the British Arch. Assoc.&rsquo; June 1866. Professor
+Buckman has likewise published a pamphlet, &lsquo;Notes on the
+Roman Villa at Chedworth,&rsquo; 2nd edit. 1873 Cirencester.</p>
+
+<p><a name="footnote187"></a><a href="#citation187"
+class="footnote">[187]</a> These details are taken from the
+&lsquo;Penny Cyclopædia,&rsquo; article Hampshire.</p>
+
+<p><a name="footnote210"></a><a href="#citation210"
+class="footnote">[210]</a> &ldquo;On the denudation of
+South Wales,&rdquo; &amp;c., &lsquo;Memoirs of the Geological
+Survey of Great Britain,&rsquo; vol. 1., p. 297, 1846.</p>
+
+<p><a name="footnote211"></a><a href="#citation211"
+class="footnote">[211]</a> &lsquo;Geological
+Magazine,&rsquo; October and November, 1867, vol. iv. pp. 447 and
+483. Copious references on the subject are given in this
+remarkable memoir.</p>
+
+<p><a name="footnote212"></a><a href="#citation212"
+class="footnote">[212]</a> A. Tylor &ldquo;On changes of
+the sea-level,&rdquo; &amp;c., &lsquo; Philosophical Mag.&rsquo;
+(Ser. 4th) vol. v., 1853, p. 258. Archibald Geikie,
+Transactions Geolog. Soc. of Glasgow, vol. iii., p. 153 (read
+March, 1868). Croll &ldquo;On Geological Time,&rdquo;
+&lsquo;Philosophical Mag.,&rsquo; May, August, and November,
+1868. See also Croll, &lsquo;Climate and Time,&rsquo; 1875,
+Chap. XX. For some recent information on the amount of
+sediment brought down by rivers, see &lsquo;Nature,&rsquo;
+Sept. 23rd, 1880. Mr. T. Mellard Reade has published
+some interesting articles on the astonishing amount of matter
+brought down in solution by rivers. See Address, Geolog.
+Soc., Liverpool, 1876&ndash;77.</p>
+
+<p><a name="footnote213"></a><a href="#citation213"
+class="footnote">[213]</a> &ldquo;An account of the fine
+dust which often falls on Vessels in the Atlantic Ocean,&rdquo;
+Proc. Geolog. Soc. of London, June 4th, 1845.</p>
+
+<p><a name="footnote215"></a><a href="#citation215"
+class="footnote">[215]</a> For La Plata, see my
+&lsquo;Journal of Researches,&rsquo; during the voyage of the
+<i>Beagle</i>, 1845, p. 133. Élie de Beaumont has
+given (&lsquo;Le&ccedil;ons de Géolog. pratique,&rsquo;
+tom. I. 1845, p. 183) an excellent account of the enormous
+quantity of dust which is transported in some countries. I
+cannot but think that Mr. Proctor has somewhat exaggerated
+(&lsquo;Pleasant Ways in Science,&rsquo; 1879, p. 379) the agency
+of dust in a humid country like Great Britain. James Geikie
+has given (&lsquo;Prehistoric Europe,&rsquo; 1880, p. 165) a full
+abstract of Richthofen&rsquo;s views, which, however, he
+disputes.</p>
+
+<p><a name="footnote217a"></a><a href="#citation217a"
+class="footnote">[217a]</a> These statements are taken from
+Hensen in &lsquo;Zeitschrift f&uuml;r wissenschaft.
+Zoologie.&rsquo; Bd. xxviii., 1877, p. 360. Those with
+respect to peat are taken from Mr. A. A. Julien in &lsquo;Proc.
+American Assoc. Science,&rsquo; 1879, p. 354.</p>
+
+<p><a name="footnote217b"></a><a href="#citation217b"
+class="footnote">[217b]</a> I have given some facts on the
+climate necessary or favourable for the formation of peat, in my
+&lsquo;Journal of Researches,&rsquo; 1845, p. 287.</p>
+
+<p><a name="footnote220"></a><a href="#citation220"
+class="footnote">[220]</a> A. A. Julien &ldquo;On the
+Geological action of the Humus-acids,&rdquo; &lsquo;Proc.
+American Assoc. Science,&rsquo; vol. xxviii., 1879, p. 311.
+Also on &ldquo;Chemical erosion on Mountain Summits;&rdquo;
+&lsquo;New York Academy of Sciences,&rsquo; Oct. 14, 1878, as
+quoted in the &lsquo;American Naturalist.&rsquo; See also,
+on this subject, S. W. Johnson, &lsquo;How Crops Feed,&rsquo;
+1870, p. 138.</p>
+
+<p><a name="footnote222"></a><a href="#citation222"
+class="footnote">[222]</a> See, for references on this
+subject, S. W. Johnson, &lsquo;How Crops Feed,&rsquo; 1870, p.
+326.</p>
+
+<p><a name="footnote223"></a><a href="#citation223"
+class="footnote">[223]</a> This statement is taken from Mr.
+Julien, &lsquo;Proc. American Assoc. Science,&rsquo; vol.
+xxviii., 1879, p. 330.</p>
+
+<p><a name="footnote224a"></a><a href="#citation224a"
+class="footnote">[224a]</a> The preservative power of a
+layer of mould and turf is often shown by the perfect state of
+the glacial scratches on rocks when first uncovered. Mr. J.
+Geikie maintains, in his last very interesting work
+(&lsquo;Prehistoric Europe,&rsquo; 1881), that the more perfect
+scratches are probably due to the last access of cold and
+increase of ice, during the long-continued, intermittent glacial
+period.</p>
+
+<p><a name="footnote224b"></a><a href="#citation224b"
+class="footnote">[224b]</a> Many geologists have felt much
+surprise at the complete disappearance of flints over wide and
+nearly level areas, from which the chalk has been removed by
+subaerial denudation. But the surface of every flint is
+coated by an opaque modified layer, which will just yield to a
+steel point, whilst the freshly fractured, translucent surface
+will not thus yield. The removal by atmospheric agencies of
+the outer modified surfaces of freely exposed flints, though no
+doubt excessively slow, together with the modification travelling
+inwards, will, as may be suspected, ultimately lead to their
+complete disintegration, notwithstanding that they appear to be
+so extremely durable.</p>
+
+<p><a name="footnote225a"></a><a href="#citation225a"
+class="footnote">[225a]</a> &lsquo;Archives de Zoolog.
+expér.&rsquo; tom. iii. 1874, p. 409.</p>
+
+<p><a name="footnote225b"></a><a href="#citation225b"
+class="footnote">[225b]</a> &lsquo;Nouvelles Archives du
+Muséum,&rsquo; tom. viii. 1872, pp. 95, 131.</p>
+
+<p><a name="footnote226"></a><a href="#citation226"
+class="footnote">[226]</a> Morren, in speaking of the earth
+in the alimentary canals of worms, says,
+&ldquo;præsepè cum lapillis commixtam vidi:&rdquo;
+&lsquo;De Lumbrici terrestris Hist. Nat.&rsquo; &amp;c., 1829, p.
+16.</p>
+
+<p><a name="footnote227"></a><a href="#citation227"
+class="footnote">[227]</a> Perrier, &lsquo;Archives de
+Zoolog. expér.&rsquo; tom. iii. 1874, p. 419.</p>
+
+<p><a name="footnote228a"></a><a href="#citation228a"
+class="footnote">[228a]</a> Morren, &lsquo;De Lumbrici
+terrestris Hist. Nat.&rsquo; &amp;c., p. 16.</p>
+
+<p><a name="footnote228b"></a><a href="#citation228b"
+class="footnote">[228b]</a> &lsquo;Archives de Zoolog.
+expér.&rsquo; tom. iii. 1874, p. 418.</p>
+
+<p><a name="footnote234"></a><a href="#citation234"
+class="footnote">[234]</a> This conclusion reminds me of
+the vast amount of extremely fine chalky mud which is found
+within the lagoons of many atolls, where the sea is tranquil and
+waves cannot triturate the blocks of coral. This mud must,
+as I believe (&lsquo;The Structure and Distribution of
+Coral-Reefs,&rsquo; 2nd edit. 1874, p. 19), be attributed to the
+innumerable annelids and other animals which burrow into the dead
+coral, and to the fishes, Holothurians, &amp;c., which browse on
+the living corals.</p>
+
+<p><a name="footnote236"></a><a href="#citation236"
+class="footnote">[236]</a> Anniversary Address: &lsquo;The
+Quarterly Journal of the Geological Soc.&rsquo; May 1880, p.
+59.</p>
+
+<p><a name="footnote244"></a><a href="#citation244"
+class="footnote">[244]</a> Mr. James Wallace has pointed
+out that it is necessary to take into consideration the
+possibility of burrows being made at right angles to the surface
+instead of vertically down, in which case the lateral
+displacement of the soil would be increased.</p>
+
+<p><a name="footnote259"></a><a href="#citation259"
+class="footnote">[259]</a> &lsquo;Elements of
+Geology,&rsquo; 1865, p. 20.</p>
+
+<p><a name="footnote265"></a><a href="#citation265"
+class="footnote">[265]</a> &lsquo;Le&ccedil;ons de
+Géologie pratique, 1845; cinquième
+Le&ccedil;on. All Élie de Beaumont&rsquo;s arguments
+are admirably controverted by Prof. A. Geikie in his essay in
+Transact. Geolog. Soc. of Glasgow, vol. iii. p. 153, 1868.</p>
+
+<p><a name="footnote266"></a><a href="#citation266"
+class="footnote">[266]</a> &lsquo;Illustrations of the
+Huttonian Theory of the Earth,&rsquo; p. 107.</p>
+
+<p><a name="footnote269"></a><a href="#citation269"
+class="footnote">[269]</a> Mr. E. Tylor in his Presidential
+address (&lsquo;Journal of the Anthropological Institute,&rsquo;
+May 1880, p. 451) remarks: &ldquo;It appears from several papers
+of the Berlin Society as to the German &lsquo;high-fields&rsquo;
+or &lsquo;heathen-fields&rsquo; (Hoch&auml;cker, and
+Heiden&auml;cker) that they correspond much in their situation on
+hills and wastes with the &lsquo;elf-furrows&rsquo; of Scotland,
+which popular mythology accounts for by the story of the fields
+having been put under a Papal interdict, so that people took to
+cultivating the hills. There seems reason to suppose that,
+like the tilled plots in the Swedish forest which tradition
+ascribes to the old &lsquo;hackers,&rsquo; the German
+heathen-fields represent tillage by an ancient and barbaric
+population.&rdquo;</p>
+
+<p><a name="footnote284"></a><a href="#citation284"
+class="footnote">[284]</a> White of Selborne has some good
+remarks on the service performed by worms in loosening, &amp;c.,
+the soil. Edit, by L. Jenyns, 1843, p. 281.</p>
+
+<p><a name="footnote285"></a><a href="#citation285"
+class="footnote">[285]</a> &lsquo;Zeitschrift f&uuml;r
+wissenschaft. Zoolog.&rsquo; B. xxviii. 1877, p. 360.</p>
+
+<div style='display:block; margin-top:4em'>*** END OF THE PROJECT GUTENBERG EBOOK THE FORMATION OF VEGETABLE MOULD ***</div>
+<div style='text-align:left'>
+
+<div style='display:block; margin:1em 0'>
+Updated editions will replace the previous one&#8212;the old editions will
+be renamed.
+</div>
+
+<div style='display:block; margin:1em 0'>
+Creating the works from print editions not protected by U.S. copyright
+law means that no one owns a United States copyright in these works,
+so the Foundation (and you!) can copy and distribute it in the United
+States without permission and without paying copyright
+royalties. Special rules, set forth in the General Terms of Use part
+of this license, apply to copying and distributing Project
+Gutenberg&#8482; electronic works to protect the PROJECT GUTENBERG&#8482;
+concept and trademark. Project Gutenberg is a registered trademark,
+and may not be used if you charge for an eBook, except by following
+the terms of the trademark license, including paying royalties for use
+of the Project Gutenberg trademark. If you do not charge anything for
+copies of this eBook, complying with the trademark license is very
+easy. You may use this eBook for nearly any purpose such as creation
+of derivative works, reports, performances and research. Project
+Gutenberg eBooks may be modified and printed and given away--you may
+do practically ANYTHING in the United States with eBooks not protected
+by U.S. copyright law. Redistribution is subject to the trademark
+license, especially commercial redistribution.
+</div>
+
+<div style='margin:0.83em 0; font-size:1.1em; text-align:center'>START: FULL LICENSE<br />
+<span style='font-size:smaller'>THE FULL PROJECT GUTENBERG LICENSE<br />
+PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK</span>
+</div>
+
+<div style='display:block; margin:1em 0'>
+To protect the Project Gutenberg&#8482; mission of promoting the free
+distribution of electronic works, by using or distributing this work
+(or any other work associated in any way with the phrase &#8220;Project
+Gutenberg&#8221;), you agree to comply with all the terms of the Full
+Project Gutenberg&#8482; License available with this file or online at
+www.gutenberg.org/license.
+</div>
+
+<div style='display:block; font-size:1.1em; margin:1em 0; font-weight:bold'>
+Section 1. General Terms of Use and Redistributing Project Gutenberg&#8482; electronic works
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.A. By reading or using any part of this Project Gutenberg&#8482;
+electronic work, you indicate that you have read, understand, agree to
+and accept all the terms of this license and intellectual property
+(trademark/copyright) agreement. If you do not agree to abide by all
+the terms of this agreement, you must cease using and return or
+destroy all copies of Project Gutenberg&#8482; electronic works in your
+possession. If you paid a fee for obtaining a copy of or access to a
+Project Gutenberg&#8482; electronic work and you do not agree to be bound
+by the terms of this agreement, you may obtain a refund from the person
+or entity to whom you paid the fee as set forth in paragraph 1.E.8.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.B. &#8220;Project Gutenberg&#8221; is a registered trademark. It may only be
+used on or associated in any way with an electronic work by people who
+agree to be bound by the terms of this agreement. There are a few
+things that you can do with most Project Gutenberg&#8482; electronic works
+even without complying with the full terms of this agreement. See
+paragraph 1.C below. There are a lot of things you can do with Project
+Gutenberg&#8482; electronic works if you follow the terms of this
+agreement and help preserve free future access to Project Gutenberg&#8482;
+electronic works. See paragraph 1.E below.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.C. The Project Gutenberg Literary Archive Foundation (&#8220;the
+Foundation&#8221; or PGLAF), owns a compilation copyright in the collection
+of Project Gutenberg&#8482; electronic works. Nearly all the individual
+works in the collection are in the public domain in the United
+States. If an individual work is unprotected by copyright law in the
+United States and you are located in the United States, we do not
+claim a right to prevent you from copying, distributing, performing,
+displaying or creating derivative works based on the work as long as
+all references to Project Gutenberg are removed. Of course, we hope
+that you will support the Project Gutenberg&#8482; mission of promoting
+free access to electronic works by freely sharing Project Gutenberg&#8482;
+works in compliance with the terms of this agreement for keeping the
+Project Gutenberg&#8482; name associated with the work. You can easily
+comply with the terms of this agreement by keeping this work in the
+same format with its attached full Project Gutenberg&#8482; License when
+you share it without charge with others.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.D. The copyright laws of the place where you are located also govern
+what you can do with this work. Copyright laws in most countries are
+in a constant state of change. If you are outside the United States,
+check the laws of your country in addition to the terms of this
+agreement before downloading, copying, displaying, performing,
+distributing or creating derivative works based on this work or any
+other Project Gutenberg&#8482; work. The Foundation makes no
+representations concerning the copyright status of any work in any
+country other than the United States.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E. Unless you have removed all references to Project Gutenberg:
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.1. The following sentence, with active links to, or other
+immediate access to, the full Project Gutenberg&#8482; License must appear
+prominently whenever any copy of a Project Gutenberg&#8482; work (any work
+on which the phrase &#8220;Project Gutenberg&#8221; appears, or with which the
+phrase &#8220;Project Gutenberg&#8221; is associated) is accessed, displayed,
+performed, viewed, copied or distributed:
+</div>
+
+<blockquote>
+  <div style='display:block; margin:1em 0'>
+    This eBook is for the use of anyone anywhere in the United States and most
+    other parts of the world at no cost and with almost no restrictions
+    whatsoever. You may copy it, give it away or re-use it under the terms
+    of the Project Gutenberg License included with this eBook or online
+    at <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you
+    are not located in the United States, you will have to check the laws
+    of the country where you are located before using this eBook.
+  </div>
+</blockquote>
+
+<div style='display:block; margin:1em 0'>
+1.E.2. If an individual Project Gutenberg&#8482; electronic work is
+derived from texts not protected by U.S. copyright law (does not
+contain a notice indicating that it is posted with permission of the
+copyright holder), the work can be copied and distributed to anyone in
+the United States without paying any fees or charges. If you are
+redistributing or providing access to a work with the phrase &#8220;Project
+Gutenberg&#8221; associated with or appearing on the work, you must comply
+either with the requirements of paragraphs 1.E.1 through 1.E.7 or
+obtain permission for the use of the work and the Project Gutenberg&#8482;
+trademark as set forth in paragraphs 1.E.8 or 1.E.9.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.3. If an individual Project Gutenberg&#8482; electronic work is posted
+with the permission of the copyright holder, your use and distribution
+must comply with both paragraphs 1.E.1 through 1.E.7 and any
+additional terms imposed by the copyright holder. Additional terms
+will be linked to the Project Gutenberg&#8482; License for all works
+posted with the permission of the copyright holder found at the
+beginning of this work.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.4. Do not unlink or detach or remove the full Project Gutenberg&#8482;
+License terms from this work, or any files containing a part of this
+work or any other work associated with Project Gutenberg&#8482;.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.5. Do not copy, display, perform, distribute or redistribute this
+electronic work, or any part of this electronic work, without
+prominently displaying the sentence set forth in paragraph 1.E.1 with
+active links or immediate access to the full terms of the Project
+Gutenberg&#8482; License.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.6. You may convert to and distribute this work in any binary,
+compressed, marked up, nonproprietary or proprietary form, including
+any word processing or hypertext form. However, if you provide access
+to or distribute copies of a Project Gutenberg&#8482; work in a format
+other than &#8220;Plain Vanilla ASCII&#8221; or other format used in the official
+version posted on the official Project Gutenberg&#8482; website
+(www.gutenberg.org), you must, at no additional cost, fee or expense
+to the user, provide a copy, a means of exporting a copy, or a means
+of obtaining a copy upon request, of the work in its original &#8220;Plain
+Vanilla ASCII&#8221; or other form. Any alternate format must include the
+full Project Gutenberg&#8482; License as specified in paragraph 1.E.1.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.7. Do not charge a fee for access to, viewing, displaying,
+performing, copying or distributing any Project Gutenberg&#8482; works
+unless you comply with paragraph 1.E.8 or 1.E.9.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.8. You may charge a reasonable fee for copies of or providing
+access to or distributing Project Gutenberg&#8482; electronic works
+provided that:
+</div>
+
+<div style='margin-left:0.7em;'>
+    <div style='text-indent:-0.7em'>
+        &bull; You pay a royalty fee of 20% of the gross profits you derive from
+        the use of Project Gutenberg&#8482; works calculated using the method
+        you already use to calculate your applicable taxes. The fee is owed
+        to the owner of the Project Gutenberg&#8482; trademark, but he has
+        agreed to donate royalties under this paragraph to the Project
+        Gutenberg Literary Archive Foundation. Royalty payments must be paid
+        within 60 days following each date on which you prepare (or are
+        legally required to prepare) your periodic tax returns. Royalty
+        payments should be clearly marked as such and sent to the Project
+        Gutenberg Literary Archive Foundation at the address specified in
+        Section 4, &#8220;Information about donations to the Project Gutenberg
+        Literary Archive Foundation.&#8221;
+    </div>
+
+    <div style='text-indent:-0.7em'>
+        &bull; You provide a full refund of any money paid by a user who notifies
+        you in writing (or by e-mail) within 30 days of receipt that s/he
+        does not agree to the terms of the full Project Gutenberg&#8482;
+        License. You must require such a user to return or destroy all
+        copies of the works possessed in a physical medium and discontinue
+        all use of and all access to other copies of Project Gutenberg&#8482;
+        works.
+    </div>
+
+    <div style='text-indent:-0.7em'>
+        &bull; You provide, in accordance with paragraph 1.F.3, a full refund of
+        any money paid for a work or a replacement copy, if a defect in the
+        electronic work is discovered and reported to you within 90 days of
+        receipt of the work.
+    </div>
+
+    <div style='text-indent:-0.7em'>
+        &bull; You comply with all other terms of this agreement for free
+        distribution of Project Gutenberg&#8482; works.
+    </div>
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.E.9. If you wish to charge a fee or distribute a Project
+Gutenberg&#8482; electronic work or group of works on different terms than
+are set forth in this agreement, you must obtain permission in writing
+from the Project Gutenberg Literary Archive Foundation, the manager of
+the Project Gutenberg&#8482; trademark. Contact the Foundation as set
+forth in Section 3 below.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.F.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.F.1. Project Gutenberg volunteers and employees expend considerable
+effort to identify, do copyright research on, transcribe and proofread
+works not protected by U.S. copyright law in creating the Project
+Gutenberg&#8482; collection. Despite these efforts, Project Gutenberg&#8482;
+electronic works, and the medium on which they may be stored, may
+contain &#8220;Defects,&#8221; such as, but not limited to, incomplete, inaccurate
+or corrupt data, transcription errors, a copyright or other
+intellectual property infringement, a defective or damaged disk or
+other medium, a computer virus, or computer codes that damage or
+cannot be read by your equipment.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the &#8220;Right
+of Replacement or Refund&#8221; described in paragraph 1.F.3, the Project
+Gutenberg Literary Archive Foundation, the owner of the Project
+Gutenberg&#8482; trademark, and any other party distributing a Project
+Gutenberg&#8482; electronic work under this agreement, disclaim all
+liability to you for damages, costs and expenses, including legal
+fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT
+LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE
+PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE
+TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE
+LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR
+INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH
+DAMAGE.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a
+defect in this electronic work within 90 days of receiving it, you can
+receive a refund of the money (if any) you paid for it by sending a
+written explanation to the person you received the work from. If you
+received the work on a physical medium, you must return the medium
+with your written explanation. The person or entity that provided you
+with the defective work may elect to provide a replacement copy in
+lieu of a refund. If you received the work electronically, the person
+or entity providing it to you may choose to give you a second
+opportunity to receive the work electronically in lieu of a refund. If
+the second copy is also defective, you may demand a refund in writing
+without further opportunities to fix the problem.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.F.4. Except for the limited right of replacement or refund set forth
+in paragraph 1.F.3, this work is provided to you &#8216;AS-IS&#8217;, WITH NO
+OTHER WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
+LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.F.5. Some states do not allow disclaimers of certain implied
+warranties or the exclusion or limitation of certain types of
+damages. If any disclaimer or limitation set forth in this agreement
+violates the law of the state applicable to this agreement, the
+agreement shall be interpreted to make the maximum disclaimer or
+limitation permitted by the applicable state law. The invalidity or
+unenforceability of any provision of this agreement shall not void the
+remaining provisions.
+</div>
+
+<div style='display:block; margin:1em 0'>
+1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the
+trademark owner, any agent or employee of the Foundation, anyone
+providing copies of Project Gutenberg&#8482; electronic works in
+accordance with this agreement, and any volunteers associated with the
+production, promotion and distribution of Project Gutenberg&#8482;
+electronic works, harmless from all liability, costs and expenses,
+including legal fees, that arise directly or indirectly from any of
+the following which you do or cause to occur: (a) distribution of this
+or any Project Gutenberg&#8482; work, (b) alteration, modification, or
+additions or deletions to any Project Gutenberg&#8482; work, and (c) any
+Defect you cause.
+</div>
+
+<div style='display:block; font-size:1.1em; margin:1em 0; font-weight:bold'>
+Section 2. Information about the Mission of Project Gutenberg&#8482;
+</div>
+
+<div style='display:block; margin:1em 0'>
+Project Gutenberg&#8482; is synonymous with the free distribution of
+electronic works in formats readable by the widest variety of
+computers including obsolete, old, middle-aged and new computers. It
+exists because of the efforts of hundreds of volunteers and donations
+from people in all walks of life.
+</div>
+
+<div style='display:block; margin:1em 0'>
+Volunteers and financial support to provide volunteers with the
+assistance they need are critical to reaching Project Gutenberg&#8482;&#8217;s
+goals and ensuring that the Project Gutenberg&#8482; collection will
+remain freely available for generations to come. In 2001, the Project
+Gutenberg Literary Archive Foundation was created to provide a secure
+and permanent future for Project Gutenberg&#8482; and future
+generations. To learn more about the Project Gutenberg Literary
+Archive Foundation and how your efforts and donations can help, see
+Sections 3 and 4 and the Foundation information page at www.gutenberg.org.
+</div>
+
+<div style='display:block; font-size:1.1em; margin:1em 0; font-weight:bold'>
+Section 3. Information about the Project Gutenberg Literary Archive Foundation
+</div>
+
+<div style='display:block; margin:1em 0'>
+The Project Gutenberg Literary Archive Foundation is a non-profit
+501(c)(3) educational corporation organized under the laws of the
+state of Mississippi and granted tax exempt status by the Internal
+Revenue Service. The Foundation&#8217;s EIN or federal tax identification
+number is 64-6221541. Contributions to the Project Gutenberg Literary
+Archive Foundation are tax deductible to the full extent permitted by
+U.S. federal laws and your state&#8217;s laws.
+</div>
+
+<div style='display:block; margin:1em 0'>
+The Foundation&#8217;s business office is located at 809 North 1500 West,
+Salt Lake City, UT 84116, (801) 596-1887. Email contact links and up
+to date contact information can be found at the Foundation&#8217;s website
+and official page at www.gutenberg.org/contact
+</div>
+
+<div style='display:block; font-size:1.1em; margin:1em 0; font-weight:bold'>
+Section 4. Information about Donations to the Project Gutenberg Literary Archive Foundation
+</div>
+
+<div style='display:block; margin:1em 0'>
+Project Gutenberg&#8482; depends upon and cannot survive without widespread
+public support and donations to carry out its mission of
+increasing the number of public domain and licensed works that can be
+freely distributed in machine-readable form accessible by the widest
+array of equipment including outdated equipment. Many small donations
+($1 to $5,000) are particularly important to maintaining tax exempt
+status with the IRS.
+</div>
+
+<div style='display:block; margin:1em 0'>
+The Foundation is committed to complying with the laws regulating
+charities and charitable donations in all 50 states of the United
+States. Compliance requirements are not uniform and it takes a
+considerable effort, much paperwork and many fees to meet and keep up
+with these requirements. We do not solicit donations in locations
+where we have not received written confirmation of compliance. To SEND
+DONATIONS or determine the status of compliance for any particular state
+visit <a href="https://www.gutenberg.org/donate/">www.gutenberg.org/donate</a>.
+</div>
+
+<div style='display:block; margin:1em 0'>
+While we cannot and do not solicit contributions from states where we
+have not met the solicitation requirements, we know of no prohibition
+against accepting unsolicited donations from donors in such states who
+approach us with offers to donate.
+</div>
+
+<div style='display:block; margin:1em 0'>
+International donations are gratefully accepted, but we cannot make
+any statements concerning tax treatment of donations received from
+outside the United States. U.S. laws alone swamp our small staff.
+</div>
+
+<div style='display:block; margin:1em 0'>
+Please check the Project Gutenberg web pages for current donation
+methods and addresses. Donations are accepted in a number of other
+ways including checks, online payments and credit card donations. To
+donate, please visit: www.gutenberg.org/donate
+</div>
+
+<div style='display:block; font-size:1.1em; margin:1em 0; font-weight:bold'>
+Section 5. General Information About Project Gutenberg&#8482; electronic works
+</div>
+
+<div style='display:block; margin:1em 0'>
+Professor Michael S. Hart was the originator of the Project
+Gutenberg&#8482; concept of a library of electronic works that could be
+freely shared with anyone. For forty years, he produced and
+distributed Project Gutenberg&#8482; eBooks with only a loose network of
+volunteer support.
+</div>
+
+<div style='display:block; margin:1em 0'>
+Project Gutenberg&#8482; eBooks are often created from several printed
+editions, all of which are confirmed as not protected by copyright in
+the U.S. unless a copyright notice is included. Thus, we do not
+necessarily keep eBooks in compliance with any particular paper
+edition.
+</div>
+
+<div style='display:block; margin:1em 0'>
+Most people start at our website which has the main PG search
+facility: <a href="https://www.gutenberg.org">www.gutenberg.org</a>.
+</div>
+
+<div style='display:block; margin:1em 0'>
+This website includes information about Project Gutenberg&#8482;,
+including how to make donations to the Project Gutenberg Literary
+Archive Foundation, how to help produce our new eBooks, and how to
+subscribe to our email newsletter to hear about new eBooks.
+</div>
+
+</div>
+
+</body>
+</html>
diff --git a/2355-h/images/cover.jpg b/2355-h/images/cover.jpg
new file mode 100644
index 0000000..85a3238
--- /dev/null
+++ b/2355-h/images/cover.jpg
diff --git a/2355-h/images/p116b.jpg b/2355-h/images/p116b.jpg
new file mode 100644
index 0000000..1e4a5a9
--- /dev/null
+++ b/2355-h/images/p116b.jpg
diff --git a/2355-h/images/p116s.jpg b/2355-h/images/p116s.jpg
new file mode 100644
index 0000000..1e71948
--- /dev/null
+++ b/2355-h/images/p116s.jpg
diff --git a/2355-h/images/p124b.jpg b/2355-h/images/p124b.jpg
new file mode 100644
index 0000000..e1132f5
--- /dev/null
+++ b/2355-h/images/p124b.jpg
diff --git a/2355-h/images/p124s.jpg b/2355-h/images/p124s.jpg
new file mode 100644
index 0000000..e147904
--- /dev/null
+++ b/2355-h/images/p124s.jpg
diff --git a/2355-h/images/p168b.jpg b/2355-h/images/p168b.jpg
new file mode 100644
index 0000000..6a00883
--- /dev/null
+++ b/2355-h/images/p168b.jpg
diff --git a/2355-h/images/p168s.jpg b/2355-h/images/p168s.jpg
new file mode 100644
index 0000000..5f69c28
--- /dev/null
+++ b/2355-h/images/p168s.jpg
diff --git a/2355-h/images/p17b.jpg b/2355-h/images/p17b.jpg
new file mode 100644
index 0000000..24bd745
--- /dev/null
+++ b/2355-h/images/p17b.jpg
diff --git a/2355-h/images/p17s.jpg b/2355-h/images/p17s.jpg
new file mode 100644
index 0000000..abcdb41
--- /dev/null
+++ b/2355-h/images/p17s.jpg
diff --git a/2355-h/images/p186b.jpg b/2355-h/images/p186b.jpg
new file mode 100644
index 0000000..9c4f0a8
--- /dev/null
+++ b/2355-h/images/p186b.jpg
diff --git a/2355-h/images/p186s.jpg b/2355-h/images/p186s.jpg
new file mode 100644
index 0000000..f3f26ac
--- /dev/null
+++ b/2355-h/images/p186s.jpg
diff --git a/2355-h/images/p188b.jpg b/2355-h/images/p188b.jpg
new file mode 100644
index 0000000..fec649a
--- /dev/null
+++ b/2355-h/images/p188b.jpg
diff --git a/2355-h/images/p188s.jpg b/2355-h/images/p188s.jpg
new file mode 100644
index 0000000..c98cc0d
--- /dev/null
+++ b/2355-h/images/p188s.jpg
diff --git a/2355-h/images/p190b.jpg b/2355-h/images/p190b.jpg
new file mode 100644
index 0000000..bfb78e0
--- /dev/null
+++ b/2355-h/images/p190b.jpg
diff --git a/2355-h/images/p190s.jpg b/2355-h/images/p190s.jpg
new file mode 100644
index 0000000..5cc18e4
--- /dev/null
+++ b/2355-h/images/p190s.jpg
diff --git a/2355-h/images/p192b.jpg b/2355-h/images/p192b.jpg
new file mode 100644
index 0000000..8b0d223
--- /dev/null
+++ b/2355-h/images/p192b.jpg
diff --git a/2355-h/images/p192s.jpg b/2355-h/images/p192s.jpg
new file mode 100644
index 0000000..dcf28b7
--- /dev/null
+++ b/2355-h/images/p192s.jpg
diff --git a/2355-h/images/p194b.jpg b/2355-h/images/p194b.jpg
new file mode 100644
index 0000000..0a2de3c
--- /dev/null
+++ b/2355-h/images/p194b.jpg
diff --git a/2355-h/images/p194s.jpg b/2355-h/images/p194s.jpg
new file mode 100644
index 0000000..6c42b59
--- /dev/null
+++ b/2355-h/images/p194s.jpg
diff --git a/2355-h/images/p196b.jpg b/2355-h/images/p196b.jpg
new file mode 100644
index 0000000..2082c32
--- /dev/null
+++ b/2355-h/images/p196b.jpg
diff --git a/2355-h/images/p196s.jpg b/2355-h/images/p196s.jpg
new file mode 100644
index 0000000..cec5e81
--- /dev/null
+++ b/2355-h/images/p196s.jpg
diff --git a/LICENSE.txt b/LICENSE.txt
new file mode 100644
index 0000000..6312041
--- /dev/null
+++ b/LICENSE.txt
@@ -0,0 +1,11 @@
+This eBook, including all associated images, markup, improvements,
+metadata, and any other content or labor, has been confirmed to be
+in the PUBLIC DOMAIN IN THE UNITED STATES.
+
+Procedures for determining public domain status are described in
+the "Copyright How-To" at https://www.gutenberg.org.
+
+No investigation has been made concerning possible copyrights in
+jurisdictions other than the United States. Anyone seeking to utilize
+this eBook outside of the United States should confirm copyright
+status under the laws that apply to them.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..cd8f3cd
--- /dev/null
+++ b/README.md
@@ -0,0 +1,2 @@
+Project Gutenberg (https://www.gutenberg.org) public repository for
+eBook #2355 (https://www.gutenberg.org/ebooks/2355)
diff --git a/old/vgmld10.txt b/old/vgmld10.txt
new file mode 100644
index 0000000..77cc80a
--- /dev/null
+++ b/old/vgmld10.txt
@@ -0,0 +1,6283 @@
+Project Gutenberg Etext Formation of Vegetable Mould, by Darwin
+#9 in our series by Charles Darwin
+
+
+Copyright laws are changing all over the world, be sure to check
+the copyright laws for your country before posting these files!!
+
+Please take a look at the important information in this header.
+We encourage you to keep this file on your own disk, keeping an
+electronic path open for the next readers.  Do not remove this.
+
+
+**Welcome To The World of Free Plain Vanilla Electronic Texts**
+
+**Etexts Readable By Both Humans and By Computers, Since 1971**
+
+*These Etexts Prepared By Hundreds of Volunteers and Donations*
+
+Information on contacting Project Gutenberg to get Etexts, and
+further information is included below.  We need your donations.
+
+
+The Formation of Vegetable Mould through the action of worms with
+observations of their habits
+
+by Charles Darwin
+
+October, 2000  [Etext #2355]
+
+
+Project Gutenberg Etext Formation of Vegetable Mould, by Darwin
+*****This file should be named vgmld10.txt or vgmld10.zip******
+
+Corrected EDITIONS of our etexts get a new NUMBER, vgmld11.txt
+VERSIONS based on separate sources get new LETTER, vgmld10a.txt
+
+
+Scanned and proofed by David Price
+ccx074@coventry.ac.uk
+
+Project Gutenberg Etexts are usually created from multiple editions,
+all of which are in the Public Domain in the United States, unless a
+copyright notice is included.  Therefore, we usually do NOT keep any
+of these books in compliance with any particular paper edition.
+
+
+We are now trying to release all our books one month in advance
+of the official release dates, leaving time for better editing.
+
+Please note:  neither this list nor its contents are final till
+midnight of the last day of the month of any such announcement.
+The official release date of all Project Gutenberg Etexts is at
+Midnight, Central Time, of the last day of the stated month.  A
+preliminary version may often be posted for suggestion, comment
+and editing by those who wish to do so.  To be sure you have an
+up to date first edition [xxxxx10x.xxx] please check file sizes
+in the first week of the next month.  Since our ftp program has
+a bug in it that scrambles the date [tried to fix and failed] a
+look at the file size will have to do, but we will try to see a
+new copy has at least one byte more or less.
+
+
+Information about Project Gutenberg (one page)
+
+We produce about two million dollars for each hour we work.  The
+time it takes us, a rather conservative estimate, is fifty hours
+to get any etext selected, entered, proofread, edited, copyright
+searched and analyzed, the copyright letters written, etc.  This
+projected audience is one hundred million readers.  If our value
+per text is nominally estimated at one dollar then we produce $2
+million dollars per hour this year as we release thirty-six text
+files per month, or 432 more Etexts in 1999 for a total of 2000+
+If these reach just 10% of the computerized population, then the
+total should reach over 200 billion Etexts given away this year.
+
+The Goal of Project Gutenberg is to Give Away One Trillion Etext
+Files by December 31, 2001.  [10,000 x 100,000,000 = 1 Trillion]
+This is ten thousand titles each to one hundred million readers,
+which is only ~5% of the present number of computer users.
+
+At our revised rates of production, we will reach only one-third
+of that goal by the end of 2001, or about 3,333 Etexts unless we
+manage to get some real funding; currently our funding is mostly
+from Michael Hart's salary at Carnegie-Mellon University, and an
+assortment of sporadic gifts; this salary is only good for a few
+more years, so we are looking for something to replace it, as we
+don't want Project Gutenberg to be so dependent on one person.
+
+We need your donations more than ever!
+
+
+All donations should be made to "Project Gutenberg/CMU": and are
+tax deductible to the extent allowable by law.  (CMU = Carnegie-
+Mellon University).
+
+For these and other matters, please mail to:
+
+Project Gutenberg
+P. O. Box  2782
+Champaign, IL 61825
+
+When all other email fails. . .try our Executive Director:
+Michael S. Hart <hart@pobox.com>
+hart@pobox.com forwards to hart@prairienet.org and archive.org
+if your mail bounces from archive.org, I will still see it, if
+it bounces from prairienet.org, better resend later on. . . .
+
+We would prefer to send you this information by email.
+
+******
+
+To access Project Gutenberg etexts, use any Web browser
+to view http://promo.net/pg.  This site lists Etexts by
+author and by title, and includes information about how
+to get involved with Project Gutenberg.  You could also
+download our past Newsletters, or subscribe here.  This
+is one of our major sites, please email hart@pobox.com,
+for a more complete list of our various sites.
+
+To go directly to the etext collections, use FTP or any
+Web browser to visit a Project Gutenberg mirror (mirror
+sites are available on 7 continents; mirrors are listed
+at http://promo.net/pg).
+
+Mac users, do NOT point and click, typing works better.
+
+Example FTP session:
+
+ftp sunsite.unc.edu
+login: anonymous
+password: your@login
+cd pub/docs/books/gutenberg
+cd etext90 through etext99
+dir [to see files]
+get or mget [to get files. . .set bin for zip files]
+GET GUTINDEX.??  [to get a year's listing of books, e.g., GUTINDEX.99]
+GET GUTINDEX.ALL [to get a listing of ALL books]
+
+***
+
+**Information prepared by the Project Gutenberg legal advisor**
+
+(Three Pages)
+
+
+***START**THE SMALL PRINT!**FOR PUBLIC DOMAIN ETEXTS**START***
+Why is this "Small Print!" statement here?  You know: lawyers.
+They tell us you might sue us if there is something wrong with
+your copy of this etext, even if you got it for free from
+someone other than us, and even if what's wrong is not our
+fault.  So, among other things, this "Small Print!" statement
+disclaims most of our liability to you.  It also tells you how
+you can distribute copies of this etext if you want to.
+
+*BEFORE!* YOU USE OR READ THIS ETEXT
+By using or reading any part of this PROJECT GUTENBERG-tm
+etext, you indicate that you understand, agree to and accept
+this "Small Print!" statement.  If you do not, you can receive
+a refund of the money (if any) you paid for this etext by
+sending a request within 30 days of receiving it to the person
+you got it from.  If you received this etext on a physical
+medium (such as a disk), you must return it with your request.
+
+ABOUT PROJECT GUTENBERG-TM ETEXTS
+This PROJECT GUTENBERG-tm etext, like most PROJECT GUTENBERG-
+tm etexts, is a "public domain" work distributed by Professor
+Michael S. Hart through the Project Gutenberg Association at
+Carnegie-Mellon University (the "Project").  Among other
+things, this means that no one owns a United States copyright
+on or for this work, so the Project (and you!) can copy and
+distribute it in the United States without permission and
+without paying copyright royalties.  Special rules, set forth
+below, apply if you wish to copy and distribute this etext
+under the Project's "PROJECT GUTENBERG" trademark.
+
+To create these etexts, the Project expends considerable
+efforts to identify, transcribe and proofread public domain
+works.  Despite these efforts, the Project's etexts and any
+medium they may be on may contain "Defects".  Among other
+things, Defects may take the form of incomplete, inaccurate or
+corrupt data, transcription errors, a copyright or other
+intellectual property infringement, a defective or damaged
+disk or other etext medium, a computer virus, or computer
+codes that damage or cannot be read by your equipment.
+
+LIMITED WARRANTY; DISCLAIMER OF DAMAGES
+But for the "Right of Replacement or Refund" described below,
+[1] the Project (and any other party you may receive this
+etext from as a PROJECT GUTENBERG-tm etext) disclaims all
+liability to you for damages, costs and expenses, including
+legal fees, and [2] YOU HAVE NO REMEDIES FOR NEGLIGENCE OR
+UNDER STRICT LIABILITY, OR FOR BREACH OF WARRANTY OR CONTRACT,
+INCLUDING BUT NOT LIMITED TO INDIRECT, CONSEQUENTIAL, PUNITIVE
+OR INCIDENTAL DAMAGES, EVEN IF YOU GIVE NOTICE OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+If you discover a Defect in this etext within 90 days of
+receiving it, you can receive a refund of the money (if any)
+you paid for it by sending an explanatory note within that
+time to the person you received it from.  If you received it
+on a physical medium, you must return it with your note, and
+such person may choose to alternatively give you a replacement
+copy.  If you received it electronically, such person may
+choose to alternatively give you a second opportunity to
+receive it electronically.
+
+THIS ETEXT IS OTHERWISE PROVIDED TO YOU "AS-IS".  NO OTHER
+WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, ARE MADE TO YOU AS
+TO THE ETEXT OR ANY MEDIUM IT MAY BE ON, INCLUDING BUT NOT
+LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
+PARTICULAR PURPOSE.
+
+Some states do not allow disclaimers of implied warranties or
+the exclusion or limitation of consequential damages, so the
+above disclaimers and exclusions may not apply to you, and you
+may have other legal rights.
+
+INDEMNITY
+You will indemnify and hold the Project, its directors,
+officers, members and agents harmless from all liability, cost
+and expense, including legal fees, that arise directly or
+indirectly from any of the following that you do or cause:
+[1] distribution of this etext, [2] alteration, modification,
+or addition to the etext, or [3] any Defect.
+
+DISTRIBUTION UNDER "PROJECT GUTENBERG-tm"
+You may distribute copies of this etext electronically, or by
+disk, book or any other medium if you either delete this
+"Small Print!" and all other references to Project Gutenberg,
+or:
+
+[1]  Only give exact copies of it.  Among other things, this
+     requires that you do not remove, alter or modify the
+     etext or this "small print!" statement.  You may however,
+     if you wish, distribute this etext in machine readable
+     binary, compressed, mark-up, or proprietary form,
+     including any form resulting from conversion by word pro-
+     cessing or hypertext software, but only so long as
+     *EITHER*:
+
+     [*]  The etext, when displayed, is clearly readable, and
+          does *not* contain characters other than those
+          intended by the author of the work, although tilde
+          (~), asterisk (*) and underline (_) characters may
+          be used to convey punctuation intended by the
+          author, and additional characters may be used to
+          indicate hypertext links; OR
+
+     [*]  The etext may be readily converted by the reader at
+          no expense into plain ASCII, EBCDIC or equivalent
+          form by the program that displays the etext (as is
+          the case, for instance, with most word processors);
+          OR
+
+     [*]  You provide, or agree to also provide on request at
+          no additional cost, fee or expense, a copy of the
+          etext in its original plain ASCII form (or in EBCDIC
+          or other equivalent proprietary form).
+
+[2]  Honor the etext refund and replacement provisions of this
+     "Small Print!" statement.
