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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"> </div> +<p style="text-align: center">LONDON<br /> +JOHN MURRAY, ALBEMARLE STREET<br /> +<span class="GutSmall">1904</span></p> + +<div class="gapspace"> </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"> </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>–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—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.</p> +</td> +<td><p style="text-align: right"><span class="indexpageno"><a +href="#page7">7</a></span>–15</p> +</td> +</tr> +<tr> +<td colspan="2"><p style="text-align: center">CHAPTER II.<br /> +<span class="GutSmall">HABITS OF WORMS—</span><span +class="GutSmall"><i>continued</i></span><span +class="GutSmall">.</span></p> +</td> +</tr> +<tr> +<td><p>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.</p> +</td> +<td><p style="text-align: right"><span class="indexpageno"><a +href="#page52">52</a></span>–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—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.</p> +</td> +<td><p style="text-align: right"><span class="indexpageno"><a +href="#page121">121</a></span>–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—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.</p> +</td> +<td><p style="text-align: right"><span class="indexpageno"><a +href="#page164">164</a></span>–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—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.</p> +</td> +<td><p style="text-align: right"><span class="indexpageno"><a +href="#page209">209</a></span>–236</p> +</td> +</tr> +<tr> +<td colspan="2"><p style="text-align: center">CHAPTER VI.<br /> +<span class="GutSmall">THE DENUDATION OF THE +LAND—</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—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.</p> +</td> +<td><p style="text-align: right"><span class="indexpageno"><a +href="#page237">237</a></span>–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—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.</p> +</td> +<td><p style="text-align: right"><span class="indexpageno"><a +href="#page280">280</a></span>–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 +“de minimis non curat lex,” 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> “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.</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> “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.”</p> + +<p>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.” <a +name="citation4a"></a><a href="#footnote4a" +class="citation">[4a]</a> 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. <a name="citation4b"></a><a href="#footnote4b" +class="citation">[4b]</a> 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.”</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 +“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.</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 /> + + +<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—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.</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’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>.—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>.—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’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—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.</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 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.</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>.—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. <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,—a result which has +surprised me more than anything else in regard to worms.</p> + +<p><i>Food and Digestion</i>.—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>.—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>μ</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 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.</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. “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.” <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, “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.” <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—</span><span +class="GutSmall"><i>continued</i></span><span +class="GutSmall">.</span></h2> +<p class="gutsumm">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.</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’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, &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, &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.” <a +name="citation58"></a><a href="#footnote58" +class="citation">[58]</a> 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.</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, &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, &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>.—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—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>.—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 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.</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 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>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>.—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’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.</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, &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’ 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.</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:—</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>—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>—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>—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>—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>—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>—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>—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>—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—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. <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>.—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’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 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.</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>.—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.</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’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.</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 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.</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 +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.</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>.—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 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.</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—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.</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 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.</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 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.</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, +“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.