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+*** START OF THE PROJECT GUTENBERG EBOOK 43320 ***
+
+THE WONDER BOOK OF
+
+VOLCANOES AND EARTHQUAKES
+
+[Illustration: MOUNT VESUVIUS IN ERUPTION]
+
+
+
+
+THE
+WONDER BOOK
+OF
+VOLCANOES AND EARTHQUAKES
+
+BY
+Professor EDWIN J. HOUSTON, Ph.D.
+
+NEW YORK
+FREDERICK A. STOKES COMPANY
+Publishers
+
+
+
+
+Copyright, 1907, by
+FREDERICK A. STOKES COMPANY
+
+_All rights reserved_
+
+_October, 1907_
+
+
+
+
+ACKNOWLEDGMENTS
+
+
+We take this opportunity of acknowledging the courtesy of the
+following publishers, who have helped us in connection with the
+illustrations of this book:--
+
+Henry Holt and Company ("Physiography," by Rollin D. Salisbury).
+
+D. Appleton and Company (Figs. 13, 35, 39, 40, 41, 42, 43, 44, 45 and
+46, "Volcanoes: What They Are and What They Teach," by J. W. Judd;
+Fig. 15, "Principles of Geology," by Sir C. Lyell).
+
+The American Book Company ("Manual of Geology," by James Dwight Dana).
+
+G. P. Putnam's Sons ("Earthquakes in the Light of the New Seismology,"
+by C. E. Dutton).
+
+The Clarendon Press ("Geology: Chemical, Physical, and
+Stratigraphical," by Joseph Prestwich).
+
+            THE PUBLISHERS.
+
+
+
+
+CONTENTS
+
+
+CHAPTER                                                      PAGE
+
+I. THE VOLCANIC ERUPTION OF KRAKATOA IN 1883                    1
+
+II. SOME EFFECTS OF THE ERUPTION OF KRAKATOA                   12
+
+III. THE VOLCANIC ISLAND OF HAWAII                             26
+
+IV. THE VOLCANIC ISLAND OF ICELAND                             46
+
+V. VESUVIUS                                                    58
+
+VI. OTHER VOLCANOES OF THE MEDITERRANEAN                       73
+
+VII. ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND
+     OTHER VOLCANOES OF MEXICO                                 85
+
+VIII. COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA         91
+
+IX. THE VOLCANIC MOUNTAINS OF SOUTH AMERICA                    97
+
+X. VOLCANOES OF THE UNITED STATES                             105
+
+XI. THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC
+    ISLANDS OF THE LESSER ANTILLES                            117
+
+XII. SOME OTHER NOTED VOLCANIC MOUNTAINS                      125
+
+XIII. JORULLO, A YOUNG VOLCANIC MOUNTAIN                      130
+
+XIV. MID-OCEAN VOLCANIC ISLANDS                               137
+
+XV. SUBMARINE VOLCANOES                                       141
+
+XVI. DISTRIBUTION OF THE EARTH'S VOLCANOES                    148
+
+XVII. VOLCANOES OF THE GEOLOGICAL PAST                        153
+
+XVIII. LAPLACE'S NEBULAR HYPOTHESIS                           157
+
+XIX. THE EARTH'S HEATED INTERIOR, THE CAUSE OF VOLCANOES      165
+
+XX. SOME FORMS OF LAVA                                        178
+
+XXI. MUD VOLCANOES AND HOT SPRINGS                            193
+
+XXII. THE VOLCANOES OF THE MOON                               207
+
+XXIII. EARTHQUAKES                                            219
+
+XXIV. SOME OF THE PHENOMENA OF EARTHQUAKES                    231
+
+XXV. THE EARTHQUAKE OF CALABRIA IN 1783                       245
+
+XXVI. THE GREAT LISBON EARTHQUAKE OF 1755                     252
+
+XXVII. THE EARTHQUAKE OF CUTCH, INDIA, IN 1819                257
+
+XXVIII. THE SAN FRANCISCO EARTHQUAKE OF APRIL 18, 1906        262
+
+XXIX. SOME OTHER NOTABLE EARTHQUAKES                          269
+
+XXX. SODOM AND GOMORRAH AND THE CITIES OF THE PLAIN           281
+
+XXXI. INSTRUMENTS FOR RECORDING AND MEASURING EARTHQUAKE
+      SHOCKS                                                  290
+
+XXXII. SEAQUAKES                                              296
+
+XXXIII. THE DISTRIBUTION OF EARTHQUAKES                       303
+
+XXXIV. THE CAUSES OF EARTHQUAKES                              308
+
+XXXV. EARTHQUAKES OF THE GEOLOGICAL PAST--CATACLYSMS          319
+
+XXXVI. THE KIMBERLY DIAMOND FIELDS AND THEIR VOLCANIC
+       ORIGIN                                                 326
+
+XXXVII. THE FABLED CONTINENT OF ATLANTIS                      335
+
+XXXVIII. PLATO'S ACCOUNT OF ATLANTIS                          344
+
+XXXIX. NATURE'S WARNING OF COMING EARTHQUAKES                 364
+
+
+
+
+FULL PAGE ILLUSTRATIONS
+
+
+                                                             PAGE
+
+MT. VESUVIUS IN ERUPTION                             Frontispiece
+
+STONES AND LAVA THROWN UPWARDS--ERUPTION OF
+  MOKUAWEOWEO, HAWAII, JULY 4-21, 1899                    fac. 36
+
+COTOPAXI                                                      102
+
+THE LAVA FLOW OF THE CRATER OF KILAUEA, HAWAIIAN ISLANDS      184
+
+A SAN FRANCISCO PAVEMENT TORN BY THE EARTHQUAKE               266
+
+
+
+
+ILLUSTRATIONS IN TEXT
+
+
+FIG.                                                         PAGE
+
+1. THE SUNDA ISLANDS                                            3
+
+2. KRAKATOA BEFORE THE ERUPTION                                 4
+
+3. KRAKATOA AFTER THE ERUPTION                                  4
+
+4. VOLCANIC DUST AS IT APPEARS UNDER THE MICROSCOPE            19
+
+5. THE HAWAIIAN ISLANDS                                        27
+
+6. HAWAII                                                      29
+
+7. PANORAMA OF MOKUAWEOWEO                                     35
+
+8. VIEW OF THE CRATER OF KILAUEA FROM THE VOLCANO HOUSE        35
+
+9. CRATER OF KILAUEA                                           40
+
+10. SECTIONS OF KILAUEA AT DIFFERENT PERIODS                   42
+
+11. ICELAND                                                    47
+
+12. THE MEDITERRANEAN                                          59
+
+13. THE VOLCANIC DISTRICT AROUND VESUVIUS                      60
+
+14. MT. ETNA                                                   77
+
+15. STROMBOLI, VIEWED FROM THE NORTHWEST, APRIL, 1874          79
+
+16. MEXICO AND CENTRAL AMERICA                                 86
+
+17. SOUTH AMERICA                                              98
+
+18. THE UNITED STATES                                         106
+
+19. PANORAMA FROM THE MESA AT THE EDGE OF MT. TAYLOR          110
+
+20. VOLCANIC NECKS, EDGE OF MESA AT MT. TAYLOR                111
+
+21. THE LESSER ANTILLES                                       118
+
+22. GRAHAM'S ISLAND--A RECENT VOLCANIC ISLAND                 143
+
+23. ALEUTIAN ISLANDS                                          146
+
+24. MAP OF THE WORLD, SHOWING LOCATION OF ACTIVE AND
+    RECENTLY EXTINCT VOLCANOES                                 150
+
+25. VOLCANIC VESICLES                                         183
+
+26. THREAD-LACE SCORIÆ FROM KILAUEA                           185
+
+27. THREAD-LACE SCORIÆ FROM KILAUEA                           185
+
+28. FROST-LIKE LAVA CRYSTALS                                  187
+
+29. FROST-LIKE LAVA CRYSTALS                                  187
+
+30. BASALTIC COLUMNS, ISLE OF CYCLOPS, ITALY                  188
+
+31. COLUMNAR AND NON-COLUMNAR BASALT                          189
+
+32, 33. DRIBLET CONES                                         190
+
+34. LAVA STALACTITES                                          191
+
+35. CRATER OF THE GREAT GEYSER OF ICELAND                     202
+
+36. GIANT GEYSER                                              203
+
+37. BEE HIVE                                                  203
+
+38. BEE HIVE GEYSER OF ICELAND                                205
+
+39. HEAVY STONE OBELISKS TWISTED BY CALABRIAN EARTHQUAKE
+    OF 1783                                                   229
+
+40. CIRCULAR HOLLOW FORMED BY CALABRIAN EARTHQUAKE            239
+
+41. SECTION OF CIRCULAR HOLLOW FORMED BY CALABRIAN
+    EARTHQUAKE                                                239
+
+42. MAP OF THE CALABRIAN EARTHQUAKE OF 1783                   246
+
+43. FISSURES CAUSED BY THE CALABRIAN EARTHQUAKE               249
+
+44. MAP SHOWING DISTRICT VISITED BY THE EARTHQUAKE OF
+    CUTCH OF 1819                                             258
+
+45. SINDREE BEFORE THE EARTHQUAKE OF 1819                     259
+
+46. SINDREE AFTER THE EARTHQUAKE OF 1819                      260
+
+47. MAP OF WESTERN COAST OF CALIFORNIA SHOWING POSITION
+    OF SAN FRANCISCO                                          263
+
+48. NEW ZEALAND                                               274
+
+49. MAP SHOWING REGION AFFECTED BY THE CHARLESTON
+    EARTHQUAKE OF 1886                                        277
+
+50. SYRIA                                                     282
+
+51. COMPLEX RECORD OF SEISMOGRAPH                             293
+
+52. LONG DISTANCE SEISMOGRAM                                  293
+
+53. VICENTINI VERTICAL PENDULUM                               294
+
+54. VICENTINI PENDULUM AND RECORDER                           295
+
+55. DAVISON'S EARTHQUAKE MAP OF JAPAN                         306
+
+
+
+
+THE WONDER BOOK OF
+
+VOLCANOES AND EARTHQUAKES
+
+
+
+
+THE WONDER BOOK OF VOLCANOES
+
+AND EARTHQUAKES
+
+
+
+
+CHAPTER I
+
+THE VOLCANIC ERUPTION OF KRAKATOA IN 1883
+
+
+Krakatoa is a little island in the Straits of Sunda, about thirty
+miles west of the island of Java, and nearly the same distance east
+of the island of Sumatra. It is uninhabited and very small, measuring
+about five miles in length and less than three miles in width. Its
+total area is only thirteen square miles. This little piece of land
+made itself famous by what took place on it during the month of
+August, 1883.