+
+[3]  Pay a trademark license fee to the Project of 20% of the
+     net profits you derive calculated using the method you
+     already use to calculate your applicable taxes.  If you
+     don't derive profits, no royalty is due.  Royalties are
+     payable to "Project Gutenberg Association/Carnegie-Mellon
+     University" within the 60 days following each
+     date you prepare (or were legally required to prepare)
+     your annual (or equivalent periodic) tax return.
+
+WHAT IF YOU *WANT* TO SEND MONEY EVEN IF YOU DON'T HAVE TO?
+The Project gratefully accepts contributions in money, time,
+scanning machines, OCR software, public domain etexts, royalty
+free copyright licenses, and every other sort of contribution
+you can think of.  Money should be paid to "Project Gutenberg
+Association / Carnegie-Mellon University".
+
+*END*THE SMALL PRINT! FOR PUBLIC DOMAIN ETEXTS*Ver.04.29.93*END*
+
+
+
+
+
+Scanned and proofed by David Price
+ccx074@coventry.ac.uk
+
+
+
+
+
+THE FORMATION OF VEGETABLE MOULD
+THROUGH THE ACTION OF WORMS
+WITH OBSERVATIONS ON THEIR HABITS.
+
+by Charles Darwin
+
+
+
+
+INTRODUCTION.
+
+
+
+The share which worms have taken in the formation of the layer of 
+vegetable mould, which covers the whole surface of the land in 
+every moderately humid country, is the subject of the present 
+volume.  This mould is generally of a blackish colour and a few 
+inches in thickness.  In different districts it differs but little 
+in appearance, although it may rest on various subsoils.  The 
+uniform fineness of the particles of which it is composed is one of 
+its chief characteristic features; and this may be well observed in 
+any gravelly country, where a recently-ploughed field immediately 
+adjoins one which has long remained undisturbed for pasture, and 
+where the vegetable mould is exposed on the sides of a ditch or 
+hole.  The subject may appear an insignificant one, but we shall 
+see that it possesses some interest; and the maxim "de minimis non 
+curat lex," does not apply to science.  Even Elie de Beaumont, who 
+generally undervalues small agencies and their accumulated effects, 
+remarks:  {1} "La couche tres-mince de la terre vegetale est un 
+monument d'une haute antiquite, et, par le fait de sa permanence, 
+un objet digne d'occuper le geologue, et capable de lui fournir des 
+remarques interessantes."  Although the superficial layer of 
+vegetable mould as a whole no doubt is of the highest antiquity, 
+yet in regard to its permanence, we shall hereafter see reason to 
+believe that its component particles are in most cases removed at 
+not a very slow rate, and are replaced by others due to the 
+disintegration of the underlying materials.
+
+As I was led to keep in my study during many months worms in pots 
+filled with earth, I became interested in them, and wished to learn 
+how far they acted consciously, and how much mental power they 
+displayed.  I was the more desirous to learn something on this 
+head, as few observations of this kind have been made, as far as I 
+know, on animals so low in the scale of organization and so poorly 
+provided with sense-organs, as are earth-worms.
+
+In the year 1837, a short paper was read by me before the 
+Geological Society of London, {2} "On the Formation of Mould," in 
+which it was shown that small fragments of burnt marl, cinders, 
+&c., which had been thickly strewed over the surface of several 
+meadows, were found after a few years lying at the depth of some 
+inches beneath the turf, but still forming a layer.  This apparent 
+sinking of superficial bodies is due, as was first suggested to me 
+by Mr. Wedgwood of Maer Hall in Staffordshire, to the large 
+quantity of fine earth continually brought up to the surface by 
+worms in the form of castings.  These castings are sooner or later 
+spread out and cover up any object left on the surface.  I was thus 
+led to conclude that all the vegetable mould over the whole country 
+has passed many times through, and will again pass many times 
+through, the intestinal canals of worms.  Hence the term "animal 
+mould" would be in some respects more appropriate than that 
+commonly used of "vegetable mould."
+
+Ten years after the publication of my paper, M. D'Archiac, 
+evidently influenced by the doctrines of Elie de Beaumont, wrote 
+about my "singuliere theorie," and objected that it could apply 
+only to "les prairies basses et humides;" and that "les terres 
+labourees, les bois, les prairies elevees, n'apportent aucune 
+preuve a l'appui de cette maniere de voir." {3}  But M. D'Archiac 
+must have thus argued from inner consciousness and not from 
+observation, for worms abound to an extraordinary degree in kitchen 
+gardens where the soil is continually worked, though in such loose 
+soil they generally deposit their castings in any open cavities or 
+within their old burrows instead of on the surface.  Hensen 
+estimates that there are about twice as many worms in gardens as in 
+corn-fields. {4}  With respect to "prairies elevees," I do not know 
+how it may be in France, but nowhere in England have I seen the 
+ground so thickly covered with castings as on commons, at a height 
+of several hundred feet above the sea.  In woods again, if the 
+loose leaves in autumn are removed, the whole surface will be found 
+strewed with castings.  Dr. King, the superintendent of the Botanic 
+Garden in Calcutta, to whose kindness I am indebted for many 
+observations on earth-worms, informs me that he found, near Nancy 
+in France, the bottom of the State forests covered over many acres 
+with a spongy layer, composed of dead leaves and innumerable worm-
+castings.  He there heard the Professor of "Amenagement des Forets" 
+lecturing to his pupils, and pointing out this case as a "beautiful 
+example of the natural cultivation of the soil; for year after year 
+the thrown-up castings cover the dead leaves; the result being a 
+rich humus of great thickness."
+
+In the year 1869, Mr. Fish {5} rejected my conclusions with respect 
+to the part which worms have played in the formation of vegetable 
+mould, merely on account of their assumed incapacity to do so much 
+work.  He remarks that "considering their weakness and their size, 
+the work they are represented to have accomplished is stupendous."  
+Here we have an instance of that inability to sum up the effects of 
+a continually recurrent cause, which has often retarded the 
+progress of science, as formerly in the case of geology, and more 
+recently in that of the principle of evolution.
+
+Although these several objections seemed to me to have no weight, 
+yet I resolved to make more observations of the same kind as those 
+published, and to attack the problem on another side; namely, to 
+weigh all the castings thrown up within a given time in a measured 
+space, instead of ascertaining the rate at which objects left on 
+the surface were buried by worms.  But some of my observations have 
+been rendered almost superfluous by an admirable paper by Hensen, 
+already alluded to, which appeared in 1877. {6}  Before entering on 
+details with respect to the castings, it will be advisable to give 
+some account of the habits of worms from my own observations and 
+from those of other naturalists.
+
+[FIRST EDITION, October 10th, 1881.]
+
+
+
+CHAPTER I--HABITS OF WORMS.
+
+
+
+Nature of the sites inhabited--Can live long under water--
+Nocturnal--Wander about at night--Often lie close to the mouths of 
+their burrows, and are thus destroyed in large numbers by birds--
+Structure--Do not possess eyes, but can distinguish between light 
+and darkness--Retreat rapidly when brightly illuminated, not by a 
+reflex action--Power of attention--Sensitive to heat and cold--
+Completely deaf--Sensitive to vibrations and to touch--Feeble power 
+of smell--Taste--Mental qualities--Nature of food--Omnivorous--
+Digestion--Leaves before being swallowed, moistened with a fluid of 
+the nature of the pancreatic secretion--Extra-stomachal digestion--
+Calciferous glands, structure of--Calcareous concretions formed in 
+the anterior pair of glands--The calcareous matter primarily an 
+excretion, but secondarily serves to neutralise the acids generated 
+during the digestive process.
+
+
+Earth-worms are distributed throughout the world under the form of 
+a few genera, which externally are closely similar to one another.  
+The British species of Lumbricus have never been carefully 
+monographed; but we may judge of their probable number from those 
+inhabiting neighbouring countries.  In Scandinavia there are eight 
+species, according to Eisen; {7} but two of these rarely burrow in 
+the ground, and one inhabits very wet places or even lives under 
+the water.  We are here concerned only with the kinds which bring 
+up earth to the surface in the form of castings.  Hoffmeister says 
+that the species in Germany are not well known, but gives the same 
+number as Eisen, together with some strongly marked varieties. {8}
+
+Earth-worms abound in England in many different stations.  Their 
+castings may be seen in extraordinary numbers on commons and chalk-
+downs, so as almost to cover the whole surface, where the soil is 
+poor and the grass short and thin.  But they are almost or quite as 
+numerous in some of the London parks, where the grass grows well 
+and the soil appears rich.  Even on the same field worms are much 
+more frequent in some places than in others, without any visible 
+difference in the nature of the soil.  They abound in paved court-
+yards close to houses; and an instance will be given in which they 
+had burrowed through the floor of a very damp cellar.  I have seen 
+worms in black peat in a boggy field; but they are extremely rare, 
+or quite absent in the drier, brown, fibrous peat, which is so much 
+valued by gardeners.  On dry, sandy or gravelly tracks, where heath 
+with some gorse, ferns, coarse grass, moss and lichens alone grow, 
+hardly any worms can be found.  But in many parts of England, 
+wherever a path crosses a heath, its surface becomes covered with a 
+fine short sward.  Whether this change of vegetation is due to the 
+taller plants being killed by the occasional trampling of man and 
+animals, or to the soil being occasionally manured by the droppings 
+from animals, I do not know. {9}  On such grassy paths worm-
+castings may often be seen.  On a heath in Surrey, which was 
+carefully examined, there were only a few castings on these paths, 
+where they were much inclined; but on the more level parts, where a 
+bed of fine earth had been washed down from the steeper parts and 
+had accumulated to a thickness of a few inches, worm-castings 
+abounded.  These spots seemed to be overstocked with worms, so that 
+they had been compelled to spread to a distance of a few feet from 
+the grassy paths, and here their castings had been thrown up among 
+the heath; but beyond this limit, not a single casting could be 
+found.  A layer, though a thin one, of fine earth, which probably 
+long retains some moisture, is in all cases, as I believe, 
+necessary for their existence; and the mere compression of the soil 
+appears to be in some degree favourable to them, for they often 
+abound in old gravel walks, and in foot-paths across fields.
+
+Beneath large trees few castings can be found during certain 
+seasons of the year, and this is apparently due to the moisture 
+having been sucked out of the ground by the innumerable roots of 
+the trees; for such places may be seen covered with castings after 
+the heavy autumnal rains.  Although most coppices and woods support 
+many worms, yet in a forest of tall and ancient beech-trees in 
+Knole Park, where the ground beneath was bare of all vegetation, 
+not a single casting could be found over wide spaces, even during 
+the autumn.  Nevertheless, castings were abundant on some grass-
+covered glades and indentations which penetrated this forest.  On 
+the mountains of North Wales and on the Alps, worms, as I have been 
+informed, are in most places rare; and this may perhaps be due to 
+the close proximity of the subjacent rocks, into which worms cannot 
+burrow during the winter so as to escape being frozen.  Dr. 
+McIntosh, however, found worm-castings at a height of 1500 feet on 
+Schiehallion in Scotland.  They are numerous on some hills near 
+Turin at from 2000 to 3000 feet above the sea, and at a great 
+altitude on the Nilgiri Mountains in South India and on the 
+Himalaya.
+
+Earth-worms must be considered as terrestrial animals, though they 
+are still in one sense semi-aquatic, like the other members of the 
+great class of annelids to which they belong.  M. Perrier found 
+that their exposure to the dry air of a room for only a single 
+night was fatal to them.  On the other hand he kept several large 
+worms alive for nearly four months, completely submerged in water. 
+{10}  During the summer when the ground is dry, they penetrate to a 
+considerable depth and cease to work, as they do during the winter 
+when the ground is frozen.  Worms are nocturnal in their habits, 
+and at night may be seen crawling about in large numbers, but 
+usually with their tails still inserted in their burrows.  By the 
+expansion of this part of their bodies, and with the help of the 
+short, slightly reflexed bristles, with which their bodies are 
+armed, they hold so fast that they can seldom be dragged out of the 
+ground without being torn into pieces. {11}  During the day they 
+remain in their burrows, except at the pairing season, when those 
+which inhabit adjoining burrows expose the greater part of their 
+bodies for an hour or two in the early morning.  Sick individuals, 
+which are generally affected by the parasitic larvae of a fly, must 
+also be excepted, as they wander about during the day and die on 
+the surface.  After heavy rain succeeding dry weather, an 
+astonishing number of dead worms may sometimes be seen lying on the 
+ground.  Mr. Galton informs me that on one such occasion (March, 
+1881), the dead worms averaged one for every two and a half paces 
+in length on a walk in Hyde Park, four paces in width.  He counted 
+no less than 45 dead worms in one place in a length of sixteen 
+paces.  From the facts above given, it is not probable that these 
+worms could have been drowned, and if they had been drowned they 
+would have perished in their burrows.  I believe that they were 
+already sick, and that their deaths were merely hastened by the 
+ground being flooded.
+
+It has often been said that under ordinary circumstances healthy 
+worms never, or very rarely, completely leave their burrows at 
+night; but this is an error, as White of Selborne long ago knew.  
+In the morning, after there has been heavy rain, the film of mud or 
+of very fine sand over gravel-walks is often plainly marked with 
+their tracks.  I have noticed this from August to May, both months 
+included, and it probably occurs during the two remaining months of 
+the year when they are wet.  On these occasions, very few dead 
+worms could anywhere be seen.  On January 31, 1881, after a long-
+continued and unusually severe frost with much snow, as soon as a 
+thaw set in, the walks were marked with innumerable tracks.  On one 
+occasion, five tracks were counted crossing a space of only an inch 
+square.  They could sometimes be traced either to or from the 
+mouths of the burrows in the gravel-walks, for distances between 2 
+or 3 up to 15 yards.  I have never seen two tracks leading to the 
+same burrow; nor is it likely, from what we shall presently see of 
+their sense-organs, that a worm could find its way back to its 
+burrow after having once left it.  They apparently leave their 
+burrows on a voyage of discovery, and thus they find new sites to 
+inhabit.
+
+Morren states {12} that worms often lie for hours almost motionless 
+close beneath the mouths of their burrows.  I have occasionally 
+noticed the same fact with worms kept in pots in the house; so that 
+by looking down into their burrows, their heads could just be seen.  
+If the ejected earth or rubbish over the burrows be suddenly 
+removed, the end of the worm's body may very often be seen rapidly 
+retreating.  This habit of lying near the surface leads to their 
+destruction to an immense extent.  Every morning during certain 
+seasons of the year, the thrushes and blackbirds on all the lawns 
+throughout the country draw out of their holes an astonishing 
+number of worms, and this they could not do, unless they lay close 
+to the surface.  It is not probable that worms behave in this 
+manner for the sake of breathing fresh air, for we have seen that 
+they can live for a long time under water.  I believe that they lie 
+near the surface for the sake of warmth, especially in the morning; 
+and we shall hereafter find that they often coat the mouths of 
+their burrows with leaves, apparently to prevent their bodies from 
+coming into close contact with the cold damp earth.  It is said 
+that they completely close their burrows during the winter.
+
+Structure.--A few remarks must be made on this subject.  The body 
+of a large worm consists of from 100 to 200 almost cylindrical 
+rings or segments, each furnished with minute bristles.  The 
+muscular system is well developed.  Worms can crawl backwards as 
+well as forwards, and by the aid of their affixed tails can retreat 
+with extraordinary rapidity into their burrows.  The mouth is 
+situated at the anterior end of the body, and is provided with a 
+little projection (lobe or lip, as it has been variously called) 
+which is used for prehension.  Internally, behind the mouth, there 
+is a strong pharynx, shown in the accompanying diagram (Fig. 1) 
+which is pushed forwards when the animal eats, and this part 
+corresponds, according to Perrier, with the protrudable trunk or 
+proboscis of other annelids.  The pharynx leads into the 
+oesophagus, on each side of which in the lower part there are three 
+pairs of large glands, which secrete a surprising amount of 
+carbonate of lime.  These calciferous glands are highly remarkable, 
+for nothing like them is known in any other animal.  Their use will 
+be discussed when we treat of the digestive process.  In most of 
+the species, the oesophagus is enlarged into a crop in front of the 
+gizzard.  This latter organ is lined with a smooth thick chitinous 
+membrane, and is surrounded by weak longitudinal, but powerful 
+transverse muscles.  Perrier saw these muscles in energetic action; 
+and, as he remarks, the trituration of the food must be chiefly 
+effected by this organ, for worms possess no jaws or teeth of any 
+kind.  Grains of sand and small stones, from the 1/20 to a little 
+more than the 1/10 inch in diameter, may generally be found in 
+their gizzards and intestines.  As it is certain that worms swallow 
+many little stones, independently of those swallowed while 
+excavating their burrows, it is probable that they serve, like 
+mill-stones, to triturate their food.  The gizzard opens into the 
+intestine, which runs in a straight course to the vent at the 
+posterior end of the body.  The intestine presents a remarkable 
+structure, the typhlosolis, or, as the old anatomists called it, an 
+intestine within an intestine; and Claparede {13} has shown that 
+this consists of a deep longitudinal involution of the walls of the 
+intestine, by which means an extensive absorbent surface is gained.
+
+The circulatory system is well developed.  Worms breathe by their 
+skin, as they do not possess any special respiratory organs.  The 
+two sexes are united in the same individual, but two individuals 
+pair together.  The nervous system is fairly well developed; and 
+the two almost confluent cerebral ganglia are situated very near to 
+the anterior end of the body.
+
+Senses.--Worms are destitute of eyes, and at first I thought that 
+they were quite insensible to light; for those kept in confinement 
+were repeatedly observed by the aid of a candle, and others out of 
+doors by the aid of a lantern, yet they were rarely alarmed, 
+although extremely timid animals.  Other persons have found no 
+difficulty in observing worms at night by the same means. {14}
+
+Hoffmeister, however, states {15} that worms, with the exception of 
+a few individuals, are extremely sensitive to light; but he admits 
+that in most cases a certain time is requisite for its action.  
+These statements led me to watch on many successive nights worms 
+kept in pots, which were protected from currents of air by means of 
+glass plates.  The pots were approached very gently, in order that 
+no vibration of the floor should be caused.  When under these 
+circumstances worms were illuminated by a bull's-eye lantern having 
+slides of dark red and blue glass, which intercepted so much light 
+that they could be seen only with some difficulty, they were not at 
+all affected by this amount of light, however long they were 
+exposed to it.  The light, as far as I could judge, was brighter 
+than that from the full moon.  Its colour apparently made no 
+difference in the result.  When they were illuminated by a candle, 
+or even by a bright paraffin lamp, they were not usually affected 
+at first.  Nor were they when the light was alternately admitted 
+and shut off.  Sometimes, however, they behaved very differently, 
+for as soon as the light fell on them, they withdrew into their 
+burrows with almost instantaneous rapidity.  This occurred perhaps 
+once out of a dozen times.  When they did not withdraw instantly, 
+they often raised the anterior tapering ends of their bodies from 
+the ground, as if their attention was aroused or as if surprise was 
+felt; or they moved their bodies from side to side as if feeling 
+for some object.  They appeared distressed by the light; but I 
+doubt whether this was really the case, for on two occasions after 
+withdrawing slowly, they remained for a long time with their 
+anterior extremities protruding a little from the mouths of their 
+burrows, in which position they were ready for instant and complete 
+withdrawal.
+
+When the light from a candle was concentrated by means of a large 
+lens on the anterior extremity, they generally withdrew instantly; 
+but this concentrated light failed to act perhaps once out of half 
+a dozen trials.  The light was on one occasion concentrated on a 
+worm lying beneath water in a saucer, and it instantly withdrew 
+into its burrow.  In all cases the duration of the light, unless 
+extremely feeble, made a great difference in the result; for worms 
+left exposed before a paraffin lamp or a candle invariably 
+retreated into their burrows within from five to fifteen minutes; 
+and if in the evening the pots were illuminated before the worms 
+had come out of their burrows, they failed to appear.
+
+From the foregoing facts it is evident that light affects worms by 
+its intensity and by its duration.  It is only the anterior 
+extremity of the body, where the cerebral ganglia lie, which is 
+affected by light, as Hoffmeister asserts, and as I observed on 
+many occasions.  If this part is shaded, other parts of the body 
+may be fully illuminated, and no effect will be produced.  As these 
+animals have no eyes, we must suppose that the light passes through 
+their skins, and in some manner excites their cerebral ganglia.  It 
+appeared at first probable that the different manner in which they 
+were affected on different occasions might be explained, either by 
+the degree of extension of their skin and its consequent 
+transparency, or by some particular incident of the light; but I 
+could discover no such relation.  One thing was manifest, namely, 
+that when worms were employed in dragging leaves into their burrows 
+or in eating them, and even during the short intervals whilst they 
+rested from their work, they either did not perceive the light or 
+were regardless of it; and this occurred even when the light was 
+concentrated on them through a large lens.  So, again, whilst they 
+are paired, they will remain for an hour or two out of their 
+burrows, fully exposed to the morning light; but it appears from 
+what Hoffmeister says that a light will occasionally cause paired 
+individuals to separate.
+
+When a worm is suddenly illuminated and dashes like a rabbit into 
+its burrow--to use the expression employed by a friend--we are at 
+first led to look at the action as a reflex one.  The irritation of 
+the cerebral ganglia appears to cause certain muscles to contract 
+in an inevitable manner, independently of the will or consciousness 
+of the animal, as if it were an automaton.  But the different 
+effect which a light produced on different occasions, and 
+especially the fact that a worm when in any way employed and in the 
+intervals of such employment, whatever set of muscles and ganglia 
+may then have been brought into play, is often regardless of light, 
+are opposed to the view of the sudden withdrawal being a simple 
+reflex action.  With the higher animals, when close attention to 
+some object leads to the disregard of the impressions which other 
+objects must be producing on them, we attribute this to their 
+attention being then absorbed; and attention implies the presence 
+of a mind.  Every sportsman knows that he can approach animals 
+whilst they are grazing, fighting or courting, much more easily 
+than at other times.  The state, also, of the nervous system of the 
+higher animals differs much at different times, for instance, a 
+horse is much more readily startled at one time than at another.  
+The comparison here implied between the actions of one of the 
+higher animals and of one so low in the scale as an earth-worm, may 
+appear far-fetched; for we thus attribute to the worm attention and 
+some mental power, nevertheless I can see no reason to doubt the 
+justice of the comparison.
+
+Although worms cannot be said to possess the power of vision, their 
+sensitiveness to light enables them to distinguish between day and 
+night; and they thus escape extreme danger from the many diurnal 
+animals which prey on them.  Their withdrawal into their burrows 
+during the day appears, however, to have become an habitual action; 
+for worms kept in pots covered by glass plates, over which sheets 
+of black paper were spread, and placed before a north-east window, 
+remained during the day-time in their burrows and came out every 
+night; and they continued thus to act for a week.  No doubt a 
+little light may have entered between the sheets of glass and the 
+blackened paper; but we know from the trials with coloured glass, 
+that worms are indifferent to a small amount of light.
+
+Worms appear to be less sensitive to moderate radiant heat than to 
+a bright light.  I judge of this from having held at different 
+times a poker heated to dull redness near some worms, at a distance 
+which caused a very sensible degree of warmth in my hand.  One of 
+them took no notice; a second withdrew into its burrow, but not 
+quickly; the third and fourth much more quickly, and the fifth as 
+quickly as possible.  The light from a candle, concentrated by a 
+lens and passing through a sheet of glass which would intercept 
+most of the heat-rays, generally caused a much more rapid retreat 
+than did the heated poker.  Worms are sensitive to a low 
+temperature, as may be inferred from their not coming out of their 
+burrows during a frost.
+
+Worms do not possess any sense of hearing.  They took not the least 
+notice of the shrill notes from a metal whistle, which was 
+repeatedly sounded near them; nor did they of the deepest and 
+loudest tones of a bassoon.  They were indifferent to shouts, if 
+care was taken that the breath did not strike them.  When placed on 
+a table close to the keys of a piano, which was played as loudly as 
+possible, they remained perfectly quiet.
+
+Although they are indifferent to undulations in the air audible by 
+us, they are extremely sensitive to vibrations in any solid object.  
+When the pots containing two worms which had remained quite 
+indifferent to the sound of the piano, were placed on this 
+instrument, and the note C in the bass clef was struck, both 
+instantly retreated into their burrows.  After a time they emerged, 
+and when G above the line in the treble clef was struck they again 
+retreated.  Under similar circumstances on another night one worm 
+dashed into its burrow on a very high note being struck only once, 
+and the other worm when C in the treble clef was struck.  On these 
+occasions the worms were not touching the sides of the pots, which 
+stood in saucers; so that the vibrations, before reaching their 
+bodies, had to pass from the sounding board of the piano, through 
+the saucer, the bottom of the pot and the damp, not very compact 
+earth on which they lay with their tails in their burrows.  They 
+often showed their sensitiveness when the pot in which they lived, 
+or the table on which the pot stood, was accidentally and lightly 
+struck; but they appeared less sensitive to such jars than to the 
+vibrations of the piano; and their sensitiveness to jars varied 
+much at different times.
+
+It has often been said that if the ground is beaten or otherwise 
+made to tremble, worms believe that they are pursued by a mole and 
+leave their burrows.  From one account that I have received, I have 
+no doubt that this is often the case; but a gentleman informs me 
+that he lately saw eight or ten worms leave their burrows and crawl 
+about the grass on some boggy land on which two men had just 
+trampled while setting a trap; and this occurred in a part of 
+Ireland where there were no moles.  I have been assured by a 
+Volunteer that he has often seen many large earth-worms crawling 
+quickly about the grass, a few minutes after his company had fired 
+a volley with blank cartridges.  The Peewit (Tringa vanellus, 
+Linn.) seems to know instinctively that worms will emerge if the 
+ground is made to tremble; for Bishop Stanley states (as I hear 
+from Mr. Moorhouse) that a young peewit kept in confinement used to 
+stand on one leg and beat the turf with the other leg until the 
+worms crawled out of their burrows, when they were instantly 
+devoured.  Nevertheless, worms do not invariably leave their 
+burrows when the ground is made to tremble, as I know by having 
+beaten it with a spade, but perhaps it was beaten too violently.
+
+The whole body of a worm is sensitive to contact.  A slight puff of 
+air from the mouth causes an instant retreat.  The glass plates 
+placed over the pots did not fit closely, and blowing through the 
+very narrow chinks thus left, often sufficed to cause a rapid 
+retreat.  They sometimes perceived the eddies in the air caused by 
+quickly removing the glass plates.  When a worm first comes out of 
+its burrow, it generally moves the much extended anterior extremity 
+of its body from side to side in all directions, apparently as an 
+organ of touch; and there is some reason to believe, as we shall 
+see in the next chapter, that they are thus enabled to gain a 
+general notion of the form of an object.  Of all their senses that 
+of touch, including in this term the perception of a vibration, 
+seems much the most highly developed.
+
+In worms the sense of smell apparently is confined to the 
+perception of certain odours, and is feeble.  They were quite 
+indifferent to my breath, as long as I breathed on them very 
+gently.  This was tried, because it appeared possible that they 
+might thus be warned of the approach of an enemy.  They exhibited 
+the same indifference to my breath whilst I chewed some tobacco, 
+and while a pellet of cotton-wool with a few drops of millefleurs 
+perfume or of acetic acid was kept in my mouth.  Pellets of cotton-
+wool soaked in tobacco juice, in millefleurs perfume, and in 
+paraffin, were held with pincers and were waved about within two or 
+three inches of several worms, but they took no notice.  On one or 
+two occasions, however, when acetic acid had been placed on the 
+pellets, the worms appeared a little uneasy, and this was probably 
+due to the irritation of their skins.  The perception of such 
+unnatural odours would be of no service to worms; and as such timid 
+creatures would almost certainly exhibit some signs of any new 
+impression, we may conclude that they did not perceive these 
+odours.
+
+The result was different when cabbage-leaves and pieces of onion 
+were employed, both of which are devoured with much relish by 
+worms.  Small square pieces of fresh and half-decayed cabbage-
+leaves and of onion bulbs were on nine occasions buried in my pots, 
+beneath about 0.25 of an inch of common garden soil; and they were 
+always discovered by the worms.  One bit of cabbage was discovered 
+and removed in the course of two hours; three were removed by the 
+next morning, that is, after a single night; two others after two 
+nights; and the seventh bit after three nights.  Two pieces of 
+onion were discovered and removed after three nights.  Bits of 
+fresh raw meat, of which worms are very fond, were buried, and were 
+not discovered within forty-eight hours, during which time they had 
+not become putrid.  The earth above the various buried objects was 
+generally pressed down only slightly, so as not to prevent the 
+emission of any odour.  On two occasions, however, the surface was 
+well watered, and was thus rendered somewhat compact.  After the 
+bits of cabbage and onion had been removed, I looked beneath them 
+to see whether the worms had accidentally come up from below, but 
+there was no sign of a burrow; and twice the buried objects were 
+laid on pieces of tin-foil which were not in the least displaced.  
+It is of course possible that the worms whilst moving about on the 
+surface of the ground, with their tails affixed within their 
+burrows, may have poked their heads into the places where the above 
+objects were buried; but I have never seen worms acting in this 
+manner.  Some pieces of cabbage-leaf and of onion were twice buried 
+beneath very fine ferruginous sand, which was slightly pressed down 
+and well watered, so as to be rendered very compact, and these 
+pieces were never discovered.  On a third occasion the same kind of 
+sand was neither pressed down nor watered, and the pieces of 
+cabbage were discovered and removed after the second night.  These 
+several facts indicate that worms possess some power of smell; and 
+that they discover by this means odoriferous and much-coveted kinds 
+of food.
+
+It may be presumed that all animals which feed on various 
+substances possess the sense of taste, and this is certainly the 
+case with worms.  Cabbage-leaves are much liked by worms; and it 
+appears that they can distinguish between different varieties; but 
+this may perhaps be owing to differences in their texture.  On 
+eleven occasions pieces of the fresh leaves of a common green 
+variety and of the red variety used for pickling were given them, 
+and they preferred the green, the red being either wholly neglected 
+or much less gnawed.  On two other occasions, however, they seemed 
+to prefer the red.  Half-decayed leaves of the red variety and 
+fresh leaves of the green were attacked about equally.  When leaves 
+of the cabbage, horse-radish (a favourite food) and of the onion 
+were given together, the latter were always, and manifestly 
+preferred.  Leaves of the cabbage, lime-tree, Ampelopsis, parsnip 
+(Pastinaca), and celery (Apium) were likewise given together; and 
+those of the celery were first eaten.  But when leaves of cabbage, 
+turnip, beet, celery, wild cherry and carrots were given together, 
+the two latter kinds, especially those of the carrot, were 
+preferred to all the others, including those of celery.  It was 
+also manifest after many trials that wild cherry leaves were 
+greatly preferred to those of the lime-tree and hazel (Corylus).  
+According to Mr. Bridgman the half-decayed leaves of Phlox verna 
+are particularly liked by worms. {16}
+
+Pieces of the leaves of cabbage, turnip, horse-radish and onion 
+were left on the pots during 22 days, and were all attacked and had 
+to be renewed; but during the whole of this time leaves of an 
+Artemisia and of the culinary sage, thyme and mint, mingled with 
+the above leaves, were quite neglected excepting those of the mint, 
+which were occasionally and very slightly nibbled.  These latter 
+four kinds of leaves do not differ in texture in a manner which 
+could make them disagreeable to worms; they all have a strong 
+taste, but so have the four first mentioned kinds of leaves; and 
+the wide difference in the result must be attributed to a 
+preference by the worms for one taste over another.
+
+Mental Qualities.--There is little to be said on this head.  We 
+have seen that worms are timid.  It may be doubted whether they 
+suffer as much pain when injured, as they seem to express by their 
+contortions.  Judging by their eagerness for certain kinds of food, 
+they must enjoy the pleasure of eating.  Their sexual passion is 
+strong enough to overcome for a time their dread of light.  They 
+perhaps have a trace of social feeling, for they are not disturbed 
+by crawling over each other's bodies, and they sometimes lie in 
+contact.  According to Hoffmeister they pass the winter either 
+singly or rolled up with others into a ball at the bottom of their 
+burrows. {17}  Although worms are so remarkably deficient in the 
+several sense-organs, this does not necessarily preclude 
+intelligence, as we know from such cases as those of Laura 
+Bridgman; and we have seen that when their attention is engaged, 
+they neglect impressions to which they would otherwise have 
+attended; and attention indicates the presence of a mind of some 
+kind.  They are also much more easily excited at certain times than 
+at others.  They perform a few actions instinctively, that is, all 
+the individuals, including the young, perform such actions in 
+nearly the same fashion.  This is shown by the manner in which the 
+species of Perichaeta eject their castings, so as to construct 
+towers; also by the manner in which the burrows of the common 
+earth-worm are smoothly lined with fine earth and often with little 
+stones, and the mouths of their burrows with leaves.  One of their 
+strongest instincts is the plugging up the mouths of their burrows 
+with various objects; and very young worms act in this manner.  But 
+some degree of intelligence appears, as we shall see in the next 
+chapter, to be exhibited in this work,--a result which has 
+surprised me more than anything else in regard to worms.
+
+Food and Digestion.--Worms are omnivorous.  They swallow an 
+enormous quantity of earth, out of which they extract any 
+digestible matter which it may contain; but to this subject I must 
+recur.  They also consume a large number of half-decayed leaves of 
+all kinds, excepting a few which have an unpleasant taste or are 
+too tough for them; likewise petioles, peduncles, and decayed 
+flowers.  But they will also consume fresh leaves, as I have found 
+by repeated trials.  According to Morren {18} they will eat 
+particles of sugar and liquorice; and the worms which I kept drew 
+many bits of dry starch into their burrows, and a large bit had its 
+angles well rounded by the fluid poured out of their mouths.  But 
+as they often drag particles of soft stone, such as of chalk, into 
+their burrows, I feel some doubt whether the starch was used as 
+food.  Pieces of raw and roasted meat were fixed several times by 
+long pins to the surface of the soil in my pots, and night after 
+night the worms could be seen tugging at them, with the edges of 
+the pieces engulfed in their mouths, so that much was consumed.  
+Raw fat seems to be preferred even to raw meat or to any other 
+substance which was given them, and much was consumed.  They are 
+cannibals, for the two halves of a dead worm placed in two of the 
+pots were dragged into the burrows and gnawed; but as far as I 
+could judge, they prefer fresh to putrid meat, and in so far I 
+differ from Hoffmeister.
+
+Leon Fredericq states {19} that the digestive fluid of worms is of 
+the same nature as the pancreatic secretion of the higher animals; 
+and this conclusion agrees perfectly with the kinds of food which 
+worms consume.  Pancreatic juice emulsifies fat, and we have just 
+seen how greedily worms devour fat; it dissolves fibrin, and worms 
+eat raw meat; it converts starch into grape-sugar with wonderful 
+rapidity, and we shall presently show that the digestive fluid of 
+worms acts on starch. {20}  But they live chiefly on half-decayed 
+leaves; and these would be useless to them unless they could digest 
+the cellulose forming the cell-walls; for it is well known that all 
+other nutritious substances are almost completely withdrawn from 
+leaves, shortly before they fall off.  It has, however, now been 
+ascertained that some forms of cellulose, though very little or not 
+at all attacked by the gastric secretion of the higher animals, are 
+acted on by that from the pancreas. {21}
+
+The half-decayed or fresh leaves which worms intend to devour, are 
+dragged into the mouths of their burrows to a depth of from one to 
+three inches, and are then moistened with a secreted fluid.  It has 
+been assumed that this fluid serves to hasten their decay; but a 
+large number of leaves were twice pulled out of the burrows of 
+worms and kept for many weeks in a very moist atmosphere under a 
+bell-glass in my study; and the parts which had been moistened by 
+the worms did not decay more quickly in any plain manner than the 
+other parts.  When fresh leaves were given in the evening to worms 
+kept in confinement and examined early on the next morning, 
+therefore not many hours after they had been dragged into the 
+burrows, the fluid with which they were moistened, when tested with 
+neutral litmus paper, showed an alkaline reaction.  This was 
+repeatedly found to be the case with celery, cabbage and turnip 
+leaves.  Parts of the same leaves which had not been moistened by 
+the worms, were pounded with a few drops of distilled water, and 
+the juice thus extracted was not alkaline.  Some leaves, however, 
+which had been drawn into burrows out of doors, at an unknown 
+antecedent period, were tried, and though still moist, they rarely 
+exhibited even a trace of alkaline reaction.
+
+The fluid, with which the leaves are bathed, acts on them whilst 
+they are fresh or nearly fresh, in a remarkable manner; for it 
+quickly kills and discolours them.  Thus the ends of a fresh 
+carrot-leaf, which had been dragged into a burrow, were found after 
+twelve hours of a dark brown tint.  Leaves of celery, turnip, 
+maple, elm, lime, thin leaves of ivy, and, occasionally those of 
+the cabbage were similarly acted on.  The end of a leaf of Triticum 
+repens, still attached to a growing plant, had been drawn into a 
+burrow, and this part was dark brown and dead, whilst the rest of 
+the leaf was fresh and green.  Several leaves of lime and elm 
+removed from burrows out of doors were found affected in different 
+degrees.  The first change appears to be that the veins become of a 
+dull reddish-orange.  The cells with chlorophyll next lose more or 
+less completely their green colour, and their contents finally 
+become brown.  The parts thus affected often appeared almost black 
+by reflected light; but when viewed as a transparent object under 
+the microscope, minute specks of light were transmitted, and this 
+was not the case with the unaffected parts of the same leaves.  
+These effects, however, merely show that the secreted fluid is 
+highly injurious or poisonous to leaves; for nearly the same 
+effects were produced in from one to two days on various kinds of 
+young leaves, not only by artificial pancreatic fluid, prepared 
+with or without thymol, but quickly by a solution of thymol by 
+itself.  On one occasion leaves of Corylus were much discoloured by 
+being kept for eighteen hours in pancreatic fluid, without any 
+thymol.  With young and tender leaves immersion in human saliva 
+during rather warm weather, acted in the same manner as the 
+pancreatic fluid, but not so quickly.  The leaves in all these 
+cases often became infiltrated with the fluid.
+
+Large leaves from an ivy plant growing on a wall were so tough that 
+they could not be gnawed by worms, but after four days they were 
+affected in a peculiar manner by the secretion poured out of their 
+mouths.  The upper surfaces of the leaves, over which the worms had 
+crawled, as was shown by the dirt left on them, were marked in 
+sinuous lines, by either a continuous or broken chain of whitish 
+and often star-shaped dots, about 2 mm. in diameter.  The 
+appearance thus presented was curiously like that of a leaf, into 
+which the larva of some minute insect had burrowed.  But my son 
+Francis, after making and examining sections, could nowhere find 
+that the cell-walls had been broken down or that the epidermis had 
+been penetrated.  When the section passed through the whitish dots, 
+the grains of chlorophyll were seen to be more or less discoloured, 
+and some of the palisade and mesophyll cells contained nothing but 
+broken down granular matter.  These effects must be attributed to 
+the transudation of the secretion through the epidermis into the 
+cells.
+
+The secretion with which worms moisten leaves likewise acts on the 
+starch-granules within the cells.  My son examined some leaves of 
+the ash and many of the lime, which had fallen off the trees and 
+had been partly dragged into worm-burrows.  It is known that with 
+fallen leaves the starch-grains are preserved in the guard-cells of 
+the stomata.  Now in several cases the starch had partially or 
+wholly disappeared from these cells, in the parts which had been 
+moistened by the secretion; while it was still well preserved in 
+the other parts of the same leaves.  Sometimes the starch was 
+dissolved out of only one of the two guard-cells.  The nucleus in 
+one case had disappeared, together with the starch-granules.  The 
+mere burying of lime-leaves in damp earth for nine days did not 
+cause the destruction of the starch-granules.  On the other hand, 
+the immersion of fresh lime and cherry leaves for eighteen hours in 
+artificial pancreatic fluid, led to the dissolution of the starch-
+granules in the guard-cells as well as in the other cells.
+
+From the secretion with which the leaves are moistened being 
+alkaline, and from its acting both on the starch-granules and on 
+the protoplasmic contents of the cells, we may infer that it 
+resembles in nature not saliva, {22} but pancreatic secretion; and 
+we know from Fredericq that a secretion of this kind is found in 
+the intestines of worms.  As the leaves which are dragged into the 
+burrows are often dry and shrivelled, it is indispensable for their 
+disintegration by the unarmed mouths of worms that they should 
+first be moistened and softened; and fresh leaves, however soft and 
+tender they may be, are similarly treated, probably from habit.  
+The result is that they are partially digested before they are 
+taken into the alimentary canal.  I am not aware of any other case 
+of extra-stomachal digestion having been recorded.  The boa-
+constrictor is said to bathe its prey with saliva, but this is 
+doubtful; and it is done solely for the sake of lubricating its 
+prey.  Perhaps the nearest analogy may be found in such plants as 
+Drosera and Dionaea; for here animal matter is digested and 
+converted into peptone not within a stomach, but on the surfaces of 
+the leaves.
+
+Calciferous Glands.--These glands (see Fig. 1), judging from their 
+size and from their rich supply of blood-vessels, must be of much 
+importance to the animal.  But almost as many theories have been 
+advanced on their use as there have been observers.  They consist 
+of three pairs, which in the common earth-worm debouch into the 
+alimentary canal in advance of the gizzard, but posteriorly to it 
+in Urochaeta and some other genera. {23}  The two posterior pairs 
+are formed by lamellae, which, according to Claparede, are 
+diverticula from the oesophagus. {24}  These lamellae are coated 
+with a pulpy cellular layer, with the outer cells lying free in 
+infinite numbers.  If one of these glands is punctured and 
+squeezed, a quantity of white pulpy matter exudes, consisting of 
+these free cells.  They are minute, and vary in diameter from 2 to 
+6 microns.  They contain in their centres a little excessively fine 
+granular matter; but they look so like oil globules that Claparede 
+and others at first treated them with ether.  This produces no 
+effect; but they are quickly dissolved with effervescence in acetic 
+acid, and when oxalate of ammonia is added to the solution a white 
+precipitate is thrown down.  We may therefore conclude that they 
+contain carbonate of lime.  If the cells are immersed in a very 
+little acid, they become more transparent, look like ghosts, and 
+are soon lost to view; but if much acid is added, they disappear 
+instantly.  After a very large number have been dissolved, a 
+flocculent residue is left, which apparently consists of the 
+delicate ruptured cell-walls.  In the two posterior pairs of glands 
+the carbonate of lime contained in the cells occasionally 
+aggregates into small rhombic crystals or into concretions, which 
+lie between the lamellae; but I have seen only one case, and 
+Claparede only a very few such cases.
+
+The two anterior glands differ a little in shape from the four 
+posterior ones, by being more oval.  They differ also conspicuously 
+in generally containing several small, or two or three larger, or a 
+single very large concretion of carbonate of lime, as much as 1.5 
+mm. in diameter.  When a gland includes only a few very small 
+concretions, or, as sometimes happens, none at all, it is easily 
+overlooked.  The large concretions are round or oval, and 
+exteriorly almost smooth.  One was found which filled up not only 
+the whole gland, as is often the case, but its neck; so that it 
+resembled an olive-oil flask in shape.  These concretions when 
+broken are seen to be more or less crystalline in structure.  How 
+they escape from the gland is a marvel; but that they do escape is 
+certain, for they are often found in the gizzard, intestines, and 
+in the castings of worms, both with those kept in confinement and 
+those in a state of nature.
+
+Claparede says very little about the structure of the two anterior 
+glands, and he supposes that the calcareous matter of which the 
+concretions are formed is derived from the four posterior glands.  
+But if an anterior gland which contains only small concretions is 
+placed in acetic acid and afterwards dissected, or if sections are 
+made of such a gland without being treated with acid, lamellae like 
+those in the posterior glands and coated with cellular matter could 
+be plainly seen, together with a multitude of free calciferous 
+cells readily soluble in acetic acid.  When a gland is completely 
+filled with a single large concretion, there are no free cells, as 
+these have been all consumed in forming the concretion.  But if 
+such a concretion, or one of only moderately large size, is 
+dissolved in acid, much membranous matter is left, which appears to 
+consist of the remains of the formerly active lamellae.  After the 
+formation and expulsion of a large concretion, new lamellae must be 
+developed in some manner.  In one section made by my son, the 
+process had apparently commenced, although the gland contained two 
+rather large concretions, for near the walls several cylindrical 
+and oval pipes were intersected, which were lined with cellular 
+matter and were quite filled with free calciferous cells.  A great 
+enlargement in one direction of several oval pipes would give rise 
+to the lamellae.