</p> + +<p>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.</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—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.</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,—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, 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.</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 +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.</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 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.</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 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.</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 +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.</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, 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. <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 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.</p> + +<p>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.</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 “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.</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, “a +distinct, very even, narrow line of coal-ashes, mixed with small +coal, perfectly parallel with the top-sward.” <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 “some years afterwards” +these were found “several inches below the surface, at a +uniform depth.”</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, “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.</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>.—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’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.</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 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.</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 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.</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 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.</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 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.</p> + +<div class="gapspace"> </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>.—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’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, <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, “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.</p> + +<p><i>Weight of the earth ejected from a single burrow</i>, +<i>and from all the burrows within a given space</i>.—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.—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.—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.—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.) 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</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 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.</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. +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.</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’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.</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>.—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 1½ 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:—</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 14¾ 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 21½ 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—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.</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—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.</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, +&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.” <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>.—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, <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°; 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.</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 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.</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 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.</p> + +<p>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.</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.—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.—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"> </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.—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.</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 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.</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>.—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’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>.—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°; 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>.—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. <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 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.</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 +“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.</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 “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.</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 49½ 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, “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.”</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 “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.</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 “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.</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’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 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.</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° +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.</p> + +<p><i>Wroxeter</i>, <i>Shropshire</i>.—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.</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 +“Old Works.”</p> +<table> +<tr> +<td><p> </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 “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°.</p> +<table> +<tr> +<td><p> </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 9½ +inches deep stopped by concrete</p> +</td> +<td><p style="text-align: right">9½</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 “Old Works” and “Shop +Leasows,” I believe nearly as high as the upper part of the +latter field.</p> +<table> +<tr> +<td><p> </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> </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 “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.</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"> </div> +<p><i>Conclusion</i>.—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—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.</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,—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.” <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 “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.</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 “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. <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’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 “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.”