+
+Krakatoa is one of the many islands that form the large island chain
+known as the Sunda Islands. The most important islands of this chain
+are Sumatra, Java, Sumbawa, Flores, and Ceram. Between Sumatra and
+Java, the largest two of these islands, there is a channel called the
+Straits of Sunda that connects the waters of the Indian Ocean with
+those of the Pacific Ocean. The Straits of Sunda is an important piece
+of water that forms one of the great highways to the East. Shipping
+is, therefore, always to be found in its waters.
+
+As can be seen by the map, Krakatoa is not far from the Equator,
+being situated in lat. 6° 7' S. and long. 105° 26' E. from Greenwich.
+Since there are about sixty-nine miles in every degree of latitude,
+Krakatoa is about 420 miles south of the Equator, and is about
+twenty-five miles from Java. Java is part of the Dutch East Indies,
+which includes Java, Celebes, the Spice Islands, and parts of Borneo
+and Sumatra. Batavia, the principal seaport of Java, near the
+northwest coast, is a great shipping centre, visited by vessels from
+nearly all parts of the world. It has, however, no harbor, but is
+approached from the ocean by means of a canal two miles in length, the
+sides of which are provided with massive brick walls. Besides Batavia,
+which is situated about one hundred English miles east of Krakatoa,
+there are many smaller towns or villages, the most important of which
+is Anjer, a thriving seaport town, where sailing vessels obtain their
+supplies of food and fresh water. Before the eruption of Krakatoa,
+Anjer was provided with a strong, stone lighthouse.
+
+Java is especially noted for its production of coffee, in which it is
+second only to Brazil. Its area is about the same as that of the State
+of New York. Java is one of the most densely populated parts of the
+world, containing nearly four times as many people as the whole State
+of New York.
+
+These facts about the situation and surroundings of Krakatoa are
+necessary to an understanding of the wonderful thing that happened on
+it during the month of August, 1883. In that month Krakatoa suffered a
+most tremendous explosive volcanic eruption, for it is a volcano.
+
+[Illustration: FIG. 1. THE SUNDA ISLANDS]
+
+A volcano is a mountain or hill, generally conical in shape, having
+at the top a nearly central opening, called a _crater_, from which
+at times melted rock and lava, vapor and gases escape. The lava
+either flows down the side of the mountain in a liquid condition, or
+is thrown upwards into the air. If the distance the lava is thrown
+upwards is sufficiently great the melted matter solidifies before it
+falls to the earth. In such cases the largest fragments form what are
+called _volcanic cinders_, the smaller pieces, _volcanic ashes_, and
+the extremely small particles, _volcanic dust_. If, however, the lava
+is thrown to a comparatively small height, it is still melted when it
+falls, and is then known as _volcanic drops_ or _driblets_.
+
+[Illustration: FIG. 2. KRAKATOA BEFORE THE ERUPTION]
+
+It is not surprising that Krakatoa is a volcanic island, since it lies
+in one of the most active belts of volcanic islands in the world, and
+near the coasts of the most active of these islands; i. e., Java.
+This belt, as shown in the map, includes, besides the Sunda Island
+chain, parts of Gilolo, Celebes, Mindanao and the Philippine Islands.
+These islands lie between Asia on the northwest and Australia on the
+southeast.
+
+[Illustration: FIG. 3. KRAKATOA AFTER THE ERUPTION]
+
+There is no other part of the world with, perhaps, the single
+exception of Japan, where so many active volcanoes are crowded in
+so small a space. The island of Java, small as it is, has nearly
+fifty volcanoes, of which at least twenty-eight are active. They are
+situated in a lofty range running from east to west, some of the
+peaks of which are more than 10,000 feet above the level of the sea.
+Volcanic eruptions are so frequent that the island is seldom free from
+them.
+
+As will be seen from the map shown in Fig. 2, Krakatoa consists of
+three groups of volcanic mountains, the southern group giving the name
+of Krakatoa to the island. Strictly speaking, this mountain was called
+_Rakata_, but as it is now generally known as Krakatoa, it would be
+unwise to attempt to call it by any other name. The central mountain
+or group of mountains is known as Danan, and consists largely of part
+of an old crater. The group of mountains which lies near the northern
+end of the island was known as Perboawatan. From the centre of this
+latter group of mountains are several old lava streams consisting
+of a variety of lava resembling a dark-colored glass, known to
+mineralogists as _obsidian_, or _volcanic glass_.
+
+Although Krakatoa was always a volcano, yet between the years 1680 and
+1883, it was in the condition of a sleeping or extinct volcano. There
+had been a severe explosive eruption in the year 1680, that caused
+great loss of life and property, but ever since that time all activity
+had ceased and it seemed that the volcano would never again burst out.
+In other words, it was generally regarded as a trustworthy, sedate,
+quiet, inoffensive and perfectly safe volcano, that had become extinct.
+
+The long continued quiet of Krakatoa was broken on the 20th of May,
+1883, when the inhabitants of Batavia on the island of Java were
+terrified by noises like the firing of great guns, that were first
+heard between ten and eleven o'clock in the morning. These noises
+were accompanied by the shaking of the ground and buildings. The
+sleeping volcano of Krakatoa was evidently growing restless, but no
+great damage was done and soon all was again quiet. The disturbances
+were merely the forerunner of the terrible eruption soon to follow,
+and confidence was soon restored. But suddenly, on Sunday, August
+26th, 1883, almost without any further warnings, Krakatoa burst into
+terrible activity and began an explosive eruption that has never been
+equalled in severity in the memory of man.
+
+That memorable Sunday of August 26th, 1883, came during a season of
+the year known as the _dry monsoon_, a name given the season of the
+periodical winds from the Indian Ocean. Batavia, and the surrounding
+country, greatly needed rain, for in this part of the world it seldom
+rains from April to October, although the air is very moist and damp.
+For this reason the beginning of the wet season is always welcomed.
+When, therefore, the rumbling sounds of the approaching catastrophe of
+Krakatoa were heard in Batavia, the people, believing that the noises
+were due to peals of thunder, rejoiced, for all thought they heralded
+an earlier setting in of the wet monsoon. But when the rumbling
+sounds increased and reports were heard like heavy artillery, it was
+clear that the sounds were the beginning of a volcanic eruption, a
+phenomenon with which they were only too well acquainted, but, as
+volcanic eruptions were far from being uncommon in Java, no one was
+very greatly frightened.
+
+But this time the noises increased to such an extent that the people
+became alarmed. Throughout the night the appalling sounds continued
+and were accompanied by shakings of the earth sufficiently strong to
+shake the houses violently. Sleep was out of the question. Many of
+the people left their houses and remained all night in the open air,
+fearing the shocks would bring the houses down over their heads.
+
+The morning instead of heralding the dawn of a beautiful tropical day,
+with its bright, cheerful sunlight, brought with it skies covered
+with gray clouds that completely hid the sun. The rumbling sounds,
+however, had decreased, and the people were beginning to congratulate
+themselves that the dangers were over, when suddenly, the sky grew
+darker, and there began a shower of ashes that soon covered the
+streets and houses of the city. About seven o'clock on the morning of
+August 27th, a most tremendous crash was heard. The sky rapidly became
+so dark that it was soon necessary to light the lamps in the houses
+of Batavia, and some of the neighboring towns in the western part of
+Java. In addition to this the air was filled with vapor, while every
+now and then earthquake shocks were again felt. These shocks were
+accompanied by terrific noises like those produced by the explosion of
+heavy artillery. The noises rapidly increased in number and intensity
+until they produced a nearly continuous roar, the nature of which it
+is almost impossible to describe since it is probable that such sounds
+had never been heard before by man. It is a curious fact, which, I
+believe, has never been satisfactorily explained, that in most cases
+the people in the immediate neighborhood of the volcano, as, for
+example, those on board vessels in the Straits of Sunda, did not hear
+the terrific noises at all. Possibly they were too loud and simply
+gave a single inward impetus to the drum of the ear and then held it
+in position.
+
+Probably some of my readers may remember that witty description given
+by Dr. Oliver Wendell Holmes of an alleged effort made by all the
+people of the world to find out whether or not there is a man in the
+moon. This wonderful plan was as follows:
+
+Careful calculations were made to ascertain when it would be the same
+time over all the earth so that all the people of the earth could
+simultaneously shout at the top of their voices. In this way it was
+hoped that the man in the moon, if there were such a person, would
+notice the noise.
+
+The story goes on to tell how when the time approached for the great
+experiment, and all were ready to shout as loud as they could, that
+each person reasoning to himself or herself, that amid so great a
+noise no one could notice whether his or her voice was omitted,
+determined to remain silent, so as to be able to hear the noise and
+the better to observe what the man in the moon would do when the sound
+reached him. The result was that every person on the earth remained
+silent and simply listened, so that the earth was never so quiet
+before.