+
+Besides the free calciferous cells in which no nucleus was visible, 
+other and rather larger free cells were seen on three occasions; 
+and these contained a distinct nucleus and nucleolus.  They were 
+only so far acted on by acetic acid that the nucleus was thus 
+rendered more distinct.  A very small concretion was removed from 
+between two of the lamellae within an anterior gland.  It was 
+imbedded in pulpy cellular matter, with many free calciferous 
+cells, together with a multitude of the larger, free, nucleated 
+cells, and these latter cells were not acted on by acetic acid, 
+while the former were dissolved.  From this and other such cases I 
+am led to suspect that the calciferous cells are developed from the 
+larger nucleated ones; but how this was effected was not 
+ascertained.
+
+When an anterior gland contains several minute concretions, some of 
+these are generally angular or crystalline in outline, while the 
+greater number are rounded with an irregular mulberry-like surface.  
+Calciferous cells adhered to many parts of these mulberry-like 
+masses, and their gradual disappearance could be traced while they 
+still remained attached.  It was thus evident that the concretions 
+are formed from the lime contained within the free calciferous 
+cells.  As the smaller concretions increase in size, they come into 
+contact and unite, thus enclosing the now functionless lamellae; 
+and by such steps the formation of the largest concretions could be 
+followed.  Why the process regularly takes place in the two 
+anterior glands, and only rarely in the four posterior glands, is 
+quite unknown.  Morren says that these glands disappear during the 
+winter; and I have seen some instances of this fact, and others in 
+which either the anterior or posterior glands were at this season 
+so shrunk and empty, that they could be distinguished only with 
+much difficulty.
+
+With respect to the function of the calciferous glands, it is 
+probable that they primarily serve as organs of excretion, and 
+secondarily as an aid to digestion.  Worms consume many fallen 
+leaves; and it is known that lime goes on accumulating in leaves 
+until they drop off the parent-plant, instead of being re-absorbed 
+into the stem or roots, like various other organic and inorganic 
+substances. {25}  The ashes of a leaf of an acacia have been known 
+to contain as much as 72 per cent. of lime.  Worms therefore would 
+be liable to become charged with this earth, unless there were some 
+special means for its excretion; and the calciferous glands are 
+well adapted for this purpose.  The worms which live in mould close 
+over the chalk, often have their intestines filled with this 
+substance, and their castings are almost white.  Here it is evident 
+that the supply of calcareous matter must be super-abundant.  
+Nevertheless with several worms collected on such a site, the 
+calciferous glands contained as many free calciferous cells, and 
+fully as many and large concretions, as did the glands of worms 
+which lived where there was little or no lime; and this indicates 
+that the lime is an excretion, and not a secretion poured into the 
+alimentary canal for some special purpose.
+
+On the other hand, the following considerations render it highly 
+probable that the carbonate of lime, which is excreted by the 
+glands, aids the digestive process under ordinary circumstances.  
+Leaves during their decay generate an abundance of various kinds of 
+acids, which have been grouped together under the term of humus 
+acids.  We shall have to recur to this subject in our fifth 
+chapter, and I need here only say that these acids act strongly on 
+carbonate of lime.  The half-decayed leaves which are swallowed in 
+such large quantities by worms would, therefore, after they have 
+been moistened and triturated in the alimentary canal, be apt to 
+produce such acids.  And in the case of several worms, the contents 
+of the alimentary canal were found to be plainly acid, as shown by 
+litmus paper.  This acidity cannot be attributed to the nature of 
+the digestive fluid, for pancreatic fluid is alkaline; and we have 
+seen that the secretion which is poured out of the mouths of worms 
+for the sake of preparing the leaves for consumption, is likewise 
+alkaline.  The acidity can hardly be due to uric acid, as the 
+contents of the upper part of the intestine were often acid.  In 
+one case the contents of the gizzard were slightly acid, those of 
+the upper intestines being more plainly acid.  In another case the 
+contents of the pharynx were not acid, those of the gizzard 
+doubtfully so, while those of the intestine were distinctly acid at 
+a distance of 5 cm. below the gizzard.  Even with the higher 
+herbivorous and omnivorous animals, the contents of the large 
+intestine are acid.  "This, however, is not caused by any acid 
+secretion from the mucous membrane; the reaction of the intestinal 
+walls in the larger as in the small intestine is alkaline.  It must 
+therefore arise from acid fermentations going on in the contents 
+themselves . . .  In Carnivora the contents of the coecum are said 
+to be alkaline, and naturally the amount of fermentation will 
+depend largely on the nature of the food." {26}
+
+With worms not only the contents of the intestines, but their 
+ejected matter or the castings, are generally acid.  Thirty 
+castings from different places were tested, and with three or four 
+exceptions were found to be acid; and the exceptions may have been 
+due to such castings not having been recently ejected; for some 
+which were at first acid, were on the following morning, after 
+being dried and again moistened, no longer acid; and this probably 
+resulted from the humus acids being, as is known to be the case, 
+easily decomposed.  Five fresh castings from worms which lived in 
+mould close over the chalk, were of a whitish colour and abounded 
+with calcareous matter; and these were not in the least acid.  This 
+shows how effectually carbonate of lime neutralises the intestinal 
+acids.  When worms were kept in pots filled with fine ferruginous 
+sand, it was manifest that the oxide of iron, with which the grains 
+of silex were coated, had been dissolved and removed from them in 
+the castings.
+
+The digestive fluid of worms resembles in its action, as already 
+stated, the pancreatic secretion of the higher animals; and in 
+these latter, "pancreatic digestion is essentially alkaline; the 
+action will not take place unless some alkali be present; and the 
+activity of an alkaline juice is arrested by acidification, and 
+hindered by neutralization." {27}  Therefore it seems highly 
+probable that the innumerable calciferous cells, which are poured 
+from the four posterior glands into the alimentary canal of worms, 
+serve to neutralise more or less completely the acids there 
+generated by the half-decayed leaves.  We have seen that these 
+cells are instantly dissolved by a small quantity of acetic acid, 
+and as they do not always suffice to neutralise the contents of 
+even the upper part of the alimentary canal, the lime is perhaps 
+aggregated into concretions in the anterior pair of glands, in 
+order that some may be carried down to the posterior parts of the 
+intestine, where these concretions would be rolled about amongst 
+the acid contents.  The concretions found in the intestines and in 
+the castings often have a worn appearance, but whether this is due 
+to some amount of attrition or of chemical corrosion could not be 
+told.  Claparede believes that they are formed for the sake of 
+acting as mill-stones, and of thus aiding in the trituration of the 
+food.  They may give some aid in this way; but I fully agree with 
+Perrier that this must be of quite subordinate importance, seeing 
+that the object is already attained by stones being generally 
+present in the gizzards and intestines of worms.
+
+
+
+CHAPTER II--HABITS OF WORMS--continued.
+
+
+
+Manner in which worms seize objects--Their power of suction--The 
+instinct of plugging up the mouths of their burrows--Stones piled 
+over the burrows--The advantages thus gained--Intelligence shown by 
+worms in their manner of plugging up their burrows--Various kinds 
+of leaves and other objects thus used--Triangles of paper--Summary 
+of reasons for believing that worms exhibit some intelligence--
+Means by which they excavate their burrows, by pushing away the 
+earth and swallowing it--Earth also swallowed for the nutritious 
+matter which it contains--Depth to which worms burrow, and the 
+construction of their burrows--Burrows lined with castings, and in 
+the upper part with leaves--The lowest part paved with little 
+stones or seeds--Manner in which the castings are ejected--The 
+collapse of old burrows--Distribution of worms--Tower-like castings 
+in Bengal--Gigantic castings on the Nilgiri Mountains--Castings 
+ejected in all countries.
+
+
+In the pots in which worms were kept, leaves were pinned down to 
+the soil, and at night the manner in which they were seized could 
+be observed.  The worms always endeavoured to drag the leaves 
+towards their burrows; and they tore or sucked off small fragments, 
+whenever the leaves were sufficiently tender.  They generally 
+seized the thin edge of a leaf with their mouths, between the 
+projecting upper and lower lip; the thick and strong pharynx being 
+at the same time, as Perrier remarks, pushed forward within their 
+bodies, so as to afford a point of resistance for the upper lip.  
+In the case of broad flat objects they acted in a wholly different 
+manner.  The pointed anterior extremity of the body, after being 
+brought into contact with an object of this kind, was drawn within 
+the adjoining rings, so that it appeared truncated and became as 
+thick as the rest of the body.  This part could then be seen to 
+swell a little; and this, I believe, is due to the pharynx being 
+pushed a little forwards.  Then by a slight withdrawal of the 
+pharynx or by its expansion, a vacuum was produced beneath the 
+truncated slimy end of the body whilst in contact with the object; 
+and by this means the two adhered firmly together. {28}  That under 
+these circumstances a vacuum was produced was plainly seen on one 
+occasion, when a large worm lying beneath a flaccid cabbage leaf 
+tried to drag it away; for the surface of the leaf directly over 
+the end of the worm's body became deeply pitted.  On another 
+occasion a worm suddenly lost its hold on a flat leaf; and the 
+anterior end of the body was momentarily seen to be cup-formed.  
+Worms can attach themselves to an object beneath water in the same 
+manner; and I saw one thus dragging away a submerged slice of an 
+onion-bulb.
+
+The edges of fresh or nearly fresh leaves affixed to the ground 
+were often nibbled by the worms; and sometimes the epidermis and 
+all the parenchyma on one side was gnawed completely away over a 
+considerable space; the epidermis alone on the opposite side being 
+left quite clean.  The veins were never touched, and leaves were 
+thus sometimes partly converted into skeletons.  As worms have no 
+teeth and as their mouths consist of very soft tissue, it may be 
+presumed that they consume by means of suction the edges and the 
+parenchyma of fresh leaves, after they have been softened by the 
+digestive fluid.  They cannot attack such strong leaves as those of 
+sea-kale or large and thick leaves of ivy; though one of the latter 
+after it had become rotten was reduced in parts to the state of a 
+skeleton.
+
+Worms seize leaves and other objects, not only to serve as food, 
+but for plugging up the mouths of their burrows; and this is one of 
+their strongest instincts.  They sometimes work so energetically 
+that Mr. D. F. Simpson, who has a small walled garden where worms 
+abound in Bayswater, informs me that on a calm damp evening he 
+there heard so extraordinary a rustling noise from under a tree 
+from which many leaves had fallen, that he went out with a light 
+and discovered that the noise was caused by many worms dragging the 
+dry leaves and squeezing them into the burrows.  Not only leaves, 
+but petioles of many kinds, some flower-peduncles, often decayed 
+twigs of trees, bits of paper, feathers, tufts of wool and horse-
+hairs are dragged into their burrows for this purpose.  I have seen 
+as many as seventeen petioles of a Clematis projecting from the 
+mouth of one burrow, and ten from the mouth of another.  Some of 
+these objects, such as the petioles just named, feathers, &c., are 
+never gnawed by worms.  In a gravel-walk in my garden I found many 
+hundred leaves of a pine-tree (P. austriaca or nigricans) drawn by 
+their bases into burrows.  The surfaces by which these leaves are 
+articulated to the branches are shaped in as peculiar a manner as 
+is the joint between the leg-bones of a quadruped; and if these 
+surfaces had been in the least gnawed, the fact would have been 
+immediately visible, but there was no trace of gnawing.  Of 
+ordinary dicotyledonous leaves, all those which are dragged into 
+burrows are not gnawed.  I have seen as many as nine leaves of the 
+lime-tree drawn into the same burrow, and not nearly all of them 
+had been gnawed; but such leaves may serve as a store for future 
+consumption.  Where fallen leaves are abundant, many more are 
+sometimes collected over the mouth of a burrow than can be used, so 
+that a small pile of unused leaves is left like a roof over those 
+which have been partly dragged in.
+
+A leaf in being dragged a little way into a cylindrical burrow is 
+necessarily much folded or crumpled.  When another leaf is drawn 
+in, this is done exteriorly to the first one, and so on with the 
+succeeding leaves; and finally all become closely folded and 
+pressed together.  Sometimes the worm enlarges the mouth of its 
+burrow, or makes a fresh one close by, so as to draw in a still 
+larger number of leaves.  They often or generally fill up the 
+interstices between the drawn-in leaves with moist viscid earth 
+ejected from their bodies; and thus the mouths of the burrows are 
+securely plugged.  Hundreds of such plugged burrows may be seen in 
+many places, especially during the autumnal and early winter 
+months.  But, as will hereafter be shown, leaves are dragged into 
+the burrows not only for plugging them up and for food, but for the 
+sake of lining the upper part or mouth.
+
+When worms cannot obtain leaves, petioles, sticks, &c., with which 
+to plug up the mouths of their burrows, they often protect them by 
+little heaps of stones; and such heaps of smooth rounded pebbles 
+may frequently be seen on gravel-walks.  Here there can be no 
+question about food.  A lady, who was interested in the habits of 
+worms, removed the little heaps of stones from the mouths of 
+several burrows and cleared the surface of the ground for some 
+inches all round.  She went out on the following night with a 
+lantern, and saw the worms with their tails fixed in their burrows, 
+dragging the stones inwards by the aid of their mouths, no doubt by 
+suction.  "After two nights some of the holes had 8 or 9 small 
+stones over them; after four nights one had about 30, and another 
+34 stones." {29}  One stone--which had been dragged over the 
+gravel-walk to the mouth of a burrow weighed two ounces; and this 
+proves how strong worms are.  But they show greater strength in 
+sometimes displacing stones in a well-trodden gravel-walk; that 
+they do so, may be inferred from the cavities left by the displaced 
+stones being exactly filled by those lying over the mouths of 
+adjoining burrows, as I have myself observed.
+
+Work of this kind is usually performed during the night; but I have 
+occasionally known objects to be drawn into the burrows during the 
+day.  What advantage the worms derive from plugging up the mouths 
+of their burrows with leaves, &c., or from piling stones over them, 
+is doubtful.  They do not act in this manner at the times when they 
+eject much earth from their burrows; for their castings then serve 
+to cover the mouths.  When gardeners wish to kill worms on a lawn, 
+it is necessary first to brush or rake away the castings from the 
+surface, in order that the lime-water may enter the burrows. {30}  
+It might be inferred from this fact that the mouths are plugged up 
+with leaves, &c., to prevent the entrance of water during heavy 
+rain; but it may be urged against this view that a few, loose, 
+well-rounded stones are ill-adapted to keep out water.  I have 
+moreover seen many burrows in the perpendicularly cut turf-edgings 
+to gravel-walks, into which water could hardly flow, as well 
+plugged as burrows on a level surface.  It is not probable that the 
+plugs or piles of stones serve to conceal the burrows from 
+scolopendras, which, according to Hoffmeister, {31} are the 
+bitterest enemies of worms, or from the larger species of Carabus 
+and Staphylinus which attack them ferociously, for these animals 
+are nocturnal, and the burrows are opened at night.  May not worms 
+when the mouth of the burrow is protected be able to remain with 
+safety with their heads close to it, which we know that they like 
+to do, but which costs so many of them their lives?  Or may not the 
+plugs check the free ingress of the lowest stratum of air, when 
+chilled by radiation at night, from the surrounding ground and 
+herbage?  I am inclined to believe in this latter view:  firstly, 
+because when worms were kept in pots in a room with a fire, in 
+which case cold air could not enter the burrows, they plugged them 
+up in a slovenly manner; and secondarily, because they often coat 
+the upper part of their burrows with leaves, apparently to prevent 
+their bodies from coming into close contact with the cold damp 
+earth.  Mr. E. Parfitt has suggested to me that the mouths of the 
+burrows are closed in order that the air within them may be kept 
+thoroughly damp, and this seems the most probable explanation of 
+the habit.  But the plugging-up process may serve for all the above 
+purposes.
+
+Whatever the motive may be, it appears that worms much dislike 
+leaving the mouths of their burrows open.  Nevertheless they will 
+reopen them at night, whether or not they can afterwards close 
+them.  Numerous open burrows may be seen on recently-dug ground, 
+for in this case the worms eject their castings in cavities left in 
+the ground, or in the old burrows instead of piling them over the 
+mouths of their burrows, and they cannot collect objects on the 
+surface by which the mouths might be protected.  So again on a 
+recently disinterred pavement of a Roman villa at Abinger 
+(hereafter to be described) the worms pertinaciously opened their 
+burrows almost every night, when these had been closed by being 
+trampled on, although they were rarely able to find a few minute 
+stones wherewith to protect them.
+
+Intelligence shown by worms in their manner of plugging up their 
+burrows.--If a man had to plug up a small cylindrical hole, with 
+such objects as leaves, petioles or twigs, he would drag or push 
+them in by their pointed ends; but if these objects were very thin 
+relatively to the size of the hole, he would probably insert some 
+by their thicker or broader ends.  The guide in his case would be 
+intelligence.  It seemed therefore worth while to observe carefully 
+how worms dragged leaves into their burrows; whether by their tips 
+or bases or middle parts.  It seemed more especially desirable to 
+do this in the case of plants not natives to our country; for 
+although the habit of dragging leaves into their burrows is 
+undoubtedly instinctive with worms, yet instinct could not tell 
+them how to act in the case of leaves about which their progenitors 
+knew nothing.  If, moreover, worms acted solely through instinct or 
+an unvarying inherited impulse, they would draw all kinds of leaves 
+into their burrows in the same manner.  If they have no such 
+definite instinct, we might expect that chance would determine 
+whether the tip, base or middle was seized.  If both these 
+alternatives are excluded, intelligence alone is left; unless the 
+worm in each case first tries many different methods, and follows 
+that alone which proves possible or the most easy; but to act in 
+this manner and to try different methods makes a near approach to 
+intelligence.
+
+In the first place 227 withered leaves of various kinds, mostly of 
+English plants, were pulled out of worm-burrows in several places.  
+Of these, 181 had been drawn into the burrows by or near their 
+tips, so that the foot-stalk projected nearly upright from the 
+mouth of the burrow; 20 had been drawn in by their bases, and in 
+this case the tips projected from the burrows; and 26 had been 
+seized near the middle, so that these had been drawn in 
+transversely and were much crumpled.  Therefore 80 per cent. 
+(always using the nearest whole number) had been drawn in by the 
+tip, 9 per cent. by the base or foot-stalk, and 11 per cent. 
+transversely or by the middle.  This alone is almost sufficient to 
+show that chance does not determine the manner in which leaves are 
+dragged into the burrows.
+
+Of the above 227 leaves, 70 consisted of the fallen leaves of the 
+common lime-tree, which is almost certainly not a native of 
+England.  These leaves are much acuminated towards the tip, and are 
+very broad at the base with a well-developed foot-stalk.  They are 
+thin and quite flexible when half-withered.  Of the 70, 79 per 
+cent. had been drawn in by or near the tip; 4 per cent. by or near 
+the base; and 17 per cent. transversely or by the middle.  These 
+proportions agree very closely, as far as the tip is concerned, 
+with those before given.  But the percentage drawn in by the base 
+is smaller, which may be attributed to the breadth of the basal 
+part of the blade.  We here, also, see that the presence of a foot-
+stalk, which it might have been expected would have tempted the 
+worms as a convenient handle, has little or no influence in 
+determining the manner in which lime leaves are dragged into the 
+burrows.  The considerable proportion, viz., 17 per cent., drawn in 
+more or less transversely depends no doubt on the flexibility of 
+these half-decayed leaves.  The fact of so many having been drawn 
+in by the middle, and of some few having been drawn in by the base, 
+renders it improbable that the worms first tried to draw in most of 
+the leaves by one or both of these methods, and that they 
+afterwards drew in 79 per cent. by their tips; for it is clear that 
+they would not have failed in drawing them in by the base or 
+middle.
+
+The leaves of a foreign plant were next searched for, the blades of 
+which were not more pointed towards the apex than towards the base.  
+This proved to be the case with those of a laburnum (a hybrid 
+between Cytisus alpinus and laburnum) for on doubling the terminal 
+over the basal half, they generally fitted exactly; and when there 
+was any difference, the basal half was a little the narrower.  It 
+might, therefore, have been expected that an almost equal number of 
+these leaves would have been drawn in by the tip and base, or a 
+slight excess in favour of the latter.  But of 73 leaves (not 
+included in the first lot of 227) pulled out of worm-burrows, 63 
+per cent. had been drawn in by the tip; 27 per cent. by the base, 
+and 10 per cent. transversely.  We here see that a far larger 
+proportion, viz., 27 per cent. were drawn in by the base than in 
+the case of lime leaves, the blades of which are very broad at the 
+base, and of which only 4 per cent. had thus been drawn in.  We may 
+perhaps account for the fact of a still larger proportion of the 
+laburnum leaves not having been drawn in by the base, by worms 
+having acquired the habit of generally drawing in leaves by their 
+tips and thus avoiding the foot-stalk.  For the basal margin of the 
+blade in many kinds of leaves forms a large angle with the foot-
+stalk; and if such a leaf were drawn in by the foot-stalk, the 
+basal margin would come abruptly into contact with the ground on 
+each side of the burrow, and would render the drawing in of the 
+leaf very difficult.
+
+Nevertheless worms break through their habit of avoiding the foot-
+stalk, if this part offers them the most convenient means for 
+drawing leaves into their burrows.  The leaves of the endless 
+hybridised varieties of the Rhododendron vary much in shape; some 
+are narrowest towards the base and others towards the apex.  After 
+they have fallen off, the blade on each side of the midrib often 
+becomes curled up while drying, sometimes along the whole length, 
+sometimes chiefly at the base, sometimes towards the apex.  Out of 
+28 fallen leaves on one bed of peat in my garden, no less than 23 
+were narrower in the basal quarter than in the terminal quarter of 
+their length; and this narrowness was chiefly due to the curling in 
+of the margins.  Out of 36 fallen leaves on another bed, in which 
+different varieties of the Rhododendron grew, only 17 were narrower 
+towards the base than towards the apex.  My son William, who first 
+called my attention to this case, picked up 237 fallen leaves in 
+his garden (where the Rhododendron grows in the natural soil) and 
+of these 65 per cent. could have been drawn by worms into their 
+burrows more easily by the base or foot-stalk than by the tip; and 
+this was partly due to the shape of the leaf and in a less degree 
+to the curling in of the margins:  27 per cent. could have been 
+drawn in more easily by the tip than by the base:  and 8 per cent. 
+with about equal ease by either end.  The shape of a fallen leaf 
+ought to be judged of before one end has been drawn into a burrow, 
+for after this has happened, the free end, whether it be the base 
+or apex, will dry more quickly than the end imbedded in the damp 
+ground; and the exposed margins of the free end will consequently 
+tend to become more curled inwards than they were when the leaf was 
+first seized by the worm.  My son found 91 leaves which had been 
+dragged by worms into their burrows, though not to a great depth; 
+of these 66 per cent. had been drawn in by the base or foot-stalk; 
+and 34 per cent, by the tip.  In this case, therefore, the worms 
+judged with a considerable degree of correctness how best to draw 
+the withered leaves of this foreign plant into their burrows; 
+notwithstanding that they had to depart from their usual habit of 
+avoiding the foot-stalk.
+
+On the gravel-walks in my garden a very large number of leaves of 
+three species of Pinus (P. austriaca, nigricans and sylvestris) are 
+regularly drawn into the mouths of worm burrows.  These leaves 
+consist of two so-called needles, which are of considerable length 
+in the two first and short in the last named species, and are 
+united to a common base; and it is by this part that they are 
+almost invariably drawn into the burrows.  I have seen only two or 
+at most three exceptions to this rule with worms in a state of 
+nature.  As the sharply pointed needles diverge a little, and as 
+several leaves are drawn into the same burrow, each tuft forms a 
+perfect chevaux de frise.  On two occasions many of these tufts 
+were pulled up in the evening, but by the following morning fresh 
+leaves had been pulled in, and the burrows were again well 
+protected.  These leaves could not be dragged into the burrows to 
+any depth, except by their bases, as a worm cannot seize hold of 
+the two needles at the same time, and if one alone were seized by 
+the apex, the other would be pressed against the ground and would 
+resist the entry of the seized one.  This was manifest in the above 
+mentioned two or three exceptional cases.  In order, therefore, 
+that worms should do their work well, they must drag pine-leaves 
+into their burrows by their bases, where the two needles are 
+conjoined.  But how they are guided in this work is a perplexing 
+question.
+
+This difficulty led my son Francis and myself to observe worms in 
+confinement during several nights by the aid of a dim light, while 
+they dragged the leaves of the above named pines into their 
+burrows.  They moved the anterior extremities of their bodies about 
+the leaves, and on several occasions when they touched the sharp 
+end of a needle they withdrew suddenly as if pricked.  But I doubt 
+whether they were hurt, for they are indifferent to very sharp 
+objects, and will swallow even rose-thorns and small splinters of 
+glass.  It may also be doubted, whether the sharp ends of the 
+needles serve to tell them that this is the wrong end to seize; for 
+the points were cut off many leaves for a length of about one inch, 
+and fifty-seven of them thus treated were drawn into the burrows by 
+their bases, and not one by the cut-off ends.  The worms in 
+confinement often seized the needles near the middle and drew them 
+towards the mouths of their burrows; and one worm tried in a 
+senseless manner to drag them into the burrow by bending them.  
+They sometimes collected many more leaves over the mouths of their 
+burrows (as in the case formerly mentioned of lime-leaves) than 
+could enter them.  On other occasions, however, they behaved very 
+differently; for as soon as they touched the base of a pine-leaf, 
+this was seized, being sometimes completely engulfed in their 
+mouths, or a point very near the base was seized, and the leaf was 
+then quickly dragged or rather jerked into their burrows.  It 
+appeared both to my son and myself as if the worms instantly 
+perceived as soon as they had seized a leaf in the proper manner.  
+Nine such cases were observed, but in one of them the worm failed 
+to drag the leaf into its burrow, as it was entangled by other 
+leaves lying near.  In another case a leaf stood nearly upright 
+with the points of the needles partly inserted into a burrow, but 
+how placed there was not seen; and then the worm reared itself up 
+and seized the base, which was dragged into the mouth of the burrow 
+by bowing the whole leaf.  On the other hand, after a worm had 
+seized the base of a leaf, this was on two occasions relinquished 
+from some unknown motive.
+
+As already remarked, the habit of plugging up the mouths of the 
+burrows with various objects, is no doubt instinctive in worms; and 
+a very young one, born in one of my pots, dragged for some little 
+distance a Scotch-fir leaf, one needle of which was as long and 
+almost as thick as its own body.  No species of pine is endemic in 
+this part of England, it is therefore incredible that the proper 
+manner of dragging pine-leaves into the burrows can be instinctive 
+with our worms.  But as the worms on which the above observations 
+were made, were dug up beneath or near some pines, which had been 
+planted there about forty years, it was desirable to prove that 
+their actions were not instinctive.  Accordingly, pine-leaves were 
+scattered on the ground in places far removed from any pine-tree, 
+and 90 of them were drawn into the burrows by their bases.  Only 
+two were drawn in by the tips of the needles, and these were not 
+real exceptions, as one was drawn in for a very short distance, and 
+the two needles of the other cohered.  Other pine-leaves were given 
+to worms kept in pots in a warm room, and here the result was 
+different; for out of 42 leaves drawn into the burrows, no less 
+than i6 were drawn in by the tips of the needles.  These worms, 
+however, worked in a careless or slovenly manner; for the leaves 
+were often drawn in to only a small depth; sometimes they were 
+merely heaped over the mouths of the burrows, and sometimes none 
+were drawn in.  I believe that this carelessness may be accounted 
+for either by the warmth of the air, or by its dampness, as the 
+pots were covered by glass plates; the worms consequently did not 
+care about plugging up their holes effectually.  Pots tenanted by 
+worms and covered with a net which allowed the free entrance of 
+air, were left out of doors for several nights, and now 72 leaves 
+were all properly drawn in by their bases.
+
+It might perhaps be inferred from the facts as yet given, that 
+worms somehow gain a general notion of the shape or structure of 
+pine-leaves, and perceive that it is necessary for them to seize 
+the base where the two needles are conjoined.  But the following 
+cases make this more than doubtful.  The tips of a large number of 
+needles of P. austriaca were cemented together with shell-lac 
+dissolved in alcohol, and were kept for some days, until, as I 
+believe, all odour or taste had been lost; and they were then 
+scattered on the ground where no pine-trees grew, near burrows from 
+which the plugging had been removed.  Such leaves could have been 
+drawn into the burrows with equal ease by either end; and judging 
+from analogy and more especially from the case presently to be 
+given of the petioles of Clematis montana, I expected that the apex 
+would have been preferred.  But the result was that out of 121 
+leaves with the tips cemented, which were drawn into burrows, 108 
+were drawn in by their bases, and only 13 by their tips.  Thinking 
+that the worms might possibly perceive and dislike the smell or 
+taste of the shell-lac, though this was very improbable, especially 
+after the leaves had been left out during several nights, the tips 
+of the needles of many leaves were tied together with fine thread.  
+Of leaves thus treated 150 were drawn into burrows--123 by the base 
+and 27 by the tied tips; so that between four land five times as 
+many were drawn in by the base as by the tip.  It is possible that 
+the short cut-off ends of the thread with which they were tied, may 
+have tempted the worms to drag in a larger proportional number by 
+the tips than when cement was used.  Of the leaves with tied and 
+cemented tips taken together (271 in number) 85 per cent. were 
+drawn in by the base and 15 per cent. by the tips.  We may 
+therefore infer that it is not the divergence of the two needles 
+which leads worms in a state of nature almost invariably to drag 
+pine-leaves into their burrows by the base.  Nor can it be the 
+sharpness of the points of the needles which determines them; for, 
+as we have seen, many leaves with the points cut off were drawn in 
+by their bases.  We are thus led to conclude, that with pine-leaves 
+there must be something attractive to worms in the base, 
+notwithstanding that few ordinary leaves are drawn in by the base 
+or foot-stalk.
+
+Petioles.--We will now turn to the petioles or foot-stalks of 
+compound leaves, after the leaflets have fallen off.  Those from 
+Clematis montana, which grew over a verandah, were dragged early in 
+January in large numbers into the burrows on an adjoining gravel-
+walk, lawn, and flower-bed.  These petioles vary from 2.5 to 4.5 
+inches in length, are rigid and of nearly uniform thickness, except 
+close to the base where they thicken rather abruptly, being here 
+about twice as thick as in any other part.  The apex is somewhat 
+pointed, but soon withers and is then easily broken off.  Of these 
+petioles, 314 were pulled out of burrows in the above specified 
+sites; and it was found that 76 per cent. had been drawn in by 
+their tips, and 24 per cent by their bases; so that those drawn in 
+by the tip were a little more than thrice as many as those drawn in 
+by the base.  Some of those extracted from the well-beaten gravel-
+walk were kept separate from the others; and of these (59 in 
+number) nearly five times as many had been drawn in by the tip as 
+by the base; whereas of those extracted from the lawn and flower-
+bed, where from the soil yielding more easily, less care would be 
+necessary in plugging up the burrows, the proportion of those drawn 
+in by the tip (130) to those drawn in by the base (48) was rather 
+less than three to one.  That these petioles had been dragged into 
+the burrows for plugging them up, and not for food, was manifest, 
+as neither end, as far as I could see, had been gnawed.  As several 
+petioles are used to plug up the same burrow, in one case as many 
+as 10, and in another case as many as 15, the worms may perhaps at 
+first draw in a few by the thicker end so as to save labour; but 
+afterwards a large majority are drawn in by the pointed end, in 
+order to plug up the hole securely.
+
+The fallen petioles of our native ash-tree were next observed, and 
+the rule with most objects, viz., that a large majority are dragged 
+into the burrows by the more pointed end, had not here been 
+followed; and this fact much surprised me at first.  These petioles 
+vary in length from 5 to 8.5 inches; they are thick and fleshy 
+towards the base, whence they taper gently towards the apex, which 
+is a little enlarged and truncated where the terminal leaflet had 
+been originally attached.  Under some ash-trees growing in a grass-
+field, 229 petioles were pulled out of worm burrows early in 
+January, and of these 51.5 per cent. had been drawn in by the base, 
+and 48.5 per cent. by the apex.  This anomaly was however readily 
+explained as soon as the thick basal part was examined; for in 78 
+out of 103 petioles, this part had been gnawed by worms, just above 
+the horse-shoe shaped articulation.  In most cases there could be 
+no mistake about the gnawing; for ungnawed petioles which were 
+examined after being exposed to the weather for eight additional 
+weeks had not become more disintegrated or decayed near the base 
+than elsewhere.  It is thus evident that the thick basal end of the 
+petiole is drawn in not solely for the sake of plugging up the 
+mouths of the burrows, but as food.  Even the narrow truncated tips 
+of some few petioles had been gnawed; and this was the case in 6 
+out of 37 which were examined for this purpose.  Worms, after 
+having drawn in and gnawed the basal end, often push the petioles 
+out of their burrows; and then drag in fresh ones, either by the 
+base for food, or by the apex for plugging up the mouth more 
+effectually.  Thus, out of 37 petioles inserted by their tips, 5 
+had been previously drawn in by the base, for this part had been 
+gnawed.  Again, I collected a handful of petioles lying loose on 
+the ground close to some plugged-up burrows, where the surface was 
+thickly strewed with other petioles which apparently had never been 
+touched by worms; and 14 out of 47 (i.e. nearly one-third), after 
+having had their bases gnawed had been pushed out of the burrows 
+and were now lying on the ground.  From these several facts we may 
+conclude that worms draw in some petioles of the ash by the base to 
+serve as food, and others by the tip to plug up the mouths of their 
+burrows in the most efficient manner.
+
+The petioles of Robinia pseudo-acacia vary from 4 or 5 to nearly 12 
+inches in length; they are thick close to the base before the 
+softer parts have rotted off, and taper much towards the upper end.  
+They are so flexible that I have seen some few doubled up and thus 
+drawn into the burrows of worms.  Unfortunately these petioles were 
+not examined until February, by which time the softer parts had 
+completely rotted off, so that it was impossible to ascertain 
+whether worms had gnawed the bases, though this is in itself 
+probable.  Out of 121 petioles extracted from burrows early in 
+February, 68 were imbedded by the base, and 53 by the apex.  On 
+February 5 all the petioles which had been drawn into the burrows 
+beneath a Robinia, were pulled up; and after an interval of eleven 
+days, 35 petioles had been again dragged in, 19 by the base, and 16 
+by the apex.  Taking these two lots together, 56 per cent. were 
+drawn in by the base, and 44 per cent. by the apex.  As all the 
+softer parts had long ago rotted off, we may feel sure, especially 
+in the latter case, that none had been drawn in as food.  At this 
+season, therefore, worms drag these petioles into their burrows 
+indifferently by either end, a slight preference being given to the 
+base.  This latter fact may be accounted for by the difficulty of 
+plugging up a burrow with objects so extremely thin as are the 
+upper ends.  In support of this view, it may be stated that out of 
+the 16 petioles which had been drawn in by their upper ends, the 
+more attenuated terminal portion of 7 had been previously broken 
+off by some accident.
+
+Triangles of paper.--Elongated triangles were cut out of moderately 
+stiff writing-paper, which was rubbed with raw fat on both sides, 
+so as to prevent their becoming excessively limp when exposed at 
+night to rain and dew.  The sides of all the triangles were three 
+inches in length, with the bases of 120 one inch, and of the other 
+183 half an inch in length.  These latter triangles were very 
+narrow or much acuminated. {32}  As a check on the observations 
+presently to be given, similar triangles in a damp state were 
+seized by a very narrow pair of pincers at different points and at 
+all inclinations with reference to the margins, and were then drawn 
+into a short tube of the diameter of a worm-burrow.  If seized by 
+the apex, the triangle was drawn straight into the tube, with its 
+margins infolded; if seized at some little distance from the apex, 
+for instance at half an inch, this much was doubled back within the 
+tube.  So it was with the base and basal angles, though in this 
+case the triangles offered, as might have been expected, much more 
+resistance to being drawn in.  If seized near the middle the 
+triangle was doubled up, with the apex and base left sticking out 
+of the tube.  As the sides of the triangles were three inches in 
+length, the result of their being drawn into a tube or into a 
+burrow in different ways, may be conveniently divided into three 
+groups:  those drawn in by the apex or within an inch of it; those 
+drawn in by the base or within an inch of it; and those drawn in by 
+any point in the middle inch.
+
+In order to see how the triangles would be seized by worms, some in 
+a damp state were given to worms kept in confinement.  They were 
+seized in three different manners in the case of both the narrow 
+and broad triangles:  viz., by the margin; by one of the three 
+angles, which was often completely engulfed in their mouths; and 
+lastly, by suction applied to any part of the flat surface.  If 
+lines parallel to the base and an inch apart, are drawn across a 
+triangle with the sides three inches in length, it will be divided 
+into three parts of equal length.  Now if worms seized 
+indifferently by chance any part, they would assuredly seize on the 
+basal part or division far oftener than on either of the two other 
+divisions.  For the area of the basal to the apical part is as 5 to 
+1, so that the chance of the former being drawn into a burrow by 
+suction, will be as 5 to 1, compared with the apical part.  The 
+base offers two angles and the apex only one, so that the former 
+would have twice as good a chance (independently of the size of the 
+angles) of being engulfed in a worm's mouth, as would the apex.  It 
+should, however, be stated that the apical angle is not often 
+seized by worms; the margin at a little distance on either side 
+being preferred.  I judge of this from having found in 40 out of 46 
+cases in which triangles had been drawn into burrows by their 
+apical ends, that the tip had been doubled back within the burrow 
+for a length of between 1/20 of an inch and 1 inch.  Lastly, the 
+proportion between the margins of the basal and apical parts is as 
+3 to 2 for the broad, and 2.5 to 2 for the narrow triangles.  From 
+these several considerations it might certainly have been expected, 
+supposing that worms seized hold of the triangles by chance, that a 
+considerably larger proportion would have been dragged into the 
+burrows by the basal than by the apical part; but we shall 
+immediately see how different was the result.
+
+Triangles of the above specified sizes were scattered on the ground 
+in many places and on many successive nights near worm-burrows, 
+from which the leaves, petioles, twigs, &c., with which they had 
+been plugged, were removed.  Altogether 303 triangles were drawn by 
+worms into their burrows:  12 others were drawn in by both ends, 
+but as it was impossible to judge by which end they had been first 
+seized, these are excluded.  Of the 303, 62 per cent. had been 
+drawn in by the apex (using this term for all drawn in by the 
+apical part, one inch in length); 15 per cent. by the middle; and 
+23 per cent. by the basal part.  If they had been drawn 
+indifferently by any point, the proportion for the apical, middle 
+and basal parts would have been 33.3 per cent. for each; but, as we 
+have just seen, it might have been expected that a much larger 
+proportion would have been drawn in by the basal than by any other 
+part.  As the case stands, nearly three times as many were drawn in 
+by the apex as by the base.  If we consider the broad triangles by 
+themselves, 59 per cent. were drawn in by the apex, 25 per cent. by 
+the middle, and 16 per cent. by the base.  Of the narrow triangles, 
+65 per cent. were drawn in by the apex, 14 per cent, by the middle, 
+and 21 per cent. by the base; so that here those drawn in by the 
+apex were more than 3 times as many as those drawn in by the base.  
+We may therefore conclude that the manner in which the triangles 
+are drawn into the burrows is not a matter of chance.
+
+In eight cases, two triangles had been drawn into the same burrow, 
+and in seven of these cases, one had been drawn in by the apex and 
+the other by the base.  This again indicates that the result is not 
+determined by chance.  Worms appear sometimes to revolve in the act 
+of drawing in the triangles, for five out of the whole lot had been 
+wound into an irregular spire round the inside of the burrow.  
+Worms kept in a warm room drew 63 triangles into their burrows; 
+but, as in the case of the pine-leaves, they worked in a rather 
+careless manner, for only 44 per cent. were drawn in by the apex, 
+22 per cent. by the middle, and 33 per cent. by the base.  In five 
+cases, two triangles were drawn into the same burrow.
+
+It may be suggested with much apparent probability that so large a 
+proportion of the triangles were drawn in by the apex, not from the 
+worms having selected this end as the most convenient for the 
+purpose, but from having first tried in other ways and failed.  
+This notion was countenanced by the manner in which worms in 
+confinement were seen to drag about and drop the triangles; but 
+then they were working carelessly.  I did not at first perceive the 
+importance of this subject, but merely noticed that the bases of 
+those triangles which had been drawn in by the apex, were generally 
+clean and not crumpled.  The subject was afterwards attended to 
+carefully.  In the first place several triangles which had been 
+drawn in by the basal angles, or by the base, or a little above the 
+base, and which were thus much crumpled and dirtied, were left for 
+some hours in water and were then well shaken while immersed; but 
+neither the dirt nor the creases were thus removed.  Only slight 
+creases could be obliterated, even by pulling the wet triangles 
+several times through my fingers.  Owing to the slime from the 
+worms' bodies, the dirt was not easily washed off.  We may 
+therefore conclude that if a triangle, before being dragged in by 
+the apex, had been dragged into a burrow by its base with even a 
+slight degree of force, the basal part would long retain its 
+creases and remain dirty.  The condition of 89 triangles (65 narrow 
+and 24 broad ones), which had been drawn in by the apex, was 
+observed; and the bases of only 7 of them were at all creased, 
+being at the same time generally dirty.  Of the 82 uncreased 
+triangles, 14 were dirty at the base; but it does not follow from 
+this fact that these had first been dragged towards the burrows by 
+their bases; for the worms sometimes covered large portions of the 
+triangles with slime, and these when dragged by the apex over the 
+ground would be dirtied; and during rainy weather, the triangles 
+were often dirtied over one whole side or over both sides.  If the 
+worms had dragged the triangles to the mouths of their burrows by 
+their bases, as often as by their apices, and had then perceived, 
+without actually trying to draw them into the burrow, that the 
+broader end was not well adapted for this purpose--even in this 
+case a large proportion would probably have had their basal ends 
+dirtied.  We may therefore infer--improbable as is the inference--
+that worms are able by some means to judge which is the best end by 
+which to draw triangles of paper into their burrows.
+
+The percentage results of the foregoing observations on the manner 
+in which worms draw various kinds of objects into the mouths of 
+their burrows may be abridged as follows:-
+
+
+                             Drawn
+                             into the    Drawn in, Drawn in,
+Nature of Object.            burrows,    by or     by or
+                             by or       near      near
+                             near the    the       the
+                             apex.       middle.   base.
+Leaves of various kinds          80        11         9
+- of the Lime, basal margin
+  of blade broad, apex
+  acuminated                     79        17         4
+- of a Laburnum, basal part of
+  blade as narrow as, or some-
+  times little narrower than
+  the apical part                63        10        27
+- of the Rhododendron, basal
+  part of blade often narrower
+  than the apical part           34       ...        66
+- of Pine-trees, consisting of
+  two needles arising from a
+  common base                    ...      ...       100
+Petioles of a Clematis,
+  somewhat pointed at the apex,
+  and blunt at the base          76       ...        24
+- of the Ash, the thick basal
+  end often drawn in to serve
+  as food                       48.5      ...      51.5
+- of Robinia, extremely thin,
+  especially towards the apex,
+  so as to be ill-fitted for
+  plugging up the burrows        44      ...        56
+Triangles of paper, of the
+  two sizes                      62       15        23
+- of the broad ones alone        59       25        16
+- of the narrow ones alone       65       14        21
+
+
+If we consider these several  cases, we can hardly escape from the 
+conclusion that worms show some degree of intelligence in their 
+manner of plugging up their burrows.  Each particular object is 
+seized in too uniform a manner, and from causes which we can 
+generally understand, for the result to be attributed to mere 
+chance.  That every object has not been drawn in by its pointed 
+end, may be accounted for by labour having been saved through some 
+being inserted by their broader or thicker ends.  No doubt worms 
+are led by instinct to plug up their burrows; and it might have 
+been expected that they would have been led by instinct how best to 
+act in each particular case, independently of intelligence.  We see 
+how difficult it is to judge whether intelligence comes into play, 
+for even plants might sometimes be thought to be thus directed; for 
+instance when displaced leaves re-direct their upper surfaces 
+towards the light by extremely complicated movements and by the 
+shortest course.  With animals, actions appearing due to 
+intelligence may be performed through inherited habit without any 
+intelligence, although aboriginally thus acquired.  Or the habit 
+may have been acquired through the preservation and inheritance of 
+beneficial variations of some other habit; and in this case the new 
+habit will have been acquired independently of intelligence 
+throughout the whole course of its development.  There is no a 
+priori improbability in worms having acquired special instincts 
+through either of these two latter means.  Nevertheless it is 
+incredible that instincts should have been developed in reference 
+to objects, such as the leaves of petioles of foreign plants, 
+wholly unknown to the progenitors of the worms which act in the 
+described manner.  Nor are their actions so unvarying or inevitable 
+as are most true instincts.