</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 “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. <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 “impleta tenuissimâ terrâ, veluti in +pulverem redactâ.” <a name="citation228a"></a><a +href="#footnote228a" class="citation">[228a]</a> Perrier +also speaks of “l’état de pâte +excessivement fine à laquelle est réduite la terre +qu’ils rejettent,” &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, &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 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.</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 “terra +tenuissima,”—the “pâte excessivement +fine,”—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. +“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.” <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—</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—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.</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 “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.</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>.—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.</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° +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′.</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° 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. <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 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.</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 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.</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 +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.”</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° 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.</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’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°.</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 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.</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 +“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 <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.” 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.”</p> + +<p><i>Ledges of earth on steep hill-sides</i>.—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° 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°, 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>.—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.</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, “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.” <a name="citation266"></a><a href="#footnote266" +class="citation">[266]</a></p> + +<p><i>Ancient encampments and tumuli</i>.—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.</p> + +<p><i>Fields formerly ploughed</i>.—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 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.</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° 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.</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° 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.</p> + +<p><i>Formation and amount of mould over the Chalk +Formation</i>.—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.</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°; 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.</p> + +<p>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.</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°, 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.</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—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.</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° 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.</p> + +<div class="gapspace"> </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"> </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, &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, &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"> </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’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> ‘Leçons de +Géologie Pratique,’ tom. i. 1845, p. 140.</p> + +<p><a name="footnote3"></a><a href="#citation3" +class="footnote">[3]</a> ‘Transactions Geolog. +Soc.’ vol. v. p. 505. Read November 1, 1837.</p> + +<p><a name="footnote4a"></a><a href="#citation4a" +class="footnote">[4a]</a> ‘Histoire des +progrès de la Géologie,’ tom. i. 1847, p. +224.</p> + +<p><a name="footnote4b"></a><a href="#citation4b" +class="footnote">[4b]</a> ‘Zeitschrift für +wissenschaft. Zoologie,’ B. xxviii. 1877, p. 361.</p> + +<p><a name="footnote5"></a><a href="#citation5" +class="footnote">[5]</a> ‘Gardeners’ +Chronicle,’ April 17, 1869, p. 418.</p> + +<p><a name="footnote6"></a><a href="#citation6" +class="footnote">[6]</a> 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.</p> + +<p><a name="footnote8a"></a><a href="#citation8a" +class="footnote">[8a]</a> ‘Bidrag till Skandinaviens +Oligochætfauna,’ 1871.</p> + +<p><a name="footnote8b"></a><a href="#citation8b" +class="footnote">[8b]</a> ‘Die bis jetzt bekannten +Arten aus der Familie der Regenwürmer,’ 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 (‘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.”</p> + +<p><a name="footnote11"></a><a href="#citation11" +class="footnote">[11]</a> 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.</p> + +<p><a name="footnote12"></a><a href="#citation12" +class="footnote">[12]</a> Morren, ‘De Lumbrici +terrestris Hist. Nat.’ &c., 1829, p. 67.</p> + +<p><a name="footnote14"></a><a href="#citation14" +class="footnote">[14]</a> ‘De Lumbrici terrestris +Hist. Nat.’ &c., p. 14.</p> + +<p><a name="footnote17"></a><a href="#citation17" +class="footnote">[17]</a> Histolog. Untersuchungen +über die Regenwürmer. ‘Zeitschrift für +wissenschaft. Zoologie,’ 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 (‘The Zoologist,’ 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> ‘Familie der +Regenwürmer,’ 1845, p. 18.</p> + +<p><a name="footnote31"></a><a href="#citation31" +class="footnote">[31]</a> ‘The Zoologist,’ vol. +vii. 1849, p. 2576.</p> + +<p><a name="footnote32"></a><a href="#citation32" +class="footnote">[32]</a> ‘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.”</p> + +<p><a name="footnote33"></a><a href="#citation33" +class="footnote">[33]</a> ‘De Lumbrici terrestris +Hist. Nat.’ p. 19.</p> + +<p><a name="footnote34"></a><a href="#citation34" +class="footnote">[34]</a> ‘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.</p> + +<p><a name="footnote35a"></a><a href="#citation35a" +class="footnote">[35a]</a> On the action of the pancreatic +ferment, see ‘A Text-Book of Physiology,’ by Michael +Foster, 2nd edit. pp. 198–203. 1878.</p> + +<p><a name="footnote35b"></a><a href="#citation35b" +class="footnote">[35b]</a> Schmulewitsch, ‘Action des +Sucs digestifs sur la Cellulose.’ Bull. de +l’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 ‘Zeitschrift für +wissenschaft. Zoologie,’ B. xix. 1869, p. 601.</p> + +<p><a name="footnote41a"></a><a href="#citation41a" +class="footnote">[41a]</a> Perrier, ‘Archives de +Zoolog. expér.’ July, 1874, pp. 416, 419.</p> + +<p><a name="footnote41b"></a><a href="#citation41b" +class="footnote">[41b]</a> ‘Zeitschrift für +wissenschaft. Zoologie,’ B. xix, 1869, pp. +603–606.