+
+Had Oliver Wendell Holmes, or any other person conceiving the witty
+idea, lived during the time of the great explosive eruption of
+Krakatoa, on that memorable August 27th, 1883, he might have taken
+the opportunity of observing the man in the moon, had he not been
+frightened by what was occurring, for certainly never before were
+such tremendous or terrifying sounds produced, for these sounds, as
+we shall see shortly, were actually heard for distances of more than
+3,000 miles from the volcano.
+
+There were two different kinds of waves produced in the air by the
+tremendous forces at work in the eruption of Krakatoa; namely,
+atmospheric waves and sound waves.
+
+The atmospheric waves showed their presence in the air by means of
+changes produced in the atmospheric pressure. Now, while these
+changes cannot readily be felt by man, yet their presence can be
+easily shown by the use of instruments called _barometers_.
+
+There are in different parts of the world, buildings called
+_meteorological observatories_, that are provided, among other
+instruments, with recording barometers. These instruments caught
+the great atmospheric waves that were produced by the eruption of
+Krakatoa. In this manner, the astounding fact was learned that the
+waves starting from the volcano travelled no less than seven times
+around the world. When we say astounding, it must not be understood
+that the formation of such waves was at all contrary to the known laws
+of physics. On the contrary, provided the force of the eruption was
+sufficiently great, such waves must have been produced in the great
+ærial ocean. The astonishing, or wonderful thing, was that the force
+setting up these waves was so great that it caused them to move seven
+times around the globe.
+
+The atmospheric waves were so powerful that it will be worth our while
+to describe them in detail. Starting from the volcano of Krakatoa,
+as a centre, these waves moved outwards in all directions, becoming
+gradually larger and larger until they reached a point halfway round
+the globe, or 180° from Krakatoa. The waves did not, however, stop
+here, but continued moving onward, now growing smaller and smaller
+until they reached a point in North America, immediately opposite
+Krakatoa. Such a point on a globe is called an _antipodal point_.[1]
+The waves did not stop at this point, but again advanced moving toward
+Krakatoa, growing larger and larger until they again reached a point
+halfway around the globe, or 180° from Krakatoa, when they again
+continued moving but now continually growing smaller and smaller,
+until they reached Krakatoa. Here they again began moving completely
+around the globe, and this was continued for as many as seven times.
+It must not be supposed that the waves ceased on the seventh time
+around. On the contrary, they, probably, kept on moving for many
+additional times, but they were then so feeble that even the sensitive
+recording barometers were unable to detect their presence.
+
+There was another kind of waves in the atmosphere that did not require
+barometers for their detection. These were the sound waves, and can
+readily be detected by the human ear.
+
+Now, in the case of the great eruption of Krakatoa, the intensity of
+the sounds was so great that the sounds could be heard distinctly at
+distances of several thousand miles from Krakatoa.
+
+The sound waves so closely resembled the explosion of artillery that
+at Acheen, a port on the northern coast of Sumatra, 1,073 miles from
+Krakatoa, the authorities, believing that an attack was being made on
+the port, placed all their troops under arms to repel the invaders.
+The sounds were also distinctly heard at Bangkok, in Siam, a distance
+of 1,413 miles from the volcano. They were also heard at the Chagos
+Islands, a group of islands situated in the Indian Ocean about 2,267
+miles from Krakatoa.
+
+Two steamers at Singapore, 522 miles distant, were despatched to find
+the vessel that was believed to be firing guns as distress signals.
+
+The sounds were distinctly heard in parts of South Australia, 2,100
+miles distant, and in Western Australia, at 1,700 miles distance.
+
+But it will be unnecessary to give any further details of the great
+distances at which these sounds were actually heard. It will suffice
+to say that they were heard as far off as about 3,000 miles.
+
+It is difficult to picture to one's self such great distances.
+Assuming the greatest distances to be in the neighborhood of 3,000
+miles, it would be as if a sound produced, say, in Boston, New York,
+or Philadelphia, was so loud that it could be heard in Amsterdam,
+London, or Paris.
+
+Some idea of the intensity of these sounds can be had from the fact
+that in Batavia, when, in accordance with usage, a gun was fired from
+one of the forts at eight o'clock in the morning, two hours before the
+greatest intensity of the sounds had been reached, the sound of the
+gun could scarcely be heard above the continuous roar.
+
+While, of course, the principal reason the sound waves were carried
+so far was the great force causing the eruption, yet these distances
+were increased by the fact that the explosion occurred in a region
+almost entirely surrounded by great bodies of water. The waves could,
+therefore, be readily carried along the surface of the sea. Had there
+been a high mountain wall, like the Andes of South America, on one
+side of the volcano they would probably have been shut off in this
+direction a short distance from where they were produced.
+
+
+
+
+CHAPTER II
+
+SOME EFFECTS OF THE ERUPTION OF KRAKATOA
+
+
+Besides the sound waves in the air, there were waves in the waters of
+the ocean. Suddenly, without any warning, the people of Batavia were
+surprised by a huge wave that, crossing the Straits of Sunda, entered
+the ship canal before referred to as connecting the city with the
+ocean, and, rising above the brick wall, poured over the surrounding
+country.
+
+Although Batavia was 100 English miles from Krakatoa, yet after
+travelling this distance the wave was sufficiently strong to enter
+the city and flood its streets with water to a depth of several feet.
+Fortunately, the loss of life was small in the city of Batavia, but
+very great in the surrounding towns and villages.
+
+The ocean waves varied in height at different times of the eruption.
+The greatest were from fifty to eighty feet high. Just imagine the
+effect of a wave twice the height of an ordinary house. The waves
+caused great damage to the shipping in the neighborhood. In one
+instance, a vessel was carried one and a half miles inland and left on
+dry land thirty feet above the level of the sea.
+
+The total loss of life by the waves has been estimated at 35,000
+people; besides this, of course, there was a great amount of property
+destroyed. The greatest loss was in the immediate neighborhood of
+Krakatoa. Gigantic waves swept over the lowlands lying near the
+shores of Sumatra and Java, where over areas several miles in width
+nearly everything was destroyed, the houses, trees, and people being
+swept away and the surface of the land greatly changed. The towns of
+Karang and Anjer, as well as numerous smaller villages, were almost
+completely destroyed.
+
+The seaport town of Anjer, by far the most important of the above
+towns, was almost completely swept away. The heavy stone lighthouse
+was so completely obliterated that no traces of its heavy stone
+foundations could afterwards be found. The Rev. Phillip Neale,
+formerly a British chaplain at Batavia, from whose account of the
+eruption of Krakatoa some of the above facts have been taken, tells
+of the brave action of the keeper of the lighthouse at Anjer. Besides
+his work as lighthouse keeper, to see that the light was constantly
+burning during the night, he was charged with telegraphing to Batavia
+the names of all passing vessels. On the fateful morning of the great
+catastrophe, observing that the sun did not rise, he kept the light of
+the lighthouse burning, and, notwithstanding the danger to which he
+was exposed, continued at his post in order to send word to Batavia of
+the passing of an English steamer. While doing this the lighthouse was
+swept away and the brave man perished.
+
+The following verbal account of the destruction of the port of Anjer
+was given by a Dutch pilot stationed at Anjer. This description is
+quoted by the Rev. Mr. Neale from an article prepared by him for
+publication in "The Leisure Hour."
+
+      "I have lived in Anjer all my life, and little thought the
+      old town would have been destroyed in the way it has. I am
+      getting on in years, and quite expected to have laid my
+      bones in the little cemetery near the shore, but not even
+      that has escaped and some of the bodies have actually been
+      washed out of their graves and carried out to sea. The
+      whole town has been swept away, and I have lost everything
+      except my life. The wonder is that I escaped at all. I can
+      never be too thankful for such a miraculous escape as I had.
+
+      "The eruption began on the Sunday afternoon. We did
+      not take much notice at first, until the reports grew
+      very loud. Then we noticed that Krakatoa was completely
+      enveloped in smoke. Afterwards came on the thick darkness,
+      so black and intense that I could not see my hand before
+      my eyes. It was about this time that a message came
+      from Batavia inquiring as to explosive shocks, and the
+      last telegram sent off from us was telling you about
+      the darkness and smoke. Towards night everything became
+      worse. The reports became deafening, the natives cowered
+      down panic-stricken, and a red, fiery glare was visible
+      in the sky above the burning mountain. Although Krakatoa
+      was twenty-five miles away, the concussion and vibration
+      from the constantly repeated shocks were most terrifying.
+      Many of the houses shook so much that we feared every
+      minute would bring them down. There was little sleep for
+      any of us that dreadful night. Before daybreak on Monday,
+      on going out of doors, I found the shower of ashes had
+      commenced, and this gradually increased in force until at
+      length large pieces of pumice stone kept falling around.
+      About six A. M. I was walking along the beach.
+      There was no sign of the sun, as usual, and the sky had a
+      dull, depressing look. Some of the darkness of the previous
+      day had cleared off, but it was not very light even then.
+      Looking out to sea I noticed a dark, black object through
+      the gloom, travelling towards the shore.
+
+      "At first sight it seemed like a low range of hills rising
+      out of the water, but I knew there was nothing of the kind
+      in that part of the Sunda Strait. A second glance--and a
+      very hurried one it was--convinced me that it was a lofty
+      ridge of water many feet high, and worse still, that it
+      would soon break upon the coast near the town. There was
+      no time to give any warning, and so I turned and ran for
+      my life. My running days have long gone by, but you may
+      be sure that I did my best. In a few minutes I heard the
+      water with a loud roar break upon the shore. Everything
+      was engulfed. Another glance around showed the houses
+      being swept away and the trees thrown down on every side.