+
+As worms are not guided by special instincts in each particular 
+case, though possessing a general instinct to plug up their 
+burrows, and as chance is excluded, the next most probable 
+conclusion seems to be that they try in many different ways to draw 
+in objects, and at last succeed in some one way.  But it is 
+surprising that an animal so low in the scale as a worm should have 
+the capacity for acting in this manner, as many higher animals have 
+no such capacity.  For instance, ants may be seen vainly trying to 
+drag an object transversely to their course, which could be easily 
+drawn longitudinally; though after a time they generally act in a 
+wiser manner, M. Fabre states {33} that a Sphex--an insect 
+belonging to the same highly-endowed order with ants--stocks its 
+nest with paralysed grass-hoppers, which are invariably dragged 
+into the burrow by their antennae.  When these were cut off close 
+to the head, the Sphex seized the palpi; but when these were 
+likewise cut off, the attempt to drag its prey into the burrow was 
+given up in despair.  The Sphex had not intelligence enough to 
+seize one of the six legs or the ovipositor of the grasshopper, 
+which, as M. Fabre remarks, would have served equally well.  So 
+again, if the paralysed prey with an egg attached to it be taken 
+out of the cell, the Sphex after entering and finding the cell 
+empty, nevertheless closes it up in the usual elaborate manner.  
+Bees will try to escape and go on buzzing for hours on a window, 
+one half of which has been left open.  Even a pike continued during 
+three months to dash and bruise itself against the glass sides of 
+an aquarium, in the vain attempt to seize minnows on the opposite 
+side. {34}  A cobra-snake was seen by Mr. Layard {35} to act much 
+more wisely than either the pike or the Sphex; it had swallowed a 
+toad lying within a hole, and could not withdraw its head; the toad 
+was disgorged, and began to crawl away; it was again swallowed and 
+again disgorged; and now the snake had learnt by experience, for it 
+seized the toad by one of its legs and drew it out of the hole.  
+The instincts of even the higher animals are often followed in a 
+senseless or purposeless manner:  the weaver-bird will 
+perseveringly wind threads through the bars of its cage, as if 
+building a nest:  a squirrel will pat nuts on a wooden floor, as if 
+he had just buried them in the ground:  a beaver will cut up logs 
+of wood and drag them about, though there is no water to dam up; 
+and so in many other cases.
+
+Mr. Romanes, who has specially studied the minds of animals, 
+believes that we can safely infer intelligence, only when we see an 
+individual profiting by its own experience.  By this test the cobra 
+showed some intelligence; but this would have been much plainer if 
+on a second occasion he had drawn a toad out of a hole by its leg.  
+The Sphex failed signally in this respect.  Now if worms try to 
+drag objects into their burrows first in one way and then in 
+another, until they at last succeed, they profit, at least in each 
+particular instance, by experience.
+
+But evidence has been advanced showing that worms do not habitually 
+try to draw objects into their burrows in many different ways.  
+Thus half-decayed lime-leaves from their flexibility could have 
+been drawn in by their middle or basal parts, and were thus drawn 
+into the burrows in considerable numbers; yet a large majority were 
+drawn in by or near the apex.  The petioles of the Clematis could 
+certainly have been drawn in with equal ease by the base and apex; 
+yet three times and in certain cases five times as many were drawn 
+in by the apex as by the base.  It might have been thought that the 
+foot-stalks of leaves would have tempted the worms as a convenient 
+handle; yet they are not largely used, except when the base of the 
+blade is narrower than the apex.  A large number of the petioles of 
+the ash are drawn in by the base; but this part serves the worms as 
+food.  In the case of pine-leaves worms plainly show that they at 
+least do not seize the leaf by chance; but their choice does not 
+appear to be determined by the divergence of the two needles, and 
+the consequent advantage or necessity of drawing them into their 
+burrows by the base.  With respect to the triangles of paper, those 
+which had been drawn in by the apex rarely had their bases creased 
+or dirty; and this shows that the worms had not often first tried 
+to drag them in by this end.
+
+If worms are able to judge, either before drawing or after having 
+drawn an object close to the mouths of their burrows, how best to 
+drag it in, they must acquire some notion of its general shape.  
+This they probably acquire by touching it in many places with the 
+anterior extremity of their bodies, which serves as a tactile 
+organ.  It may be well to remember how perfect the sense of touch 
+becomes in a man when born blind and deaf, as are worms.  If worms 
+have the power of acquiring some notion, however rude, of the shape 
+of an object and of their burrows, as seems to be the case, they 
+deserve to be called intelligent; for they then act in nearly the 
+same manner as would a man under similar circumstances.
+
+To sum up, as chance does not determine the manner in which objects 
+are drawn into the burrows, and as the existence of specialized 
+instincts for each particular case cannot be admitted, the first 
+and most natural supposition is that worms try all methods until 
+they at last succeed; but many appearances are opposed to such a 
+supposition.  One alternative alone is left, namely, that worms, 
+although standing low in the scale of organization, possess some 
+degree of intelligence.  This will strike every one as very 
+improbable; but it may be doubted whether we know enough about the 
+nervous system of the lower animals to justify our natural distrust 
+of such a conclusion.  With respect to the small size of the 
+cerebral ganglia, we should remember what a mass of inherited 
+knowledge, with some power of adapting means to an end, is crowded 
+into the minute brain of a worker-ant.
+
+Means by which worms excavate their burrows.--This is effected in 
+two ways; by pushing away the earth on all sides, and by swallowing 
+it.  In the former case, the worm inserts the stretched out and 
+attenuated anterior extremity of its body into any little crevice, 
+or hole; and then, as Perrier remarks, {36} the pharynx is pushed 
+forwards into this part, which consequently swells and pushes away 
+the earth on all sides.  The anterior extremity thus serves as a 
+wedge.  It also serves, as we have before seen, for prehension and 
+suction, and as a tactile organ.  A worm was placed on loose mould, 
+and it buried itself in between two and three minutes.  On another 
+occasion four worms disappeared in 15 minutes between the sides of 
+the pot and the earth, which had been moderately pressed down.  On 
+a third occasion three large worms and a small one were placed on 
+loose mould well mixed with fine sand and firmly pressed down, and 
+they all disappeared, except the tail of one, in 35 minutes.  On a 
+fourth occasion six large worms were placed on argillaceous mud 
+mixed with sand firmly pressed down, and they disappeared, except 
+the extreme tips of the tails of two of them, in 40 minutes.  In 
+none of these cases, did the worms swallow, as far as could be 
+seen, any earth.  They generally entered the ground close to the 
+sides of the pot.
+
+A pot was next filled with very fine ferruginous sand, which was 
+pressed down, well watered, and thus rendered extremely compact.  A 
+large worm left on the surface did not succeed in penetrating it 
+for some hours, and did not bury itself completely until 25 hrs. 40 
+min. had elapsed.  This was effected by the sand being swallowed, 
+as was evident by the large quantity ejected from the vent, long 
+before the whole body had disappeared.  Castings of a similar 
+nature continued to be ejected from the burrow during the whole of 
+the following day.
+
+As doubts have been expressed by some writers whether worms ever 
+swallow earth solely for the sake of making their burrows, some 
+additional cases may be given.  A mass of fine reddish sand, 23 
+inches in thickness, left on the ground for nearly two years, had 
+been penetrated in many places by worms; and their castings 
+consisted partly of the reddish sand and partly of black earth 
+brought up from beneath the mass.  This sand had been dug up from a 
+considerable depth, and was of so poor a nature that weeds could 
+not grow on it.  It is therefore highly improbable that it should 
+have been swallowed by the worms as food.  Again in a field near my 
+house the castings frequently consist of almost pure chalk, which 
+lies at only a little depth beneath the surface; and here again it 
+is very improbable that the chalk should have been swallowed for 
+the sake of the very little organic matter which could have 
+percolated into it from the poor overlying pasture.  Lastly, a 
+casting thrown up through the concrete and decayed mortar between 
+the tiles, with which the now ruined aisle of Beaulieu Abbey had 
+formerly been paved, was washed, so that the coarser matter alone 
+was left.  This consisted of grains of quartz, micaceous slate, 
+other rocks, and bricks or tiles, many of them from 1/20 to 1/10 
+inch in diameter.  No one will suppose that these grains were 
+swallowed as food, yet they formed more than half of the casting, 
+for they weighed 19 grains, the whole casting having weighed 33 
+grains.  Whenever a worm burrows to a depth of some feet in 
+undisturbed compact ground, it must form its passage by swallowing 
+the earth; for it is incredible that the ground could yield on all 
+sides to the pressure of the pharynx when pushed forwards within 
+the worm's body.
+
+That worms swallow a larger quantity of earth for the sake of 
+extracting any nutritious matter which it may contain than for 
+making their burrows, appears to me certain.  But as this old 
+belief has been doubted by so high an authority as Claparede, 
+evidence in its favour must be given in some detail.  There is no a 
+priori improbability in such a belief, for besides other annelids, 
+especially the Arenicola marina, which throws up such a profusion 
+of castings on our tidal sands, and which it is believed thus 
+subsists, there are animals belonging to the most distinct classes, 
+which do not burrow, but habitually swallow large quantities of 
+sand; namely, the molluscan Onchidium and many Echinoderms. {37}
+
+If earth were swallowed only when worms deepened their burrows or 
+made new ones, castings would be thrown up only occasionally; but 
+in many places fresh castings may be seen every morning, and the 
+amount of earth ejected from the same burrow on successive days is 
+large.  Yet worms do not burrow to a great depth, except when the 
+weather is very dry or intensely cold.  On my lawn the black 
+vegetable mould or humus is only about 5 inches in thickness, and 
+overlies light-coloured or reddish clayey soil:  now when castings 
+are thrown up in the greatest profusion, only a small proportion 
+are light coloured, and it is incredible that the worms should 
+daily make fresh burrows in every direction in the thin superficial 
+layer of dark-coloured mould, unless they obtained nutriment of 
+some kind from it.  I have observed a strictly analogous case in a 
+field near my house where bright red clay lay close beneath the 
+surface.  Again on one part of the Downs near Winchester the 
+vegetable mould overlying the chalk was found to be only from 3 to 
+4 inches in thickness; and the many castings here ejected were as 
+black as ink and did not effervesce with acids; so that the worms 
+must have confined themselves to this thin superficial layer of 
+mould, of which large quantities were daily swallowed.  In another 
+place at no great distance the castings were white; and why the 
+worms should have burrowed into the chalk in some places and not in 
+others, I am unable to conjecture.
+
+Two great piles of leaves had been left to decay in my grounds, and 
+months after their removal, the bare surface, several yards in 
+diameter, was so thickly covered during several months with 
+castings that they formed an almost continuous layer; and the large 
+number of worms which lived here must have subsisted during these 
+months on nutritious matter contained in the black earth.
+
+The lowest layer from another pile of decayed leaves mixed with 
+some earth was examined under a high power, and the number of 
+spores of various shapes and sizes which it contained was 
+astonishingly great; and these crushed in the gizzards of worms may 
+largely aid in supporting them.  Whenever castings are thrown up in 
+the greatest number, few or no leaves are drawn into the burrows; 
+for instance the turf along a hedgerow, about 200 yards in length, 
+was daily observed in the autumn during several weeks, and every 
+morning many fresh castings were seen; but not a single leaf was 
+drawn into these burrows.  These castings from their blackness and 
+from the nature of the subsoil could not have been brought up from 
+a greater depth than 6 or 8 inches.  On what could these worms have 
+subsisted during this whole time, if not on matter contained in the 
+black earth?  On the other hand, whenever a large number of leaves 
+are drawn into the burrows, the worms seem to subsist chiefly on 
+them, for few earth-castings are then ejected on the surface.  This 
+difference in the behaviour of worms at different times, perhaps 
+explains a statement by Claparede, namely, that triturated leaves 
+and earth are always found in distinct parts of their intestines.
+
+Worms sometimes abound in places where they can rarely or never 
+obtain dead or living leaves; for instance, beneath the pavement in 
+well-swept courtyards, into which leaves are only occasionally 
+blown.  My son Horace examined a house, one corner of which had 
+subsided; and he found here in the cellar, which was extremely 
+damp, many small worm-castings thrown up between the stones with 
+which the cellar was paved; and in this case it is improbable that 
+the worms could ever have obtained leaves.  Mr. A. C. Horner 
+confirms this account, as he has seen castings in the cellars of 
+his house, which is an old one at Tonbridge.
+
+But the best evidence, known to me, of worms subsisting for at 
+least considerable periods of time solely on the organic matter 
+contained in earth, is afforded by some facts communicated to me by 
+Dr. King.  Near Nice large castings abound in extraordinary 
+numbers, so that 5 or 6 were often found within the space of a 
+square foot.  They consist of fine, pale-coloured earth, containing 
+calcareous matter, which after having passed through the bodies of 
+worms and being dried, coheres with considerable force.  I have 
+reason to believe that these castings had been formed by species of 
+Perichaeta, which have been naturalized here from the East. {38}  
+They rise like towers, with their summits often a little broader 
+than their bases, sometimes to a height of above 3 and often to a 
+height of 2.5 inches.  The tallest of those which were measured was 
+3.3 inches in height and 1 inch in diameter.  A small cylindrical 
+passage runs up the centre of each tower, through which the worm 
+ascends to eject the earth which it has swallowed, and thus to add 
+to its height.  A structure of this kind would not allow leaves 
+being easily dragged from the surrounding ground into the burrows; 
+and Dr. King, who looked carefully, never saw even a fragment of a 
+leaf thus drawn in.  Nor could any trace be discovered of the worms 
+having crawled down the exterior surfaces of the towers in search 
+of leaves; and had they done so, tracks would almost certainly have 
+been left on the upper part whilst it remained soft.  It does not, 
+however, follow that these worms do not draw leaves into their 
+burrows during some other season of the year, at which time they 
+would not build up their towers.
+
+From the several foregoing cases, it can hardly be doubted that 
+worms swallow earth, not only for the sake of making their burrows, 
+but for obtaining food.  Hensen, however, concludes from his 
+analyses of mould that worms probably could not live on ordinary 
+vegetable mould, though he admits that they might be nourished to 
+some extent by leaf-mould. {39}  But we have seen that worms 
+eagerly devour raw meat, fat, and dead worms; and ordinary mould 
+can hardly fail to contain many ova, larvae, and small living or 
+dead creatures, spores of cryptogamic plants, and micrococci, such 
+as those which give rise to saltpetre.  These various organisms, 
+together with some cellulose from any leaves and roots not utterly 
+decayed, might well account for such large quantities of mould 
+being swallowed by worms.  It may be worth while here to recall the 
+fact that certain species of Utricularia, which grow in damp places 
+in the tropics, possess bladders beautifully constructed for 
+catching minute subterranean animals; and these traps would not 
+have been developed unless many small animals inhabited such soil.
+
+The depth to which worms penetrate, and the construction of their 
+burrows.--Although worms usually live near the surface, yet they 
+burrow to a considerable depth during long-continued dry weather 
+and severe cold.  In Scandinavia, according to Eisen, and in 
+Scotland, according to Mr. Lindsay Carnagie, the burrows run down 
+to a depth of from 7 to 8 feet; in North Germany, according to 
+Hoffmeister, from 6 to 8 feet, but Hensen says, from 3 to 6 feet.  
+This latter observer has seen worms frozen at a depth of 1.5 feet 
+beneath the surface.  I have not myself had many opportunities for 
+observation, but I have often met with worms at depths of 3 to 4 
+feet.  In a bed of fine sand overlying the chalk, which had never 
+been disturbed, a worm was cut into two at 55 inches, and another 
+was found here at Down in December at the bottom of its burrow, at 
+61 inches beneath the surface.  Lastly, in earth near an old Roman 
+Villa, which had not been disturbed for many centuries, a worm was 
+met with at a depth of 66 inches; and this was in the middle of 
+August.
+
+The burrows run down perpendicularly, or more commonly a little 
+obliquely.  They are said sometimes to branch, but as far as I have 
+seen this does not occur, except in recently dug ground and near 
+the surface.  They are generally, or as I believe invariably, lined 
+with a thin layer of fine, dark-coloured earth voided by the worms; 
+so that they must at first be made a little wider than their 
+ultimate diameter.  I have seen several burrows in undisturbed sand 
+thus lined at a depth of 4 ft. 6 in.; and others close to the 
+surface thus lined in recently dug ground.  The walls of fresh 
+burrows are often dotted with little globular pellets of voided 
+earth, still soft and viscid; and these, as it appears, are spread 
+out on all sides by the worm as it travels up or down its burrow.  
+The lining thus formed becomes very compact and smooth when nearly 
+dry, and closely fits the worm's body.  The minute reflexed 
+bristles which project in rows on all sides from the body, thus 
+have excellent points of support; and the burrow is rendered well 
+adapted for the rapid movement of the animal.  The lining appears 
+also to strengthen the walls, and perhaps saves the worm's body 
+from being scratched.  I think so because several burrows which 
+passed through a layer of sifted coal-cinders, spread over turf to 
+a thickness of 1.5 inch, had been thus lined to an unusual 
+thickness.  In this case the worms, judging from the castings, had 
+pushed the cinders away on all sides and had not swallowed any of 
+them.  In another place, burrows similarly lined, passed through a 
+layer of coarse coal-cinders, 3.5 inches in thickness.  We thus see 
+that the burrows are not mere excavations, but may rather be 
+compared with tunnels lined with cement.
+
+The mouths of the burrow are in addition often lined with leaves; 
+and this is an instinct distinct from that of plugging them up, and 
+does not appear to have been hitherto noticed.  Many leaves of the 
+Scotch-fir or pine (Pinus sylvestris) were given to worms kept in 
+confinement in two pots; and when after several weeks the earth was 
+carefully broken up, the upper parts of three oblique burrows were 
+found surrounded for lengths of 7, 4, and 3.5 inches with pine-
+leaves, together with fragments of other leaves which had been 
+given the worms as food.  Glass beads and bits of tile, which had 
+been strewed on the surface of the soil, were stuck into the 
+interstices between the pine-leaves; and these interstices were 
+likewise plastered with the viscid castings voided by the worms.  
+The structures thus formed cohered so well, that I succeeded in 
+removing one with only a little earth adhering to it.  It consisted 
+of a slightly curved cylindrical case, the interior of which could 
+be seen through holes in the sides and at either end.  The pine-
+leaves had all been drawn in by their bases; and the sharp points 
+of the needles had been pressed into the lining of voided earth.  
+Had this not been effectually done, the sharp points would have 
+prevented the retreat of the worms into their burrows; and these 
+structures would have resembled traps armed with converging points 
+of wire, rendering the ingress of an animal easy and its egress 
+difficult or impossible.  The skill shown by these worms is 
+noteworthy and is the more remarkable, as the Scotch pine is not a 
+native of this district.
+
+After having examined these burrows made by worms in confinement, I 
+looked at those in a flower-bed near some Scotch pines.  These had 
+all been plugged up in the ordinary manner with the leaves of this 
+tree, drawn in for a length of from 1 to 1.5 inch; but the mouths 
+of many of them were likewise lined with them, mingled with 
+fragments of other kinds of leaves, drawn in to a depth of 4 or 5 
+inches.  Worms often remain, as formerly stated, for a long time 
+close to the mouths of their burrows, apparently for warmth; and 
+the basket-like structures formed of leaves would keep their bodies 
+from coming into close contact with the cold damp earth.  That they 
+habitually rested on the pine-leaves, was rendered probable by 
+their clean and almost polished surfaces.
+
+The burrows which run far down into the ground, generally, or at 
+least often, terminate in a little enlargement or chamber.  Here, 
+according to Hoffmeister, one or several worms pass the winter 
+rolled up into a ball.  Mr. Lindsay Carnagie informed me (1838) 
+that he had examined many burrows over a stone-quarry in Scotland, 
+where the overlying boulder-clay and mould had recently been 
+cleared away, and a little vertical cliff thus left.  In several 
+cases the same burrow was a little enlarged at two or three points 
+one beneath the other; and all the burrows terminated in a rather 
+large chamber, at a depth of 7 or 8 feet from the surface.  These 
+chambers contained many small sharp bits of stone and husks of 
+flax-seeds.  They must also have contained living seeds, for on the 
+following spring Mr. Carnagie saw grass-plants sprouting out of 
+some of the intersected chambers.  I found at Abinger in Surrey two 
+burrows terminating in similar chambers at a depth of 36 and 41 
+inches, and these were lined or paved with little pebbles, about as 
+large as mustard seeds; and in one of the chambers there was a 
+decayed oat-grain, with its husk.  Hensen likewise states that the 
+bottoms of the burrows are lined with little stones; and where 
+these could not be procured, seeds, apparently of the pear, had 
+been used, as many as fifteen having been carried down into a 
+single burrow, one of which had germinated. {40}  We thus see how 
+easily a botanist might be deceived who wished to learn how long 
+deeply buried seeds remained alive, if he were to collect earth 
+from a considerable depth, on the supposition that it could contain 
+only seeds which had long lain buried.  It is probable that the 
+little stones, as well as the seeds, are carried down from the 
+surface by being swallowed; for a surprising number of glass beads, 
+bits of tile and of glass were certainly thus carried down by worms 
+kept in pots; but some may have been carried down within their 
+mouths.  The sole conjecture which I can form why worms line their 
+winter-quarters with little stones and seeds, is to prevent their 
+closely coiled-up bodies from coming into close contact with the 
+surrounding cold soil; and such contact would perhaps interfere 
+with their respiration which is effected by the skin alone.
+
+A worm after swallowing earth, whether for making its burrow or for 
+food, soon comes to the surface to empty its body.  The ejected 
+earth is thoroughly mingled with the intestinal secretions, and is 
+thus rendered viscid.  After being dried it sets hard.  I have 
+watched worms during the act of ejection, and when the earth was in 
+a very liquid state it was ejected in little spurts, and by a slow 
+peristaltic movement when not so liquid.  It is not cast 
+indifferently on any side, but with some care, first on one and 
+then on another side; the tail being used almost like a trowel.  
+When a worm comes to the surface to eject earth, the tail 
+protrudes, but when it collects leaves its head must protrude.  
+Worms therefore must have the power of turning round in their 
+closely-fitting burrows; and this, as it appears to us, would be a 
+difficult feat.  As soon as a little heap has been formed, the worm 
+apparently avoids, for the sake of safety, protruding its tail; and 
+the earthy matter is forced up through the previously deposited 
+soft mass.  The mouth of the same burrow is used for this purpose 
+for a considerable time.  In the case of the tower-like castings 
+(see Fig. 2) near Nice, and of the similar but still taller towers 
+from Bengal (hereafter to be described and figured), a considerable 
+degree of skill is exhibited in their construction.  Dr. King also 
+observed that the passage up these towers hardly ever ran in the 
+same exact line with the underlying burrow, so that a thin 
+cylindrical object such as a haulm of grass, could not be passed 
+down the tower into the burrow; and this change of direction 
+probably serves in some manner as a protection.
+
+Worms do not always eject their castings on the surface of the 
+ground.  When they can find any cavity, as when burrowing in newly 
+turned-up earth, or between the stems of banked-up plants, they 
+deposit their castings in such places.  So again any hollow beneath 
+a large stone lying on the surface of the ground, is soon filled up 
+with their castings.  According to Hensen, old burrows are 
+habitually used for this purpose; but as far as my experience 
+serves, this is not the case, excepting with those near the surface 
+in recently dug ground.  I think that Hensen may have been deceived 
+by the walls of old burrows, lined with black earth, having sunk in 
+or collapsed; for black streaks are thus left, and these are 
+conspicuous when passing through light-coloured soil, and might be 
+mistaken for completely filled-up burrows.
+
+It is certain that old burrows collapse in the course of time; for 
+as we shall see in the next chapter, the fine earth voided by 
+worms, if spread out uniformly, would form in many places in the 
+course of a year a layer 0.2 of an inch in thickness; so that at 
+any rate this large amount is not deposited within the old unused 
+burrows.  If the burrows did not collapse, the whole ground would 
+be first thickly riddled with holes to a depth of about ten inches, 
+and in fifty years a hollow unsupported space, ten inches in depth, 
+would be left.  The holes left by the decay of successively formed 
+roots of trees and plants must likewise collapse in the course of 
+time.
+
+The burrows of worms run down perpendicularly or a little 
+obliquely, and where the soil is at all argillaceous, there is no 
+difficulty in believing that the walls would slowly flow or slide 
+inwards during very wet weather.  When, however, the soil is sandy 
+or mingled with many small stones, it can hardly be viscous enough 
+to flow inwards during even the wettest weather; but another agency 
+may here come into play.  After much rain the ground swells, and as 
+it cannot expand laterally, the surface rises; during dry weather 
+it sinks again.  For instance, a large flat stone laid on the 
+surface of a field sank 3.33 mm. whilst the weather was dry between 
+May 9th and June 13th, and rose 1.91 mm, between September 7th and 
+19th of the same year, much rain having fallen during the latter 
+part of this time.  During frosts and thaws the movements were 
+twice as great.  These observations were made by my son Horace, who 
+will hereafter publish an account of the movements of this stone 
+during successive wet and dry seasons, and of the effects of its 
+being undermined by worms.  Now when the ground swells, if it be 
+penetrated by cylindrical holes, such as worm-burrows, their walls 
+will tend to yield and be pressed inwards; and the yielding will be 
+greater in the deeper parts (supposing the whole to be equally 
+moistened) from the greater weight of the superincumbent soil which 
+has to be raised, than in the parts near the surface.  When the 
+ground dries, the walls will shrink a little and the burrows will 
+be a little enlarged.  Their enlargement, however, through the 
+lateral contraction of the ground, will not be favoured, but rather 
+opposed, by the weight of the superincumbent soil.
+
+Distribution of Worms.--Earth-worms are found in all parts of the 
+world, and some of the genera have an enormous range. {41}  They 
+inhabit the most isolated islands; they abound in Iceland, and are 
+known to exist in the West Indies, St. Helena, Madagascar, New 
+Caledonia and Tahiti.  In the Antarctic regions, worms from 
+Kerguelen Land have been described by Ray Lankester; and I found 
+them in the Falkland Islands.  How they reach such isolated islands 
+is at present quite unknown.  They are easily killed by salt-water, 
+and it does not appear probable that young worms or their egg-
+capsules could be carried in earth adhering to the feet or beaks of 
+land-birds.  Moreover Kerguelen Land is not now inhabited by any 
+land-bird.
+
+In this volume we are chiefly concerned with the earth cast up by 
+worms, and I have gleaned a few facts on this subject with respect 
+to distant lands.  Worms throw up plenty of castings in the United 
+States.  In Venezuela, castings, probably ejected by species of 
+Urochaeta, are common in the gardens and fields, but not in the 
+forests, as I hear from Dr. Ernst of Caracas.  He collected 156 
+castings from the court-yard of his house, having an area of 200 
+square yards.  They varied in bulk from half a cubic centimeter to 
+five cubic centimeters, and were on an average three cubic 
+centimeters.  They were, therefore, of small size in comparison 
+with those often found in England; for six large castings from a 
+field near my house averaged 16 cubic centimeters.  Several species 
+of earth-worms are common in St. Catharina in South Brazil, and 
+Fritz Muller informs me "that in most parts of the forests and 
+pasture-lands, the whole soil, to a depth of a quarter of a metre, 
+looks as if it had passed repeatedly through the intestines of 
+earth-worms, even where hardly any castings are to be seen on the 
+surface."  A gigantic but very rare species is found there, the 
+burrows of which are sometimes even two centimeters or nearly 0.8 
+of an inch in diameter, and which apparently penetrate the ground 
+to a great depth.
+
+In the dry climate of New South Wales, I hardly expected that worms 
+would be common; but Dr. G. Krefft of Sydney, to whom I applied, 
+after making inquiries from gardeners and others, and from his own 
+observations, informs me that their castings abound.  He sent me 
+some collected after heavy rain, and they consisted of little 
+pellets, about 0.15 inch in diameter; and the blackened sandy earth 
+of which they were formed still cohered with considerable tenacity.
+
+The late Mr. John Scott of the Botanic Gardens near Calcutta made 
+many observations for me on worms living under the hot and humid 
+climate of Bengal.  The castings abound almost everywhere, in 
+jungles and in the open ground, to a greater degree, as he thinks, 
+than in England.  After the water has subsided from the flooded 
+rice-fields, the whole surface very soon becomes studded with 
+castings--a fact which much surprised Mr. Scott, as he did not know 
+how long worms could survive beneath water.  They cause much 
+trouble in the Botanic garden, "for some of the finest of our lawns 
+can be kept in anything like order only by being almost daily 
+rolled; if left undisturbed for a few days they become studded with 
+large castings."  These closely resemble those described as 
+abounding near Nice; and they are probably the work of a species of 
+Perichaeta.  They stand up like towers, with an open passage in the 
+centre.
+
+A figure of one of these castings from a photograph is here given 
+(Fig. 3).  The largest received by me was 3.5 inches in height and 
+1.35 inch in diameter; another was only 0.75 inch in diameter and 
+2.75 in height.  In the following year, Mr. Scott measured several 
+of the largest; one was 6 inches in height and nearly 1.5 in 
+diameter:  two others were 5 inches in height and respectively 2 
+and rather more than 2.5 inches in diameter.  The average weight of 
+the 22 castings sent to me was 35 grammes (1.25 oz.); and one of 
+them weighed 44.8 grammes (or 2 oz.). All these castings were 
+thrown up either in one night or in two.  Where the ground in 
+Bengal is dry, as under large trees, castings of a different kind 
+are found in vast numbers:  these consist of little oval or conical 
+bodies, from about the 1/20 to rather above 1/10 of an inch in 
+length.  They are obviously voided by a distinct species of worms.
+
+The period during which worms near Calcutta display such 
+extraordinary activity lasts for only a little over two months, 
+namely, during the cool season after the rains.  At this time they 
+are generally found within about 10 inches beneath the surface.  
+During the hot season they burrow to a greater depth, and are then 
+found coiled up and apparently hybernating.  Mr. Scott has never 
+seen them at a greater depth than 2.5 feet, but has heard of their 
+having been found at 4 feet.  Within the forests, fresh castings 
+may be found even during the hot season.  The worms in the Botanic 
+garden, during the cool and dry season, draw many leaves and little 
+sticks into the mouths of their burrows, like our English worms; 
+but they rarely act in this manner during the rainy season.
+
+Mr. Scott saw worm-castings on the lofty mountains of Sikkim in 
+North India.  In South India Dr. King found in one place, on the 
+plateau of the Nilgiris, at an elevation of 7000 feet, "a good many 
+castings," which are interesting for their great size.  The worms 
+which eject them are seen only during the wet season, and are 
+reported to be from 12 to 15 inches in length, and as thick as a 
+man's little finger.  These castings were collected by Dr. King 
+after a period of 110 days without any rain; and they must have 
+been ejected either during the north-east or more probably during 
+the previous south-west monsoon; for their surfaces had suffered 
+some disintegration and they were penetrated by many fine roots.  A 
+drawing is here given (Fig. 4) of one which seems to have best 
+retained its original size and appearance.  Notwithstanding some 
+loss from disintegration, five of the largest of these castings 
+(after having been well sun-dried) weighed each on an average 89.5 
+grammes, or above 3 oz.; and the largest weighed 123.14 grammes, or 
+4.33 oz.,--that is, above a quarter of a pound!  The largest 
+convolutions were rather more than one inch in diameter; but it is 
+probable that they had subsided a little whilst soft, and that 
+their diameters had thus been increased.  Some had flowed so much 
+that they now consisted of a pile of almost flat confluent cakes.  
+All were formed of fine, rather light-coloured earth, and were 
+surprisingly hard and compact, owing no doubt to the animal matter 
+by which the particles of earth had been cemented together.  They 
+did not disintegrate, even when left for some hours in water.  
+Although they had been cast up on the surface of gravelly soil, 
+they contained extremely few bits of rock, the largest of which was 
+only 0.15 inch in diameter.
+
+Dr. King saw in Ceylon a worm about 2 feet in length and 0.5 inch 
+in diameter; and he was told that it was a very common species 
+during the wet season.  These worms must throw up castings at least 
+as large as those on the Nilgiri Mountains; but Dr. King saw none 
+during his short visit to Ceylon.
+
+Sufficient facts have now been given, showing that worms do much 
+work in bringing up fine earth to the surface in most or all parts 
+of the world, and under the most different climates.
+
+
+
+CHAPTER III--THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE 
+SURFACE.
+
+
+
+Rate at which various objects strewed on the surface of grass-
+fields are covered up by the castings of worms--The burial of a 
+paved path--The slow subsidence of great stones left on the 
+surface--The number of worms which live within a given space--The 
+weight of earth ejected from a burrow, and from all the burrows 
+within a given space--The thickness of the layer of mould which the 
+castings on a given space would form within a given time if 
+uniformly spread out--The slow rate at which mould can increase to 
+a great thickness--Conclusion.
+
+
+We now come to the more immediate subject of this volume, namely, 
+the amount of earth which is brought up by worms from beneath the 
+surface, and is afterwards spread out more or less completely by 
+the rain and wind.  The amount can be judged of by two methods,--by 
+the rate at which objects left on the surface are buried, and more 
+accurately by weighing the quantity brought up within a given time.  
+We will begin with the first method, as it was first followed.
+
+Near Mael Hall in Staffordshire, quick-lime had been spread about 
+the year 1827 thickly over a field of good pasture-land, which had 
+not since been ploughed.  Some square holes were dug in this field 
+in the beginning of October 1837; and the sections showed a layer 
+of turf, formed by the matted roots of the grasses, 0.5 inch in 
+thickness, beneath which, at a depth of 2.5 inches (or 3 inches 
+from the surface), a layer of the lime in powder or in small lumps 
+could be distinctly seen running all round the vertical sides of 
+the holes.  The soil beneath the layer of lime was either gravelly 
+or of a coarse sandy nature, and differed considerably in 
+appearance from the overlying dark-coloured fine mould.  Coal-
+cinders had been spread over a part of this same field either in 
+the year 1833 or 1834; and when the above holes were dug, that is 
+after an interval of 3 or 4 years, the cinders formed a line of 
+black spots round the holes, at a depth of 1 inch beneath the 
+surface, parallel to and above the white layer of lime.  Over 
+another part of this field cinders had been strewed, only about 
+half-a-year before, and these either still lay on the surface or 
+were entangled among the roots of the grasses; and I here saw the 
+commencement of the burying process, for worm-castings had been 
+heaped on several of the smaller fragments.  After an interval of 
+4.75 years this field was re-examined, and now the two layers of 
+lime and cinders were found almost everywhere at a greater depth 
+than before by nearly 1 inch, we will say by 0.75 of an inch.  
+Therefore mould to an average thickness of 0.22 of an inch had been 
+annually brought up by the worms, and had been spread over the 
+surface of this field.
+
+Coal-cinders had been strewed over another field, at a date which 
+could not be positively ascertained, so thickly that they formed 
+(October, 1837) a layer, 1 inch in thickness at a depth of about 3 
+inches from the surface.  The layer was so continuous that the 
+over-lying dark vegetable mould was connected with the sub-soil of 
+red clay only by the roots of the grasses; and when these were 
+broken, the mould and the red clay fell apart.  In a third field, 
+on which coal-cinders and burnt marl had been strewed several times 
+at unknown dates, holes were dug in 1842; and a layer of cinders 
+could be traced at a depth of 3.5 inches, beneath which at a depth 
+of 9.5 inches from the surface there was a line of cinders together 
+with burnt marl.  On the sides of one hole there were two layers of 
+cinders, at 2 and 3.5 inches beneath the surface; and below them at 
+a depth in parts of 9.5, and in other parts of 10.5 inches there 
+were fragments of burnt marl.  In a fourth field two layers of 
+lime, one above the other, could be distinctly traced, and beneath 
+them a layer of cinders and burnt marl at a depth of from 10 to 12 
+inches below the surface.
+
+A piece of waste, swampy land was enclosed, drained, ploughed, 
+harrowed and thickly covered in the year 1822 with burnt marl and 
+cinders.  It was sowed with grass seeds, and now supports a 
+tolerably good but coarse pasture.  Holes were dug in this field in 
+1837, or 15 years after its reclamation, and we see in the 
+accompanying diagram (Fig. 5), reduced to half of the natural 
+scale, that the turf was 1 inch thick, beneath which there was a 
+layer of vegetable mould 2.5 inches thick.  This layer did not 
+contain fragments of any kind; but beneath it there was a layer of 
+mould, 1.5 inch in thickness, full of fragments of burnt marl, 
+conspicuous from their red colour, one of which near the bottom was 
+an inch in length; and other fragments of coal-cinders together 
+with a few white quartz pebbles.  Beneath this layer and at a depth 
+of 4.5 inches from the surface, the original black, peaty, sandy 
+soil with a few quartz pebbles was encountered.  Here therefore the 
+fragments of burnt marl and cinders had been covered in the course 
+of 15 years by a layer of fine vegetable mould, only 2.5 inches in 
+thickness, excluding the turf.  Six and a half years subsequently 
+this field was re-examined, and the fragments were now found at 
+from 4 to 5 inches beneath the surface.  So that in this interval 
+of 6.5 years, about 1.5 inch of mould had been added to the 
+superficial layer.  I am surprised that a greater quantity had not 
+been brought up during the whole 21.5 years, for in the closely 
+underlying black, peaty soil there were many worms.  It is, 
+however, probable that formerly, whilst the land remained poor, 
+worms were scanty; and the mould would then have accumulated 
+slowly.  The average annual increase of thickness for the whole 
+period is 0.19 of an inch.
+
+Two other cases are worth recording.  In the spring of 1835, a 
+field, which had long existed as poor pasture and was so swampy 
+that it trembled slightly when stamped on, was thickly covered with 
+red sand so that the whole surface appeared at first bright red.  
+When holes were dug in this field after an interval of about 2.5 
+years, the sand formed a layer at a depth of 0.75 in. beneath the 
+surface.  In 1842 (i.e., 7 years after the sand had been laid on) 
+fresh holes were dug, and now the red sand formed a distinct layer, 
+2 inches beneath the surface, or 1.5 inch beneath the turf; so that 
+on an average, 0.21 inch of mould had been annually brought to the 
+surface.  Immediately beneath the layer of red sand, the original 
+substratum of black sandy peat extended.
+
+A grass field, likewise not far from Maer Hall, had formerly been 
+thickly covered with marl, and was then left for several years as 
+pasture; it was afterwards ploughed.  A friend had three trenches 
+dug in this field 28 years after the application of the marl, {42} 
+and a layer of the marl fragments could be traced at a depth, 
+carefully measured, of 12 inches in some parts, and of 14 inches in 
+other parts.  This difference in depth depended on the layer being 
+horizontal, whilst the surface consisted of ridges and furrows from 
+the field having been ploughed.  The tenant assured me that it had 
+never been turned up to a greater depth than from 6 to 8 inches; 
+and as the fragments formed an unbroken horizontal layer from 12 to 
+14 inches beneath the surface, these must have been buried by the 
+worms whilst the land was in pasture before it was ploughed, for 
+otherwise they would have been indiscriminately scattered by the 
+plough throughout the whole thickness of the soil.  Four-and-a-half 
+years afterwards I had three holes dug in this field, in which 
+potatoes had been lately planted, and the layer of marl-fragments 
+was now found 13 inches beneath the bottoms of the furrows, and 
+therefore probably 15 inches beneath the general level of the 
+field.  It should, however, be observed that the thickness of the 
+blackish sandy soil, which had been thrown up by the worms above 
+the marl-fragments in the course of 32.5 years, would have measured 
+less than 15 inches, if the field had always remained as pasture, 
+for the soil would in this case have been much more compact.  The 
+fragments of marl almost rested on an undisturbed substratum of 
+white sand with quartz pebbles; and as this would be little 
+attractive to worms, the mould would hereafter be very slowly 
+increased by their action.
+
+We will now give some cases of the action of worms, on land 
+differing widely from the dry sandy or the swampy pastures just 
+described.  The chalk formation extends all round my house in Kent; 
+and its surface, from having been exposed during an immense period 
+to the dissolving action of rain-water, is extremely irregular, 
+being abruptly festooned and penetrated by many deep well-like 
+cavities. {43}  During the dissolution of the chalk, the insoluble 
+matter, including a vast number of unrolled flints of all sizes, 
+has been left on the surface and forms a bed of stiff red clay, 
+full of flints, and generally from 6 to 14 feet in thickness.  Over 
+the red clay, wherever the land has long remained as pasture, there 
+is a layer a few inches in thickness, of dark-coloured vegetable 
+mould.
+
+A quantity of broken chalk was spread, on December 20, 1842, over a 
+part of a field near my house, which had existed as pasture 
+certainly for 30, probably for twice or thrice as many years.  The 
+chalk was laid on the land for the sake of observing at some future 
+period to what depth it would become buried.  At the end of 
+November, 1871, that is after an interval of 29 years, a trench was 
+dug across this part of the field; and a line of white nodules 
+could be traced on both sides of the trench, at a depth of 7 inches 
+from the surface.  The mould, therefore, (excluding the turf) had 
+here been thrown up at an average rate of 0.22 inch per year.  
+Beneath the line of chalk nodules there was in parts hardly any 
+fine earth free of flints, while in other parts there was a layer, 
+2.25 inches in thickness.  In this latter case the mould was 
+altogether 9.25 inches thick; and in one such spot a nodule of 
+chalk and a smooth flint pebble, both of which must have been left 
+at some former time on the surface, were found at this depth.  At 
+from 11 to 12 inches beneath the surface, the undisturbed reddish 
+clay, full of flints, extended.  The appearance of the above 
+nodules of chalk surprised me, much at first, as they closely 
+resembled water-worn pebbles, whereas the freshly-broken fragments 
+had been angular.  But on examining the nodules with a lens, they 
+no longer appeared water-worn, for their surfaces were pitted 
+through unequal corrosion, and minute, sharp points, formed of 
+broken fossil shells, projected from them.  It was evident that the 
+corners of the original fragments of chalk had been wholly 
+dissolved, from presenting a large surface to the carbonic acid 
+dissolved in the rain-water and to that generated in soil 
+containing vegetable matter, as well as to the humus-acids. {44}  
+The projecting corners would also, relatively to the other parts, 
+have been embraced by a larger number of living rootlets; and these 
+have the power of even attacking marble, as Sachs has shown.  Thus, 
+in the course of 29 years, buried angular fragments of chalk had 
+been converted into well-rounded nodules.
+
+Another part of this same field was mossy, and as it was thought 
+that sifted coal-cinders would improve the pasture, a thick layer 
+was spread over this part either in 1842 or 1843, and another layer 
+some years afterwards.  In 1871 a trench was here dug, and many 
+cinders lay in a line at a depth of 7 inches beneath the surface, 
+with another line at a depth of 5.5 inches parallel to the one 
+beneath.  In another part of this field, which had formerly existed 
+as a separate one, and which it was believed had been pasture-land 
+for more than a century, trenches were dug to see how thick the 
+vegetable mould was.  By chance the first trench was made at a spot 
+where at some former period, certainly more than forty years 
+before, a large hole had been filled up with coarse red clay, 
+flints, fragments of chalk, and gravel; and here the fine vegetable 
+mould was only from 4.125 to 4.375 inches in thickness.  In another 
+and undisturbed place, the mould varied much in thickness, namely, 
+from 6.5 to 8.5 inches; beneath which a few small fragments of 
+brick were found in one place.  From these several cases, it would 
+appear that during the last 29 years mould has been heaped on the 
+surface at an average annual rate of from 0.2 to 0.22 of an inch.  
+But in this district when a ploughed field is first laid down in 
+grass, the mould accumulates at a much slower rate.  The rate, 
+also, must become very much slower after a bed of mould, several 
+inches in thickness, has been formed; for the worms then live 
+chiefly near the surface, and burrow down to a greater depth so as 
+to bring up fresh earth from below, only during the winter when the 
+weather is very cold (at which time worms were found in this field 
+at a depth of 26 inches) and during summer, when the weather is 
+very dry.