</p> + +<p><a name="footnote46"></a><a href="#citation46" +class="footnote">[46]</a> De Vries, ‘Landwirth. +Jahrbücher,’ 1881, p. 77.</p> + +<p><a name="footnote49"></a><a href="#citation49" +class="footnote">[49]</a> M. Foster, ‘A Text-Book of +Physiology,’ 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 +(‘Zeitschrift für wisseuschaft. Zoolog.’ +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 ‘Gardeners’ Chronicle,’ March +28th, 1868, p. 324.</p> + +<p><a name="footnote59a"></a><a href="#citation59a" +class="footnote">[59a]</a> London’s ‘Gard. +Mag.’ xvii. p. 216, as quoted in the ‘Catalogue of +the British Museum Worms,’ 1865, p. 327.</p> + +<p><a name="footnote59b"></a><a href="#citation59b" +class="footnote">[59b]</a> ‘Familie der +Regenwürmer,’ p. 19.</p> + +<p><a name="footnote79"></a><a href="#citation79" +class="footnote">[79]</a> 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′.</p> + +<p><a name="footnote89a"></a><a href="#citation89a" +class="footnote">[89a]</a> See his interesting work, +‘Souvenirs entomologiques,’ 1879, pp. +168–177.</p> + +<p><a name="footnote89b"></a><a href="#citation89b" +class="footnote">[89b]</a> Möbius, ‘Die +Bewegungen der Thiere,’ &c., 1873, p. 111.</p> + +<p><a name="footnote90"></a><a href="#citation90" +class="footnote">[90]</a> ‘Annals and Mag. of N. +History,’ series ii. vol. ix. 1852, p. 333.</p> + +<p><a name="footnote93"></a><a href="#citation93" +class="footnote">[93]</a> ‘Archives de Zoolog. +expér.’ 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, ‘Reisen im Archipel der Philippinen,’ 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> ‘Zeitschrift für +wissenschaft. Zoolog.’ B. xxviii. 1877, p. +364.</p> + +<p><a name="footnote108"></a><a href="#citation108" +class="footnote">[108]</a> ‘Zeitschrift für +wissenschaft. Zoolog.’ B. xxviii. 1877, p. 356.</p> + +<p><a name="footnote113"></a><a href="#citation113" +class="footnote">[113]</a> Perrier, ‘Archives de +Zoolog. expér.’ 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 ‘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.</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—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.</p> + +<p><a name="footnote131"></a><a href="#citation131" +class="footnote">[131]</a> S. W. Johnson, ‘How Crops +Feed,’ 1870, p. 139.</p> + +<p><a name="footnote136a"></a><a href="#citation136a" +class="footnote">[136a]</a> ‘Nature,’ November +1877, p. 28.</p> + +<p><a name="footnote136b"></a><a href="#citation136b" +class="footnote">[136b]</a> ‘Proc. Phil. Soc.’ +of Manchester, 1877, p. 247.</p> + +<p><a name="footnote138a"></a><a href="#citation138a" +class="footnote">[138a]</a> ‘Trans. of the New +Zealand Institute,’ 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: “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’s observations, I think the prejudice will be +removed.”</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 +(‘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.”</p> + +<p><a name="footnote148"></a><a href="#citation148" +class="footnote">[148]</a> ‘Zeitschrift für +wissensch. Zoolog.’ Bd. xxviii., 1877, p. 360.</p> + +<p><a name="footnote149"></a><a href="#citation149" +class="footnote">[149]</a> See Mr. Dancer’s paper in +‘Proc. Phil. Soc. of Manchester,’ 1877, p. 248.</p> + +<p><a name="footnote166a"></a><a href="#citation166a" +class="footnote">[166a]</a> ‘Leçons de +Géologie pratique,’ 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 ‘The Times’ of January 2, +1878; and a fuller account in ‘The Builder,’ 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 +‘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.</p> + +<p><a name="footnote187"></a><a href="#citation187" +class="footnote">[187]</a> These details are taken from the +‘Penny Cyclopædia,’ article Hampshire.</p> + +<p><a name="footnote210"></a><a href="#citation210" +class="footnote">[210]</a> “On the denudation of +South Wales,” &c., ‘Memoirs of the Geological +Survey of Great Britain,’ vol. 1., p. 297, 1846.</p> + +<p><a name="footnote211"></a><a href="#citation211" +class="footnote">[211]</a> ‘Geological +Magazine,’ 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 “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.</p> + +<p><a name="footnote213"></a><a href="#citation213" +class="footnote">[213]</a> “An account of the fine +dust which often falls on Vessels in the Atlantic Ocean,” +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 +‘Journal of Researches,’ during the voyage of the +<i>Beagle</i>, 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.</p> + +<p><a name="footnote217a"></a><a href="#citation217a" +class="footnote">[217a]</a> 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.</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 +‘Journal of Researches,’ 1845, p. 287.</p> + +<p><a name="footnote220"></a><a href="#citation220" +class="footnote">[220]</a> 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.</p> + +<p><a name="footnote222"></a><a href="#citation222" +class="footnote">[222]</a> See, for references on this +subject, S. W. Johnson, ‘How Crops Feed,’ 1870, p. +326.</p> + +<p><a name="footnote223"></a><a href="#citation223" +class="footnote">[223]</a> This statement is taken from Mr. +Julien, ‘Proc. American Assoc. Science,’ 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 +(‘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.</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> ‘Archives de Zoolog. +expér.’ tom. iii. 1874, p. 409.</p> + +<p><a name="footnote225b"></a><a href="#citation225b" +class="footnote">[225b]</a> ‘Nouvelles Archives du +Muséum,’ 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, +“præsepè cum lapillis commixtam vidi:” +‘De Lumbrici terrestris Hist. Nat.’ &c., 1829, p. +16.</p> + +<p><a name="footnote227"></a><a href="#citation227" +class="footnote">[227]</a> Perrier, ‘Archives de +Zoolog. expér.’ tom. iii. 1874, p. 419.</p> + +<p><a name="footnote228a"></a><a href="#citation228a" +class="footnote">[228a]</a> Morren, ‘De Lumbrici +terrestris Hist. Nat.’ &c., p. 16.</p> + +<p><a name="footnote228b"></a><a href="#citation228b" +class="footnote">[228b]</a> ‘Archives de Zoolog. +expér.’ 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 (‘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.</p> + +<p><a name="footnote236"></a><a href="#citation236" +class="footnote">[236]</a> Anniversary Address: ‘The +Quarterly Journal of the Geological Soc.’ 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> ‘Elements of +Geology,’ 1865, p. 20.</p> + +<p><a name="footnote265"></a><a href="#citation265" +class="footnote">[265]</a> ‘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.</p> + +<p><a name="footnote266"></a><a href="#citation266" +class="footnote">[266]</a> ‘Illustrations of the +Huttonian Theory of the Earth,’ p. 107.</p> + +<p><a name="footnote269"></a><a href="#citation269" +class="footnote">[269]</a> 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.”</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, &c., +the soil. Edit, by L. Jenyns, 1843, p. 281.</p> + +<p><a name="footnote285"></a><a href="#citation285" +class="footnote">[285]</a> ‘Zeitschrift für +wissenschaft. Zoolog.’ 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—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™ electronic works to protect the PROJECT GUTENBERG™ +concept and trademark. 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