+      Breathless and exhausted I still pressed on. As I heard
+      the rushing waters behind me, I knew that it was a race
+      for life. Struggling on, a few yards more brought me to
+      some rising ground, and here the torrent of water overtook
+      me. I gave up all for lost, as I saw with dismay how high
+      the wave still was. I was soon taken off my feet and borne
+      inland by the force of the resistless mass. I remember
+      nothing more until a violent blow aroused me. Some hard,
+      firm substance seemed within my reach, and clutching it,
+      I found I had gained a place of safety. The waters swept
+      past, and I found myself clinging to a cocoanut palm-tree.
+      Most of the trees near the town were uprooted and thrown
+      down for miles, but this one fortunately had escaped and
+      myself with it.
+
+      "The huge wave rolled on, gradually decreasing in height
+      and strength until the mountain slopes at the back of
+      Anjer were reached, and then, its fury spent, the water
+      gradually receded and flowed back into the sea. The sight
+      of those receding waters haunts me still. As I clung to
+      the palm-tree, wet and exhausted, there floated past the
+      dead bodies of many a friend and neighbor. Only a mere
+      handful of the population escaped. Houses and streets were
+      completely destroyed, and scarcely a trace remains of where
+      the once busy, thriving town originally stood. Unless you
+      go yourself to see the ruin you will never believe how
+      completely the place has been swept away. Dead bodies,
+      fallen trees, wrecked houses, an immense muddy morass and
+      great pools of water, are all that is left of the town
+      where my life has been spent. My home and all my belongings
+      of course perished--even the clothes I am wearing are
+      borrowed--but I am thankful enough to have escaped with my
+      life and to be none the worse for all that I have passed
+      through."
+
+As is common in cases of earthquake waves a great depression in the
+level of the sea occurred at places great distances from Krakatoa. For
+example, at the harbor of Ceylon, the water receded so far that for
+about three minutes the boats were left high and dry, and then a huge
+wave carried them with it as it rushed over the land.
+
+Perhaps one of the best evidences of the immense power of ocean waves
+is to be seen in the massive blocks of white coral rock that were
+washed up by the waves, on parts of the coast of Java for distances of
+from two to three miles from the ocean. Many of these blocks weighed
+from twenty to thirty tons. Indeed, some of them reached the weight of
+from forty to fifty tons.
+
+It is probable that the island of Krakatoa and its neighboring smaller
+islands formed portions of a huge cone about eight miles in diameter,
+that has been broken up at some very remote but unknown time by,
+perhaps, a greater catastrophe than that of August, 1883.
+
+In the Straits of Sunda the water was raised fifty feet to eighty
+feet above the ordinary level, and produced tremendous destruction
+especially on the coasts of Java and Sumatra, sweeping away many
+villages and drowning many thousands of people. The wave had a
+velocity of progression of nearly 400 miles per hour, or eight times
+faster than an ordinary express train.
+
+When it is said that the _velocity of progression of the wave_ was
+nearly 400 miles per hour, it is not meant that a body floating on
+the ocean, such, for example, as a ship, would have been carried
+forward at this high velocity, but would merely rise and fall in a
+to-and-fro swing to about the height of the wave; that is, fifty to
+eighty feet according to what may have been the height. As in the
+case of the sound waves these motions of water covered or passed over
+nearly all the waters of the earth. The waves progressing toward the
+west, crossed the Indian Ocean reaching to the coast of Hindostan, and
+Madagascar, and sweeping around the southern part of Africa, finally
+reached the coasts of France and England, as well as the eastern part
+of North and South America. Sweeping towards the east, they reached
+the coasts of Australia, New Zealand, and crossing the vast Pacific
+Ocean were felt at Alaska and the western coasts of North and South
+America.
+
+But besides the enormous waves caused by the eruption, there were
+marked changes in the level of the land. Large portions of the coast
+of Sumatra and Java were almost annihilated, much of the original
+surface near the coast being submerged, and places that were formerly
+dry land are now covered with water to a depth of from 600 to 900 feet.
+
+The enormous amount of material thrown into the air by the forces
+of the eruption is especially characteristic of this phenomenon.
+Such quantities of pumice stone and ashes fell from the clouds that,
+sinking in the water and collecting on the bed of the channel, they
+changed the depth of the water, so as to render navigation dangerous.
+Indeed, the Sebesi Channel, lying on the north of the island of
+Krakatoa was completely blocked by a huge bank of volcanic material,
+portions of which projected above the water, forming two smaller
+islands. These, however, have since been washed away by the waves.
+
+We will not attempt to give at present any explanations as to the
+causes of this great volcanic eruption, since the different theories
+as to the cause of volcanoes will be better understood when other
+volcanic eruptions have been described. It is sufficient here to say
+that if a large quantity of water should have suddenly reached a
+great mass of molten rock, frightful explosive eruptions would have
+occurred, and if the island was resting on a submerged crater its
+sudden disappearance may be explained.
+
+Another great wonder connected with the explosive eruption of Krakatoa
+was the enormous heights to which the fine dust was thrown up into
+the air. It has been asserted that during the most intense of these
+eruptions the particles reached elevations of perhaps more than
+twenty-five miles above the level of the sea. Carried by the winds,
+the fine particles remained suspended in the air for many months,
+and gave rise to magnificent sunlight effects, such as early dawn,
+lengthened twilights, lurid skies, and gorgeous sunsets of a reddish
+tint. There were also caused curious haloes, as well as green and blue
+moons.
+
+The fine dust particles consisted of minute crystals of feldspar and
+other minerals, and when examined under the microscope presented the
+appearance shown in Fig. 4.
+
+These mineral substances permitted a portion of the light to pass
+through them, thus producing wonderful optical effects in the
+atmosphere either because they acted like minute prisms and so
+produced rainbow colors, or because they turned the rays of light out
+of their course as to produce what is called interference by color
+effects of a nature similar to the colors seen in mother-of-pearl,
+rainbow coal, or in the wing cases of many beetles. The explanations
+of these phenomena are too difficult for a book of this character.
+
+An explosive volcanic eruption is a very terrifying and wonderful
+phenomenon. Frightful roaring sounds are suddenly heard, the earth
+shakes for many miles around, when suddenly a vast quantity of molten
+rock, and sometimes huge stones, are thrown out of the crater high up
+into the air. So great is the force that throws these materials out
+of the opening that heavy masses of rocks often are ejected very much
+faster than the projectiles from the largest guns that are used in any
+of the navies of the world.
+
+[Illustration: FIG. 4. VOLCANIC DUST AS IT APPEARS UNDER THE
+MICROSCOPE]
+
+As the molten lava cools and falls in the form of prodigious clouds
+of ashes, cinders and dust, for many miles around the volcano, even
+the light of the sun is obscured, and one cannot see the hand before
+the face. Some of the materials in these clouds are so light that they
+remain suspended in the air for many hours, often indeed for many
+days, and sometimes even for years. The heavier particles, however,
+soon begin to fall, and before long the earth's surface both around
+the volcano, and often at considerable distances from it, is covered
+with a thick layer of ashes.
+
+The sounds accompanying a volcanic eruption are often terrifying. Amid
+shakings and tremblings of the earth's crust, known as earthquakes,
+there are occasionally heard noises like the explosion of huge guns.
+Sometimes these sounds follow one another so rapidly that they produce
+an almost continuous roar. Through the roar of the explosion a
+curious crackling noise can be heard, due to the fragments of stone
+hurled out of the crater striking against one another, especially as
+the stones which are thrown out of the crater and have commenced to
+fall back again to the earth, are struck by others that are still
+rising.
+
+Immense quantities of ashes, stones, vapor and gases are thrown
+upwards for great distances into the air, while, at the same time, a
+lava stream pours over the lowest side of the crater. As the column
+of ashes and cinders reaches its greatest height in the air, it
+begins to spread outward on all sides, rapidly growing like a huge
+dark mushroom. This soon shuts out the light of the sun, and from it
+showers of red hot ashes and cinders fall to the earth.
+
+It would be extremely dangerous to be on the side of the volcanic
+mountain during an explosive eruption; for, even should you escape
+falling into an opening in the side of the mountain, you might be
+killed by the huge stones that are constantly falling on all sides
+around the opening, or might be buried under the vast showers of red
+hot ashes that are poured down from the dense clouds overhanging the
+mountain, or suffocated by clouds of sulphur vapor that rush down its
+sides.
+
+When at a safe distance the sight is certainly magnificent. There is
+no light from the sun. All would be in pitch darkness but for the
+reddish glare thrown upwards by the red hot lava, by the glowing
+showers of ashes that are being rained down on the sides of the
+mountain, or by terrific lightning flashes, due to the discharge of
+the immense quantities of electricity produced by the forces of the
+eruption.
+
+Naturally a great volcanic eruption can cause a considerable loss of
+life and property. When a large lava stream begins to flow down the
+sides of the mountain, it cannot be stopped, and should it flow toward
+a village or town it is likely to destroy the town completely. Besides
+this, the vegetation of the country for many miles around is destroyed
+by the showers of red hot ashes that fall from the sky. The houses of
+neighboring cities are similarly ruined by the great conflagrations
+thus set up. Further destruction is also caused by large streams of
+mud that rush down the slopes of the mountain, or by huge waves set
+up in the ocean. If the volcano is situated, as most volcanoes are,
+near the coast, the showers of ashes and falling stones may set fire
+to vessels in the neighborhood, or the progress of such vessels may be
+seriously retarded by layers of ashes or pumice stone that float on
+the surface. Sometimes these layers are so thick as actually to bring
+ships to a complete standstill.
+
+It must not be supposed that volcanoes are in a constant state of
+eruption. On the contrary, nearly all volcanoes, after an eruption,
+become _quiet_ or _inactive_. The air soon clears by the ashes
+settling, and the sunlight again appears. A crust forms over the
+surface of the lava, which rapidly becomes hard enough to permit one
+to walk over it safely. The vegetation, which has been destroyed by
+the hot ashes, again springs up, and, if the volcano happens to be
+situated within the tropics, where there is an abundance of moisture,
+the land soon again becomes covered by a luxuriant vegetation. Most of
+the people, who have escaped sudden death during the eruption, return
+to the ruins of their houses; for it is a curious fact that no matter
+how great has been a volcanic eruption, or how far-reaching the ruin,
+the survivors, as a rule, do not appear to hesitate to return to their
+old neighborhood. In a few years the fields are re-cultivated, the
+villages are rebuilt, and the people apparently forget they are living
+over a slumbering volcano, which may at any time again burst forth in
+a dangerous eruption.