+
+A field, which adjoins the one just described, slopes in one part 
+rather steeply (viz., at from 10 degrees to 15 degrees); this part 
+was last ploughed in 1841, was then harrowed and left to become 
+pasture-land.  For several years it was clothed with an extremely 
+scant vegetation, and was so thickly covered with small and large 
+flints (some of them half as large as a child's head) that the 
+field was always called by my sons "the stony field."  When they 
+ran down the slope the stones clattered together, I remember 
+doubting whether I should live to see these larger flints covered 
+with vegetable mould and turf.  But the smaller stones disappeared 
+before many years had elapsed, as did every one of the larger ones 
+after a time; so that after thirty years (1871) a horse could 
+gallop over the compact turf from one end of the field to the 
+other, and not strike a single stone with his shoes.  To anyone who 
+remembered the appearance of the field in 1842, the transformation 
+was wonderful.  This was certainly the work of the worms, for 
+though castings were not frequent for several years, yet some were 
+thrown up month after month, and these gradually increased in 
+numbers as the pasture improved.  In the year 1871 a trench was dug 
+on the above slope, and the blades of grass were cut off close to 
+the roots, so that the thickness of the turf and of the vegetable 
+mould could be measured accurately.  The turf was rather less than 
+half an inch, and the mould, which did not contain any stones, 2.5 
+inches in thickness.  Beneath this lay coarse clayey earth full of 
+flints, like that in any of the neighbouring ploughed fields.  This 
+coarse earth easily fell apart from the overlying mould when a spit 
+was lifted up.  The average rate of accumulation of the mould 
+during the whole thirty years was only .083 inch per year (i.e., 
+nearly one inch in twelve years); but the rate must have been much 
+slower at first, and afterwards considerably quicker.
+
+The transformation in the appearance of this field, which had been 
+effected beneath my eyes, was afterwards rendered the more 
+striking, when I examined in Knole Park a dense forest of lofty 
+beech-trees, beneath which nothing grew.  Here the ground was 
+thickly strewed with large naked stones, and worm-castings were 
+almost wholly absent.  Obscure lines and irregularities on the 
+surface indicated that the land had been cultivated some centuries 
+ago.  It is probable that a thick wood of young beech-trees sprung 
+up so quickly, that time enough was not allowed for worms to cover 
+up the stones with their castings, before the site became unfitted 
+for their existence.  Anyhow the contrast between the state of the 
+now miscalled "stony field," well stocked with worms, and the 
+present state of the ground beneath the old beech-trees in Knole 
+Park, where worms appeared to be absent, was striking.
+
+A narrow path running across part of my lawn was paved in 1843 with 
+small flagstones, set edgeways; but worms threw up many castings 
+and weeds grew thickly between them.  During several years the path 
+was weeded and swept; but ultimately the weeds and worms prevailed, 
+and the gardener ceased to sweep, merely mowing off the weeds, as 
+often as the lawn was mowed.  The path soon became almost covered 
+up, and after several years no trace of it was left.  On removing, 
+in 1877, the thin overlying layer of turf, the small flag-stones, 
+all in their proper places, were found covered by an inch of fine 
+mould.
+
+Two recently published accounts of substances strewed on the 
+surface of pasture-land, having become buried through the action of 
+worms, may be here noticed.  The Rev. H. C. Key had a ditch cut in 
+a field, over which coal-ashes had been spread, as it was believed, 
+eighteen years before; and on the clean-cut perpendicular sides of 
+the ditch, at a depth of at least seven inches, there could be 
+seen, for a length of 60 yards, "a distinct, very even, narrow line 
+of coal-ashes, mixed with small coal, perfectly parallel with the 
+top-sward." {45}  This parallelism and the length of the section 
+give interest to the case.  Secondly, Mr. Dancer states {46} that 
+crushed bones had been thickly strewed over a field; and "some 
+years afterwards" these were found "several inches below the 
+surface, at a uniform depth."
+
+The Rev. Mr. Zincke informs me that he has lately had an orchard 
+dug to the unusual depth of 4 feet.  The upper 18 inches consisted 
+of dark-coloured vegetable mould, and the next 18 inches of sandy 
+loam, containing in the lower part many rolled pieces of sandstone, 
+with some bits of brick and tile, probably of Roman origin, as 
+remains of this period have been found close by.  The sandy loam 
+rested on an indurated ferruginous pan of yellow clay, on the 
+surface of which two perfect celts were found.  If, as seems 
+probable, the celts were originally left on the surface of the 
+land, they have since been covered up with earth 3 feet in 
+thickness, all of which has probably passed through the bodies of 
+worms, excepting the stones which may have been scattered on the 
+surface at different times, together with manure or by other means.  
+It is difficult otherwise to understand the source of the 18 inches 
+of sandy loam, which differed from the overlying dark vegetable 
+mould, after both had been burnt, only in being of a brighter red 
+colour, and in not being quite so fine-grained.  But on this view 
+we must suppose that the carbon in vegetable mould, when it lies at 
+some little depth beneath the surface and does not continually 
+receive decaying vegetable matter from above, loses its dark colour 
+in the course of centuries; but whether this is probable I do not 
+know.
+
+Worms appear to act in the same manner in New Zealand as in Europe; 
+for Professor J. von Haast has described {47} a section near the 
+coast, consisting of mica-schist, "covered by 5 or 6 feet of loess, 
+above which about 12 inches of vegetable soil had accumulated."  
+Between the loess and the mould there was a layer from 3 to 6 
+inches in thickness, consisting of "cores, implements, flakes, and 
+chips, all manufactured from hard basaltic rock."  It is therefore 
+probable that the aborigines, at some former period, had left these 
+objects on the surface, and that they had afterwards been slowly 
+covered up by the castings of worms.
+
+Farmers in England are well aware that objects of all kinds, left 
+on the surface of pasture-land, after a time disappear, or, as they 
+say, work themselves downwards.  How powdered lime, cinders, and 
+heavy stones, can work down, and at the same rate, through the 
+matted roots of a grass-covered surface, is a question which has 
+probably never occurred to them. {48}
+
+The Sinking of great Stones through the Action of Worms.--When a 
+stone of large size and of irregular shape is left on the surface 
+of the ground, it rests, of course, on the more protuberant parts; 
+but worms soon fill up with their castings all the hollow spaces on 
+the lower side; for, as Hensen remarks, they like the shelter of 
+stones.  As soon as the hollows are filled up, the worms eject the 
+earth which they have swallowed beyond the circumference of the 
+stones; and thus the surface of the ground is raised all round the 
+stone.  As the burrows excavated directly beneath the stone after a 
+time collapse, the stone sinks a little. {49}  Hence it is, that 
+boulders which at some ancient period have rolled down from a rocky 
+mountain or cliff on to a meadow at its base, are always somewhat 
+imbedded in the soil; and, when removed, leave an exact impression 
+of their lower surfaces in the underlying fine mould.  If, however, 
+a boulder is of such huge dimensions, that the earth beneath is 
+kept dry, such earth will not be inhabited by worms, and the 
+boulder will not sink into the ground.
+
+A lime-kiln formerly stood in a grass-field near Leith Hill Place 
+in Surrey, and was pulled down 35 years before my visit; all the 
+loose rubbish had been carted away, excepting three large stones of 
+quartzose sandstone, which it was thought might hereafter be of 
+some use.  An old workman remembered that they had been left on a 
+bare surface of broken bricks and mortar, close to the foundations 
+of the kiln; but the whole surrounding surface is now covered with 
+turf and mould.  The two largest of these stones had never since 
+been moved; nor could this easily have been done, as, when I had 
+them removed, it was the work of two men with levers.  One of these 
+stones, and not the largest, was 64 inches long, 17 inches broad, 
+and from 9 to 10 inches in thickness.  Its lower surface was 
+somewhat protuberant in the middle; and this part still rested on 
+broken bricks and mortar, showing the truth of the old workman's 
+account.  Beneath the brick rubbish the natural sandy soil, full of 
+fragments of sandstone was found; and this could have yielded very 
+little, if at all, to the weight of the stone, as might have been 
+expected if the sub-soil had been clay.  The surface of the field, 
+for a distance of about 9 inches round the stone, gradually sloped 
+up to it, and close to the stone stood in most places about 4 
+inches above the surrounding ground.  The base of the stone was 
+buried from 1 to 2 inches beneath the general level, and the upper 
+surface projected about 8 inches above this level, or about 4 
+inches above the sloping border of turf.  After the removal of the 
+stone it became evident that one of its pointed ends must at first 
+have stood clear above the ground by some inches, but its upper 
+surface was now on a level with the surrounding turf.  When the 
+stone was removed, an exact cast of its lower side, forming a 
+shallow crateriform hollow, was left, the inner surface of which 
+consisted of fine black mould, excepting where the more protuberant 
+parts rested on the brick-rubbish.  A transverse section of this 
+stone, together with its bed, drawn from measurements made after it 
+had been displaced, is here given on a scale of 0.5 inch to a foot 
+(Fig. 6).  The turf-covered border which sloped up to the stone, 
+consisted of fine vegetable mould, in one part 7 inches in 
+thickness.  This evidently consisted of worm-castings, several of 
+which had been recently ejected.  The whole stone had sunk in the 
+thirty-five years, as far as I could judge, about 1.5 inch; and 
+this must have been due to the brick-rubbish beneath the more 
+protuberant parts having been undermined by worms.  At this rate 
+the upper surface of the stone, if it had been left undisturbed, 
+would have sunk to the general level of the field in 247 years; but 
+before this could have occurred, some earth would have been washed 
+down by heavy rain from the castings on the raised border of turf 
+over the upper surface of the stone.
+
+The second stone was larger that the one just described, viz., 67 
+inches in length, 39 in breadth, and 15 in thickness.  The lower 
+surface was nearly flat, so that the worms must soon have been 
+compelled to eject their castings beyond its circumference.  The 
+stone as a whole had sunk about 2 inches into the ground.  At this 
+rate it would have required 262 years for its upper surface to have 
+sunk to the general level of the field.  The upwardly sloping, 
+turf-covered border round the stone was broader than in the last 
+case, viz., from 14 to 16 inches; and why this should be so, I 
+could see no reason.  In most parts this border was not so high as 
+in the last case, viz., from 2 to 2.5 inches, but in one place it 
+was as much as 5.5.  Its average height close to the stone was 
+probably about 3 inches, and it thinned out to nothing.  If so, a 
+layer of fine earth, 15 inches in breadth and 1.5 inch in average 
+thickness, of sufficient length to surround the whole of the much 
+elongated slab, must have been brought up by the worms in chief 
+part from beneath the stone in the course of 35 years.  This amount 
+would be amply sufficient to account for its having sunk about 2 
+inches into the ground; more especially if we bear in mind that a 
+good deal of the finest earth would have been washed by heavy rain 
+from the castings ejected on the sloping border down to the level 
+of the field.  Some fresh castings were seen close to the stone.  
+Nevertheless, on digging a large hole to a depth of 18 inches where 
+the stone had lain, only two worms and a few burrows were seen, 
+although the soil was damp and seemed favourable for worms.  There 
+were some large colonies of ants beneath the stone, and possibly 
+since their establishment the worms had decreased in number.
+
+The third stone was only about half as large as the others; and two 
+strong boys could together have rolled it over.  I have no doubt 
+that it had been rolled over at a moderately recent time, for it 
+now lay at some distance from the two other stones at the bottom of 
+a little adjoining slope.  It rested also on fine earth, instead of 
+partly on brick-rubbish.  In agreement with this conclusion, the 
+raised surrounding border of turf was only 1 inch high in some 
+parts, and 2 inches in other parts.  There were no colonies of ants 
+beneath this stone, and on digging a hole where it had lain, 
+several burrows and worms were found.
+
+At Stonehenge, some of the outer Druidical stones are now 
+prostrate, having fallen at a remote but unknown period; and these 
+have become buried to a moderate depth in the ground.  They are 
+surrounded by sloping borders of turf, on which recent castings 
+were seen.  Close to one of these fallen stones, which was 17 ft 
+long, 6 ft. broad, and 28.5 inches thick, a hole was dug; and here 
+the vegetable mould was at least 9.5 inches in thickness.  At this 
+depth a flint was found, and a little higher up on one side of the 
+hole a fragment of glass.  The base of the stone lay about 9.5 
+inches beneath the level of the surrounding ground, and its upper 
+surface 19 inches above the ground.
+
+A hole was also dug close to a second huge stone, which in falling 
+had broken into two pieces; and this must have happened long ago, 
+judging from the weathered aspect of the fractured ends.  The base 
+was buried to a depth of 10 inches, as was ascertained by driving 
+an iron skewer horizontally into the ground beneath it.  The 
+vegetable mould forming the turf-covered sloping border round the 
+stone, on which many castings had recently been ejected, was 10 
+inches in thickness; and most of this mould must have been brought 
+up by worms from beneath its base.  At a distance of 8 yards from 
+the stone, the mould was only 5.5 inches in thickness (with a piece 
+of tobacco pipe at a depth of 4 inches), and this rested on broken 
+flint and chalk which could not have easily yielded to the pressure 
+or weight of the stone.
+
+A straight rod was fixed horizontally (by the aid of a spirit-
+level) across a third fallen stone, which was 7 feet 9 inches long; 
+and the contour of the projecting parts and of the adjoining 
+ground, which was not quite level, was thus ascertained, as shown 
+in the accompanying diagram (Fig. 7) on a scale of 0.5 inch to a 
+foot.  The turf-covered border sloped up to the stone on one side 
+to a height of 4 inches, and on the opposite side to only 2.5 
+inches above the general level.  A hole was dug on the eastern 
+side, and the base of the stone was here found to lie at a depth of 
+4 inches beneath the general level of the ground, and of 8 inches 
+beneath the top of the sloping turf-covered border.
+
+
+Sufficient evidence has now been given showing that small objects 
+left on the surface of the land where worms abound soon get buried, 
+and that large stones sink slowly downwards through the same means.  
+Every step of the process could be followed, from the accidental 
+deposition of a single casting on a small object lying loose on the 
+surface, to its being entangled amidst the matted roots of the 
+turf, and lastly to its being embedded in the mould at various 
+depths beneath the surface.  When the same field was re-examined 
+after the interval of a few years, such objects were found at a 
+greater depth than before.  The straightness and regularity of the 
+lines formed by the imbedded objects, and their parallelism with 
+the surface of the land, are the most striking features of the 
+case; for this parallelism shows how equably the worms must have 
+worked; the result being, however, partly the effect of the washing 
+down of the fresh castings by rain.  The specific gravity of the 
+objects does not affect their rate of sinking, as could be seen by 
+porous cinders, burnt marl, chalk and quartz pebbles, having all 
+sunk to the same depth within the same time.  Considering the 
+nature of the substratum, which at Leith Hill Place was sandy soil 
+including many bits of rock, and at Stonehenge, chalk-rubble with 
+broken flints; considering, also, the presence of the turf-covered 
+sloping border of mould round the great fragments of stone at both 
+these places, their sinking does not appear to have been sensibly 
+aided by their weight, though this was considerable. {50}
+
+On the number of worms which live within a given space.--We will 
+now show, firstly, what a vast number of worms live unseen by us 
+beneath our feet, and, secondly, the actual weight of the earth 
+which they bring up to the surface within a given space and within 
+a given time.  Hensen, who has published so full and interesting an 
+account of the habits of worms, {51} calculates, from the number 
+which he found in a measured space, that there must exist 133,000 
+living worms in a hectare of land, or 53,767 in an acre.  This 
+latter number of worms would weigh 356 pounds, taking Hensen's 
+standard of the weight of a single worm, namely, three grams.  It 
+should, however, be noted that this calculation is founded on the 
+numbers found in a garden, and Hensen believes that worms are here 
+twice as numerous as in corn-fields.  The above result, astonishing 
+though it be, seems to me credible, judging from the number of 
+worms which I have sometimes seen, and from the number daily 
+destroyed by birds without the species being exterminated.  Some 
+barrels of bad ale were left on Mr. Miller's land, {52} in the hope 
+of making vinegar, but the vinegar proved bad, and the barrels were 
+upset.  It should be premised that acetic acid is so deadly a 
+poison to worms that Perrier found that a glass rod dipped into 
+this acid and then into a considerable body of water in which worms 
+were immersed, invariably killed them quickly.  On the morning 
+after the barrels had been upset, "the heaps of worms which lay 
+dead on the ground were so amazing, that if Mr. Miller had not seen 
+them, he could not have thought it possible for such numbers to 
+have existed in the space."  As further evidence of the large 
+number of worms which live in the ground, Hensen states that he 
+found in a garden sixty-four open burrows in a space of 14.5 square 
+feet, that is, nine in 2 square feet.  But the burrows are 
+sometimes much more numerous, for when digging in a grass-field 
+near Maer Hall, I found a cake of dry earth, as large as my two 
+open hands, which was penetrated by seven burrows, as large as 
+goose-quills.
+
+Weight of the earth ejected from a single burrow, and from all the 
+burrows within a given space.--With respect to the weight of the 
+earth daily ejected by worms, Hensen found that it amounted, in the 
+case of some worms which he kept in confinement, and which he 
+appears to have fed with leaves, to only 0.5 gram, or less than 8 
+grains per diem.  But a very much larger amount must be ejected by 
+worms in their natural state, at the periods when they consume 
+earth as food instead of leaves, and when they are making deep 
+burrows.  This is rendered almost certain by the following weights 
+of the castings thrown up at the mouths of single burrows; the 
+whole of which appeared to have been ejected within no long time, 
+as was certainly the case in several instances.  The castings were 
+dried (excepting in one specified instance) by exposure during many 
+days to the sun or before a hot fire.
+
+
+WEIGHT OF THE CASTINGS ACCUMULATED AT THE MOUTH OF A SINGLE BURROW.
+
+
+(Weight in ounces given in parenthesis--DP.)
+
+(1.)  Down, Kent (sub-soil red clay, full of flints, over-lying the 
+chalk).  The largest casting which I could find on the flanks of a 
+steep valley, the sub-soil being here shallow.  In this one case, 
+the casting was not well dried (3.98)
+
+(2.)  Down.--Largest casting which I could find (consisting chiefly 
+of calcareous matter), on extremely poor pasture land at the bottom 
+of the valley mentioned under (1.) (3.87)
+
+(3.)  Down.--A large casting, but not of unusual size, from a 
+nearly level field, poor pasture, laid down in a grass about 35 
+years before (1.22)
+
+(4.)  Down.  Average weight of 11 not large castings ejected on a 
+sloping surface on my lawn, after they had suffered some loss of 
+weight from being exposed during a considerable length of time to 
+rain (0.7)
+
+(5.)  Near Nice in France.--Average weight of 12 castings of 
+ordinary dimensions, collected by Dr. King on land which had not 
+been mown for a long time and where worms abounded, viz., a lawn 
+protected by shrubberies near the sea; soil sandy and calcareous; 
+these castings had been exposed for some time to rain, before being 
+collected, and must have lost some weight by disintegration, but 
+they still retained their form (1.37)
+
+(6.)  The heaviest of the above twelve castings (1.76)
+
+(7.)   Lower Bengal.--Average weight of 22 castings, collected by 
+Mr. J. Scott, and stated by him to have been thrown up in the 
+course of one or two nights (1.24)
+
+(8.)  The heaviest of the above 22 castings (2.09)
+
+(9.)  Nilgiri Mountains, S. India; average weight of the 5 largest 
+castings collected by Dr. King.  They had been exposed to the rain 
+of the last monsoon, and must have lost some weight (3.15)
+
+(10.)  The heaviest of the above 5 castings (4.34)
+
+
+In this table we see that castings which had been ejected at the 
+mouth of the same burrow, and which in most cases appeared fresh 
+and always retained their vermiform configuration, generally 
+exceeded an ounce in weight after being dried, and sometimes nearly 
+equalled a quarter of a pound.  On the Nilgiri mountains one 
+casting even exceeded this latter weight.  The largest castings in 
+England were found on extremely poor pasture-land; and these, as 
+far as I have seen, are generally larger than those on land 
+producing a rich vegetation.  It would appear that worms have to 
+swallow a greater amount of earth on poor than on rich land, in 
+order to obtain sufficient nutriment.
+
+With respect to the tower-like castings near Nice (Nos. 5 and 6 in 
+the above table), Dr. King often found five or six of them on a 
+square foot of surface; and these, judging from their average 
+weight, would have weighed together 7.5 ounces; so that the weight 
+of those on a square yard would have been 4 lb. 3.5 oz.  Dr. King 
+collected, near the close of the year 1872, all the castings which 
+still retained their vermiform shape, whether broken down or not, 
+from a square foot, in a place abounding with worms, on the summit 
+of a bank, where no castings could have rolled down from above.  
+These castings must have been ejected, as he judged from their 
+appearance in reference to the rainy and dry periods near Nice, 
+within the previous five or six months; they weighed 9.5 oz., or 5 
+lb. 5.5 oz. per square yard.  After an interval of four months, Dr. 
+King collected all the castings subsequently ejected on the same 
+square foot of surface, and they weighed 2.5 oz., or 1 lb. 6.5 oz. 
+per square yard.  Therefore within about ten months, or we will say 
+for safety's sake within a year, 12 oz. of castings were thrown up 
+on this one square foot, or 6.75 pounds on the square yard; and 
+this would give 14.58 tons per acre.
+
+In a field at the bottom of a valley in the chalk (see No. 2 in the 
+foregoing table), a square yard was measured at a spot where very 
+large castings abounded; they appeared, however, almost equally 
+numerous in a few other places.  These castings, which retained 
+perfectly their vermiform shape, were collected; and they weighed 
+when partially dried, 1 lb. 13.5 oz.  This field had been rolled 
+with a heavy agricultural roller fifty-two days before, and this 
+would certainly have flattened every single casting on the land.  
+The weather had been very dry for two or three weeks before the day 
+of collection, so that not one casting appeared fresh or had been 
+recently ejected.  We may therefore assume that those which were 
+weighed had been ejected within, we will say, forty days from the 
+time when the field was rolled,--that is, twelve days short of the 
+whole intervening period.  I had examined the same part of the 
+field shortly before it was rolled, and it then abounded with fresh 
+castings.  Worms do not work in dry weather during the summer, or 
+in winter during severe frosts.  If we assume that they work for 
+only half the year--though this is too low an estimate--then the 
+worms in this field would eject during the year, 8.387 pounds per 
+square yard; or 18.12 tons per acre, assuming the whole surface to 
+be equally productive in castings.
+
+In the foregoing cases some of the necessary data had to be 
+estimated, but in the two following cases the results are much more 
+trustworthy.  A lady, on whose accuracy I can implicitly rely, 
+offered to collect during a year all the castings thrown up on two 
+separate square yards, near Leith Hill Place, in Surrey.  The 
+amount collected was, however, somewhat less than that originally 
+ejected by the worms; for, as I have repeatedly observed, a good 
+deal of the finest earth is washed away, whenever castings are 
+thrown up during or shortly before heavy rain.  Small portions also 
+adhered to the surrounding blades of grass, and it required too 
+much time to detach every one of them.
+
+On sandy soil, as in the present instance, castings are liable to 
+crumble after dry weather, and particles were thus often lost.  The 
+lady also occasionally left home for a week or two, and at such 
+times the castings must have suffered still greater loss from 
+exposure to the weather.  These losses were, however, compensated 
+to some extent by the collections having been made on one of the 
+squares for four days, and on the other square for two days more 
+than the year.
+
+A space was selected (October 9th, 1870) for one of the squares on 
+a broad, grass-covered terrace, which had been mowed and swept 
+during many years.  It faced the south, but was shaded during part 
+of the day by trees.  It had been formed at least a century ago by 
+a great accumulation of small and large fragments of sandstone, 
+together with some sandy earth, rammed down level.  It is probable 
+that it was at first protected by being covered with turf.  This 
+terrace, judging from the number of castings on it, was rather 
+unfavourable for the existence of worms, in comparison with the 
+neighbouring fields and an upper terrace.  It was indeed surprising 
+that as many worms could live here as were seen; for on digging a 
+hole in this terrace, the black vegetable mould together with the 
+turf was only four inches in thickness, beneath which lay the level 
+surface of light-coloured sandy soil, with many fragments of 
+sandstone.  Before any castings were collected all the previously 
+existing ones were carefully removed.  The last day's collection 
+was on October 14th, 1871.  The castings were then well dried 
+before a fire; and they weighed exactly 3.5 lbs.  This would give 
+for an acre of similar land 7.56 tons of dry earth annually ejected 
+by worms.
+
+The second square was marked on unenclosed common land, at a height 
+of about 700 ft. above the sea, at some little distance from Leith 
+Hill Tower.  The surface was clothed with short, fine turf, and had 
+never been disturbed by the hand of man.  The spot selected 
+appeared neither particularly favourable nor the reverse for worms; 
+but I have often noticed that castings are especially abundant on 
+common land, and this may, perhaps, be attributed to the poorness 
+of the soil.  The vegetable mould was here between three and four 
+inches in thickness.  As this spot was at some distance from the 
+house where the lady lived, the castings were not collected at such 
+short intervals of time as those on the terrace; consequently the 
+loss of fine earth during rainy weather must have been greater in 
+this than in the last case.  The castings moreover were more sandy, 
+and in collecting them during dry weather they sometimes crumbled 
+into dust, and much was thus lost.  Therefore it is certain that 
+the worms brought up to the surface considerably more earth than 
+that which was collected.  The last collection was made on October 
+27th, 1871; i.e., 367 days after the square had been marked out and 
+the surface cleared of all pre-existing castings.  The collected 
+castings, after being well dried, weighed 7.453 pounds; and this 
+would give, for an acre of the same kind of land, 16.1 tons of 
+annually ejected dry earth.
+
+
+SUMMARY OF THE FOUR FOREGOING CASES.
+
+
+(1.)  Castings ejected near Nice within about a year, collected by 
+Dr. King on a square foot of surface, calculated to yield per acre 
+14.58 tons.
+
+(2.)  Castings ejected during about 40 days on a square yard, in a 
+field of poor pasture at the bottom of a large valley in the Chalk, 
+calculated to yield annually per acre 18.12 tons.
+
+(3.)  Castings collected from a square yard on an old terrace at 
+Leith Hill Place, during 369 days, calculated to yield annually per 
+acre 7.56 tons.
+
+(4.)  Castings collected from a square yard on Leith Hill Common 
+during 367 days, calculated to yield annually per acre 16.1 tons.
+
+
+The thickness of the layer of mould, which castings ejected during 
+a year would form if uniformly spread out.--As we know, from the 
+two last cases in the above summary, the weight of the dried 
+castings ejected by worms during a year on a square yard of 
+surface, I wished to learn how thick a layer of ordinary mould this 
+amount would form if spread uniformly over a square yard.  The dry 
+castings were therefore broken into small particles, and whilst 
+being placed in a measure were well shaken and pressed down.  Those 
+collected on the Terrace amounted to 124.77 cubic inches; and this 
+amount, if spread out over a square yard, would make a layer 0.9627 
+inch in thickness.  Those collected on the Common amounted to 
+197.56 cubic inches, and would make a similar layer 0.1524 inch in 
+thickness,
+
+These thicknesses must, however, be corrected, for the triturated 
+castings, after being well shaken down and pressed, did not make 
+nearly so compact a mass as vegetable mould, though each separate 
+particle was very compact.  Yet mould is far from being compact, as 
+is shown by the number of air-bubbles which rise up when the 
+surface is flooded with water.  It is moreover penetrated by many 
+fine roots.  To ascertain approximately by how much ordinary 
+vegetable mould would be increased in bulk by being broken up into 
+small particles and then dried, a thin oblong block of somewhat 
+argillaceous mould (with the turf pared off) was measured before 
+being broken up, was well dried and again measured.  The drying 
+caused it to shrink by 1/7 of its original bulk, judging from 
+exterior measurements alone.  It was then triturated and partly 
+reduced to powder, in the same manner as the castings had been 
+treated, and its bulk now exceeded (notwithstanding shrinkage from 
+drying) by 1/16 that of the original block of damp mould.  
+Therefore the above calculated thickness of the layer, formed by 
+the castings from the Terrace, after being damped and spread over a 
+square yard, would have to be reduced by 1/16; and this will reduce 
+the layer to 0.09 of an inch, so that a layer 0.9 inch in thickness 
+would be formed in the course of ten years.  On the same principle 
+the castings from the Common would make in the course of a single 
+year a layer 0.1429 inch, or in the course of 10 years 1.429 inch, 
+in thickness.  We may say in round numbers that the thickness in 
+the former case would amount to nearly 1 inch, and in the second 
+case to nearly 1.5 inch in 10 years.
+
+In order to compare these results with those deduced from the rates 
+at which small objects left on the surfaces of grass-fields become 
+buried (as described in the early part of this chapter), we will 
+give the following summary:-
+
+
+SUMMARY OF THE THICKNESS OF THE MOULD ACCUMULATED OVER OBJECTS LEFT 
+STREWED ON THE SURFACE, IN THE COURSE OF TEN YEARS.
+
+
+The accumulation of mould during 14.75 years on the surface of a 
+dry, sandy, grass-field near Maer Hall, amounted to 2.2 inches in 
+10 years.
+
+The accumulation during 21.5 years on a swampy field near Maer 
+Hall, amounted to nearly 1.9 inch in 10 years.
+
+The accumulation during 7 years on a very swampy field near Maer 
+Hall amounted to 2.1 inches in 10 years.
+
+The accumulation during 29 years, on good, argillaceous pasture-
+land over the Chalk at Down, amounted to 2.2 inches in 10 years.
+
+The accumulation during 30 years on the side of a valley over the 
+Chalk at Down, the soil being argillaceous, very poor, and only 
+just converted into pasture (so that it was for some years 
+unfavourable for worms), amounted to 0.83 inch in 10 years.
+
+
+In these cases (excepting the last) it may be seen that the amount 
+of earth brought to the surface during 10 years is somewhat greater 
+than that calculated from the castings which were actually weighed.  
+This excess may be partly accounted for by the loss which the 
+weighed castings had previously undergone through being washed by 
+rain, by the adhesion of particles to the blades of the surrounding 
+grass, and by their crumbling when dry.  Nor must we overlook other 
+agencies which in all ordinary cases add to the amount of mould, 
+and which would not be included in the castings that were 
+collected, namely, the fine earth brought up to the surface by 
+burrowing larvae and insects, especially by ants.  The earth 
+brought up by moles generally has a somewhat different appearance 
+from vegetable mould; but after a time would not be distinguishable 
+from it.  In dry countries, moreover, the wind plays an important 
+part in carrying dust from one place to another, and even in 
+England it must add to the mould on fields near great roads.  But 
+in our country these latter several agencies appear to be of quite 
+subordinate importance in comparison with the action of worms.
+
+We have no means of judging how great a weight of earth a single 
+full-sized worm ejects during a year.  Hensen estimates that 53,767 
+worms exist in an acre of land; but this is founded on the number 
+found in gardens, and he believes that only about half as many live 
+in corn-fields.  How many live in old pasture land is unknown; but 
+if we assume that half the above number, or 26,886 worms live on 
+such land, then taking from the previous summary 15 tons as the 
+weight of the castings annually thrown up on an acre of land, each 
+worm must annually eject 20 ounces.  A full-sized casting at the 
+mouth of a single burrow often exceeds, as we have seen, an ounce 
+in weight; and it is probable that worms eject more than 20 full-
+sized castings during a year.  If they eject annually more than 20 
+ounces, we may infer that the worms which live in an acre of 
+pasture land must be less than 26,886 in number.
+
+Worms live chiefly in the superficial mould, which is usually from 
+4 or 5 to 10 and even 12 inches in thickness; and it is this mould 
+which passes over and over again through their bodies and is 
+brought to the surface.  But worms occasionally burrow into the 
+subsoil to a much greater depth, and on such occasions they bring 
+up earth from this greater depth; and this process has gone on for 
+countless ages.  Therefore the superficial layer of mould would 
+ultimately attain, though at a slower and slower rate, a thickness 
+equal to the depth to which worms ever burrow, were there not other 
+opposing agencies at work which carry away to a lower level some of 
+the finest earth which is continually being brought to the surface 
+by worms.  How great a thickness vegetable mould ever attains, I 
+have not had good opportunities for observing; but in the next 
+chapter, when we consider the burial of ancient buildings, some 
+facts will be given on this head.  In the two last chapters we 
+shall see that the soil is actually increased, though only to a 
+small degree, through the agency of worms; but their chief work is 
+to sift the finer from the coarser particles, to mingle the whole 
+with vegetable debris, and to saturate it with their intestinal 
+secretions.
+
+Finally, no one who considers the facts given in this chapter--on 
+the burying of small objects and on the sinking of great stones 
+left on the surface--on the vast number of worms which live within 
+a moderate extent of ground on the weight of the castings ejected 
+from the mouth of the same burrow--on the weight of all the 
+castings ejected within a known time on a measured space--will 
+hereafter, as I believe, doubt that worms play an important part in 
+nature.
+
+
+
+CHAPTER IV--THE PART WHICH WORMS HAVE PLAYED IN THE BURIAL OF 
+ANCIENT BUILDINGS.
+
+
+
+The accumulation of rubbish on the sites of great cities 
+independent of the action of worms--The burial of a Roman villa at 
+Abinger--The floors and walls penetrated by worms--Subsidence of a 
+modern pavement--The buried pavement at Beaulieu Abbey--Roman 
+villas at Chedworth and Brading--The remains of the Roman town at 
+Silchester--The nature of the debris by which the remains are 
+covered--The penetration of the tesselated floors and walls by 
+worms--Subsidence of the floors--Thickness of the mould--The old 
+Roman city of Wroxeter--Thickness of the mould--Depth of the 
+foundations of some of the Buildings--Conclusion.
+
+
+Archaeologists are probably not aware how much they owe to worms 
+for the preservation of many ancient objects.  Coins, gold 
+ornaments, stone implements, &c., if dropped on the surface of the 
+ground, will infallibly be buried by the castings of worms in a few 
+years, and will thus be safely preserved, until the land at some 
+future time is turned up.  For instance, many years ago a grass-
+field was ploughed on the northern side of the Severn, not far from 
+Shrewsbury; and a surprising number of iron arrow-heads were found 
+at the bottom of the furrows, which, as Mr. Blakeway, a local 
+antiquary, believed, were relics of the battle of Shrewsbury in the 
+year 1403, and no doubt had been originally left strewed on the 
+battle-field.  In the present chapter I shall show that not only 
+implements, &c., are thus preserved, but that the floors and the 
+remains of many ancient buildings in England have been buried so 
+effectually, in large part through the action of worms, that they 
+have been discovered in recent times solely through various 
+accidents.  The enormous beds of rubbish, several yards in 
+thickness, which underlie many cities, such as Rome, Paris, and 
+London, the lower ones being of great antiquity, are not here 
+referred to, as they have not been in any way acted on by worms.  
+When we consider how much matter is daily brought into a great city 
+for building, fuel, clothing and food, and that in old times when 
+the roads were bad and the work of the scavenger was neglected, a 
+comparatively small amount was carried away, we may agree with Elie 
+de Beaumont, who, in discussing this subject, says, "pour une 
+voiture de materiaux qui en sort, on y en fait entrer cent." {53}  
+Nor should we overlook the effects of fires, the demolition of old 
+buildings, and the removal of rubbish to the nearest vacant space,
+
+Abinger, Surrey.--Late in the autumn of 1876, the ground in an old 
+farm-yard at this place was dug to a depth of 2 to 2.5 feet, and 
+the workmen found various ancient remains.  This led Mr. T. H. 
+Farrer of Abinger Hall to have an adjoining ploughed field 
+searched.  On a trench being dug, a layer of concrete, still partly 
+covered with tesserae (small red tiles), and surrounded on two 
+sides by broken-down walls, was soon discovered.  It is believed, 
+{54} that this room formed part of the atrium or reception-room of 
+a Roman villa.  The walls of two or three other small rooms were 
+afterwards discovered.  Many fragments of pottery, other objects, 
+and coins of several Roman emperors, dating from 133 to 361, and 
+perhaps to 375 A.D., were likewise found.  Also a half-penny of 
+George I., 1715.  The presence of this latter coin seems an 
+anomaly; but no doubt it was dropped on the ground during the last 
+century, and since then there has been ample time for its burial 
+under a considerable depth of the castings of worms.  From the 
+different dates of the Roman coins we may infer that the building 
+was long inhabited.  It was probably ruined and deserted 1400 or 
+1500 years ago.
+
+I was present during the commencement of the excavations (August 
+20, 1877) and Mr. Farrer had two deep trenches dug at opposite ends 
+of the atrium, so that I might examine the nature of the soil near 
+the remains.  The field sloped from east to west at an angle of 
+about 7 degrees; and one of the two trenches, shown in the 
+accompanying section (Fig. 8) was at the upper or eastern end.  The 
+diagram is on a scale of 1/20 of an inch to an inch; but the 
+trench, which was between 4 and 5 feet broad, and in parts above 5 
+feet deep, has necessarily been reduced out of all proportion.  The 
+fine mould over the floor of the atrium varied in thickness from 11 
+to 16 inches; and on the side of the trench in the section was a 
+little over 13 inches.  After the mould had been removed, the floor 
+appeared as a whole moderately level; but it sloped in parts at an 
+angle of 1 degree, and in one place near the outside at as much as 
+8 degrees 30 minutes.  The wall surrounding the pavement was built 
+of rough stones, and was 23 inches in thickness where the trench 
+was dug.  Its broken summit was here 13 inches, but in another part 
+15 inches, beneath the surface of the field, being covered by this 
+thickness of mould.  In one spot, however, it rose to within 6 
+inches of the surface.  On two sides of the room, where the 
+junction of the concrete floor with the bounding walls could be 
+carefully examined, there was no crack or separation.  This trench 
+afterwards proved to have been dug within an adjoining room (11 ft. 
+by 11 ft. 6 in. in size), the existence of which was not even 
+suspected whilst I was present.
+
+On the side of the trench farthest from the buried wall (W), the 
+mould varied from 9 to 14 inches in thickness; it rested on a mass 
+(B) 23 inches thick of blackish earth, including many large stones.  
+Beneath this was a thin bed of very black mould (C), then a layer 
+of earth full of fragments of mortar (D), and then another thin bed 
+(about 3 inches thick) (E) of very black mould, which rested on the 
+undisturbed subsoil (F) of firm, yellowish, argillaceous sand.  The 
+23-inch bed (B) was probably made ground, as this would have 
+brought up the floor of the room to a level with that of the 
+atrium.  The two thin beds of black mould at the bottom of the 
+trench evidently marked two former land-surfaces.  Outside the 
+walls of the northern room, many bones, ashes, oyster-shells, 
+broken pottery and an entire pot were subsequently found at a depth 
+of 16 inches beneath the surface.
+
+The second trench was dug on the western or lower side of the 
+villa:  the mould was here only 6.5 inches in thickness, and it 
+rested on a mass of fine earth full of stones, broken tiles and 
+fragments of mortar, 34 inches in thickness, beneath which was the 
+undisturbed sand.  Most of this earth had probably been washed down 
+from the upper part of the field, and the fragments of stones, 
+tiles, &c., must have come from the immediately adjoining ruins.
+
+It appears at first sight a surprising fact that this field of 
+light sandy soil should have been cultivated and ploughed during 
+many years, and that not a vestige of these buildings should have 
+been discovered.  No one even suspected that the remains of a Roman 
+villa lay hidden close beneath the surface.  But the fact is less 
+surprising when it is known that the field, as the bailiff 
+believed, had never been ploughed to a greater depth than 4 inches.  
+It is certain that when the land was first ploughed, the pavement 
+and the surrounding broken walls must have been covered by at least 
+4 inches of soil, for otherwise the rotten concrete floor would 
+have been scored by the ploughshare, the tesserae torn up, and the 
+tops of the old walls knocked down.
+
+When the concrete and tesserae were first cleared over a space of 
+14 by 9 ft., the floor which was coated with trodden-down earth 
+exhibited no signs of having been penetrated by worms; and although 
+the overlying fine mould closely resembled that which in many 
+places has certainly been accumulated by worms, yet it seemed 
+hardly possible that this mould could have been brought up by worms 
+from beneath the apparently sound floor.  It seemed also extremely 
+improbable that the thick walls, surrounding the room and still 
+united to the concrete, had been undermined by worms, and had thus 
+been caused to sink, being afterwards covered up by their castings.  
+I therefore at first concluded that all the fine mould above the 
+ruins had been washed down from the upper parts of the field; but 
+we shall soon see that this conclusion was certainly erroneous, 
+though much fine earth is known to be washed down from the upper 
+part of the field in its present ploughed state during heavy rains.
+
+Although the concrete floor did not at first appear to have been 
+anywhere penetrated by worms, yet by the next morning little cakes 
+of the trodden-down earth had been lifted up by worms over the 
+mouths of seven burrows, which passed through the softer parts of 
+the naked concrete, or between the interstices of the tesserae.  On 
+the third morning twenty-five burrows were counted; and by suddenly 
+lifting up the little cakes of earth, four worms were seen in the 
+act of quickly retreating.  Two castings were thrown up during the 
+third night on the floor, and these were of large size.  The season 
+was not favourable for the full activity of worms, and the weather 
+had lately been hot and dry, so that most of the worms now lived at 
+a considerable depth.  In digging the two trenches many open 
+burrows and some worms were encountered at between 30 and 40 inches 
+beneath the surface; but at a greater depth they became rare.  One 
+worm, however, was cut through at 48.5, and another at 51.5 inches 
+beneath the surface.  A fresh humus-lined burrow was also met with 
+at a depth of 57 and another at 65.5 inches.  At greater depths 
+than this, neither burrows nor worms were seen.
+
+As I wished to learn how many worms lived beneath the floor of the 
+atrium--a space of about 14 by 9 feet--Mr. Farrer was so kind as to 
+make observations for me, during the next seven weeks, by which 
+time the worms in the surrounding country were in full activity, 
+and were working near the surface.  It is very improbable that 
+worms should have migrated from the adjoining field into the small 
+space of the atrium, after the superficial mould in which they 
+prefer to live, had been removed.  We may therefore conclude that 
+the burrows and the castings which were seen here during the 
+ensuing seven weeks were the work of the former inhabitants of the 
+space.  I will now give a few extracts from Mr. Farrer's notes.
+
+Aug. 26th, 1877; that is, five days after the floor had been 
+cleared.  On the previous night there had been some heavy rain, 
+which washed the surface clean, and now the mouths of forty burrows 
+were counted.  Parts of the concrete were seen to be solid, and had 
+never been penetrated by worms, and here the rain-water lodged.
+
+Sept. 5th.--Tracks of worms, made during the previous night, could 
+be seen on the surface of the floor, and five or six vermiform 
+castings had been thrown up.  These were defaced.
+
+Sept. 12th.--During the last six days, the worms have not been 
+active, though many castings have been ejected in the neighbouring 
+fields; but on this day the earth was a little raised over the 
+mouths of the burrows, or castings were ejected, at ten fresh 
+points.  These were defaced.  It should be understood that when a 
+fresh burrow is spoken of, this generally means only that an old 
+burrow has been re-opened.  Mr. Farrer was repeatedly struck with 
+the pertinacity with which the worms re-opened their old burrows, 
+even when no earth was ejected from them.  I have often observed 
+the same fact, and generally the mouths of the burrows are 
+protected by an accumulation of pebbles, sticks or leaves.  Mr. 
+Farrer likewise observed that the worms living beneath the floor of 
+the atrium often collected coarse grains of sand, and such little 
+stones as they could find, round the mouths of their burrows.
+
+Sept. 13th; soft wet weather.  The mouths of the burrows were re-
+opened, or castings were ejected, at 31 points; these were all 
+defaced.
+
+Sept. 14th; 34 fresh holes or castings; all defaced.
+
+Sept. 15th; 44 fresh holes, only 5 castings; all defaced.
+
+Sept. 18th; 43 fresh holes, 8 castings; all defaced.
+
+The number of castings on the surrounding fields was now very 
+large.
+
+Sept. 19th; 40 holes, 8 castings; all defaced.
+
+Sept. 22nd; 43 holes, only a few fresh castings; all defaced.
+
+Sept. 23rd; 44 holes, 8 castings.
+
+Sept. 25th; 50 holes, no record of the number of castings.
+
+Oct. 13th;  61 holes, no record of the number of castings.
+
+After an interval of three years, Mr. Farrer, at my request, again 
+looked at the concrete floor, and found the worms still at work.
+
+Knowing what great muscular power worms possess, and seeing how 
+soft the concrete was in many parts, I was not surprised at its 
+having been penetrated by their burrows; but it is a more 
+surprising fact that the mortar between the rough stones of the 
+thick walls, surrounding the rooms, was found by Mr. Farrer to have 
+been penetrated by worms.  On August 26th, that is, five days after 
+the ruins had been exposed, he observed four open burrows on the 
+broken summit of the eastern wall (W in Fig. 8); and, on September 
+15th, other burrows similarly situated were seen.  It should also 
+be noted that in the perpendicular side of the trench (which was 
+much deeper than is represented in Fig. 8) three recent burrows 
+were seen, which ran obliquely far down beneath the base of the old 
+wall.
+
+We thus see that many worms lived beneath the floor and the walls 
+of the atrium at the time when the excavations were made; and that 
+they afterwards almost daily brought up earth to the surface from a 
+considerable depth.  There is not the slightest reason to doubt 
+that worms have acted in this manner ever since the period when the 
+concrete was sufficiently decayed to allow them to penetrate it; 
+and even before that period they would have lived beneath the 
+floor, as soon as it became pervious to rain, so that the soil 
+beneath was kept damp.  The floor and the walls must therefore have 
+been continually undermined; and fine earth must have been heaped 
+on them during many centuries, perhaps for a thousand years.  If 
+the burrows beneath the floor and walls, which it is probable were 
+formerly as numerous as they now are, had not collapsed in the 
+course of time in the manner formerly explained, the underlying 
+earth would have been riddled with passages like a sponge; and as 
+this was not the case, we may feel sure that they have collapsed.  
+The inevitable result of such collapsing during successive 
+centuries, will have been the slow subsidence of the floor and of 
+the walls, and their burial beneath the accumulated worm-castings.  
+The subsidence of a floor, whilst it still remains nearly 
+horizontal, may at first appear improbable; but the case presents 
+no more real difficulty than that of loose objects strewed on the 
+surface of a field, which, as we have seen, become buried several 
+inches beneath the surface in the course of a few years, though 
+still forming a horizontal layer parallel to the surface.  The 
+burial of the paved and level path on my lawn, which took place 
+under my own observation, is an analogous case.  Even those parts 
+of the concrete floor which the worms could not penetrate would 
+almost certainly have been undermined, and would have sunk, like 
+the great stones at Leith Hill Place and Stonehenge, for the soil 
+would have been damp beneath them.  But the rate of sinking of the 
+different parts would not have been quite equal, and the floor was 
+not quite level.  The foundations of the boundary walls lie, as 
+shown in the section, at a very small depth beneath the surface; 
+they would therefore have tended to subside at nearly the same rate 
+as the floor.  But this would not have occurred if the foundations 
+had been deep, as in the case of some other Roman ruins presently 
+to be described.
+
+Finally, we may infer that a large part of the fine vegetable 
+mould, which covered the floor and the broken-down walls of this 
+villa, in some places to a thickness of 16 inches, was brought up 
+from below by worms.  From facts hereafter to be given there can be 
+no doubt that some of the finest earth thus brought up will have 
+been washed down the sloping surface of the field during every 
+heavy shower of rain.  If this had not occurred a greater amount of 
+mould would have accumulated over the ruins than that now present.  
+But beside the castings of worms and some earth brought up by 
+insects, and some accumulation of dust, much fine earth will have 
+been washed over the ruins from the upper parts of the field, since 
+it has been under cultivation; and from over the ruins to the lower 
+parts of the slope; the present thickness of the mould being the 
+resultant of these several agencies.
+
+
+I may here append a modern instance of the sinking of a pavement, 
+communicated to me in 1871 by Mr. Ramsay, Director of the 
+Geological Survey of England.  A passage without a roof, 7 feet in 
+length by 3 feet 2 inches in width, led from his house into the 
+garden, and was paved with slabs of Portland stone.  Several of 
+these slabs were 16 inches square, others larger, and some a little 
+smaller.  This pavement had subsided about 3 inches along the 
+middle of the passage, and two inches on each side, as could be 
+seen by the lines of cement by which the slabs had been originally 
+joined to the walls.  The pavement had thus become slightly concave 
+along the middle; but there was no subsidence at the end close to 
+the house.  Mr. Ramsay could not account for this sinking, until he 
+observed that castings of black mould were frequently ejected along 
+the lines of junction between the slabs; and these castings were 
+regularly swept away.  The several lines of junction, including 
+those with the lateral walls, were altogether 39 feet 2 inches in 
+length.  The pavement did not present the appearance of ever having 
+been renewed, and the house was believed to have been built about 
+eighty-seven years ago.  Considering all these circumstances, Mr. 
+Ramsay does not doubt that the earth brought up by the worms since 
+the pavement was first laid down, or rather since the decay of the 
+mortar allowed the worms to burrow through it, and therefore within 
+a much shorter time than the eighty-seven years, has sufficed to 
+cause the sinking of the pavement to the above amount, except close 
+to the house, where the ground beneath would have been kept nearly 
+dry.
+
+Beaulieu Abbey, Hampshire.--This abbey was destroyed by Henry 
+VIII., and there now remains only a portion of the southern aisle-
+wall.  It is believed that the king had most of the stones carried 
+away for building a castle; and it is certain that they have been 
+removed.  The positions of the nave and transepts were ascertained 
+not long ago by the foundations having been found; and the place is 
+now marked by stones let into the ground.  Where the abbey formerly 
+stood, there now extends a smooth grass-covered surface, which 
+resembles in all respects the rest of the field.  The guardian, a 
+very old man, said the surface had never been levelled in his time.  
+In the year 1853, the Duke of Buccleuch had three holes dug in the 
+turf within a few yards of one another, at the western end of the 
+nave; and the old tesselated pavement of the abbey was thus 
+discovered.  These holes were afterwards surrounded by brickwork, 
+and protected by trap-doors, so that the pavement might be readily 
+inspected and preserved.  When my son William examined the place on 
+January 5, 1872, he found that the pavement in the three holes lay 
+at depths of 6.75, 10 and 11.5 inches beneath the surrounding turf-
+covered surface.  The old guardian asserted that he was often 
+forced to remove worm-castings from the pavement; and that he had 
+done so about six months before.  My son collected all from one of 
+the holes, the area of which was 5.32 square feet, and they weighed 
+7.97 ounces.  Assuming that this amount had accumulated in six 
+months, the accumulation during a year on a square yard would be 
+1.68 pounds, which, though a large amount, is very small compared 
+with what, as we have seen, is often ejected on fields and commons.  
+When I visited the abbey on June 22, 1877, the old man said that he 
+had cleared out the holes about a month before, but a good many 
+castings had since been ejected.  I suspect that he imagined that 
+he swept the pavements oftener than he really did, for the 
+conditions were in several respects very unfavourable for the 
+accumulation of even a moderate amount of castings.  The tiles are 
+rather large, viz., about 5.5 inches square, and the mortar between 
+them was in most places sound, so that the worms were able to bring 
+up earth from below only at certain points.  The tiles rested on a 
+bed of concrete, and the castings in consequence consisted in large 
+part (viz., in the proportion of 19 to 33) of particles of mortar, 
+grains of sand, little fragments of rock, bricks or tile; and such 
+substances could hardly be agreeable, and certainly not nutritious, 
+to worms.
+
+My son dug holes in several places within the former walls of the 
+abbey, at a distance of several yards from the above described 
+bricked squares.  He did not find any tiles, though these are known 
+to occur in some other parts, but he came in one spot to concrete 
+on which tiles had once rested.  The fine mould beneath the turf on 
+the sides of the several holes, varied in thickness from only 2 to 
+2.75 inches, and this rested on a layer from 8.75 to above 11 
+inches in thickness, consisting of fragments of mortar and stone-
+rubbish with the interstices compactly filled up with black mould.  
+In the surrounding field, at a distance of 20 yards from the abbey, 
+the fine vegetable mould was 11 inches thick.
+
+We may conclude from these facts that when the abbey was destroyed 
+and the stones removed, a layer of rubbish was left over the whole 
+surface, and that as soon as the worms were able to penetrate the 
+decayed concrete and the joints between the tiles, they slowly 
+filled up the interstices in the overlying rubbish with their 
+castings, which were afterwards accumulated to a thickness of 
+nearly three inches over the whole surface.  If we add to this 
+latter amount the mould between the fragments of stones, some five 
+or six inches of mould must have been brought up from beneath the 
+concrete or tiles.  The concrete or tiles will consequently have 
+subsided to nearly this amount.  The bases of the columns of the 
+aisles are now buried beneath mould and turf.  It is not probable 
+that they can have been undermined by worms, for their foundations 
+would no doubt have been laid at a considerable depth.  If they 
+have not subsided, the stones of which the columns were constructed 
+must have been removed from beneath the former level of the floor.
+
+Chedworth, Gloucestershire.--The remains of a large Roman villa 
+were discovered here in 1866, on ground which had been covered with 
+wood from time immemorial.  No suspicion seems ever to have been 
+entertained that ancient buildings lay buried here, until a 
+gamekeeper, in digging for rabbits, encountered some remains. {55}  
+But subsequently the tops of some stone walls were detected in 
+parts of the wood, projecting a little above the surface of the 
+ground.  Most of the coins found here belonged to Constans (who 
+died 350 A.D.) and the Constantine family.  My sons Francis and 
+Horace visited the place in November 1877, for the sake of 
+ascertaining what part worms may have played in the burial of these 
+extensive remains.  But the circumstances were not favourable for 
+this object, as the ruins are surrounded on three sides by rather 
+steep banks, down which earth is washed during rainy weather.  
+Moreover most of the old rooms have been covered with roofs, for 
+the protection of the elegant tesselated pavements.
+
+A few facts may, however, be given on the thickness of the soil 
+over these ruins.  Close outside the northern rooms there is a 
+broken wall, the summit of which was covered by 5 inches of black 
+mould; and in a hole dug on the outer side of this wall, where the 
+ground had never before been disturbed, black mould, full of 
+stones, 26 inches in thickness, was found, resting on the 
+undisturbed sub-soil of yellow clay.  At a depth of 22 inches from 
+the surface a pig's jaw and a fragment of a tile were found.  When 
+the excavations were first made, some large trees grew over the 
+ruins; and the stump of one has been left directly over a party-
+wall near the bath-room, for the sake of showing the thickness of 
+the superincumbent soil, which was here 38 inches.  In one small 
+room, which, after being cleared out, had not been roofed over, my 
+sons observed the hole of a worm passing through the rotten 
+concrete, and a living worm was found within the concrete.  In 
+another open room worm-castings were seen on the floor, over which 
+some earth had by this means been deposited, and here grass now 
+grew.
+
+Brading, Isle of Wight.--A fine Roman villa was discovered here in 
+1880; and by the end of October no less than 18 chambers had been 
+more or less cleared.  A coin dated 337 A.D.  was found.  My son 
+William visited the place before the excavations were completed; 
+and he informs me that most of the floors were at first covered 
+with much rubbish and fallen stones, having their interstices 
+completely filled up with mould, abounding, as the workmen said, 
+with worms, above which there was mould without any stones.  The 
+whole mass was in most places from 3 to above 4 ft. in thickness.  
+In one very large room the overlying earth was only 2 ft. 6 in. 
+thick; and after this had been removed, so many castings were 
+thrown up between the tiles that the surface had to be almost daily 
+swept.  Most of the floors were fairly level.  The tops of the 
+broken-down walls were covered in some places by only 4 or 5 inches 
+of soil, so that they were occasionally struck by the plough, but 
+in other places they were covered by from 13 to 18 inches of soil.  
+It is not probable that these walls could have been undermined by 
+worms and subsided, as they rested on a foundation of very hard red 
+sand, into which worms could hardly burrow.  The mortar, however, 
+between the stones of the walls of a hypocaust was found by my son 
+to have been penetrated by many worm-burrows.  The remains of this 
+villa stand on land which slopes at an angle of about 3 degrees; 
+and the land appears to have been long cultivated.  Therefore no 
+doubt a considerable quantity of fine earth has been washed down 
+from the upper parts of the field, and has largely aided in the 
+burial of these remains.
+
+Silchester, Hampshire.--The ruins of this small Roman town have 
+been better preserved than any other remains of the kind in 
+England.  A broken wall, in most parts from 15 to 18 feet in height 
+and about 1.5 mile in compass, now surrounds a space of about 100 
+acres of cultivated land, on which a farm-house and a church stand. 
+{56}  Formerly, when the weather was dry, the lines of the buried 
+walls could be traced by the appearance of the crops; and recently 
+very extensive excavations have been undertaken by the Duke of 
+Wellington, under the superintendence of the late Rev. J. G. Joyce, 
+by which means many large buildings have been discovered.  Mr. 
+Joyce made careful coloured sections, and measured the thickness of 
+each bed of rubbish, whilst the excavations were in progress; and 
+he has had the kindness to send me copies of several of them.  When 
+my sons Francis and Horace visited these ruins, he accompanied 
+them, and added his notes to theirs.
+
+Mr. Joyce estimates that the town was inhabited by the Romans for 
+about three centuries; and no doubt much matter must have 
+accumulated within the walls during this long period.  It appears 
+to have been destroyed by fire, and most of the stones used in the 
+buildings have since been carried away.  These circumstances are 
+unfavourable for ascertaining the part which worms have played in 
+the burial of the ruins; but as careful sections of the rubbish 
+overlying an ancient town have seldom or never before been made in 
+England, I will give copies of the most characteristic portions of 
+some of those made by Mr. Joyce.  They are of too great length to 
+be here introduced entire.
+
+An east and west section, 30 ft. in length, was made across a room 
+in the Basilica, now called the Hall of the Merchants (Fig. 9).  
+The hard concrete floor, still covered here and there with 
+tesserae, was found at 3 ft. beneath the surface of the field, 
+which was here level.  On the floor there were two large piles of 
+charred wood, one alone of which is shown in the part of the 
+section here given.  This pile was covered by a thin white layer of 
+decayed stucco or plaster, above which was a mass, presenting a 
+singularly disturbed appearance, of broken tiles, mortar, rubbish 
+and fine gravel, together 27 inches in thickness.  Mr. Joyce 
+believes that the gravel was used in making the mortar or concrete, 
+which has since decayed, some of the lime probably having been 
+dissolved.  The disturbed state of the rubbish may have been due to 
+its having been searched for building stones.  This bed was capped 
+by fine vegetable mould, 9 inches in thickness.  From these facts 
+we may conclude that the Hall was burnt down, and that much rubbish 
+fell on the floor, through and from which the worms slowly brought 
+up the mould, now forming the surface of the level field.
+
+A section across the middle of another hall in the Basilica, 32 
+feet 6 inches in length, called the AErarium, is shown in Fig. 10.  
+It appears that we have here evidence of two fires, separated by an 
+interval of time, during which the 6 inches of "mortar and concrete 
+with broken tiles" was accumulated.  Beneath one of the layers of 
+charred wood, a valuable relic, a bronze eagle, was found; and this 
+shows that the soldiers must have deserted the place in a panic.  
+Owing to the death of Mr. Joyce, I have not been able to ascertain 
+beneath which of the two layers the eagle was found.  The bed of 
+rubble overlying the undisturbed gravel originally formed, as I 
+suppose, the floor, for it stands on a level with that of a 
+corridor, outside the walls of the Hall; but the corridor is not 
+shown in the section as here given.  The vegetable mould was 16 
+inches thick in the thickest part; and the depth from the surface 
+of the field, clothed with herbage, to the undisturbed gravel, was 
+40 inches.
+
+The section shown in Fig. 11 represents an excavation made in the 
+middle of the town, and is here introduced because the bed of "rich 
+mould" attained, according to Mr. Joyce, the unusual thickness of 
+20 inches.  Gravel lay at the depth of 48 inches from the surface; 
+but it was not ascertained whether this was in its natural state, 
+or had been brought here and had been rammed down, as occurs in 
+some other places.
+
+The section shown in Fig. 12 was taken in the centre of the 
+Basilica, and though it was 5 feet in depth, the natural sub-soil 
+was not reached.  The bed marked "concrete" was probably at one 
+time a floor; and the beds beneath seem to be the remnants of more 
+ancient buildings.  The vegetable mould was here only 9 inches 
+thick.  In some other sections, not copied, we likewise have 
+evidence of buildings having been erected over the ruins of older 
+ones.  In one case there was a layer of yellow clay of very unequal 
+thickness between two beds of debris, the lower one of which rested 
+on a floor with tesserae.  The ancient broken walls appear to have 
+been sometimes roughly cut down to a uniform level, so as to serve 
+as the foundations for a temporary building; and Mr. Joyce suspects 
+that some of these buildings were wattled sheds, plastered with 
+clay, which would account for the above-mentioned layer of clay.
+
+Turning now to the points which more immediately concern us.  Worm-
+castings were observed on the floors of several of the rooms, in 
+one of which the tesselation was unusually perfect.  The tesserae 
+here consisted of little cubes of hard sandstone of about 1 inch, 
+several of which were loose or projected slightly above the general 
+level.  One or occasionally two open worm-burrows were found 
+beneath all the loose tesserae.  Worms have also penetrated the old 
+walls of these ruins.  A wall, which had just been exposed to view 
+during the excavations then in progress, was examined; it was built 
+of large flints, and was 18 inches in thickness.  It appeared 
+sound, but when the soil was removed from beneath, the mortar in 
+the lower part was found to be so much decayed that the flints fell 
+apart from their own weight.  Here, in the middle of the wall, at a 
+depth of 29 inches beneath the old floor and of 49.5 inches beneath 
+the surface of the field, a living worm was found, and the mortar 
+was penetrated by several burrows.
+
+A second wall was exposed to view for the first time, and an open 
+burrow was seen on its broken summit.  By separating the flints 
+this burrow was traced far down in the interior of the wall; but as 
+some of the flints cohered firmly, the whole mass was disturbed in 
+pulling down the wall, and the burrow could not be traced to the 
+bottom.  The foundations of a third wall, which appeared quite 
+sound, lay at a depth of 4 feet beneath one of the floors, and of 
+course at a considerably greater depth beneath the level of the 
+ground.  A large flint was wrenched out of the wall at about a foot 
+from the base, and this required much force, as the mortar was 
+sound; but behind the flint in the middle of the wall, the mortar 
+was friable, and here there were worm-burrows.  Mr. Joyce and my 
+sons were surprised at the blackness of the mortar in this and in 
+several other cases, and at the presence of mould in the interior 
+of the walls.  Some may have been placed there by the old builders 
+instead of mortar; but we should remember that worms line their 
+burrows with black humus.  Moreover open spaces would almost 
+certainly have been occasionally left between the large irregular 
+flints; and these spaces, we may feel sure, would be filled up by 
+the worms with their castings, as soon as they were able to 
+penetrate the wall.  Rain-water, oozing down the burrows would also 
+carry fine dark-coloured particles into every crevice.  Mr. Joyce 
+was at first very sceptical about the amount of work which I 
+attributed to worms; but he ends his notes with reference to the 
+last-mentioned wall by saying, "This case caused me more surprise 
+and brought more conviction to me than any other.  I should have 
+said, and did say, that it was quite impossible such a wall could 
+have been penetrated by earth-worms."
+
+In almost all the rooms the pavement has sunk considerably, 
+especially towards the middle; and this is shown in the three 
+following sections.  The measurements were made by stretching a 
+string tightly and horizontally over the floor.  The section, Fig. 
+13, was taken from north to south across a room, 18 feet 4 inches 
+in length, with a nearly perfect pavement, next to the "Red Wooden 
+Hut."  In the northern half, the subsidence amounted to 5.75 inches 
+beneath the level of the floor as it now stands close to the walls; 
+and it was greater in the northern than in the southern half; but, 
+according to Mr. Joyce, the entire pavement has obviously subsided.  
+In several places, the tesserae appeared as if drawn a little away 
+from the walls; whilst in other places they were still in close 
+contact with them.
+
+In Fig. 14, we see a section across the paved floor of the southern 
+corridor or ambulatory of a quadrangle, in an excavation made near 
+"The Spring."  The floor is 7 feet 9 inches wide, and the broken-
+down walls now project only 0.75 of an inch above its level.  The 
+field, which was in pasture, here sloped from north to south, at an 
+angle of 30 degrees, 40 seconds.  The nature of the ground at some 
+little distance on each side of the corridor is shown in the 
+section.  It consisted of earth full of stones and other debris, 
+capped with dark vegetable mould which was thicker on the lower or 
+southern than on the northern side.  The pavement was nearly level 
+along lines parallel to the side-walls, but had sunk in the middle 
+as much as 7.75 inches.
+
+A small room at no great distance from that represented in Fig. 13, 
+had been enlarged by the Roman occupier on the southern side, by an 
+addition of 5 feet 4 inches in breadth.  For this purpose the 
+southern wall of the house had been pulled down, but the 
+foundations of the old wall had been left buried at a little depth 
+beneath the pavement of the enlarged room.  Mr. Joyce believes that 
+this buried wall must have been built before the reign of Claudius 
+II., who died 270 A.D.  We see in the accompanying section, Fig. 
+15, that the tesselated pavement has subsided to a less degree over 
+the buried wall than elsewhere; so that a slight convexity or 
+protuberance here stretched in a straight line across the room.  
+This led to a hole being dug, and the buried wall was thus 
+discovered.
+
+We see in these three sections, and in several others not given, 
+that the old pavements have sunk or sagged considerably.  Mr. Joyce 
+formerly attributed this sinking solely to the slow settling of the 
+ground.  That there has been some settling is highly probable, and 
+it may be seen in Fig. 15 that the pavement for a width of 5 feet 
+over the southern enlargement of the room, which must have been 
+built on fresh ground, has sunk a little more than on the old 
+northern side.  But this sinking may possibly have had no 
+connection with the enlargement of the room; for in Fig. 13 one 
+half of the pavement has subsided more than the other half without 
+any assignable cause.  In a bricked passage to Mr. Joyce's own 
+house, laid down only about six years ago, the same kind of sinking 
+has occurred as in the ancient buildings.  Nevertheless it does not 
+appear probable that the whole amount of sinking can be thus 
+accounted for.  The Roman builders excavated the ground to an 
+unusual depth for the foundations of their walls, which were thick 
+and solid; it is therefore hardly credible that they should have 
+been careless about the solidity of the bed on which their 
+tesselated and often ornamented pavements were laid.  The sinking 
+must, as it appears to me, be attributed in chief part to the 
+pavement having been undermined by worms, which we know are still 
+at work.  Even Mr. Joyce at last admitted that this could not have 
+failed to have produced a considerable effect.  Thus also the large 
+quantity of fine mould overlying the pavements can be accounted 
+for, the presence of which would otherwise be inexplicable.  My 
+sons noticed that in one room in which the pavement had sagged very 
+little, there was an unusually small amount of overlying mould.
+
+As the foundations of the walls generally lie at a considerable 
+depth, they will either have not subsided at all through the 
+undermining action of worms, or they will have subsided much less 
+than the floor.  This latter result would follow from worms not 
+often working deep down beneath the foundations; but more 
+especially from the walls not yielding when penetrated by worms, 
+whereas the successively formed burrows in a mass of earth, equal 
+to one of the walls in depth and thickness, would have collapsed 
+many times since the desertion of the ruins, and would consequently 
+have shrunk or subsided.  As the walls cannot have sunk much or at 
+all, the immediately adjoining pavement from adhering to them will 
+have been prevented from subsiding; and thus the present curvature 
+of the pavement is intelligible.
+
+The circumstance which has surprised me most with respect to 
+Silchester is that during the many centuries which have elapsed 
+since the old buildings were deserted, the vegetable mould has not 
+accumulated over them to a greater thickness than that here 
+observed.  In most places it is only about 9 inches in thickness, 
+but in some places 12 or even more inches.  In Fig. 11, it is given 
+as 20 inches, but this section was drawn by Mr. Joyce before his 
+attention was particularly called to this subject.  The land 
+enclosed within the old walls is described as sloping slightly to 
+the south; but there are parts which, according to Mr. Joyce, are 
+nearly level, and it appears that the mould is here generally 
+thicker than elsewhere.  The surface slopes in other parts from 
+west to east, and Mr. Joyce describes one floor as covered at the 
+western end by rubbish and mould to a thickness of 28.5 inches, and 
+at the eastern end by a thickness of only 11.5 inches.  A very 
+slight slope suffices to cause recent castings to flow downwards 
+during heavy rain, and thus much earth will ultimately reach the 
+neighbouring rills and streams and be carried away.  By this means, 
+the absence of very thick beds of mould over these ancient ruins 
+may, as I believe, be explained.  Moreover most of the land here 
+has long been ploughed, and this would greatly aid the washing away 
+of the finer earth during rainy weather.
+
+The nature of the beds immediately beneath the vegetable mould in 
+some of the sections is rather perplexing.  We see, for instance, 
+in the section of an excavation in a grass meadow (Fig. 14), which 
+sloped from north to south at an angle of 30 degrees 40 seconds, 
+that the mould on the upper side is only six inches and on the 
+lower side nine inches in thickness.  But this mould lies on a mass 
+(25.5 inches in thickness on the upper side) "of dark brown mould," 
+as described by Mr. Joyce, "thickly interspersed with small pebbles 
+and bits of tiles, which present a corroded or worn appearance.  
+The state of this dark-coloured earth is like that of a field which 
+has long been ploughed, for the earth thus becomes intermingled 
+with stones and fragments of all kinds which have been much exposed 
+to the weather.  If during the course of many centuries this grass 
+meadow and the other now cultivated fields have been at times 
+ploughed, and at other times left as pasture, the nature of the 
+ground in the above section is rendered intelligible.  For worms 
+will continually have brought up fine earth from below, which will 
+have been stirred up by the plough whenever the land was 
+cultivated.  But after a time a greater thickness of fine earth 
+will thus have been accumulated than could be reached by the 
+plough; and a bed like the 25.5-inch mass, in Fig. 14, will have 
+been formed beneath the superficial mould, which latter will have 
+been brought to the surface within more recent times, and have been 
+well sifted by the worms.
+
+Wroxeter, Shropshire. --The old Roman city of Uriconium was founded 
+in the early part of the second century, if not before this date; 
+and it was destroyed, according to Mr. Wright, probably between the 
+middle of the fourth and fifth century.  The inhabitants were 
+massacred, and skeletons of women were found in the hypocausts.  
+Before the year 1859, the sole remnant of the city above ground, 
+was a portion of a massive wall about 20 ft. in height.  The 
+surrounding land undulates slightly, and has long been under 
+cultivation.  It had been noticed that the corn-crops ripened 
+prematurely in certain narrow lines, and that the snow remained 
+unmelted in certain places longer than in others.  These 
+appearances led, as I was informed, to extensive excavations being 
+undertaken.  The foundations of many large buildings and several 
+streets have thus been exposed to view.  The space enclosed within 
+the old walls is an irregular oval, about 1 mile in length.  Many 
+of the stones or bricks used in the buildings must have been 
+carried away; but the hypocausts, baths, and other underground 
+buildings were found tolerably perfect, being filled with stones, 
+broken tiles, rubbish and soil.  The old floors of various rooms 
+were covered with rubble.  As I was anxious to know how thick the 
+mantle of mould and rubbish was, which had so long concealed these 
+ruins, I applied to Dr. H. Johnson, who had superintended the 
+excavations; and he, with the greatest kindness, twice visited the 
+place to examine it in reference to my questions, and had many 
+trenches dug in four fields which had hitherto been undisturbed.  
+The results of his observations are given in the following Table.  
+He also sent me specimens of the mould, and answered, as far as he 
+could, all my questions.
+
+
+MEASUREMENTS BY DR. H. JOHNSON OF THE THICKNESS OF THE VEGETABLE 
+MOULD OVER THE ROMAN RUINS AT WROXETER.
+
+
+Trenches dug in a field called "Old Works."
+
+(Thickness of mould in inches shown in parenthesis--DP.)
+
+1.  At a depth of 36 inches undisturbed sand was reached (20)
+
+2.  At a depth of 33 inches concrete was reached (21)
+
+3. At a depth of 9 inches concrete was reached (9)
+
+Trenches dug in a field called "Shop Leasows;" this is the highest 
+field within the old walls, and slopes down from a sub-central 
+point on all sides at about an angle of 2 degrees.
+
+4.  Summit of field, trench 45 inches deep (40)
+
+5.  Close to summit of field, trench 36 inches deep (26)
+
+6.  Close to summit of field, trench 28 inches deep (28)
+
+7.  Near summit of field, trench 36 inches deep (24)
+
+8.  Near summit of field, trench at one end 39 inches deep; the 
+mould here graduated into the underlying undisturbed sand, and its 
+thickness (24 inches) is somewhat arbitrary.  At the other end of 
+the trench, a causeway was encountered at a depth of only 7 inches, 
+and the mould was here only 7 inches thick (24)
+
+9.  Trench close to the last, 28 inches in depth (24)
+
+10.  Lower part of same field, trench 30 inches deep (15)
+
+11.  Lower part of same field, trench 31 inches deep (17)
+
+12.  Lower part of same field, trench 36 inches deep, at which 
+depth undisturbed sand was reached (28)
+
+13.  In another part of same field, trench 9.5 inches deep stopped 
+by concrete (9.5)
+
+14.  In another part of same field, trench 9 inches deep, stopped 
+by concrete (9)
+
+15.  In another part of the same field, trench 24 inches deep, when 
+sand was reached (16)
+
+16.  In another part of same field, trench 30 inches deep, when 
+stones were reached; at one end of the trench mould 12 inches, at 
+the other end 14 inches thick (13)
+
+Small field between "Old Works" and "Shop Leasows," I believe 
+nearly as high as the upper part of the latter field.
+
+17.  Trench 26 inches deep (24)
+
+18.  Trench 10 inches deep, and then came upon a causeway (10)
+
+19.  Trench 34 inches deep (30)
+
+20. Trench 31 inches deep (31)
+
+Field on the western side of the space enclosed within the old 
+walls.
+
+21.  Trench 28 inches deep, when undisturbed sand was reached (16)
+
+22.  Trench 29 inches deep, when undisturbed sand was reached (15)
+
+23.  Trench 14 inches deep, and then came upon a building (14)
+
+
+Dr. Johnson distinguished as mould the earth which differed, more 
+or less abruptly, in its dark colour and in its texture from the 
+underlying sand or rubble.  In the specimens sent to me, the mould 
+resembled that which lies immediately beneath the turf in old 
+pasture-land, excepting that it often contained small stones, too 
+large to have passed through the bodies of worms.  But the trenches 
+above described were dug in fields, none of which were in pasture, 
+and all had been long cultivated.  Bearing in mind the remarks made 
+in reference to Silchester on the effects of long-continued 
+culture, combined with the action of worms in bringing up the finer 
+particles to the surface, the mould, as so designated by Dr. 
+Johnson, seems fairly well to deserve its name.  Its thickness, 
+where there was no causeway, floor or walls beneath, was greater 
+than has been elsewhere observed, namely, in many places above 2 
+ft., and in one spot above 3 ft.  The mould was thickest on and 
+close to the nearly level summit of the field called "Shop 
+Leasows," and in a small adjoining field, which, as I believe, is 
+of nearly the same height.  One side of the former field slopes at 
+an angle of rather above 2 degrees, and I should have expected that 
+the mould, from being washed down during heavy rain, would have 
+been thicker in the lower than in the upper part; but this was not 
+the case in two out of the three trenches here dug.
+
+In many places, where streets ran beneath the surface, or where old 
+buildings stood, the mould was only 8 inches in thickness; and Dr.  
+Johnson was surprised that in ploughing the land, the ruins had 
+never been struck by the plough as far as he had heard.  He thinks 
+that when the land was first cultivated the old walls were perhaps 
+intentionally pulled down, and that hollow places were filled up.  
+This may have been the case; but if after the desertion of the city 
+the land was left for many centuries uncultivated, worms would have 
+brought up enough fine earth to have covered the ruins completely; 
+that is if they had subsided from having been undermined.  The 
+foundations of some of the walls, for instance those of the portion 
+still standing about 20 feet above the ground, and those of the 
+marketplace, lie at the extraordinary depth of 14 feet; but it is 
+highly improbable that the foundations were generally so deep.  The 
+mortar employed in the buildings must have been excellent, for it 
+is still in parts extremely hard.  Wherever walls of any height 
+have been exposed to view, they are, as Dr.  Johnson believes, 
+still perpendicular.  The walls with such deep foundations cannot 
+have been undermined by worms, and therefore cannot have subsided, 
+as appears to have occurred at Abinger and Silchester.  Hence it is 
+very difficult to account for their being now completely covered 
+with earth; but how much of this covering consists of vegetable 
+mould and how much of rubble I do not know.  The market-place, with 
+the foundations at a depth of 14 feet, was covered up, as Dr.  
+Johnson believes, by between 6 and 24 inches of earth.  The tops of 
+the broken-down walls of a caldarium or bath, 9 feet in depth, were 
+likewise covered up with nearly 2 feet of earth.  The summit of an 
+arch, leading into an ash-pit 7 feet in depth, was covered up with 
+not more than 8 inches of earth.  Whenever a building which has not 
+subsided is covered with earth, we must suppose, either that the 
+upper layers of stone have been at some time carried away by man, 
+or that earth has since been washed down during heavy rain, or 
+blown down during storms, from the adjoining land; and this would 
+be especially apt to occur where the land has long been cultivated.  
+In the above cases the adjoining land is somewhat higher than the 
+three specified sites, as far as I can judge by maps and from 
+information given me by Dr.  Johnson.  If; however, a great pile of 
+broken stones, mortar, plaster, timber and ashes fell over the 
+remains of any building, their disintegration in the course of 
+time, and the sifting action of worms, would ultimately conceal the 
+whole beneath fine earth.
+
+Conclusion. --The cases given in this chapter show that worms have 
+played a considerable part in the burial and concealment of several 
+Roman and other old buildings in England; but no doubt the washing 
+down of soil from the neighbouring higher lands, and the deposition 
+of dust, have together aided largely in the work of concealment.  
+Dust would be apt to accumulate wherever old broken-down walls 
+projected a little above the then existing surface and thus 
+afforded some shelter.  The floors of the old rooms, halls and 
+passages have generally sunk, partly from the settling of the 
+ground, but chiefly from having been undermined by worms; and the 
+sinking has commonly been greater in the middle than near the 
+walls.  The walls themselves, whenever their foundations do not lie 
+at a great depth, have been penetrated and undermined by worms, and 
+have consequently subsided.  The unequal subsidence thus caused, 
+probably explains the great cracks which may be seen in many 
+ancient walls, as well as their inclination from the perpendicular.
+
+
+
+CHAPTER V--THE ACTION OF WORMS IN THE DENUDATION OF THE LAND.
+
+
+
+Evidence of the amount of denudation which the land has undergone--
+Sub-aerial denudation--The deposition of dust--Vegetable mould, its 
+dark colour and fine texture largely due to the action of worms--
+The disintegration of rocks by the humus-acids --Similar acids 
+apparently generated within the bodies of worms--The action of 
+these acids facilitated by the continued movement of the particles 
+of earth--A thick bed of mould checks the disintegration of the 
+underlying soil and rocks.  Particles of stone worn or triturated 
+in the gizzards of worms--Swallowed stones serve as mill-stones--
+The levigated state of the castings--Fragments of brick in the 
+castings over ancient buildings well rounded.  The triturating 
+power of worms not quite insignificant under a geological point of 
+view.
+
+
+No one doubts that our world at one time consisted of crystalline 
+rocks, and that it is to their disintegration through the action of 
+air, water, changes of temperature, rivers, waves of the sea, 
+earthquakes and volcanic outbursts, that we owe our sedimentary 
+formations.  These after being consolidated and sometimes 
+recrystallized, have often been again disintegrated.  Denudation 
+means the removal of such disintegrated matter to a lower level.  
+Of the many striking results due to the modern progress of geology 
+there are hardly any more striking than those which relate to 
+denudation.  It was long ago seen that there must have been an 
+immense amount of denudation; but until the successive formations 
+were carefully mapped and measured, no one fully realised how great 
+was the amount.  One of the first and most remarkable memoirs ever 
+published on this subject was that by Ramsay, {57} who in 1846 
+showed that in Wales from 9000 to 11,000 feet in thickness of solid 
+rock had been stripped off large tracks of country.  Perhaps the 
+plainest evidence of great denudation is afforded by faults or 
+cracks, which extend for many miles across certain districts, with 
+the strata on one side raised even ten thousand feet above the 
+corresponding strata on the opposite side; and yet there is not a 
+vestige of this gigantic displacement visible on the surface of the 
+land.  A huge pile of rock has been planed away on one side and not 
+a remnant left.
+
+Until the last twenty or thirty years, most geologists thought that 
+the waves of the sea were the chief agents in the work of 
+denudation; but we may now feel sure that air and rain, aided by 
+streams and rivers, are much more powerful agents,--that is if we 
+consider the whole area of the land.  The long lines of escarpment 
+which stretch across several parts of England were formerly 
+considered to be undoubtedly ancient coast-lines; but we now know 
+that they stand up above the general surface merely from resisting 
+air, rain and frost better than the adjoining formations.  It has 
+rarely been the good fortune of a geologist to bring conviction to 
+the minds of his fellow-workers on a disputed point by a single 
+memoir; but Mr. Whitaker, of the Geological Survey of England, was 
+so fortunate when, in 1867, he published his paper "On sub-aerial 
+Denudation, and on Cliffs and Escarpments of the Chalk." {58}  
+Before this paper appeared, Mr. A. Tylor had adduced important 
+evidence on sub-aerial denudation, by showing that the amount of 
+matter brought down by rivers must infallibly lower the level of 
+their drainage basins by many feet in no immense lapse of time.  
+This line of argument has since been followed up in the most 
+interesting manner by Archibald Geikie, Croll and others, in a 
+series of valuable memoirs. {59}  For the sake of those who have 
+never attended to this subject, a single instance may be here 
+given, namely, that of the Mississippi, which is chosen because the 
+amount of sediment brought down by this great river has been 
+investigated with especial care by order of the United States 
+Government.  The result is, as Mr. Croll shows, that the mean level 
+of its enormous area of drainage must be lowered 1/4566 of a foot 
+annually, or 1 foot in 4566 years.  Consequently, taking the best 
+estimate of the mean height of the North American continent, viz. 
+748 feet, and looking to the future, the whole of the great 
+Mississippi basin will be washed away, and "brought down to the 
+sea-level in less than 4,500,000 years, if no elevation of the land 
+takes place."  Some rivers carry down much more sediment relatively 
+to their size, and some much less than the Mississippi.
+
+Disintegrated matter is carried away by the wind as well as by 
+running water.  During volcanic outbursts much rock is triturated 
+and is thus widely dispersed; and in all arid countries the wind 
+plays an important part in the removal of such matter.  Wind-driven 
+sand also wears down the hardest rocks.  I have shown {60} that 
+during four months of the year a large quantity of dust is blown 
+from the north-western shores of Africa, and falls on the Atlantic 
+over a space of 1600 miles in latitude, and for a distance of from 
+300 to 600 miles from the coast.  But dust has been seen to fall at 
+a distance of 1030 miles from the shores of Africa.  During a stay 
+of three weeks at St. Jago in the Cape Verde Archipelago, the 
+atmosphere was almost always hazy, and extremely fine dust coming 
+from Africa was continually falling.  In some of this dust which 
+fell in the open ocean at a distance of between 330 and 380 miles 
+from the African coast, there were many particles of stone, about 
+1/1000 of an inch square.  Nearer to the coast the water has been 
+seen to be so much discoloured by the falling dust, that a sailing 
+vessel left a track behind her.  In countries, like the Cape Verde 
+Archipelago, where it seldom rains and there are no frosts, the 
+solid rock nevertheless disintegrates; and in conformity with the 
+views lately advanced by a distinguished Belgian geologist, De 
+Koninck, such disintegration may be attributed in chief part to the 
+action of the carbonic and nitric acids, together with the nitrates 
+and nitrites of ammonia, dissolved in the dew.
+
+In all humid, even moderately humid, countries, worms aid in the 
+work of denudation in several ways.  The vegetable mould which 
+covers, as with a mantle, the surface of the land, has all passed 
+many times through their bodies.  Mould differs in appearance from 
+the subsoil only in its dark colour, and in the absence of 
+fragments or particles of stone (when such are present in the 
+subsoil), larger than those which can pass through the alimentary 
+canal of a worm.  This sifting of the soil is aided, as has already 
+been remarked, by burrowing animals of many kinds, especially by 
+ants.  In countries where the summer is long and dry, the mould in 
+protected places must be largely increased by dust blown from other 
+and more exposed places.  For instance, the quantity of dust 
+sometimes blown over the plains of La Plata, where there are no 
+solid rocks, is so great, that during the "gran seco," 1827 to 
+1830, the appearance of the land, which is here unenclosed, was so 
+completely changed that the inhabitants could not recognise the 
+limits of their own estates, and endless lawsuits arose.  Immense 
+quantities of dust are likewise blown about in Egypt and in the 
+south of France.  In China, as Richthofen maintains, beds appearing 
+like fine sediment, several hundred feet in thickness and extending 
+over an enormous area, owe their origin to dust blown from the high 
+lands of central Asia. {61}  In humid countries like Great Britain, 
+as long as the land remains in its natural state clothed with 
+vegetation, the mould in any one place can hardly be much increased 
+by dust; but in its present condition, the fields near high roads, 
+where there is much traffic, must receive a considerable amount of 
+dust, and when fields are harrowed during dry and windy weather, 
+clouds of dust may be seen to be blown away.  But in all these 
+cases the surface-soil is merely transported from one place to 
+another.  The dust which falls so thickly within our houses 
+consists largely of organic matter, and if spread over the land 
+would in time decay and disappear almost entirely.  It appears, 
+however, from recent observations on the snow-fields of the Arctic 
+regions, that some little meteoric dust of extra mundane origin is 
+continually falling.
+
+The dark colour of ordinary mould is obviously due to the presence 
+of decaying organic matter, which, however, is present in but small 
+quantities.  The loss of weight which mould suffers when heated to 
+redness seems to be in large part due to water in combination being 
+dispelled.  In one sample of fertile mould the amount of organic 
+matter was ascertained to be only 1.76 per cent.; in some 
+artificially prepared soil it was as much as 5.5 per cent., and in 
+the famous black soil of Russia from 5 to even 12 per cent. {62}  
+In leaf-mould formed exclusively by the decay of leaves the amount 
+is much greater, and in peat the carbon alone sometimes amounts to 
+64 per cent.; but with these latter cases we are not here 
+concerned.  The carbon in the soil tends gradually to oxidise and 
+to disappear, except where water accumulates and the climate is 
+cool; {63} so that in the oldest pasture-land there is no great 
+excess of organic matter, notwithstanding the continued decay of 
+the roots and the underground stems of plants, and the occasional 
+addition of manure.  The disappearance of the organic matter from 
+mould is probably much aided by its being brought again and again 
+to the surface in the castings of worms.
+
+Worms, on the other hand, add largely to the organic matter in the 
+soil by the astonishing number of half-decayed leaves which they 
+draw into their burrows to a depth of 2 or 3 inches.  They do this 
+chiefly for obtaining food, but partly for closing the mouths of 
+their burrows and for lining the upper part.  The leaves which they 
+consume are moistened, torn into small shreds, partially digested, 
+and intimately commingled with earth; and it is this process which 
+gives to vegetable mould its uniform dark tint.  It is known that 
+various kinds of acids are generated by the decay of vegetable 
+matter; and from the contents of the intestines of worms and from 
+their castings being acid, it seems probable that the process of 
+digestion induces an analogous chemical change in the swallowed, 
+triturated, and half-decayed leaves.  The large quantity of 
+carbonate of lime secreted by the calciferous glands apparently 
+serves to neutralise the acids thus generated; for the digestive 
+fluid of worms will not act unless it be alkaline.  As the contents 
+of the upper part of their intestines are acid, the acidity can 
+hardly be due to the presence of uric acid.  We may therefore 
+conclude that the acids in the alimentary canal of worms are formed 
+during the digestive process; and that probably they are nearly of 
+the same nature as those in ordinary mould or humus.  The latter 
+are well known to have the power of de-oxidising or dissolving per-
+oxide of iron, as may be seen wherever peat overlies red sand, or 
+where a rotten root penetrates such sand.  Now I kept some worms in 
+a pot filled with very fine reddish sand, consisting of minute 
+particles of silex coated with the red oxide of iron; and the 
+burrows, which the worms made through this sand, were lined or 
+coated in the usual manner with their castings, formed of the sand 
+mingled with their intestinal secretions and the refuse of the 
+digested leaves; and this sand had almost wholly lost its red 
+colour.  When small portions of it were placed under the 
+microscope, most of the grains were seen to be transparent and 
+colourless, owing to the dissolution of the oxide; whilst almost 
+all the grains taken from other parts of the pot were coated with 
+the oxide.  Acetic acid produced hardly any effect on his sand; and 
+even hydrochloric, nitric and sulphuric acids, diluted as in the 
+Pharmacopoeia, produced less effect than did the acids in the 
+intestines of the worms.