+
+A volcano that throws out molten rock, vapor and gases is known as an
+_active volcano_. An active volcano, however, is only correctly said
+to be in a state of eruption when the quantity of the molten rock,
+lava or vapor it throws out is greatly in excess of the ordinary
+amount.
+
+Sometimes the volcanic activity so greatly decreases that the molten
+rock or lava no longer rises in the crater, but, on the contrary,
+begins to sink, so that the top of the lava in the crater is often
+at a considerable distance below its edges. The lava then begins to
+harden on the surface, and, if the time is sufficient, the hardened
+part extends for a considerable distance downward. In this way the
+opening connecting the crater with the molten lava below becomes
+gradually closed, the volcano being thus shut up, or corked, just as a
+bottle is tightly closed by means of a cork driven into the opening at
+its top so as to prevent the escape of the liquid it contains.
+
+It may sound queer to say that a volcano has its crater so corked up
+as to prevent the escape of the lava, but the idea is nevertheless
+correct and helpful. To realize the size of these huge volcanic corks
+one must remember that the craters of some volcanoes are several miles
+across. A volcano thus choked or corked up is said to be _extinct_.
+
+When we speak of an extinct volcano we do not mean that the volcano
+will never again become active. A volcano does not cease to erupt
+because there are no more molten materials in the earth to escape, but
+simply because its cork or crust of hardened lava has been driven in
+so tightly that the chances of its ever being loosened again seem to
+be very small. But small as the chances may seem we must not forget
+that the volcano may at any time become active, or go into its old
+business of throwing out materials through its crater. A volcano in
+an extinct condition is not unlike a steam boiler, the safety valve
+of which has been firmly fixed in place. If the steam continues to be
+generated in the boiler, it is only a matter of time when the boiler
+will blow up, and the explosion will be all the greater because the
+safety valve did not allow the steam to escape earlier.
+
+Sometimes an intermediate class of volcanoes called _dormant_ is
+introduced between active volcanoes on the one hand and extinct
+volcanoes on the other. The name dormant volcano, or, as the word
+means, _sleeping volcano_, is objectionable, since it might lead one
+to think that an extinct volcano is not sleeping but dead, and this is
+wrong.
+
+Since the plug of hardened lava in the volcanic crater is generally at
+a much lower level than the top of the crater, the crater will soon
+become filled to a greater or less depth with water, produced either
+by the rain, or by the melting of the snow that falls on the top of
+the mountain. Crater lakes, often of very great depths, are common in
+extinct volcanoes.
+
+Of course, when an extinct volcano again becomes active, two things
+must happen if the eruption is explosive. In the first place, the
+force of the explosion must be sufficiently great to loosen the
+stopper or plug of hardened lava which stops it. In doing this the
+mass is broken into a number of fragments that are thrown forcibly
+upwards into the air. After rising often for great heights they soon
+fall again on the sides of the mountain.
+
+But besides the breaking up of the stopper, the lake in the crater of
+the volcano is thrown out along with the cinders or ashes, producing
+very destructive flows of what are called aqueous lava or mud streams.
+These streams flow down the sides of the mountain, carrying with them
+immense quantities of both the ashes thrown out during the eruption,
+or those that have collected around the sides of the crater during
+previous eruptions. Very frequently, these streams of aqueous lava
+produce greater destruction than the molten lava.
+
+If you have ever watched common ants at work clearing out or enlarging
+their underground homes, in a piece of smooth gravel walk in your
+garden, you can form some idea why the mountain immediately around a
+volcanic crater is conical in shape. If the colony of ants happens
+to be fairly large, you can see an almost unbroken stream of these
+industrious little animals, each bearing in its mandibles a small
+grain of sand or gravel brought up from some place below the surface.
+
+Carrying it a short distance from the opening, it throws it on the
+ground, rapidly returning for another load. In this way there is
+heaped up around all sides of the opening a pile of sand or gravel,
+the outward slopes of which gives the pile a conical form. You have,
+probably, noticed that the steepness of the slopes depends on the size
+of the grains; for the larger these grains the sharper or steeper the
+slopes, the very fine grains producing flat mounds or cones.
+
+It is the same with a volcanic cone. The materials that are thrown
+upwards into the air, falling again on the mountain, collect around
+the crater on all sides, thus giving it the characteristic cone-like
+shape of the volcanic mountain. Where nothing occurs to disturb
+the formation of the cone its height above the level of the sea
+will gradually increase. Very frequently, however, during explosive
+eruptions, a large part of this cone will be blown away by the
+force of the eruption only to be again built up during some later
+eruption. Indeed, in the case of volcanic islands, the force of a
+great volcanic eruption is sometimes so great that not only is a large
+volcanic mountain blown entirely away, but a hole is left, where it
+had been standing, that extends further downwards below the level
+of the sea than the top of the mountain extended previously above
+it. The above are some, but by no means all, the wonders attending
+volcanic eruptions. We shall refer to others in subsequent chapters in
+describing particular eruptions.
+
+
+
+
+CHAPTER III
+
+THE VOLCANIC ISLAND OF HAWAII
+
+
+The volcanic island of Hawaii, the largest of the Sandwich Island
+chain, is situated in the mid Pacific, south of the Tropic of
+Cancer. As shown in Fig. 5, this island chain consists of Hawaii,
+Maui, Molokai, Oahu, Kauai, Nihau, and about eight large islands,
+together with numerous small islands, extending in a general northwest
+direction from Hawaii to Nihau, a distance of about 400 miles. Like
+most volcanic islands they lie in more or less straight lines,
+probably along fissures, in this case in two nearly parallel lines.
+The island of Nihau, however, is an exception, the direction of the
+greatest length being almost straight across the two parallel lines.
+
+The Sandwich Islands lie 2,000 miles from San Francisco in deep water,
+between 2,000 and 3,000 fathoms, or between 12,000 and 18,000 feet in
+depth. This island chain consists of great volcanic mountains, that
+had, at one time, fifteen active volcanoes of the first class. These
+are now all extinct but three, and all of these are on the island of
+Hawaii.
+
+In his report to the United States Geological Survey for 1882-83,
+Dutton states that the summit of Mt. Haleakala on East Maui is 10,350
+feet above the sea level. Oahu has peaks on its eastern side 2,900
+feet high, and peaks on the western side 3,850 feet high. The summit
+of Kauai is probably 6,200 feet above the sea.
+
+[Illustration: FIG. 5. THE HAWAIIAN ISLANDS _From U. S.
+Geological Survey_]
+
+It can be shown by deep-sea soundings that all these volcanic piles
+are the summits of a gigantic mountain mass that rises abruptly from
+the bed of the Pacific. There are reasons for believing that this
+submarine chain continues for many hundreds of miles in the same
+direction beyond Kauai.
+
+The extinct volcano, Haleakala, on East Maui appears to have been in
+eruption at a much later day than Mt. Kea, which is also an extinct
+volcano. But the natives have no traditions of any eruptions.
+
+The volcanoes on the other islands have been extinct for a very long
+time judging from the extent of their erosion. Dutton is of the
+opinion that the western islands of the chain have been extinct for
+much longer times than the remaining islands.
+
+The Sandwich Islands, also known as the Hawaiian Islands, are one of
+the colonial possessions of the United States. The island of Hawaii is
+about 2,000 miles from San Francisco. Honolulu, on the island of Oahu,
+the principal seaport of the chain, has a pleasant climate, and is an
+important coaling station for warships, commercial vessels, whalers,
+and trading ships generally.
+
+The principal product of the island is sugar cane.
+
+The island of Hawaii, as shown in map, Fig. 6, consists of five
+volcanic mountains and some small coral reefs. These mountains are:
+Mt. Kea, on the north, 13,805 feet in height; Mt. Haulalai, in the
+west central part of the island, 8,273 feet in height; Mt. Loa, in the
+south central part of the island, 13,675 feet in height; Mt. Kilauea,
+twenty miles east of the crater of Loa, 4,040 feet high at the Volcano
+House, and 4,158 feet on the highest point on the west, and Kohala,
+5,505 feet in height, running through the northwestern part of the
+island, and the Kohala mountains in the northwestern part.
+
+[Illustration: FIG. 6. HAWAII _From Dana's Manual of
+Geology_]
+
+Of these mountains, Mt. Loa and Kilauea are the only active volcanoes,
+and are in frequent eruption. Mt. Haulalai was in eruption during
+1804. Mt. Kea has not been active during historical times, while Mt.
+Kohala has been inactive for so long a time that its slopes are deeply
+gullied wherever the rivers flow down them.
+
+As you can see from the map, Hawaii is very large. It has a length of
+ninety-three miles from north to south, and a breadth of eighty miles
+from east to west, its area is about 6,500 square miles. With the
+exception of small patches of coral reefs, Hawaii is formed entirely
+of lava, and is the largest pile of lava in the world with the single
+exception of Iceland.
+
+Where the islands of the Hawaiian chain have coral reefs extending
+off their coasts, excellent harbors are found in the deep waters
+between the islands and the reefs. Hawaii, however, has no extended
+reefs of this character, and, consequently, no first-class harbors.
+Hilo, on the eastern coast, is the best harbor, and is, therefore, the
+principal settlement.