+
+Mr. A. A. Julien has lately collected all the extant information 
+about the acids generated in humus, which, according to some 
+chemists, amount to more than a dozen different kinds.  These 
+acids, as well as their acid salts (i.e., in combination with 
+potash, soda, and ammonia), act energetically on carbonate of lime 
+and on the oxides of iron.  It is also known that some of these 
+acids, which were called long ago by Thenard azohumic, are enabled 
+to dissolve colloid silica in proportion to the nitrogen which they 
+contain. {64}  In the formation of these latter acids worms 
+probably afford some aid, for Dr. H. Johnson informs me that by 
+Nessler's test he found 0.018 per cent. of ammonia in their 
+castings.
+
+It may be here added that I have recently been informed by Dr. 
+Gilbert "that several square yards on his lawn were swept clean, 
+and after two or three weeks all the worm-castings on the space 
+were collected and dried.  These were found to contain 0.35 of 
+nitrogen.  This is from two to three times as much as we find in 
+our ordinary arable surface-soil; more than in our ordinary pasture 
+surface-soil; but less than in rich kitchen-garden mould.  
+Supposing a quantity of castings equal to 10 tons in the dry state 
+were annually deposited on an acre, this would represent a manuring 
+of 78 lbs. of nitrogen per acre per annum; and this is very much 
+more than the amount of nitrogen in the annual yield of hay per 
+acre, if raised without any nitrogenous manure.  Obviously, so far 
+as the nitrogen in the castings is derived from surface-growth or 
+from surface-soil, it is not a gain to the latter; but so far as it 
+is derived from below, it is a gain."
+
+The several humus-acids, which appear, as we have just seen, to be 
+generated within the bodies of worms during the digestive process, 
+and their acid salts, play a highly important part, according to 
+the recent observations of Mr. Julien, in the disintegration of 
+various kinds of rocks.  It has long been known that the carbonic 
+acid, and no doubt nitric and nitrous acids, which are present in 
+rain-water, act in like manner.  There is, also, a great excess of 
+carbonic acid in all soils, especially in rich soils, and this is 
+dissolved by the water in the ground.  The living roots of plants, 
+moreover, as Sachs and others have shown, quickly corrode and leave 
+their impressions on polished slabs of marble, dolomite and 
+phosphate of lime.  They will attack even basalt and sandstone. 
+{65}  But we are not here concerned with agencies which are wholly 
+independent of the action of worms.
+
+The combination of any acid with a base is much facilitated by 
+agitation, as fresh surfaces are thus continually brought into 
+contact.  This will be thoroughly effected with the particles of 
+stone and earth in the intestines of worms, during the digestive 
+process; and it should be remembered that the entire mass of the 
+mould over every field, passes, in the course of a few years, 
+through their alimentary canals.  Moreover as the old burrows 
+slowly collapse, and as fresh castings are continually brought to 
+the surface, the whole superficial layer of mould slowly revolves 
+or circulates; and the friction of the particles one with another 
+will rub off the finest films of disintegrated matter as soon as 
+they are formed.  Through these several means, minute fragments of 
+rocks of many kinds and mere particles in the soil will be 
+continually exposed to chemical decomposition; and thus the amount 
+of soil will tend to increase.
+
+As worms line their burrows with their castings, and as the burrows 
+penetrate to a depth of 5 or 6, or even more feet, some small 
+amount of the humus-acids will be carried far down, and will there 
+act on the underlying rocks and fragments of rock.  Thus the 
+thickness of the soil, if none be removed from the surface, will 
+steadily though slowly tend to increase; but the accumulation will 
+after a time delay the disintegration of the underlying rocks and 
+of the more deeply seated particles.  For the humus-acids which are 
+generated chiefly in the upper layer of vegetable mould, are 
+extremely unstable compounds, and are liable to decomposition 
+before they reach any considerable depth. {66}  A thick bed of 
+overlying soil will also check the downward extension of great 
+fluctuations of temperature, and in cold countries will check the 
+powerful action of frost.  The free access of air will likewise be 
+excluded.  From these several causes disintegration would be almost 
+arrested, if the overlying mould were to increase much in 
+thickness, owing to none or little being removed from the surface. 
+{67}  In my own immediate neighbourhood we have a curious proof how 
+effectually a few feet of clay checks some change which goes on in 
+flints, lying freely exposed; for the large ones which have lain 
+for some time on the surface of ploughed fields cannot be used for 
+building; they will not cleave properly, and are said by the 
+workmen to be rotten. {68}  It is therefore necessary to obtain 
+flints for building purposes from the bed of red clay overlying the 
+chalk (the residue of its dissolution by rain-water) or from the 
+chalk itself.
+
+Not only do worms aid directly in the chemical disintegration of 
+rocks, but there is good reason to believe that they likewise act 
+in a direct and mechanical manner on the smaller particles.  All 
+the species which swallow earth are furnished with gizzards; and 
+these are lined with so thick a chitinous membrane, that Perrier 
+speaks of it, {69} as "une veritable armature."  The gizzard is 
+surrounded by powerful transverse muscles, which, according to 
+Claparede, are about ten times as thick as the longitudinal ones; 
+and Perrier saw them contracting energetically.  Worms belonging to 
+one genus, Digaster, have two distinct but quite similar gizzards; 
+and in another genus, Moniligaster, the second gizzard consists of 
+four pouches, one succeeding the other, so that it may almost be 
+said to have five gizzards. {70}  In the same manner as 
+gallinaceous and struthious birds swallow stones to aid in the 
+trituration of their food, so it appears to be with terricolous 
+worms.  The gizzards of thirty-eight of our common worms were 
+opened, and in twenty-five of them small stones or grains of sand, 
+sometimes together with the hard calcareous concretions formed 
+within the anterior calciferous glands, were found, and in two 
+others concretions alone.  In the gizzards of the remaining worms 
+there were no stones; but some of these were not real exceptions, 
+as the gizzards were opened late in the autumn, when the worms had 
+ceased to feed and their gizzards were quite empty. {71}
+
+When worms make their burrows through earth abounding with little 
+stones, no doubt many will be unavoidably swallowed; but it must 
+not be supposed that this fact accounts for the frequency with 
+which stones and sand are found in their gizzards.  For beads of 
+glass and fragments of brick and of hard tiles were scattered over 
+the surface of the earth, in pots in which worms were kept and had 
+already made their burrows; and very many of these beads and 
+fragments were picked up and swallowed by the worms, for they were 
+found in their castings, intestines, and gizzards.  They even 
+swallowed the coarse red dust, formed by the pounding of the tiles.  
+Nor can it be supposed that they mistook the beads and fragments 
+for food; for we have seen that their taste is delicate enough to 
+distinguish between different kinds of leaves.  It is therefore 
+manifest that they swallow hard objects, such as bits of stone, 
+beads of glass and angular fragments of bricks or tiles for some 
+special purpose; and it can hardly be doubted that this is to aid 
+their gizzards in crushing and grinding the earth, which they so 
+largely consume.  That such hard objects are not necessary for 
+crushing leaves, may be inferred from the fact that certain 
+species, which live in mud or water and feed on dead or living 
+vegetable matter, but which do not swallow earth, are not provided 
+with gizzards, {72} and therefore cannot have the power of 
+utilising stones.
+
+During the grinding process, the particles of earth must be rubbed 
+against one another, and between the stones and the tough lining 
+membrane of the gizzard.  The softer particles will thus suffer 
+some attrition, and will perhaps even be crushed.  This conclusion 
+is supported by the appearance of freshly ejected castings, for 
+these often reminded me of the appearance of paint which has just 
+been ground by a workman between two flat stones.  Morren remarks 
+that the intestinal canal is "impleta tenuissima terra, veluti in 
+pulverem redacta." {73}  Perrier also speaks of "l'etat de pate 
+excessivement fine a laquelle est reduite la terre qu'ils 
+rejettent," &c. {74}
+
+As the amount of trituration which the particles of earth undergo 
+in the gizzards of worms possesses some interest (as we shall 
+hereafter see), I endeavoured to obtain evidence on this head by 
+carefully examining many of the fragments which had passed through 
+their alimentary canals.  With worms living in a state of nature, 
+it is of course impossible to know how much the fragments may have 
+been worn before they were swallowed.  It is, however, clear that 
+worms do not habitually select already rounded particles, for 
+sharply angular bits of flint and of other hard rocks were often 
+found in their gizzards or intestines.  On three occasions sharp 
+spines from the stems of rose-bushes were thus found.  Worms kept 
+in confinement repeatedly swallowed angular fragments of hard tile, 
+coal, cinders, and even the sharpest fragments of glass.  
+Gallinaceous and struthious birds retain the same stones in their 
+gizzards for a long time, which thus become well rounded; but this 
+does not appear to be the case with worms, judging from the large 
+number of the fragments of tiles, glass beads, stones, &c., 
+commonly found in their castings and intestines.  So that unless 
+the same fragments were to pass repeatedly through their gizzards, 
+visible signs of attrition in the fragments could hardly be 
+expected, except perhaps in the case of very soft stones.
+
+I will now give such evidence of attrition as I have been able to 
+collect.  In the gizzards of some worms dug out of a thin bed of 
+mould over the chalk, there were many well-rounded small fragments 
+of chalk, and two fragments of the shells of a land-mollusc (as 
+ascertained by their microscopical structure), which latter were 
+not only rounded but somewhat polished.  The calcareous concretions 
+formed in the calciferous glands, which are often found in their 
+gizzards, intestines, and occasionally in their castings, when of 
+large size, sometimes appeared to have been rounded; but with all 
+calcareous bodies the rounded appearance may be partly or wholly 
+due to their corrosion by carbonic acid and the humus-acids.  In 
+the gizzards of several worms collected in my kitchen garden near a 
+hothouse, eight little fragments of cinders were found, and of 
+these, six appeared more or less rounded, as were two bits of 
+brick; but some other bits were not at all rounded.  A farm-road 
+near Abinger Hall had been covered seven years before with brick-
+rubbish to the depth of about 6 inches; turf had grown over this 
+rubbish on both sides of the road for a width of 18 inches, and on 
+this turf there were innumerable castings.  Some of them were 
+coloured of a uniform red owing to the presence of much brick-dust, 
+and they contained many particles of brick and of hard mortar from 
+1 to 3 mm. in diameter, most of which were plainly rounded; but all 
+these particles may have been rounded before they were protected by 
+the turf and were swallowed, like those on the bare parts of the 
+road which were much worn.  A hole in a pasture-field had been 
+filled up with brick-rubbish at the same time, viz., seven years 
+ago, and was now covered with turf; and here the castings contained 
+very many particles of brick, all more or less rounded; and this 
+brick-rubbish, after being shot into the hole, could not have 
+undergone any attrition.  Again, old bricks very little broken, 
+together with fragments of mortar, were laid down to form walks, 
+and were then covered with from 4 to 6 inches of gravel; six little 
+fragments of brick were extracted from castings collected on these 
+walks, three of which were plainly worn.  There were also very many 
+particles of hard mortar, about half of which were well rounded; 
+and it is not credible that these could have suffered so much 
+corrosion from the action of carbonic acid in the course of only 
+seven years.
+
+Much better evidence of the attrition of hard objects in the 
+gizzards of worms, is afforded by the state of the small fragments 
+of tiles or bricks, and of concrete in the castings thrown up where 
+ancient buildings once stood.  As all the mould covering a field 
+passes every few years through the bodies of worms, the same small 
+fragments will probably be swallowed and brought to the surface 
+many times in the course of centuries.  It should be premised that 
+in the several following cases, the finer matter was first washed 
+away from the castings, and then all the particles of bricks, tiles 
+and concrete were collected without any selection, and were 
+afterwards examined.  Now in the castings ejected between the 
+tesserae on one of the buried floors of the Roman villa at Abinger, 
+there were many particles (from to 2 mm. in diameter) of tiles and 
+concrete, which it was impossible to look at with the naked eye or 
+through a strong lens, and doubt for a moment that they had almost 
+all undergone much attrition.  I speak thus after having examined 
+small water-worn pebbles, formed from Roman bricks, which M. Henri 
+de Saussure had the kindness to send me, and which he had extracted 
+from sand and gravel beds, deposited on the shores of the Lake of 
+Geneva, at a former period when the water stood at about two metres 
+above its present level.  The smallest of these water-worn pebbles 
+of brick from Geneva resembled closely many of those extracted from 
+the gizzards of worms, but the larger ones were somewhat smoother.
+
+Four castings found on the recently uncovered, tesselated floor of 
+the great room in the Roman villa at Brading, contained many 
+particles of tile or brick, of mortar, and of hard white cement; 
+and the majority of these appeared plainly worn.  The particles of 
+mortar, however, seemed to have suffered more corrosion than 
+attrition, for grains of silex often projected from their surfaces.  
+Castings from within the nave of Beaulieu Abbey, which was 
+destroyed by Henry VIII., were collected from a level expanse of 
+turf, overlying the buried tesselated pavement, through which worm-
+burrows passed; and these castings contained innumerable particles 
+of tiles and bricks, of concrete and cement, the majority of which 
+had manifestly undergone some or much attrition.  There were also 
+many minute flakes of a micaceous slate, the points of which were 
+rounded.  If the above supposition, that in all these cases the 
+same minute fragments have passed several times through the 
+gizzards of worms, be rejected, notwithstanding its inherent 
+probability, we must then assume that in all the above cases the 
+many rounded fragments found in the castings had all accidentally 
+undergone much attrition before they were swallowed; and this is 
+highly improbable.
+
+On the other hand it must be stated that fragments of ornamental 
+tiles, somewhat harder than common tiles or bricks, which had been 
+swallowed only once by worms kept in confinement, were with the 
+doubtful exception of one or two of the smallest grains, not at all 
+rounded.  Nevertheless some of them appeared a little worn, though 
+not rounded.  Notwithstanding these cases, if we consider the 
+evidence above given, there can be little doubt that the fragments, 
+which serve as millstones in the gizzards of worms, suffer, when of 
+a not very hard texture, some amount of attrition; and that the 
+smaller particles in the earth, which is habitually swallowed in 
+such astonishingly large quantities by worms, are ground together 
+and are thus levigated.  If this be the case, the "terra 
+tenuissima,"--the "pate excessivement fine,"--of which the castings 
+largely consist, is in part due to the mechanical action of the 
+gizzard; {75} and this fine matter, as we shall see in the next 
+chapter, is that which is chiefly washed away from the innumerable 
+castings on every field during each heavy shower of rain.  If the 
+softer stones yield at all, the harder ones will suffer some slight 
+amount of wear and tear.
+
+The trituration of small particles of stone in the gizzards of 
+worms is of more importance under a geological point of view than 
+may at first appear to be the case; for Mr. Sorby has clearly shown 
+that the ordinary means of disintegration, namely, running water 
+and the waves of the sea, act with less and less power on fragments 
+of rock the smaller they are.  "Hence," as he remarks, "even making 
+no allowance for the extra buoying up of very minute particles by a 
+current of water, depending on surface cohesion, the effects of 
+wearing on the form of the grains must vary directly as their 
+diameter or thereabouts.  If so, a grain of 1/10 an inch in 
+diameter would be worn ten times as much as one of an inch in 
+diameter, and at least a hundred times as much as one of 1/100 an 
+inch in diameter.  Perhaps, then, we may conclude that a grain 1/10 
+of an inch in diameter would be worn as much or more in drifting a 
+mile as a grain 1/1000 of an inch in being drifted 100 miles.  On 
+the same principle a pebble one inch in diameter would be worn 
+relatively more by being drifted only a few hundred yards." {76}  
+Nor should we forget, in considering the power which worms exert in 
+triturating particles of rock, that there is good evidence that on 
+each acre of land, which is sufficiently damp and not too sandy, 
+gravelly or rocky for worms to inhabit, a weight of more than ten 
+tons of earth annually passes through their bodies and is brought 
+to the surface.  The result for a country of the size of Great 
+Britain, within a period not very long in a geological sense, such 
+as a million years, cannot be insignificant; for the ten tons of 
+earth has to be multiplied first by the above number of years, and 
+then by the number of acres fully stocked with worms; and in 
+England, together with Scotland, the land which is cultivated and 
+is well fitted for these animals, has been estimated at above 32 
+million acres.  The product is 320 million million tons of earth.
+
+
+
+CHAPTER VI--THE DENUDATION OF THE LAND--continued.
+
+
+
+Denudation aided by recently ejected castings flowing down inclined 
+grass-covered surfaces--The amount of earth which annually flows 
+downwards--The effect of tropical rain on worm castings--The finest 
+particles of earth washed completely away from castings--The 
+disintegration of dried castings into pellets, and their rolling 
+down inclined surfaces--The formation of little ledges on hill-
+sides, in part due to the accumulation of disintegrated castings--
+Castings blown to leeward over level land--An attempt to estimate 
+the amount thus blown--The degradation of ancient encampments and 
+tumuli--The preservation of the crowns and furrows on land 
+anciently ploughed--The formation and amount of mould over the 
+Chalk formation.
+
+We are now prepared to consider the more direct part which worms 
+take in the denudation of the land.  When reflecting on sub-aerial 
+denudation, it formerly appeared to me, as it has to others, that a 
+nearly level or very gently inclined surface, covered with turf, 
+could suffer no loss during even a long lapse of time.  It may, 
+however, be urged that at long intervals, debacles of rain or 
+water-spouts would remove all the mould from a very gentle slope; 
+but when examining the steep, turf-covered slopes in Glen Roy, I 
+was struck with the fact how rarely any such event could have 
+happened since the Glacial period, as was plain from the well-
+preserved state of the three successive "roads" or lake-margins.  
+But the difficulty in believing that earth in any appreciable 
+quantity can be removed from a gently inclined surface, covered 
+with vegetation and matted with roots, is removed through the 
+agency of worms.  For the many castings which are thrown up during 
+rain, and those thrown up some little time before heavy rain, flow 
+for a short distance down an inclined surface.  Moreover much of 
+the finest levigated earth is washed completely away from the 
+castings.  During dry weather castings often disintegrate into 
+small rounded pellets, and these from their weight often roll down 
+any slope.  This is more especially apt to occur when they are 
+started by the wind, and probably when started by the touch of an 
+animal, however small.  We shall also see that a strong wind blows 
+all the castings, even on a level field, to leeward, whilst they 
+are soft; and in like manner the pellets when they are dry.  If the 
+wind blows in nearly the direction of an inclined surface, the 
+flowing down of the castings is much aided.
+
+The observations on which these several statements are founded must 
+now be given in some detail.  Castings when first ejected are 
+viscid and soft; during rain, at which time worms apparently prefer 
+to eject them, they are still softer; so that I have sometimes 
+thought that worms must swallow much water at such times.  However 
+this may be, rain, even when not very heavy, if long continued, 
+renders recently-ejected castings semi-fluid; and on level ground 
+they then spread out into thin, circular, flat discs, exactly as 
+would so much honey or very soft mortar, with all traces of their 
+vermiform structure lost.  This latter fact was sometimes made 
+evident, when a worm had subsequently bored through a flat circular 
+disc of this kind, and heaped up a fresh vermiform mass in the 
+centre.  These flat subsided discs have been repeatedly seen by me 
+after heavy rain, in many places on land of all kinds.
+
+On the flowing of wet castings, and the rolling of dry 
+disintegrated castings down inclined surfaces.--When castings are 
+ejected on an inclined surface during or shortly before heavy rain, 
+they cannot fail to flow a little down the slope.  Thus, on some 
+steep slopes in Knole Park, which were covered with coarse grass 
+and had apparently existed in this state from time immemorial, I 
+found (Oct. 22, 1872) after several wet days that almost all the 
+many castings were considerably elongated in the line of the slope; 
+and that they now consisted of smooth, only slightly conical 
+masses.  Whenever the mouths of the burrows could be found from 
+which the earth had been ejected, there was more earth below than 
+above them.  After some heavy storms of rain (Jan. 25, 1872) two 
+rather steeply inclined fields near Down, which had formerly been 
+ploughed and were now rather sparsely clothed with poor grass, were 
+visited, and many castings extended down the slopes for a length of 
+5 inches, which was twice or thrice the usual diameter of the 
+castings thrown up on the level parts of these same fields.  On 
+some fine grassy slopes in Holwood Park, inclined at angles between 
+8 degrees and 11 degrees 30 seconds with the horizon, where the 
+surface apparently had never been disturbed by the hand of man, 
+castings abounded in extraordinary numbers:  and a space 16 inches 
+in length transversely to the slope and 6 inches in the line of the 
+slope, was completely coated, between the blades of grass, with a 
+uniform sheet of confluent and subsided castings.  Here also in 
+many places the castings had flowed down the slope, and now formed 
+smooth narrow patches of earth, 6, 7, and 7.5 inches in length.  
+Some of these consisted of two castings, one above the other, which 
+had become so completely confluent that they could hardly be 
+distinguished.  On my lawn, clothed with very fine grass, most of 
+the castings are black, but some are yellowish from earth having 
+been brought up from a greater depth than usual, and the flowing-
+down of these yellow castings after heavy rain, could be clearly 
+seen where the slope was 5 degrees; and where it was less than 1 
+degree some evidence of their flowing down could still be detected.  
+On another occasion, after rain which was never heavy, but which 
+lasted for 18 hours, all the castings on this same gently inclined 
+lawn had lost their vermiform structure; and they had flowed, so 
+that fully two-thirds of the ejected earth lay below the mouths of 
+the burrows.
+
+These observations led me to make others with more care.  Eight 
+castings were found on my lawn, where the grass-blades are fine and 
+close together, and three others on a field with coarse grass.  The 
+inclination of the surface at the eleven places where these 
+castings were collected varied between 4 degrees 30 seconds and 17 
+degrees 30 seconds; the mean of the eleven inclinations being 9 
+degrees 26 seconds.  The length of the castings in the direction of 
+the slope was first measured with as much accuracy as their 
+irregularities would permit.  It was found possible to make these 
+measurements within about of an inch, but one of the castings was 
+too irregular to admit of measurement.  The average length in the 
+direction of the slope of the remaining ten castings was 2.03 
+inches.  The castings were then divided with a knife into two parts 
+along a horizontal line passing through the mouth of the burrow, 
+which was discovered by slicing off the turf; and all the ejected 
+earth was separately collected, namely, the part above the hole and 
+the part below.  Afterwards these two parts were weighed.  In every 
+case there was much more earth below than above; the mean weight of 
+that above being 103 grains, and of that below 205 grains; so that 
+the latter was very nearly double the former.  As on level ground 
+castings are commonly thrown up almost equally round the mouths of 
+the burrows, this difference in weight indicates the amount of 
+ejected earth which had flowed down the slope.  But very many more 
+observations would be requisite to arrive at any general result; 
+for the nature of the vegetation and other accidental 
+circumstances, such as the heaviness of the rain, the direction and 
+force of the wind, &c., appear to be more important in determining 
+the quantity of the earth which flows down a slope than its angle.  
+Thus with four castings on my lawn (included in the above eleven) 
+where the mean slope was 7 degrees 19 seconds, the difference in 
+the amount of earth above and below the burrows was greater than 
+with three other castings on the same lawn where the mean slope was 
+12 degrees 5 seconds.
+
+We may, however, take the above eleven cases, which are accurate as 
+far as they go, and calculate the weight of the ejected earth which 
+annually flows down a slope having a mean inclination of 9 degrees 
+26 seconds.  This was done by my son George.  It has been shown 
+that almost exactly two-thirds of the ejected earth is found below 
+the mouth of the burrow and one-third above it.  Now if the two-
+thirds which is below the hole be divided into two equal parts, the 
+upper half of this two-thirds exactly counterbalances the one-third 
+which is above the hole, so that as far as regards the one-third 
+above and the upper half of the two-thirds below, there is no flow 
+of earth down the hill-side.  The earth constituting the lower half 
+of the two-thirds is, however, displaced through distances which 
+are different for every part of it, but which may be represented by 
+the distance between the middle point of the lower half of the two-
+thirds and the hole.  So that the average distance of displacement 
+is a half of the whole length of the worm-casting.  Now the average 
+length of ten out of the above eleven castings was 2.03 inches, and 
+half of this we may take as being 1 inch.  It may therefore be 
+concluded that one-third of the whole earth brought to the surface 
+was in these cases carried down the slope through 1 inch. {77}
+
+It was shown in the third chapter that on Leith Hill Common, dry 
+earth weighing at least 7.453 lbs. was brought up by worms to the 
+surface on a square yard in the course of a year.  If a square yard 
+be drawn on a hillside with two of its sides horizontal, then it is 
+clear that only 1/36 part of the earth brought up on that square 
+yard would be near enough to its lower side to cross it, supposing 
+the displacement of the earth to be through one inch.  But it 
+appears that only of the earth brought up can be considered to flow 
+downwards; hence 1/3 of 1/36 or 1/108 of 7.453 lbs. will cross the 
+lower side of our square yard in a year.  Now 1/108 of 7.453 lbs. 
+is 1.1 oz.  Therefore 1.1 oz. of dry earth will annually cross each 
+linear yard running horizontally along a slope having the above 
+inclination; or very nearly 7 lbs. will annually cross a horizontal 
+line, 100 yards in length, on a hill-side having this inclination.
+
+A more accurate, though still very rough, calculation can be made 
+of the bulk of earth, which in its natural damp state annually 
+flows down the same slope over a yard-line drawn horizontally 
+across it.  From the several cases given in the third chapter, it 
+is known that the castings annually brought to the surface on a 
+square yard, if uniformly spread out would form a layer 0.2 of an 
+inch in thickness:  it therefore follows by a calculation similar 
+to the one already given, that 1/3 of 0.2x36, or 2.4 cubic inches 
+of damp earth will annually cross a horizontal line one yard in 
+length on a hillside with the above inclination.  This bulk of damp 
+castings was found to weigh 1.85 oz.  Therefore 11.56 lbs. of damp 
+earth, instead of 7 lbs. of dry earth as by the former calculation, 
+would annually cross a line 100 yards in length on our inclined 
+surface.
+
+In these calculations it has been assumed that the castings flow a 
+short distance downwards during the whole year, but this occurs 
+only with those ejected during or shortly before rain; so that the 
+above results are thus far exaggerated.  On the other hand, during 
+rain much of the finest earth is washed to a considerable distance 
+from the castings, even where the slope is an extremely gentle one, 
+and is thus wholly lost as far as the above calculations are 
+concerned.  Castings ejected during dry weather and which have set 
+hard, lose in the same manner a considerable quantity of fine 
+earth.  Dried castings, moreover, are apt to disintegrate into 
+little pellets, which often roll or are blown down any inclined 
+surface.  Therefore the above result, namely, that 24 cubic inches 
+of earth (weighing 1.85 oz. whilst damp) annually crosses a yard-
+line of the specified kind, is probably not much if at all 
+exaggerated.
+
+This amount is small; but we should bear in mind how many branching 
+valleys intersect most countries, the whole length of which must be 
+very great; and that earth is steadily travelling down both turf-
+covered sides of each valley.  For every 100 yards in length in a 
+valley with sides sloping as in the foregoing cases, 480 cubic 
+inches of damp earth, weighing above 23 pounds, will annually reach 
+the bottom.  Here a thick bed of alluvium will accumulate, ready to 
+be washed away in the course of centuries, as the stream in the 
+middle meanders from side to side.
+
+If it could be shown that worms generally excavate their burrows at 
+right angles to an inclined surface, and this would be their 
+shortest course for bringing up earth from beneath, then as the old 
+burrows collapsed from the weight of the superincumbent soil, the 
+collapsing would inevitably cause the whole bed of vegetable mould 
+to sink or slide slowly down the inclined surface.  But to 
+ascertain the direction of many burrows was found too difficult and 
+troublesome.  A straight piece of wire was, however, pushed into 
+twenty-five burrows on several sloping fields, and in eight cases 
+the burrows were nearly at right angles to the slope; whilst in the 
+remaining cases they were indifferently directed at various angles, 
+either upwards or downwards with respect to the slope.
+
+In countries where the rain is very heavy, as in the tropics, the 
+castings appear, as might have been expected, to be washed down in 
+a greater degree than in England.  Mr. Scott informs me that near 
+Calcutta the tall columnar castings (previously described), the 
+diameter of which is usually between 1 and 1.5 inch, subside on a 
+level surface, after heavy rain, into almost circular, thin, flat 
+discs, between 3 and 4 and sometimes 5 inches in diameter.  Three 
+fresh castings, which had been ejected in the Botanic Gardens "on a 
+slightly inclined, grass-covered, artificial bank of loamy clay," 
+were carefully measured, and had a mean height of 2.17, and a mean 
+diameter of 1.43 inches; these after heavy rain, formed elongated 
+patches of earth, with a mean length in the direction of the slope 
+of 5.83 inches.  As the earth had spread very little up the slope, 
+a large part, judging from the original diameter of these castings, 
+must have flowed bodily downwards about 4 inches.  Moreover some of 
+the finest earth of which they were composed must have been washed 
+completely away to a still greater distance.  In drier sites near 
+Calcutta, a species of worm ejects its castings, not in vermiform 
+masses, but in little pellets of varying sizes:  these are very 
+numerous in some places, and Mr. Scott says that they "are washed 
+away by every shower."
+
+I was led to believe that a considerable quantity of fine earth is 
+washed quite away from castings during rain, from the surfaces of 
+old ones being often studded with coarse particles.  Accordingly a 
+little fine precipitated chalk, moistened with saliva or gum-water, 
+so as to be slightly viscid and of the same consistence as a fresh 
+casting, was placed on the summits of several castings and gently 
+mixed with them.  These castings were then watered through a very 
+fine rose, the drops from which were closer together than those of 
+rain, but not nearly so large as those in a thunderstorm; nor did 
+they strike the ground with nearly so much force as drops during 
+heavy rain.  A casting thus treated subsided with surprising 
+slowness, owing as I suppose to its viscidity.  It did not flow 
+bodily down the grass-covered surface of the lawn, which was here 
+inclined at an angle of 16 degrees 20 seconds; nevertheless many 
+particles of the chalk were found three inches below the casting.  
+The experiment was repeated on three other castings on different 
+parts of the lawn, which sloped at 2 degrees 30 seconds, 3 degrees 
+and 6 degrees; and particles of chalk could be seen between 4 and 5 
+inches below the casting; and after the surface had become dry, 
+particles were found in two cases at a distance of 5 and 6 inches.  
+Several other castings with precipitated chalk placed on their 
+summits were left to the natural action of the rain.  In one case, 
+after rain which was not heavy, the casting was longitudinally 
+streaked with white.  In two other cases the surface of the ground 
+was rendered somewhat white for a distance of one inch from the 
+casting; and some soil collected at a distance of 2.5 inches, where 
+the slope was 7 degrees, effervesced slightly when placed in acid.  
+After one or two weeks, the chalk was wholly or almost wholly 
+washed away from all the castings on which it had been placed, and 
+these had recovered their natural colour.
+
+It may be here remarked that after very heavy rain shallow pools 
+may be seen on level or nearly level fields, where the soil is not 
+very porous, and the water in them is often slightly muddy; when 
+such little pools have dried, the leaves and blades of grass at 
+their bottoms are generally coated with a thin layer of mud.  This 
+mud I believe is derived in large part from recently ejected 
+castings.
+
+Dr. King informs me that the majority of the before described 
+gigantic castings, which he found on a fully exposed, bare, 
+gravelly knoll on the Nilgiri Mountains in India, had been more or 
+less weathered by the previous north-east monsoon; and most of them 
+presented a subsided appearance.  The worms here eject their 
+castings only during the rainy season; and at the time of Dr. 
+King's visit no rain had fallen for 110 days.  He carefully 
+examined the ground between the place where these huge castings 
+lay, and a little watercourse at the base of the knoll, and nowhere 
+was there any accumulation of fine earth, such as would necessarily 
+have been left by the disintegration of the castings if they had 
+not been wholly removed.  He therefore has no hesitation in 
+asserting that the whole of these huge castings are annually washed 
+during the two monsoons (when about 100 inches of rain fall) into 
+the little water-course, and thence into the plains lying below at 
+a depth of 3000 or 4000 feet.
+
+Castings ejected before or during dry weather become hard, 
+sometimes surprisingly hard, from the particles of earth having 
+been cemented together by the intestinal secretions.  Frost seems 
+to be less effective in their disintegration than might have been 
+expected.  Nevertheless they readily disintegrate into small 
+pellets, after being alternately moistened with rain and again 
+dried.  Those which have flowed during rain down a slope, 
+disintegrate in the same manner.  Such pellets often roll a little 
+down any sloping surface; their descent being sometimes much aided 
+by the wind.  The whole bottom of a broad dry ditch in my grounds, 
+where there were very few fresh castings, was completely covered 
+with these pellets or disintegrated castings, which had rolled down 
+the steep sides, inclined at an angle of 27 degrees.
+
+Near Nice, in places where the great cylindrical castings, 
+previously described, abound, the soil consists of very fine 
+arenaceo-calcareous loam; and Dr. King informs me that these 
+castings are extremely liable to crumble during dry weather into 
+small fragments, which are soon acted on by rain, and then sink 
+down so as to be no longer distinguishable from the surrounding 
+soil.  He sent me a mass of such disintegrated castings, collected 
+on the top of a bank, where none could have rolled down from above.  
+They must have been ejected within the previous five or six months, 
+but they now consisted of more or less rounded fragments of all 
+sizes, from 0.75 of an inch in diameter to minute grains and mere 
+dust.  Dr. King witnessed the crumbling process whilst drying some 
+perfect castings, which he afterwards sent me.  Mr. Scott also 
+remarks on the crumbling of the castings near Calcutta and on the 
+mountains of Sikkim during the hot and dry season.
+
+When the castings near Nice had been ejected on an inclined 
+surface, the disintegrated fragments rolled downwards, without 
+losing their distinctive shape; and in some places could "be 
+collected in basketfuls."  Dr. King observed a striking instance of 
+this fact on the Corniche road, where a drain, about 2.5 feet wide 
+and 9 inches deep, had been made to catch the surface drainage from 
+the adjoining hill-side.  The bottom of this drain was covered for 
+a distance of several hundred yards, to a depth of from 1.5 to 3 
+inches, by a layer of broken castings, still retaining their 
+characteristic shape.  Nearly all these innumerable fragments had 
+rolled down from above, for extremely few castings had been ejected 
+in the drain itself.  The hill-side was steep, but varied much in 
+inclination, which Dr. King estimated at from 30 degrees to 60 
+degrees with the horizon.  He climbed up the slope, and "found 
+every here and there little embankments, formed by fragments of the 
+castings that had been arrested in their downward progress by 
+irregularities of the surface, by stones, twigs, &c.  One little 
+group of plants of Anemone hortensis had acted in this manner, and 
+quite a small bank of soil had collected round it.  Much of this 
+soil had crumbled down, but a great deal of it still retained the 
+form of castings."  Dr. King dug up this plant, and was struck with 
+the thickness of the soil which must have recently accumulated over 
+the crown of the rhizoma, as shown by the length of the bleached 
+petioles, in comparison with those of other plants of the same 
+kind, where there had been no such accumulation.  The earth thus 
+accumulated had no doubt been secured (as I have everywhere seen) 
+by the smaller roots of the plants.  After describing this and 
+other analogous cases, Dr. King concludes:  "I can have no doubt 
+that worms help greatly in the process of denudation."
+
+Ledges of earth on steep hill-sides.--Little horizontal ledges, one 
+above another, have been observed on steep grassy slopes in many 
+parts of the world.  The formation has been attributed to animals 
+travelling repeatedly along the slope in the same horizontal lines 
+while grazing, and that they do thus move and use the ledges is 
+certain; but Professor Henslow (a most careful observer) told Sir 
+J. Hooker that he was convinced that this was not the sole cause of 
+their formation.  Sir J. Hooker saw such ledges on the Himalayan 
+and Atlas ranges, where there were no domesticated animals and not 
+many wild ones; but these latter would, it is probable, use the 
+ledges at night while grazing like our domesticated animals.  A 
+friend observed for me the ledges on the Alps of Switzerland, and 
+states that they ran at 3 or 4 ft. one above the other, and were 
+about a foot in breadth.  They had been deeply pitted by the feet 
+of grazing cows.  Similar ledges were observed by the same friend 
+on our Chalk downs, and on an old talus of chalk-fragments (thrown 
+out of a quarry) which had become clothed with turf.
+
+My son Francis examined a Chalk escarpment near Lewes; and here on 
+a part which was very steep, sloping at 40 degrees with the 
+horizon, about 30 flat ledges extended horizontally for more than 
+100 yards, at an average distance of about 20 inches, one beneath 
+the other.  They were from 9 to 10 inches in breadth.  When viewed 
+from a distance they presented a striking appearance, owing to 
+their parallelism; but when examined closely, they were seen to be 
+somewhat sinuous, and one often ran into another, giving the 
+appearance of the ledge having forked into two.  They are formed of 
+light-coloured earth, which on the outside, where thickest, was in 
+one case 9 inches, and in another case between 6 and 7 inches in 
+thickness.  Above the ledges, the thickness of the earth over the 
+chalk was in the former case 4 and in the latter only 3 inches.  
+The grass grew more vigorously on the outer edges of the ledges 
+than on any other part of the slope, and here formed a tufted 
+fringe.  Their middle part was bare, but whether this had been 
+caused by the trampling of sheep, which sometimes frequent the 
+ledges, my son could not ascertain.  Nor could he feel sure how 
+much of the earth on the middle and bare parts, consisted of 
+disintegrated worm-castings which had rolled down from above; but 
+he felt convinced that some had thus originated; and it was 
+manifest that the ledges with their grass-fringed edges would 
+arrest any small object rolling down from above.
+
+At one end or side of the bank bearing these ledges, the surface 
+consisted in parts of bare chalk, and here the ledges were very 
+irregular.  At the other end of the bank, the slope suddenly became 
+less steep, and here the ledges ceased rather abruptly; but little 
+embankments only a foot or two in length were still present.  The 
+slope became steeper lower down the hill, and the regular ledges 
+then reappeared.  Another of my sons observed, on the inland side 
+of Beachy Head, where the surface sloped at about 25 degrees, many 
+short little embankments like those just mentioned.  They extended 
+horizontally and were from a few inches to two or three feet in 
+length.  They supported tufts of grass growing vigorously.  The 
+average thickness of the mould of which they were formed, taken 
+from nine measurements, was 4.5 inches; while that of the mould 
+above and beneath them was on an average only 3.2 inches, and on 
+each side, on the same level, 3.1 inches.  On the upper parts of 
+the slope, these embankments showed no signs of having been 
+trampled on by sheep, but in the lower parts such signs were fairly 
+plain.  No long continuous ledges had here been formed.
+
+If the little embankments above the Corniche road, which Dr. King 
+saw in the act of formation by the accumulation of disintegrated 
+and rolled worm-castings, were to become confluent along horizontal 
+lines, ledges would be formed.  Each embankment would tend to 
+extend laterally by the lateral extension of the arrested castings; 
+and animals grazing on a steep slope would almost certainly make 
+use of every prominence at nearly the same level, and would indent 
+the turf between them; and such intermediate indentations would 
+again arrest the castings.  An irregular ledge when once formed 
+would also tend to become more regular and horizontal by some of 
+the castings rolling laterally from the higher to the lower parts, 
+which would thus be raised.  Any projection beneath a ledge would 
+not afterwards receive disintegrated matter from above, and would 
+tend to be obliterated by rain and other atmospheric agencies.  
+There is some analogy between the formation, as here supposed, of 
+these ledges, and that of the ripples of wind-drifted sand as 
+described by Lyell. {78}
+
+The steep, grass-covered sides of a mountainous valley in 
+Westmoreland, called Grisedale, was marked in many places with 
+innumerable lines of miniature cliffs, with almost horizontal, 
+little ledges at their bases.  Their formation was in no way 
+connected with the action of worms, for castings could not anywhere 
+be seen (and their absence is an inexplicable fact), although the 
+turf lay in many places over a considerable thickness of boulder-
+clay and moraine rubbish.  Nor, as far as I could judge, was the 
+formation of these little cliffs at all closely connected with the 
+trampling of cows or sheep.  It appeared as if the whole 
+superficial, somewhat argillaceous earth, while partially held 
+together by the roots of the grasses, had slided a little way down 
+the mountain sides; and in thus sliding, had yielded and cracked in 
+horizontal lines, transversely to the slope.
+
+Castings blown to leeward by the wind.--We have seen that moist 
+castings flow, and that disintegrated castings roll down any 
+inclined surface; and we shall now see that castings, recently 
+ejected on level grass-covered surfaces, are blown during gales of 
+wind accompanied by rain to leeward.  This has been observed by me 
+many times on many fields during several successive years.  After 
+such gales, the castings present a gently inclined and smooth, or 
+sometimes furrowed, surface to windward, while they are steeply 
+inclined or precipitous to leeward, so that they resemble on a 
+miniature scale glacier-ground hillocks of rock.  They are often 
+cavernous on the leeward side, from the upper part having curled 
+over the lower part.  During one unusually heavy south-west gale 
+with torrents of rain, many castings were wholly blown to leeward, 
+so that the mouths of the burrows were left naked and exposed on 
+the windward side.  Recent castings naturally flow down an inclined 
+surface, but on a grassy field, which sloped between 10 degrees and 
+15 degrees, several were found after a heavy gale blown up the 
+slope.  This likewise occurred on another occasion on a part of my 
+lawn where the slope was somewhat less.  On a third occasion, the 
+castings on the steep, grass-covered sides of a valley, down which 
+a gale had blown, were directed obliquely instead of straight down 
+the slope; and this was obviously due to the combined action of the 
+wind and gravity.  Four castings on my lawn, where the downward 
+inclination was 0  degrees 45 seconds, 1 degree, 3 degrees and 3 
+degrees 30 seconds (mean 2 degrees 45 seconds) towards the north-
+east, after a heavy south-west gale with rain, were divided across 
+the mouths of the burrows and weighed in the manner formerly 
+described.  The mean weight of the earth below the mouths of 
+burrows and to leeward, was to that above the mouths and on the 
+windward side as 2.75 to 1; whereas we have seen that with several 
+castings which had flowed down slopes having a mean inclination of 
+9 degrees 26 seconds, and with three castings where the inclination 
+was above 12 degrees; the proportional weight of the earth below to 
+that above the burrows was as only 2 to 1.  These several cases 
+show how efficiently gales of wind accompanied by rain act in 
+displacing recently ejected castings.  We may therefore conclude 
+that even a moderately strong wind will produce some slight effect 
+on them.
+
+Dry and indurated castings, after their disintegration into small 
+fragments or pellets, are sometimes, probably often, blown by a 
+strong wind to leeward.  This was observed on four occasions, but I 
+did not sufficiently attend to this point.  One old casting on a 
+gently sloping bank was blown quite away by a strong south-west 
+wind.  Dr. King believes that the wind removes the greater part of 
+the old crumbling castings near Nice.  Several old castings on my 
+lawn were marked with pins and protected from any disturbance.  
+They were examined after an interval of 10 weeks, during which time 
+the weather had been alternately dry and rainy.  Some, which were 
+of a yellowish colour had been washed almost completely away, as 
+could be seen by the colour of the surrounding ground.  Others had 
+completely disappeared, and these no doubt had been blown away.  
+Lastly, others still remained and would long remain, as blades of 
+grass had grown through them.  On poor pasture-land, which has 
+never been rolled and has not been much trampled on by animals, the 
+whole surface is sometimes dotted with little pimples, through and 
+on which grass grows; and these pimples consist of old worm-
+castings.
+
+In all the many observed cases of soft castings blown to leeward, 
+this had been effected by strong winds accompanied by rain.  As 
+such winds in England generally blow from the south and south-west, 
+earth must on the whole tend to travel over our fields in a north 
+and north-east direction.  This fact is interesting, because it 
+might be thought that none could be removed from a level, grass-
+covered surface by any means.  In thick and level woods, protected 
+from the wind, castings will never be removed as long as the wood 
+lasts; and mould will here tend to accumulate to the depth at which 
+worms can work.  I tried to procure evidence as to how much mould 
+is blown, whilst in the state of castings, by our wet southern 
+gales to the north-east, over open and flat land, by looking to the 
+level of the surface on opposite sides of old trees and hedge-rows; 
+but I failed owing to the unequal growth of the roots of trees and 
+to most pasture-land having been formerly ploughed.
+
+On an open plain near Stonehenge, there exist shallow circular 
+trenches, with a low embankment outside, surrounding level spaces 
+50 yards in diameter.  These rings appear very ancient, and are 
+believed to be contemporaneous with the Druidical stones.  Castings 
+ejected within these circular spaces, if blown to the north-east by 
+south-west winds would form a layer of mould within the trench, 
+thicker on the north-eastern than on any other side.  But the site 
+was not favourable for the action of worms, for the mould over the 
+surrounding Chalk formation with flints, was only 3.37 inches in 
+thickness, from a mean of six observations made at a distance of 10 
+yards outside the embankment.  The thickness of the mould within 
+two of the circular trenches was measured every 5 yards all round, 
+on the inner sides near the bottom.  My son Horace protracted these 
+measurements on paper; and though the curved line representing the 
+thickness of the mould was extremely irregular, yet in both 
+diagrams it could be seen to be thicker on the north-eastern side 
+than elsewhere.  When a mean of all the measurements in both the 
+trenches was laid down and the line smoothed, it was obvious that 
+the mould was thickest in the quarter of the circle between north-
+west and north-east; and thinnest in the quarter between south-east 
+and south-west, especially at this latter point.  Besides the 
+foregoing measurements, six others were taken near together in one 
+of the circular trenches, on the north-east side; and the mould 
+here had a mean thickness of 2.29 inches; while the mean of six 
+other measurements on the south-west side was only 1.46 inches.  
+These observations indicate that the castings had been blown by the 
+south-west winds from the circular enclosed space into the trench 
+on the north-east side; but many more measurements in other 
+analogous cases would be requisite for a trustworthy result.
+
+The amount of fine earth brought to the surface under the form of 
+castings, and afterwards transported by the winds accompanied by 
+rain, or that which flows and rolls down an inclined surface, no 
+doubt is small in the course of a few scores of years; for 
+otherwise all the inequalities in our pasture fields would be 
+smoothed within a much shorter period than appears to be the case.  
+But the amount which is thus transported in the course of thousands 
+of years cannot fail to be considerable and deserves attention.  E. 
+de Beaumont looks at the vegetable mould which everywhere covers 
+the land as a fixed line, from which the amount of denudation may 
+be measured. {79}  He ignores the continued formation of fresh 
+mould by the disintegration of the underlying rocks and fragments 
+of rock; and it is curious to find how much more philosophical were 
+the views maintained long ago, by Playfair, who, in 1802, wrote, 
+"In the permanence of a coat of vegetable mould on the surface of 
+the earth, we have a demonstrative proof of the continued 
+destruction of the rocks." {80}
+
+Ancient encampments and tumuli.--E. de Beaumont adduces the present 
+state of many ancient encampments and tumuli and of old ploughed 
+fields, as evidence that the surface of the land undergoes hardly 
+any degradation.  But it does not appear that he ever examined the 
+thickness of the mould over different parts of such old remains.  
+He relies chiefly on indirect, but apparently trustworthy, evidence 
+that the slopes of the old embankments are the same as they 
+originally were; and it is obvious that he could know nothing about 
+their original heights.  In Knole Park a mound had been thrown up 
+behind the rifle-targets, which appeared to have been formed of 
+earth originally supported by square blocks of turf.  The sides 
+sloped, as nearly as I could estimate them, at an angle of 45 
+degrees or 50 degrees with the horizon, and they were covered, 
+especially on the northern side, with long coarse grass, beneath 
+which many worm-castings were found.  These had flowed bodily 
+downwards, and others had rolled down as pellets.  Hence it is 
+certain that as long as a mound of this kind is tenanted by worms, 
+its height will be continually lowered.  The fine earth which flows 
+or rolls down the sides of such a mound accumulates at its base in 
+the form of a talus.  A bed, even a very thin bed, of fine earth is 
+eminently favourable for worms; so that a greater number of 
+castings would tend to be ejected on a talus thus formed than 
+elsewhere; and these would be partially washed away by every heavy 
+shower and be spread over the adjoining level ground.  The final 
+result would be the lowering of the whole mound, whilst the 
+inclination of the sides would not be greatly lessened.  The same 
+result would assuredly follow with ancient embankments and tumuli; 
+except where they had been formed of gravel or of nearly pure sand, 
+as such matter is unfavourable for worms.  Many old fortifications 
+and tumuli are believed to be at least 2000 years old; and we 
+should bear in mind that in many places about one inch of mould is 
+brought to the surface in 5 years or two inches in 10 years.  
+Therefore in so long a period as 2000 years, a large amount of 
+earth will have been repeatedly brought to the surface on most old 
+embankments and tumuli, especially on the talus round their bases, 
+and much of this earth will have been washed completely away.  We 
+may therefore conclude that all ancient mounds, when not formed of 
+materials unfavourable to worms, will have been somewhat lowered in 
+the course of centuries, although their inclinations may not have 
+been greatly changed.
+
+Fields formerly ploughed.--From a very remote period and in many 
+countries, land has been ploughed, so that convex beds, called 
+crowns or ridges, usually about 8 feet across and separated by 
+furrows, have been thrown up.  The furrows are directed so as to 
+carry off the surface water.  In my attempts to ascertain how long 
+a time these crowns and furrows last, when ploughed land has been 
+converted into pasture, obstacles of many kinds were encountered.  
+It is rarely known when a field was last ploughed; and some fields 
+which were thought to have been in pasture from time immemorial 
+were afterwards discovered to have been ploughed only 50 or 60 
+years before.  During the early part of the present century, when 
+the price of corn was very high, land of all kinds seems to have 
+been ploughed in Britain.  There is, however, no reason to doubt 
+that in many cases the old crowns and furrows have been preserved 
+from a very ancient period. {81}  That they should have been 
+preserved for very unequal lengths of time would naturally follow 
+from the crowns, when first thrown up, having differed much in 
+height in different districts, as is now the case with recently 
+ploughed land.
+
+In old pasture fields, the mould, wherever measurements were made, 
+was found to be from 0.5 to 2 inches thicker in the furrows than on 
+the crowns; but this would naturally follow from the finer earth 
+having been washed from the crowns into the furrows before the land 
+was well clothed with turf; and it is impossible to tell what part 
+worms may have played in the work.  Nevertheless from what we have 
+seen, castings would certainly tend to flow and to be washed during 
+heavy rain from the crowns into the furrows.  But as soon as a bed 
+of fine earth had by any means been accumulated in the furrows, it 
+would be more favourable for worms than the other parts, and a 
+greater number of castings would be thrown up here than elsewhere; 
+and as the furrows on sloping land are usually directed so as to 
+carry off the surface water, some of the finest earth would be 
+washed from the castings which had been here ejected and be carried 
+completely away.  The result would be that the furrows would be 
+filled up very slowly, while the crowns would be lowered perhaps 
+still more slowly by the flowing and rolling of the castings down 
+their gentle inclinations into the furrows.
+
+Nevertheless it might be expected that old furrows, especially 
+those on a sloping surface, would in the course of time be filled 
+up and disappear.  Some careful observers, however, who examined 
+fields for me in Gloucestershire and Staffordshire could not detect 
+any difference in the state of the furrows in the upper and lower 
+parts of sloping fields, supposed to have been long in pasture; and 
+they came to the conclusion that the crowns and furrows would last 
+for an almost endless number of centuries.  On the other hand the 
+process of obliteration seems to have commenced in some places.  
+Thus in a grass field in North Wales, known to have been ploughed 
+about 65 years ago, which sloped at an angle of 15 degrees to the 
+north-east, the depth of the furrows (only 7 feet apart) was 
+carefully measured, and was found to be about 4.5 inches in the 
+upper part of the slope, and only 1 inch near the base, where they 
+could be traced with difficulty.  On another field sloping at about 
+the same angle to the south-west, the furrows were scarcely 
+perceptible in the lower part; although these same furrows when 
+followed on to some adjoining level ground were from 2.5 to 3.5 
+inches in depth.  A third and closely similar case was observed.  
+In a fourth case, the mould in a furrow in the upper part of a 
+sloping field was 2.5 inches, and in the lower part 4.5 inches in 
+thickness.
+
+On the Chalk Downs at about a mile distance from Stonehenge, my son 
+William examined a grass-covered, furrowed surface, sloping at from 
+8 degrees to 10 degrees, which an old shepherd said had not been 
+ploughed within the memory of man.  The depth of one furrow was 
+measured at 16 points in a length of 68 paces, and was found to be 
+deeper where the slope was greatest and where less earth would 
+naturally tend to accumulate, and at the base it almost 
+disappeared.  The thickness of the mould in this furrow in the 
+upper part was 2.5 inches, which increased to 5 inches, a little 
+above the steepest part of the slope; and at the base, in the 
+middle of the narrow valley, at a point which the furrow if 
+continued would have struck, it amounted to 7 inches.  On the 
+opposite side of the valley, there were very faint, almost 
+obliterated, traces of furrows.  Another analogous but not so 
+decided a case was observed at a few miles' distance from 
+Stonehenge.  On the whole it appears that the crowns and furrows on 
+land formerly ploughed, but now covered with grass, tend slowly to 
+disappear when the surface is inclined; and this is probably in 
+large part due to the action of worms; but that the crowns and 
+furrows last for a very long time when the surface is nearly level.
+
+Formation and amount of mould over the Chalk Formation.--Worm-
+castings are often ejected in extraordinary numbers on steep, 
+grass-covered slopes, where the Chalk comes close to the surface, 
+as my son William observed near Winchester and elsewhere.  If such 
+castings are largely washed away during heavy rains, it is 
+difficult to understand at first how any mould can still remain on 
+our Downs, as there does not appear any evident means for supplying 
+the loss.  There is, moreover, another cause of loss, namely, in 
+the percolation of the finer particles of earth into the fissures 
+in the chalk and into the chalk itself.  These considerations led 
+me to doubt for a time whether I had not exaggerated the amount of 
+fine earth which flows or rolls down grass-covered slopes under the 
+form of castings; and I sought for additional information.  In some 
+places, the castings on Chalk Downs consist largely of calcareous 
+matter, and here the supply is of course unlimited.  But in other 
+places, for instance on a part of Teg Down near Winchester, the 
+castings were all black and did not effervesce with acids.  The 
+mould over the chalk was here only from 3 to 4 inches in thickness.  
+So again on the plain near Stonehenge, the mould, apparently free 
+from calcareous matter, averaged rather less than 3.5 inches in 
+thickness.  Why worms should penetrate and bring up chalk in some 
+places and not in others I do not know.
+
+In many districts where the land is nearly level, a bed several 
+feet in thickness of red clay full of unworn flints overlies the 
+Upper Chalk.  This overlying matter, the surface of which has been 
+converted into mould, consists of the undissolved residue from the 
+chalk.  It may be well here to recall the case of the fragments of 
+chalk buried beneath worm-castings on one of my fields, the angles 
+of which were so completely rounded in the course of 29 years that 
+the fragments now resembled water-worn pebbles.  This must have 
+been effected by the carbonic acid in the rain and in the ground, 
+by the humus-acids, and by the corroding power of living roots.  
+Why a thick mass of residue has not been left on the Chalk, 
+wherever the land is nearly level, may perhaps be accounted for by 
+the percolation of the fine particles into the fissures, which are 
+often present in the chalk and are either open or are filled up 
+with impure chalk, or into the solid chalk itself.  That such 
+percolation occurs can hardly be doubted.  My son collected some 
+powdered and fragmentary chalk beneath the turf near Winchester; 
+the former was found by Colonel Parsons, R. E., to contain 10 per 
+cent., and the fragments 8 per cent. of earthy matter.  On the 
+flanks of the escarpment near Abinger in Surrey, some chalk close 
+beneath a layer of flints, 2 inches in thickness and covered by 8 
+inches of mould, yielded a residue of 3.7 per cent. of earthy 
+matter.  On the other hand the Upper Chalk properly contains, as I 
+was informed by the late David Forbes who had made many analyses, 
+only from 1 to 2 per cent. of earthy matter; and two samples from 
+pits near my house contained 1.3 and 0.6 per cent.  I mention these 
+latter cases because, from the thickness of the overlying bed of 
+red clay with flints, I had imagined that the underlying chalk 
+might here be less pure than elsewhere.  The cause of the residue 
+accumulating more in some places than in others, may be attributed 
+to a layer of argillaceous matter having been left at an early 
+period on the chalk, and this would check the subsequent 
+percolation of earthy matter into it.
+
+From the facts now given we may conclude that castings ejected on 
+our Chalk Downs suffer some loss by the percolation of their finer 
+matter into the chalk.  But such impure superficial chalk, when 
+dissolved, would leave a larger supply of earthy matter to be added 
+to the mould than in the case of pure chalk.  Besides the loss 
+caused by percolation, some fine earth is certainly washed down the 
+sloping grass-covered surfaces of our Downs.  The washing-down 
+process, however, will be checked in the course of time; for 
+although I do not know how thin a layer of mould suffices to 
+support worms, yet a limit must at last be reached; and then their 
+castings would cease to be ejected or would become scanty.
+
+The following cases show that a considerable quantity of fine earth 
+is washed down.  The thickness of the mould was measured at points 
+12 yards apart across a small valley in the Chalk near Winchester.  
+The sides sloped gently at first; then became inclined at about 20 
+degrees; then more gently to near the bottom, which transversely 
+was almost level and about 50 yards across.  In the bottom, the 
+mean thickness of the mould from five measurements was 8.3 inches; 
+whilst on the sides of the valley, where the inclination varied 
+between 14 degrees and 20 degrees, its mean thickness was rather 
+less than 3.5 inches.  As the turf-covered bottom of the valley 
+sloped at an angle of only between 2 degrees and 3 degrees, it is 
+probable that most of the 8.3-inch layer of mould had been washed 
+down from the flanks of the valley, and not from the upper part.  
+But as a shepherd said that he had seen water flowing in this 
+valley after the sudden thawing of snow, it is possible that some 
+earth may have been brought down from the upper part; or, on the 
+other hand, that some may have been carried further down the 
+valley.  Closely similar results, with respect to the thickness of 
+the mould, were obtained in a neighbouring valley.
+
+St. Catherine's Hill, near Winchester, is 327 feet in height, and 
+consists of a steep cone of chalk about 0.25 of a mile in diameter.  
+The upper part was converted by the Romans, or, as some think, by 
+the ancient Britons, into an encampment, by the excavation of a 
+deep and broad ditch all round it.  Most of the chalk removed 
+during the work was thrown upwards, by which a projecting bank was 
+formed; and this effectually prevents worm-castings (which are 
+numerous in parts), stones, and other objects from being washed or 
+rolled into the ditch.  The mould on the upper and fortified part 
+of the hill was found to be in most places only from 2.5 to 3.5 
+inches in thickness; whereas it had accumulated at the foot of the 
+embankment above the ditch to a thickness in most places of from 8 
+to 9.5 inches.  On the embankment itself the mould was only 1 to 
+1.5 inch in thickness; and within the ditch at the bottom it varied 
+from 2.5 to 3.5, but was in one spot 6 inches in thickness.  On the 
+north-west side of the hill, either no embankment had ever been 
+thrown up above the ditch, or it had subsequently been removed; so 
+that here there was nothing to prevent worm-castings, earth and 
+stones being washed into the ditch, at the bottom of which the 
+mould formed a layer from 11 to 22 inches in thickness.  It should 
+however be stated that here and on other parts of the slope, the 
+bed of mould often contained fragments of chalk and flint which had 
+obviously rolled down at different times from above.  The 
+interstices in the underlying fragmentary chalk were also filled up 
+with mould.
+
+My son examined the surface of this hill to its base in a south-
+west direction.  Beneath the great ditch, where the slope was about 
+24 degrees, the mould was very thin, namely, from 1.5 to 2.5 
+inches; whilst near the base, where the slope was only 3 degrees to 
+4 degrees, it increased to between 8 and 9 inches in thickness.  We 
+may therefore conclude that on this artificially modified hill, as 
+well as in the natural valleys of the neighbouring Chalk Downs, 
+some fine earth, probably derived in large part from worm-castings, 
+is washed down, and accumulates in the lower parts, notwithstanding 
+the percolation of an unknown quantity into the underlying chalk; a 
+supply of fresh earthy matter being afforded by the dissolution of 
+the chalk through atmospheric and other agencies.
+
+
+
+CHAPTER VII--CONCLUSION.
+
+
+
+Summary of the part which worms have played in the history of the 
+world--Their aid in the disintegration of rocks--In the denudation 
+of the land--In the preservation of ancient remains--In the 
+preparation of the soil for the growth of plants--Mental powers of 
+worms--Conclusion.
+
+Worms have played a more important part in the history of the world 
+than most persons would at first suppose.  In almost all humid 
+countries they are extraordinarily numerous, and for their size 
+possess great muscular power.  In many parts of England a weight of 
+more than ten tons (10,516 kilogrammes) of dry earth annually 
+passes through their bodies and is brought to the surface on each 
+acre of land; so that the whole superficial bed of vegetable mould 
+passes through their bodies in the course of every few years.  From 
+the collapsing of the old burrows the mould is in constant though 
+slow movement, and the particles composing it are thus rubbed 
+together.  By these means fresh surfaces are continually exposed to 
+the action of the carbonic acid in the soil, and of the humus-acids 
+which appear to be still more efficient in the decomposition of 
+rocks.  The generation of the humus-acids is probably hastened 
+during the digestion of the many half-decayed leaves which worms 
+consume.  Thus the particles of earth, forming the superficial 
+mould, are subjected to conditions eminently favourable for their 
+decomposition and disintegration.  Moreover, the particles of the 
+softer rocks suffer some amount of mechanical trituration in the 
+muscular gizzards of worms, in which small stones serve as mill-
+stones.
+
+The finely levigated castings, when brought to the surface in a 
+moist condition, flow during rainy weather down any moderate slope; 
+and the smaller particles are washed far down even a gently 
+inclined surface.  Castings when dry often crumble into small 
+pellets and these are apt to roll down any sloping surface.  Where 
+the land is quite level and is covered with herbage, and where the 
+climate is humid so that much dust cannot be blown away, it appears 
+at first sight impossible that there should be any appreciable 
+amount of sub-aerial denudation; but worm-castings are blown, 
+especially whilst moist and viscid, in one uniform direction by the 
+prevalent winds which are accompanied by rain.  By these several 
+means the superficial mould is prevented from accumulating to a 
+great thickness; and a thick bed of mould checks in many ways the 
+disintegration of the underlying rocks and fragments of rock.
+
+The removal of worm-castings by the above means leads to results 
+which are far from insignificant.  It has been shown that a layer 
+of earth, 0.2 of an inch in thickness, is in many places annually 
+brought to the surface; and if a small part of this amount flows, 
+or rolls, or is washed, even for a short distance, down every 
+inclined surface, or is repeatedly blown in one direction, a great 
+effect will be produced in the course of ages.  It was found by 
+measurements and calculations that on a surface with a mean 
+inclination of 9 degrees 26 seconds, 2.4 cubic inches of earth 
+which had been ejected by worms crossed, in the course of a year, a 
+horizontal line one yard in length; so that 240 cubic inches would 
+cross a line 100 yards in length.  This latter amount in a damp 
+state would weigh 11.5 pounds.  Thus a considerable weight of earth 
+is continually moving down each side of every valley, and will in 
+time reach its bed.  Finally this earth will be transported by the 
+streams flowing in the valleys into the ocean, the great receptacle 
+for all matter denuded from the land.  It is known from the amount 
+of sediment annually delivered into the sea by the Mississippi, 
+that its enormous drainage-area must on an average be lowered 
+.00263 of an inch each year; and this would suffice in four and 
+half million years to lower the whole drainage-area to the level of 
+the sea-shore.  So that, if a small fraction of the layer of fine 
+earth, 0.2 of an inch in thickness, which is annually brought to 
+the surface by worms, is carried away, a great result cannot fail 
+to be produced within a period which no geologist considers 
+extremely long.
+
+
+Archaeologists ought to be grateful to worms, as they protect and 
+preserve for an indefinitely long period every object, not liable 
+to decay, which is dropped on the surface of the land, by burying 
+it beneath their castings.  Thus, also, many elegant and curious 
+tesselated pavements and other ancient remains have been preserved; 
+though no doubt the worms have in these cases been largely aided by 
+earth washed and blown from the adjoining land, especially when 
+cultivated.  The old tesselated pavements have, however, often 
+suffered by having subsided unequally from being unequally 
+undermined by the worms.  Even old massive walls may be undermined 
+and subside; and no building is in this respect safe, unless the 
+foundations lie 6 or 7 feet beneath the surface, at a depth at 
+which worms cannot work.  It is probable that many monoliths and 
+some old walls have fallen down from having been undermined by 
+worms.
+
+
+Worms prepare the ground {82} in an excellent manner for the growth 
+of fibrous-rooted plants and for seedlings of all kinds.  They 
+periodically expose the mould to the air, and sift it so that no 
+stones larger than the particles which they can swallow are left in 
+it.  They mingle the whole intimately together, like a gardener who 
+prepares fine soil for his choicest plants.  In this state it is 
+well fitted to retain moisture and to absorb all soluble 
+substances, as well as for the process of nitrification.  The bones 
+of dead animals, the harder parts of insects, the shells of land-
+molluscs, leaves, twigs, &c., are before long all buried beneath 
+the accumulated castings of worms, and are thus brought in a more 
+or less decayed state within reach of the roots of plants.  Worms 
+likewise drag an infinite number of dead leaves and other parts of 
+plants into their burrows, partly for the sake of plugging them up 
+and partly as food.
+
+The leaves which are dragged into the burrows as food, after being 
+torn into the finest shreds, partially digested, and saturated with 
+the intestinal and urinary secretions, are commingled with much 
+earth.  This earth forms the dark coloured, rich humus which almost 
+everywhere covers the surface of the land with a fairly well-
+defined layer or mantle.  Hensen {83} placed two worms in a vessel 
+18 inches in diameter, which was filled with sand, on which fallen 
+leaves were strewed; and these were soon dragged into their burrows 
+to a depth of 3 inches.  After about 6 weeks an almost uniform 
+layer of sand, a centimeter (0.4 inch) in thickness, was converted 
+into humus by having passed through the alimentary canals of these 
+two worms.  It is believed by some persons that worm-burrows, which 
+often penetrate the ground almost perpendicularly to a depth of 5 
+or 6 feet, materially aid in its drainage; notwithstanding that the 
+viscid castings piled over the mouths of the burrows prevent or 
+check the rain-water directly entering them.  They allow the air to 
+penetrate deeply into the ground.  They also greatly facilitate the 
+downward passage of roots of moderate size; and these will be 
+nourished by the humus with which the burrows are lined.  Many 
+seeds owe their germination to having been covered by castings; and 
+others buried to a considerable depth beneath accumulated castings 
+lie dormant, until at some future time they are accidentally 
+uncovered and germinate.
+
+Worms are poorly provided with sense-organs, for they cannot be 
+said to see, although they can just distinguish between light and 
+darkness; they are completely deaf, and have only a feeble power of 
+smell; the sense of touch alone is well developed.  They can 
+therefore learn but little about the outside world, and it is 
+surprising that they should exhibit some skill in lining their 
+burrows with their castings and with leaves, and in the case of 
+some species in piling up their castings into tower-like 
+constructions.  But it is far more surprising that they should 
+apparently exhibit some degrees of intelligence instead of a mere 
+blind instinctive impulse, in their manner of plugging up the 
+mouths of their burrows.  They act in nearly the same manner as 
+would a man, who had to close a cylindrical tube with different 
+kinds of leaves, petioles, triangles of paper, &c., for they 
+commonly seize such objects by their pointed ends.  But with thin 
+objects a certain number are drawn in by their broader ends.  They 
+do not act in the same unvarying manner in all cases, as do most of 
+the lower animals; for instance, they do not drag in leaves by 
+their foot-stalks, unless the basal part of the blade is as narrow 
+as the apex, or narrower than it.
+
+
+When we behold a wide, turf-covered expanse, we should remember 
+that its smoothness, on which so much of its beauty depends, is 
+mainly due to all the inequalities having been slowly levelled by 
+worms.  It is a marvellous reflection that the whole of the 
+superficial mould over any such expanse has passed, and will again 
+pass, every few years through the bodies of worms.  The plough is 
+one of the most ancient and most valuable of man's inventions; but 
+long before he existed the land was in fact regularly ploughed, and 
+still continues to be thus ploughed by earth-worms.  It may be 
+doubted whether there are many other animals which have played so 
+important a part in the history of the world, as have these lowly 
+organized creatures.  Some other animals, however, still more lowly 
+organized, namely corals, have done far more conspicuous work in 
+having constructed innumerable reefs and islands in the great 
+oceans; but these are almost confined to the tropical zones.
+
+
+
+Footnotes:
+
+{1}  'Lecons de Geologie Pratique,' tom. i. 1845, p. 140.
+
+{2}  'Transactions Geolog. Soc.' vol. v. p. 505.  Read November 1, 
+1837.
+
+{3}  'Histoire des progres de la Geologie,' tom. i. 1847, p. 224.
+
+{4}  'Zeitschrift fur wissenschaft.  Zoologie,' B. xxviii. 1877, p. 
+361.
+
+{5}  'Gardeners' Chronicle,' April 17, 1869, p. 418.
+
+{6}  Mr. Darwin's attention was called by Professor Hensen to P. E. 
+Muller's work on Humus in 'Tidsskrift for Skovbrug,' Band iii. Heft 
+1 and 2, Copenhagen, 1878.  He had, however, no opportunity of 
+consulting Muller's work.  Dr. Muller published a second paper in 
+1884 in the same periodical--a Danish journal of forestry.  His 
+results have also been published in German, in a volume entitled 
+'Studien uber die naturlichen Humusformen, unter deren Einwirkung 
+auf Vegetation und Boden,' 8vo., Berlin, 1887.
+
+{7}  'Bidrag till Skandinaviens Oligochaetfauna,' 1871.
+
+{8}  'Die bis jetzt bekannten Arten aus der Familie der 
+Regenwurmer,' 1845.
+
+{9}  There is even some reason to believe that pressure is actually 
+favourable to the growth of grasses, for Professor Buckman, who 
+made many observations on their growth in the experimental gardens 
+of the Royal Agricultural College, remarks ('Gardeners' Chronicle,' 
+1854, p. 619):  "Another circumstance in the cultivation of grasses 
+in the separate form or small patches, is the impossibility of 
+rolling or treading them firmly, without which no pasture can 
+continue good."
+
+{10}  I shall have occasion often to refer to M. Perrier's 
+admirable memoir, 'Organisation des Lombriciens terrestres' in 
+'Archives de Zoolog. exper.' tom. iii. 1874, p. 372.  C. F. Morren 
+('De Lumbrici terrestris Hist. Nat.' 1829, p. 14) found that worms 
+endured immersion for fifteen to twenty days in summer, but that in 
+winter they died when thus treated.
+
+{11}  Morren, 'De Lumbrici terrestris Hist. Nat.' &c., 1829, p. 67.
+
+{12}  'De Lumbrici terrestris Hist. Nat.' &c., p. 14.
+
+{13}  Histolog.  Untersuchungen uber die Regenwurmer.  'Zeitschrift 
+fur wissenschaft.  Zoologie,' B. xix., 1869, p. 611.
+
+{14}  For instance, Mr. Bridgman and Mr. Newman ('The Zoologist,' 
+vol. vii. 1849, p. 2576), and some friends who observed worms for 
+me.
+
+{15}  'Familie der Regenwurmer,' 1845, p. 18.
+
+{16}  'The Zoologist,' vol. vii. 1849, p. 2576.
+
+{17}  'Familie der Regenwurmer,' p. 13.  Dr. Sturtevant states in 
+the 'New York Weekly Tribune' (May 19, 1880) that he kept three 
+worms in a pot, which was allowed to become extremely dry; and 
+these worms were found "all entwined together, forming a round mass 
+and in good condition."
+
+{18}  'De Lumbrici terrestris Hist. Nat.' p. 19.
+
+{19}  'Archives de Zoologie experimentale,' tom. vii. 1878, p. 394.  
+When I wrote the above passage, I was not aware that Krukenberg 
+('Untersuchungen a. d. physiol.  Inst. d. Univ.  Heidelberg,' Bd. 
+ii. p. 37, 1877) had previously investigated the digestive juice of 
+Lumbricus.  He states that it contains a peptic, and diastatic, as 
+well as a tryptic ferment.
+
+{20}  On the action of the pancreatic ferment, see 'A Text-Book of 
+Physiology,' by Michael Foster, 2nd edit. pp. 198-203.  1878.
+
+{21}  Schmulewitsch, 'Action des Sucs digestifs sur la Cellulose.'  
+Bull. de l'Acad. Imp. de St. Petersbourg, tom. xxv. p. 549.  1879. 
+
+{22}  Claparede doubts whether saliva is secreted by worms:  see 
+'Zeitschrift fur wissenschaft.  Zoologie,' B. xix. 1869, p. 601.
+
+{23}  Perrier, 'Archives de Zoolog. exper.' July, 1874, pp. 416, 
+419.
+
+{24}  'Zeitschrift fur wissenschaft.  Zoologie,' B. xix, 1869, pp. 
+603-606.
+
+{25}  De Vries, 'Landwirth. Jahrbucher,' 1881, p. 77.
+
+{26}  M. Foster, 'A Text-Book of Physiology,' 2nd edit. 1878, p. 
+243.
+
+{27}  M. Foster, ut sup. p. 200.
+
+{28}  Claparede remarks ('Zeitschrift fur wisseuschaft.  Zoolog.' 
+B. 19, 1869, p. 602) that the pharynx appears from its structure to 
+be adapted for suction.
+
+{29}  An account of her observations is given in the 'Gardeners' 
+Chronicle,' March 28th, 1868, p. 324.
+
+{30}  London's 'Gard. Mag.' xvii. p. 216, as quoted in the 
+'Catalogue of the British Museum Worms,' 1865, p. 327.
+
+{31}  'Familie der Regenwurmer,' p. 19.
+
+{32}  In these narrow triangles the apical angle is 9 degrees 34 
+seconds, and the basal angles 85 degrees 13 seconds.  In the 
+broader triangles the apical angle is 19 degrees 10 seconds and the 
+basal angles 80 degrees 25 seconds.
+
+{33}  See his interesting work, 'Souvenirs entomologiques,' 1879, 
+pp. 168-177.
+
+{34}  Mobius, 'Die Bewegungen der Thiere,' &c., 1873, p. 111.
+
+{35}  'Annals and Mag. of N. History,' series ii. vol. ix. 1852, p. 
+333.
+
+{36}  'Archives de Zoolog. exper.' tom. iii. 1874, p. 405.
+
+{37}  I state this on the authority of Semper, 'Reisen im Archipel 
+der Philippinen,' Th. ii. 1877, p. 30.
+
+{38}  Dr. King gave me some worms collected near Nice, which, as he 
+believes, had constructed these castings.  They were sent to M. 
+Perrier, who with great kindness examined and named them for me:  
+they consisted of Perichaeta affinis, a native of Cochin China and 
+of the Philippines; P. Luzonica, a native of Luzon in the 
+Philippines; and P. Houlleti, which lives near Calcutta.  M. 
+Perrier informs me that species of Perichaeta have been naturalized 
+in the gardens near Montpellier and in Algiers.  Before I had any 
+reason to suspect that the tower-like castings from Nice had been 
+formed by worms not endemic in the country, I was greatly surprised 
+to see how closely they resembled castings sent to me from near 
+Calcutta, where it is known that species of Perichaeta abound.
+
+{39}  'Zeitschrift fur wissenschaft.  Zoolog.'  B. xxviii. 1877, p. 
+364.
+
+{40}  'Zeitschrift fur wissenschaft.  Zoolog.' B. xxviii. 1877, p. 
+356.
+
+{41}  Perrier, 'Archives de Zoolog. exper.' tom. 3, p. 378, 1874.
+
+{42}  This case is given in a postscript to my paper in the 
+'Transact. Geolog. Soc.'  (Vol. v. p. 505), and contains a serious 
+error, as in the account received I mistook the figure 30 for 80.  
+The tenant, moreover, formerly said that he had marled the field 
+thirty years before, but was now positive that this was done in 
+1809, that is twenty-eight years before the first examination of 
+the field by my friend.  The error, as far as the figure 80 is 
+concerned, was corrected in an article by me, in the 'Gardeners' 
+Chronicle,' 1844, p. 218.
+
+{43}  These pits or pipes are still in process of formation.  
+During the last forty years I have seen or heard of five cases, in 
+which a circular space, several feet in diameter, suddenly fell in, 
+leaving on the field an open hole with perpendicular sides, some 
+feet in depth.  This occurred in one of my own fields, whilst it 
+was being rolled, and the hinder quarters of the shaft horse fell 
+in; two or three cart-loads of rubbish were required to fill up the 
+hole.  The subsidence occurred where there was a broad depression, 
+as if the surface had fallen in at several former periods.  I heard 
+of a hole which must have been suddenly formed at the bottom of a 
+small shallow pool, where sheep had been washed during many years, 
+and into which a man thus occupied fell to his great terror.  The 
+rain-water over this whole district sinks perpendicularly into the 
+ground, but the chalk is more porous in certain places than in 
+others.  Thus the drainage from the overlying clay is directed to 
+certain points, where a greater amount of calcareous matter is 
+dissolved than elsewhere.  Even narrow open channels are sometimes 
+formed in the solid chalk.  As the chalk is slowly dissolved over 
+the whole country, but more in some parts than in others, the 
+undissolved residue--that is the overlying mass of red clay with 
+flints,--likewise sinks slowly down, and tends to fill up the pipes 
+or cavities.  But the upper part of the red clay holds together, 
+aided probably by the roots of plants, for a longer time than the 
+lower parts, and thus forms a roof, which sooner or later falls in, 
+as in the above mentioned five cases.  The downward movement of the 
+clay may be compared with that of a glacier, but is incomparably 
+slower; and this movement accounts for a singular fact, namely, 
+that the much elongated flints which are embedded in the chalk in a 
+nearly horizontal position, are commonly found standing nearly or 
+quite upright in the red clay.  This fact is so common that the 
+workmen assured me that this was their natural position.  I roughly 
+measured one which stood vertically, and it was of the same length 
+and of the same relative thickness as one of my arms.  These 
+elongated flints must get placed in their upright position, on the 
+same principle that a trunk of a tree left on a glacier assumes a 
+position parallel to the line of motion.  The flints in the clay 
+which form almost half its bulk, are very often broken, though not 
+rolled or abraded; and this may he accounted for by their mutual 
+pressure, whilst the whole mass is subsiding.  I may add that the 
+chalk here appears to have been originally covered in parts by a 
+thin bed of fine sand with some perfectly rounded flint pebbles, 
+probably of Tertiary age; for such sand often partly fills up the 
+deeper pits or cavities in the chalk.
+
+{44}  S. W. Johnson, 'How Crops Feed,' 1870, p. 139.
+
+{45}  'Nature,' November 1877, p. 28.
+
+{46}  'Proc. Phil. Soc.' of Manchester, 1877, p. 247.
+
+{47}  'Trans. of the New Zealand Institute,' vol. xii., 1880, p. 
+152.
+
+{48}  Mr. Lindsay Carnagie, in a letter (June 1838) to Sir C. 
+Lyell, remarks that Scotch farmers are afraid of putting lime on 
+ploughed land until just before it is laid down for pasture, from a 
+belief that it has some tendency to sink.  He adds:  "Some years 
+since, in autumn, I laid lime on an oat-stubble and ploughed it 
+down; thus bringing it into immediate contact with the dead 
+vegetable matter, and securing its thorough mixture through the 
+means of all the subsequent operations of fallow.  In consequence 
+of the above prejudice, I was considered to have committed a great 
+fault; but the result was eminently successful, and the practice 
+was partially followed.  By means of Mr. Darwin's observations, I 
+think the prejudice will be removed."
+
+{49}  This conclusion, which, as we shall immediately see, is fully 
+justified, is of some little importance, as the so-called bench-
+stones, which surveyors fix in the ground as a record of their 
+levels, may in time become false standards.  My son Horace intends 
+at some future period to ascertain how far this has occurred.
+
+{50}  Mr. R. Mallet remarks ('Quarterly Journal of Geolog. Soc.' 
+vol. xxxiii., 1877, p. 745) that "the extent to which the ground 
+beneath the foundations of ponderous architectural structures, such 
+as cathedral towers, has been known to become compressed, is as 
+remarkable as it is instructive and curious.  The amount of 
+depression in some cases may be measured by feet."  He instances 
+the Tower of Pisa, but adds that it was founded on "dense clay."
+
+{51}  'Zeitschrift fur wissensch. Zoolog.' Bd. xxviii., 1877, p. 
+360.
+
+{52}  See Mr. Dancer's paper in 'Proc. Phil. Soc. of Manchester,' 
+1877, p. 248.
+
+{53}  'Lecons de Geologie pratique,' 1845, p. 142.
+
+{54}  A short account of this discovery was published in 'The 
+Times' of January 2, 1878; and a fuller account in 'The Builder,' 
+January 5, 1878.
+
+{55}  Several accounts of these ruins have been published; the best 
+is by Mr. James Farrer in 'Proc. Soc. of Antiquaries of Scotland,' 
+vol. vi., Part II., 1867, p. 278.  Also J. W. Grover, 'Journal of 
+the British Arch. Assoc.' June 1866.  Professor Buckman has 
+likewise published a pamphlet, 'Notes on the Roman Villa at 
+Chedworth,' 2nd edit. 1873 Cirencester.
+
+{56}  These details are taken from the 'Penny Cyclopaedia,' article 
+Hampshire.
+
+{57}  "On the denudation of South Wales," &c., 'Memoirs of the 
+Geological Survey of Great Britain,' vol. 1., p. 297, 1846.
+
+{58}  'Geological Magazine,' October and November, 1867, vol.  iv.  
+pp.  447 and 483.  Copious references on the subject are given in 
+this remarkable memoir.
+
+{59}  A. Tylor "On changes of the sea-level," &c., ' Philosophical 
+Mag.' (Ser. 4th) vol. v., 1853, p. 258.  Archibald Geikie, 
+Transactions Geolog. Soc. of Glasgow, vol. iii., p. 153 (read 
+March, 1868).  Croll "On Geological Time," 'Philosophical Mag.,' 
+May, August, and November, 1868.  See also Croll, 'Climate and 
+Time,' 1875, Chap. XX.  For some recent information on the amount 
+of sediment brought down by rivers, see 'Nature,' Sept.  23rd, 
+1880.  Mr. T. Mellard Reade has published some interesting articles 
+on the astonishing amount of matter brought down in solution by 
+rivers.  See Address, Geolog. Soc., Liverpool, 1876-77.
+
+{60}  "An account of the fine dust which often falls on Vessels in 
+the Atlantic Ocean," Proc. Geolog. Soc. of London, June 4th, 1845.
+
+{61}  For La Plata, see my 'Journal of Researches,' during the 
+voyage of the Beagle, 1845, p. 133.  Elie de Beaumont has given 
+('Lecons de Geolog. pratique,' tom. I. 1845, p. 183) an excellent 
+account of the enormous quantity of dust which is transported in 
+some countries.  I cannot but think that Mr. Proctor has somewhat 
+exaggerated ('Pleasant Ways in Science,' 1879, p. 379) the agency 
+of dust in a humid country like Great Britain.  James Geikie has 
+given ('Prehistoric Europe,' 1880, p. 165) a full abstract of 
+Richthofen's views, which, however, he disputes.
+
+{62}  These statements are taken from Hensen in 'Zeitschrift fur 
+wissenschaft. Zoologie.' Bd. xxviii., 1877, p. 360.  Those with 
+respect to peat are taken from Mr. A. A. Julien in 'Proc. American 
+Assoc. Science,' 1879, p. 354.
+
+{63}  I have given some facts on the climate necessary or 
+favourable for the formation of peat, in my 'Journal of 
+Researches,' 1845, p. 287.
+
+{64}  A. A. Julien "On the Geological action of the Humus-acids," 
+'Proc. American Assoc. Science,' vol.  xxviii., 1879, p. 311.  Also 
+on "Chemical erosion on Mountain Summits;" 'New York Academy of 
+Sciences,' Oct. 14, 1878, as quoted in the 'American Naturalist.'  
+See also, on this subject, S. W. Johnson, 'How Crops Feed,' 1870, 
+p. 138.
+
+{65}  See, for references on this subject, S. W. Johnson, 'How 
+Crops Feed,' 1870, p. 326.
+
+{66}  This statement is taken from Mr. Julien, 'Proc. American 
+Assoc. Science,' vol.  xxviii., 1879, p. 330.
+
+{67}  The preservative power of a layer of mould and turf is often 
+shown by the perfect state of the glacial scratches on rocks when 
+first uncovered.  Mr. J. Geikie maintains, in his last very 
+interesting work ('Prehistoric Europe,' 1881), that the more 
+perfect scratches are probably due to the last access of cold and 
+increase of ice, during the long-continued, intermittent glacial 
+period.
+
+{68}  Many geologists have felt much surprise at the complete 
+disappearance of flints over wide and nearly level areas, from 
+which the chalk has been removed by subaerial denudation.  But the 
+surface of every flint is coated by an opaque modified layer, which 
+will just yield to a steel point, whilst the freshly fractured, 
+translucent surface will not thus yield.  The removal by 
+atmospheric agencies of the outer modified surfaces of freely 
+exposed flints, though no doubt excessively slow, together with the 
+modification travelling inwards, will, as may be suspected, 
+ultimately lead to their complete disintegration, notwithstanding 
+that they appear to be so extremely durable.
+
+{69}  'Archives de Zoolog. exper.' tom. iii. 1874, p. 409.
+
+{70}  'Nouvelles Archives du Museum,' tom. viii. 1872, pp.  95, 
+131.
+
+{71}  Morren, in speaking of the earth in the alimentary canals of 
+worms, says, "praesepe cum lapillis commixtam vidi:" 'De Lumbrici 
+terrestris Hist. Nat.' &c., 1829, p. 16.
+
+{72}  Perrier, 'Archives de Zoolog. exper.' tom. iii. 1874, p. 419.
+
+{73}  Morren, 'De Lumbrici terrestris Hist. Nat.' &c., p. 16.
+
+{74}  'Archives de Zoolog. exper.' tom. iii. 1874, p. 418.
+
+{75}  This conclusion reminds me of the vast amount of extremely 
+fine chalky mud which is found within the lagoons of many atolls, 
+where the sea is tranquil and waves cannot triturate the blocks of 
+coral.  This mud must, as I believe ('The Structure and 
+Distribution of Coral-Reefs,' 2nd edit. 1874, p. 19), be attributed 
+to the innumerable annelids and other animals which burrow into the 
+dead coral, and to the fishes, Holothurians, &c., which browse on 
+the living corals.
+
+{76}  Anniversary Address:  'The Quarterly Journal of the 
+Geological Soc.' May 1880, p. 59.
+
+{77}  Mr. James Wallace has pointed out that it is necessary to 
+take into consideration the possibility of burrows being made at 
+right angles to the surface instead of vertically down, in which 
+case the lateral displacement of the soil would be increased.
+
+{78}  'Elements of Geology,' 1865, p. 20.
+
+{79}  'Lecons de Geologie pratique, 1845; cinquieme Lecon.  All 
+Elie de Beaumont's arguments are admirably controverted by Prof. A. 
+Geikie in his essay in Transact. Geolog. Soc. of Glasgow, vol. iii. 
+p. 153, 1868.
+
+{80}  'Illustrations of the Huttonian Theory of the Earth,' p. 107.
+
+{81}  Mr. E. Tylor in his Presidential address ('Journal of the 
+Anthropological Institute,' May 1880, p. 451) remarks:  "It appears 
+from several papers of the Berlin Society as to the German 'high-
+fields' or 'heathen-fields' (Hochacker, and Heidenacker) that they 
+correspond much in their situation on hills and wastes with the 
+'elf-furrows' of Scotland, which popular mythology accounts for by 
+the story of the fields having been put under a Papal interdict, so 
+that people took to cultivating the hills.  There seems reason to 
+suppose that, like the tilled plots in the Swedish forest which 
+tradition ascribes to the old 'hackers,' the German heathen-fields 
+represent tillage by an ancient and barbaric population."
+
+{82}  White of Selborne has some good remarks on the service 
+performed by worms in loosening, &c., the soil.  Edit, by L. 
+Jenyns, 1843, p. 281.
+
+{83}  'Zeitschrift fur wissenschaft. Zoolog.' B. xxviii. 1877, p. 
+360.
+
+
+
+
+
+End of the Project Gutenberg eText Vegetable Mould and Earth-Worms
+**Project Gutenberg Etext Formation of Vegetable Mould, by Darwin
+
diff --git a/old/vgmld10.zip b/old/vgmld10.zip
new file mode 100644
index 0000000..64e52a9
--- /dev/null
+++ b/old/vgmld10.zip