+
+A very brief examination of the map of Hawaii will show you that there
+are no rivers on the island, except on the sides exposed to the wind,
+that is, on the northern and northeastern slopes. Since the yearly
+rainfall on Hawaii is large, being in the neighborhood of a hundred
+inches, you will understand that considerable rain water falls on the
+island. In those parts of the island where it does not run off the
+surface it must drain downward through the loose piles of broken rocks
+or cinders. A rainfall of one hundred inches a year means that if all
+the rain which falls on each square foot of surface was collected
+in a flat vessel one foot square with vertical sides it would fill
+the vessel to the depth of one hundred inches, or over eight feet.
+The drainage of the rainwater downwards through these parts of the
+island, must, therefore, be large.
+
+Another curious fact you can notice on the map, is that the lava
+streams of the past fifty years from Mt. Loa indicated by heavy
+dotted lines, in no cases begin at the crater, but start at fairly
+considerable distances from it. Later on in this chapter we shall
+explain the reason for this curious fact.
+
+Since practically the whole of Hawaii has been formed from the streams
+of lava that have flowed at one time or another, you can understand
+how great these flows must have been. But to do this fully you must
+not only take into consideration the portions of the island that
+lie above the ocean and reach into the air at its greatest height
+to 13,805 feet above its surface, you must also remember that this
+mountain rises from a deep ocean, so that if all the water were
+removed, you would see Hawaii towering up above the former level
+of the sea to the height of about 31,000 feet, or higher than Mt.
+Everest, the highest point on the earth above the present sea level.
+This would be, approximately, five and eight-tenths miles. You can
+understand, therefore, how great the flow of lava must have been.
+
+We shall begin the description of Hawaii with the active volcano of
+Mt. Loa, or, as it is sometimes called in Hawaii, "The White Mountain."
+
+You will remember that the eruption of Krakatoa was of the explosive
+type. Practically no melted rock or lava escaped from the crater.
+Indeed, if it had escaped it would not have been seen; for, not only
+the cone near the crater, but also much of the mountain itself was
+blown completely out of sight and covered by the waters of the ocean.
+
+The eruptions of Mt. Loa are of an entirely different type. In Loa
+there are no explosions, the eruptions being what are called the
+non-explosive or quiet volcanic eruption type. It will be necessary to
+explain some of the peculiarities of this kind of eruptions.
+
+There is a great difference in the liquidity or the ease with which
+different kinds of lava flow. Some lava is very thick or viscid,
+or is sticky like thick molasses or tar, and therefore flows very
+sluggishly. Other lava is thin or mobile, more closely resembling
+water in the ease with which it flows. Now, in the case of a volcanic
+mountain of fairly considerable height, where the lava possesses
+marked liquidity, the lava as it rises from great depths in the tube
+of the volcano seldom flows over the top or rim of the crater. This is
+not because the force that brings the lava up is unable to carry it
+a few thousand feet higher, so that it can run over the brim of the
+crater, but because the walls of the volcanic mountains are unable to
+stand the great pressure which the mass of liquid lava exerts against
+their sides.
+
+It can be shown that a column of liquid lava 500 feet high, will exert
+a pressure on the walls of the crater of about 625 pounds to the
+square inch. Therefore, in very high volcanic mountains, long before
+the lava can reach the edge of the crater and overflow, the pressure
+becomes so great, that cracks or fissures are made in the sides of
+the mountain, through which the lava is quietly discharged; when, of
+course, the level of the lava in the crater falls considerably. In
+volcanoes of the explosive type, no matter what may be the condition
+of lava, should a large quantity of water suddenly find an entrance to
+a large body of molten lava at some distance below the surface, the
+lava would be suddenly thrown explosively into the air, where being
+chilled, it would afterwards descend in showers of ashes, cinders, or
+volcanic dust.
+
+In some volcanic mountains such as Mt. Loa, the crater, instead
+of being situated at the top of a conical pass of ashes or other
+material, consists of a pit-like depression, generally occupying a
+level tract or plain at the top of the mountain. This pit is known
+as a _caldera_, or _caldron_, or what you might, perhaps, call a
+huge kettle or boiler. The pit has more or less vertical sides that
+extend downwards for unknown depths to the place from which the lava
+comes. The vertical walls of the caldera are not, however, smooth, but
+exhibit numerous horizontal ledges, that mark places where portions of
+the floor of the caldera were situated at different times.
+
+At the bottom of the large pit or caldera on the summit of Mt. Loa
+can be seen the level floor formed of hardened lava. This floor is
+surrounded by vertical walls on which can be seen the broken edges of
+the old lake bed.
+
+Captain Dutton, in a paper on Hawaiian volcanoes, prepared for the
+United States Geological Survey, and published in its Fourth Annual
+Report for 1882-83, thus describes the appearance at the great crater
+as it was in 1882.
+
+      "The summit of Mauna Loa (Mt. Loa), is a broad and large
+      platform about five miles in length and four miles in
+      width, within which is sunken the great caldera called
+      Mokuaweoweo. The distance from the point where we first
+      reach the summit to the brink of the pit is about a mile
+      and a half. The surface of the platform is much more rugged
+      than the slopes just ascended. It is riven with cracks, and
+      small faults,[2] and piles of shattered rock are seen on
+      every hand. Nowhere is there to be seen the semblance of
+      a cinder cone. Doubtless many eruptions have broken forth
+      from the various fissures on this summit, but only here
+      and there can insignificant traces of such catastrophes
+      be definitely distinguished. The absence of fragmental
+      ejecta (broken rock that are thrown out) is extraordinary.
+      The shattered blocks, slabs, and spalls (chips) which
+      everywhere cumber the surface appear to have resulted from
+      the spontaneous shivering and shattering of the lava sheets
+      by their own internal tensions as they cooled.
+
+Fig. 7, taken from Dutton's report, gives the general shape of this
+great caldera. Dutton's description of the same is as follows:
+
+      "The length of the main caldera is a little less than
+      three miles and its width about a mile and three-quarters.
+      Its floor, viewed from above, appears to be composed of a
+      series of flat surfaces occupying two distinct levels, the
+      higher upon the surface of the black ledge, the lower lying
+      within the ledge. Upon the western side is a small cinder
+      cone standing close upon the border of the black ledge.
+      It is the only one visible, either within the caldera or
+      upon the surrounding summit. Its height is about 125 or 130
+      feet. It was seen in operation, throwing up steam, clots of
+      lava, and lapilli (some of the larger pieces of fragmentary
+      lava) in the year 1878. The only other diversifications of
+      the floor are many cracks which traverse it, the larger of
+      which are distinctly visible from above. Some of them are
+      considerably faulted. There is no difficulty in recognizing
+      the fact that the whole floor has been produced by the
+      sinkage of the lava beds which once continued over the
+      entire extent of the depression, their undersides having
+      been melted off most probably by the fires beneath. The
+      lava beds in the immediate vicinity of the brink upon the
+      summit platform wear the aspect of some antiquity. They
+      have become brown and carious by weathering, and, although
+      no soil is generated, little drifts of gravel are seen
+      here and there mixed with pumice. Since the caldera was
+      formed there is no indication that the lavas have anywhere
+      overflowed its rim. And yet it is a very strange fact that
+      within a half mile, and again within a mile to a mile and
+      a half, lavas have been repeatedly erupted within the last
+      forty years from the summit platform, and have outflowed
+      at points situated from 700 to 900 feet above the level of
+      the lava lake within. Traces may also be seen, at varying
+      distances back of the rim, of very many eruptions in which
+      the rocks betoken great recency, although no dates can be
+      assigned to their occurrence."
+
+[Illustration: FIG. 7. PANORAMA OF MOKUAWEOWEO _From U. S.
+Geological Survey_]
+
+[Illustration: FIG. 8. VIEW OF THE CRATER OF KILAUEA FROM THE
+VOLCANO HOUSE _From U. S. Geological Survey_]
+
+During his visit to this great pit, Captain Dutton succeeded in
+climbing down the almost vertical walls on the side of the crater,
+and, reaching the surface of the hardened lake, walked over it. It
+must have required no little courage to thus venture on the thin
+floor of a lake which he knew was filled to great depths with red hot
+boiling lava, for he was walking over the surface of a slumbering
+volcano, that might at almost any moment awaken, and opening, swallow
+him and his companions. Through enormous cracks in the floor, he could
+feel the heat from the molten mass, while, through the same openings
+came suggestive whiffs of sulphur vapor.
+
+During the eruption of this mountain, on January 23d, 1859, the light
+from the glowing lava streams was bright enough to read fine print at
+Hilo, a distance of thirty-five miles.
+
+During the eruption of 1852, a stream of white-hot lava was thrown up
+into the air from one of the fissures to a height of from 300 to 400
+feet.
+
+[Illustration: STONES AND LAVA THROWN UPWARDS--ERUPTION OF
+MOKUAWEOWEO, HAWAII, JULY 4-21, 1899 _From a Stereograph,
+Copyright, by Underwood & Underwood_]
+
+When an eruption takes place in Mt. Loa the column of lava slowly
+rises in the crater, threatening to overflow its lowest edges, but
+before this can take place the pressure becomes so great that some
+portion of the mountain below the crater is fractured and the lava
+quietly escapes.
+
+During some conditions of the mountain every fifteen or twenty minutes
+a column of highly glowing lava is shot upwards like a fountain to
+a height of 500 feet and over, falling back into the lake in fiery
+spray. Unusual heights of these streams are generally followed by an
+eruption.
+
+These curious jets of molten rock certainly cannot be due to the
+pressure of higher columns of lava, since the crater itself is near
+the top of a high plain. They are believed to be due to steam formed
+by the penetration of the rain water that falls on this part of the
+mountain.
+
+You can now understand why the lava streams escaping from Mt. Loa as
+shown on the map, in Fig. 6, do not begin at the level of the crater;
+for the discharge of the lava does not take place over the rim of
+the crater, but through the cracks or fissures formed further down
+the sides of the mountains. It must not be supposed, however, that
+the fissures are limited to the sides of the mountain where they can
+be seen. They probably occur in many places below the surface of the
+water on some part of the bed of the ocean.
+
+The crevices that are formed in this manner in the sides of the
+mountain vary greatly in size, some being so narrow that the lava
+scarcely flows through them at all but simply fills up the crevice,
+hardens on cooling, and mends the cracks in the mountains, in the way
+that a crack is mended in a piece of china by the use of glue or in
+a wall of masonry by mortar. Through the largest crevices or cracks,
+however, large lava streams may continue to flow often for several
+weeks, or even longer.
+
+Sometimes, especially towards the close of the eruptive flow, the
+lava may escape disruptively, so that small cones are formed along
+the lines of the fissures. Cones of this character are called lateral
+cones, and in the case of a volcanic island, where the lava flows out
+below the level of the water, the lateral cones sometimes project
+above the water and form volcanic islands or dangerous shoals that
+impede navigation.
+
+When the lava pours out of a crevice in the side of the mountain, a
+river of molten rock rushes down the slopes, at first like a torrent,
+but on reaching the more nearly level ground, it spreads out in great
+lava lakes or fields, the surface of which takes on the characteristic
+black appearance of basalt, a certain kind of glass, for the lavas of
+Mt. Loa are generally basaltic. After an eruption the hardened floor
+of lava in the caldera, being no longer supported by the liquid mass
+formerly below it, falls in, leaving a large cavity with only the
+edges of the old floor clinging to the sides of the pit.
+
+It will be interesting to give a short account of some of the great
+lava streams that have been poured out at different times from Mt. Loa.
+
+In the great eruption of August 11th, 1855, the lava escaped through
+fissures from two to thirty inches in width. Then, flowing in a
+continuous stream, it did not stop until it was within five miles of
+Hilo.
+
+In the eruption of January 23d, 1859, the lava stream flowed towards
+the northwest on the east side of Haulalai, reaching the sea in eight
+days.
+
+The eruption of March 27th, 1868, was characterized by severe
+earthquake shocks, one of which, occurring on the second of April,
+destroyed many houses and produced huge fissures in the earth. These
+shocks produced great earthquake waves that reached distant coasts.
+
+Mt. Kilauea, lies at a lower level towards the east. This crater is
+situated at 4,040 feet above the level of the sea, and is nearly 6,000
+feet below the caldera on the top of Mt. Loa.
+
+Fig. 8, taken from the United States Geological Survey, Fourth
+Annual Report, for 1882-83, shows a view of Kilauea from the Volcano
+House. Dutton gives the following description of the appearance of
+Halemaumau, the pit crater or caldera of Kilauea.
+
+      "In front of us and right beneath our feet, over the crest
+      of a nearly vertical wall, more than 700 feet below, is
+      outspread the broad floor of the far-famed Kilauea. It
+      is a pit about three and a half miles in length, and two
+      and a half miles in width, nearly elliptical in plan and
+      surrounded with cliffs, for the most part inaccessible to
+      human foot, and varying in altitude from a little more than
+      300 feet to a little more than 700 feet. The altitude of
+      the point on which we stand is about 4,200 feet above the
+      sea....
+
+      "The object upon which the attention is instantly fixed
+      is a large chaotic pile of rocks, situated in the centre
+      of the amphitheatre, rising to a height which by an
+      eye estimate appears to be about 350 to 400 feet. From
+      innumerable places in its mass volumes of steam are poured
+      forth and borne away to the leeward by the trade wind. The
+      color of the pile is intensely black....
+
+      "Around it spreads out the slightly undulated floor of the
+      amphitheatre, as black as midnight. To the left of the
+      steaming pile is an opening in the floor of the crater,
+      within which we behold the ruddy gleams of boiling lava.
+      From numerous points in the surrounding floor clouds of
+      steam issue forth and melt away in the steady flow of the
+      wind. The vapors issue most copiously from an area situated
+      to the right of the central pile, and in the southern
+      portion of the amphitheatre. Desolation and horror reign
+      supreme. The engirdling walls everywhere hedge it in. But
+      upon their summits, and upon the receiving platform beyond,
+      are all the wealth and luxuriance of tropical vegetation
+      heightening the contrast of the desolation below...."
+
+[Illustration: FIG. 9. CRATER OF KILAUEA _From Dana's Manual
+of Geology_]
+
+Fig. 9 represents the pit-like crater of Kilauea as it appeared after
+the eruption of 1886. Here, as will be seen, there are several lakes
+of lava, the largest of which is known as Halemaumau. The eruption of
+1886, like all the eruptions of Kilauea, consisted of the escape of
+the lava from an opening on the side of the mountain below the crater,
+and a sinking in of the hardened floor of the crater. The figure also
+shows the position of the New Lake that lies east of Halemaumau. The
+extent and appearance of each of these lakes are constantly changing,
+both as to height and area.
+
+Dutton gives the following description of the appearance of the lake
+of lava, and some curious phenomena that occur on its surface. He is
+describing the general appearance of the pool of molten lava covered
+as it is with a hardened black crust:
+
+      "The surface of the lake is covered over with a black
+      solidified crust showing a rim of fire all around its edge.
+      At numerous points at the edge of the crust jets of fire
+      are seen spouting upwards, throwing up a spray of glowing
+      lava drops, and emitting a dull, simmering sound. The heat
+      for the time being is not intense. Now and then a fountain
+      breaks out in the middle of the lake and boils freely for a
+      few minutes. It then becomes quiet, but only to renew the
+      operation at some other point. Gradually the spurting and
+      fretting at the edges augment. A belch of lava is thrown
+      up here and there to the height of five or six feet, and
+      falls back upon the crust. Presently, near the edge, a
+      cake of the crust cracks off, and one edge of it bending
+      downwards descends beneath the lava, and the whole cake
+      disappears, disclosing a naked surface of liquid fire.
+      Again it coats over and turns black. This operation is
+      repeated edgewise at some other part of the lake. Suddenly
+      a network of cracks shoots through the entire crust. Piece
+      after piece of it turns its edge downwards and sinks with
+      a grand commotion, leaving the whole pool a single expanse
+      of liquid lava. The lake surges feebly for awhile, but soon
+      comes to rest. The heat is now insupportable, and for a
+      time it is necessary to withdraw from the immediate brink."
+
+It is very curious to think of cakes of hardened lava floating on the
+surface of molten lava, but, of course, this is just as natural as
+cakes of ice floating on the surface of water; for a cake of hardened
+lava is, as you will understand, only a cake of frozen lava, and,
+being lighter than the molten lava, must, of course, float on its
+surface.
+
+The disappearance of these cakes of frozen lava and their remelting is
+still more curious, and can be explained as follows: The frozen or
+solidified mass of black basalt is a trifle lighter than the lava on
+which it is floating only while its temperature is high, and therefore
+expanded by heat. As soon as it cools, its density increases, and when
+it becomes a little greater than that of the liquid lava, it begins to
+sink and soon disappears.
+
+[Illustration: FIG. 10. SECTIONS OF KILAUEA AT DIFFERENT
+PERIODS _From Dana's Manual of Geology_]
+
+Professor Dana, who has made a careful study of the phenomena of
+Kilauea, shows in Fig. 10, a cross section of Kilauea at different
+times. Before the eruption of 1823, the depth of the crater was from
+800 to 1,000 feet. At the eruption the bottom 600 to 800 feet, making
+the depth of Kilauea over this deeper central part about 1,500 feet.
+The varying depths at different dates are clearly marked on the
+drawing.
+
+The eruptions of Kilauea generally occur as follows:
+
+First there is a slow rising of the lava in the crater. This rising
+continues until the pressure is so great that the mountain is ruptured
+at some lower place. Next a discharge of the lava and a sinking to a
+level in the conduit that will depend on the position of the crevice.
+Then a gradual falling in of the hardened floor of the lake, a portion
+of the horizontal walls remaining on the sides of the caldera.
+
+The eruption of Kilauea, however, has not always been of the quiet
+type. There was an eruption in the year 1789 that would appear to
+have been of the explosive variety. The following account is given by
+Dana as taken from a history of the Sandwich Islands by the Rev. I.
+Dibble, published in 1843:
+
+"The army of Keoua, a Hawaiian chief, being pursued by Kamehamoha,
+were at the time near Kilauea. For two preceding nights there had
+been eruptions, with ejections of stones and cinders. The army of
+Keoua set out on their way in three different companies. The company
+in advance had not proceeded far before the ground began to shake and
+rock beneath their feet, and it became quite impossible to stand.
+Soon a dense cloud of darkness was seen to rise out of the crater,
+and, almost at the same instant, the thunder began to roar in the
+heavens and the lightning to flash. It continued to ascend and spread
+around until the whole region was enveloped, and the light of day
+was entirely excluded. The darkness was the more terrific, being
+made visible by an awful glare from streams of red and blue light,
+variously combined through the action of the fires of the pit and the
+flashes of lightning above. Soon followed an immense volume of sand
+and cinders, which were thrown to a great height, and came down in a
+destructive shower for many miles around. A few of the forward company
+were burned to death by the sand, and all of them experienced a
+suffocating sensation. The rear company, which was nearest the volcano
+at the time, suffered little injury, and after the earthquake and
+shower of sand had passed over, hastened on to greet their comrades
+ahead on their escape from so imminent a peril. But what was their
+surprise and consternation to find the centre company a collection
+of corpses! Some were lying down, and others were sitting upright,
+clasping with dying grasp their wives and children, and joining noses
+(the mode of expressing affection) as in the act of taking leave. So
+much like life they looked that at first they supposed them merely
+at rest, and it was not until they had come up to them and handled
+them that they could detect their mistake." Mr. Dibble adds: "A blast
+of sulphurous gas, a shower of heated embers, or a volume of heated
+steam would sufficiently account for this sudden death. Some of the
+narrators who saw the corpses, affirm that though in no place deeply
+burnt, yet they were thoroughly scorched." As you will see in Chapter
+XI, this sudden and awful death due to highly heated air and dust
+particles, caused even a greater loss of life in the catastrophic
+eruption of Pelée, in Martinique on May 8, 1902.
+
+By reason of its situation at a lower level on the slopes of Mt. Loa,
+Kilauea was at one time thought to be one of the craters lower down
+on the slopes of Loa. This was the opinion of Professor Dana when he
+examined the district in 1840. Since this time the region has been
+more carefully studied, and Mt. Loa and Kilauea, are now generally
+regarded as separate and independent volcanoes, neither of which acts
+as a safety valve for the other.
+
+We shall not attempt in this chapter to say anything concerning the
+sources or places from where these great supplies of lava have been
+drawn. This will be left to some subsequent chapter, after we have
+described still other volcanoes.
+
+The outlines of mountains like Mt. Loa or Kilauea differ greatly from
+mountains like Vesuvius; their slopes, like the slopes of all other
+Hawaii volcanoes, have an inclination which does not exceed 10°.
+The lava streams, therefore, as they flow down the mountains, move
+more slowly than they would were the slopes more precipitous, as in
+mountains like Vesuvius.
+
+There have been many eruptions of Kilauea. That which occurred in the
+year 1840, was of great magnitude (see map, Fig. 6), and began in a
+fissure southwest of the crater. The principal eruption, however,
+broke out about twelve miles from the sea coast, and about twenty-five
+miles east of Kilauea. Here an enormous mass of lava forming a stream
+nearly three miles wide reached the ocean at Nanawale.
+
+When an eruption takes place on Mt. Loa through a fissure at the
+height of 10,000 to 13,000 feet the length of the lava streams is
+frequently as great as twenty-five to thirty miles. Often the lava
+though hardening at the surface will continue to flow underneath
+through huge tunnels, of which the top and sides are composed of
+solidified parts of the same lava stream. After the flow has ceased
+long hollow tunnels often remain. If the lower end of such a tunnel
+containing molten lava is momentarily closed, the pressure of the
+lava above may not only burst through the obstruction, but may even
+throw the lava upwards in jets 300 to 700 feet high. Probably most of
+you have seen illumined fountains where jets of water are beautifully
+lighted up by different colored electric lights placed below them.
+Such fountains, however, can but poorly compare either in beauty or
+grandeur with these wonderful lava fountains, common on the slopes of
+Mt. Loa during an eruption.
+
+
+
+
+CHAPTER IV
+
+THE VOLCANIC ISLAND OF ICELAND
+
+
+The island of Iceland consists of a number of volcanic mountains some
+of which are still active. As can be seen from the map, shown in
+Fig. 11, Iceland lies in the North Atlantic Ocean, immediately below
+the Arctic Circle, about 250 miles east of Greenland, and 600 miles
+west of Norway. Its length from east to west is about 300 miles, and
+its breadth about 200 miles, its total area, including the adjacent
+islands, being more than 40,000 square miles.
+
+Were all the water removed from the North Atlantic Ocean, it would be
+seen that Iceland rests on the bed of the Atlantic, on a submarine
+plateau or highland; for, in this part of the ocean the water is only
+from 1,500 to 3,000 feet deep. This submarine plateau extends as far
+as Norway on the east, Greenland on the north, and the island of Jan
+Mayen on the northeast. Immediately north of the plateau the ocean
+suddenly drops to a depth of 12,000 to 15,000 feet.
+
+[Illustration: FIG. 11. ICELAND]
+
+Toward the south the plateau extends with but few interruptions
+through the middle of the ocean to a shoal known as the _Dolphin
+Shoal_, as far as lat. 25° N. This part of the ocean, which can only
+relatively be called a shoal, is not generally deeper than 9,600 feet,
+although in some places the water is more than 12,000 feet deep. On
+each side of the Dolphin Shoal the water is much deeper, being in
+places 15,000 feet on the east, while on the west there are depths
+as great as from 17,000 to 21,000 feet.
+
+This sunken plateau, possibly including the shallower plateau on the
+north, is believed by some to be the remains of the fabled continent
+of _Atlantis_, to which we shall refer in another part of this book.
+
+The coast line of Iceland is unbroken on the southeast, but the
+remainder of the coast is deeply indented with bays or fiords in which
+are many excellent harbors.
+
+Iceland is liable to frequent earthquake shocks and volcanic
+eruptions. From careful records that have been preserved in the
+history of the island, we learn that since the beginning of the
+twelfth century there have practically never been intervals longer
+than forty years, and more generally not longer than twenty years,
+in which there has not been a great earthquake or a great volcanic
+eruption. These volcanic eruptions are often very protracted. For
+example, one eruption of the volcano Hecla continued for six years
+without ceasing. Sir Charles Lyell, the great English geologist,
+writes as follows about Iceland:
+
+      "Earthquakes have often shaken the whole island at once,
+      causing great changes in the interior, such as the sinking
+      down of hills, the rending of mountains, the desertion of
+      rivers by their channels, and the appearance of new lakes.
+      New islands have often been thrown up near the coast, some
+      of which still exist, while others have disappeared, either
+      by subsidences or the action of the waves.
+
+      "In the interval between eruptions innumerable hot springs
+      afford vent to the subterranean heat, and solfataras
+      discharge copious streams of inflammable matter. The
+      volcanoes in different parts of the island are observed,
+      like those of the Phlegræan Fields, Italy, to be in
+      activity by turns, one vent often serving for a time as a
+      safety valve for the rest. Many cones are often thrown
+      up in one eruption and in this case they take a linear
+      direction, running generally from southeast to northwest."
+
+The volcanic eruptions of Iceland belong for the greater part to the
+fissure type. During a volcanic eruption in Iceland the ground is
+split in fissures or cracks, generally parallel to each other, and
+varying in width from a few inches to several yards. These fissures
+extend for great distances across the country. The lava quietly wells
+out along the fissures not unlike the way quiet spring waters flow
+from their reservoirs.
+
+According to Dr. Th. Thoroddsen, the Icelandic geologist, there are
+two systems of fissures extending through Iceland, from southwest to
+northeast in the southern part of the island, and from north to south
+in the northern part. Where two lines of fissures cross each other the
+points of intersection may be especially active.
+
+Dr. Th. Thoroddsen arranges the volcanoes of Iceland under three
+heads, i. e., _cone-shaped volcanoes_; _lava cones_; and _chains of
+craters_, the last being the commonest. Out of 107 volcanoes examined
+by him in Iceland, eight were of the Vesuvian type, or were built up
+of layers of lava and volcanic ashes; sixteen were of the lava-cone
+type, similar to Mt. Loa, of the Hawaiian Islands, and the remaining
+eighty-three were of the type of crater chains.
+
+The volcano of Snaefell Jökul, 4,710 feet above the level of the
+ocean, is built up of alternate layers of lava and hardened volcanic
+mud. It is not, however, a true cone-shaped mountain.
+
+The largest volcano in Iceland, the Dyngjufköll, with its immense
+crater of Askja, has an area of some twenty-five square miles. In its
+form it resembles Snaefell.
+
+Volcanoes of the lava-cone type have been built up entirely of lava
+and have a slight angle of inclination. These volcanoes range in size
+from small hillocks to the largest mountains on the island. Their
+cones generally stand on a base of wide circumference and frequently
+rise to great heights, the top being occupied by a caldera, or pit
+crater like that on Mt. Loa or Kilauea.
+
+Volcanoes of the type of chain-craters follow the natural fissures in
+the crust. These craters are generally low, seldom being more than 350
+feet high.
+
+There are also seen in Iceland caldron-shaped depressions that have
+been formed by explosive eruptions. One of the best instances of such
+craters is Viti, on the side of Mt. Krafla. This crater was formed by
+the sudden eruption of May 17th, 1724.
+
+The lava sometimes quietly runs out of the entire length of the
+fissure without forming any cone. This was the case of a great fissure
+known as the Eldgja Chasm. Here three lava streams covered an area of
+270 square miles.
+
+As the lava comes out of the fissures, it generally produces long
+ramparts of slags, and blocks of lava that are piled up on either side
+of the fissure. Sometimes a line of low cones is built up. These cones
+consist of heaps of slag, cinders, and blocks of lava. Their craters
+are not rounded as in the case of volcanoes of the Vesuvian type, but
+are oblong, or have their greatest diameter extending in a direction
+of the fissure.
+
+Icelandic lava as it escapes from the fissures is peculiar in that
+it is very viscid or plastic and can be readily drawn out into long
+threads that can be spun into ropes. When such lava runs down the
+sides of a steep slope, it often splits on cooling into separate
+blocks. Where it runs over flat, level ground, however, it spreads
+uniformly on all sides, producing vast level lava deserts that are as
+flat as the surface of a well built floor.
+
+There are many rivers in the north and the west of Iceland. Now, as
+the lava streams flow out of the fissures they enter the channels of
+the rivers so that the streams of water must find new paths to the
+sea, and this operation may be repeated again and again. Often the
+time between eruptions is long enough to give the rivers opportunity
+to cut deep channels or gorges in their new channels; but on the next
+escape of the lava these gorges and valleys are again filled with the
+molten rock, and the rivers must begin their channel cutting all over.
+
+You will note the frequent use of the word Jökul, as Snaefell Jökul,
+Skaptar Jökul, Orefa Jökul, etc. The name Jökul means a large mass of
+ice, or a mountain that is continually covered with snow, for example,
+Snaefell Jökul, is a beautifully shaped, snow-covered mountain
+situated on a point of land on the western coast of the island,
+extending out nearly fifty miles into the sea, between the Faxa Fiord
+and the Briela Fiord. It is a very conspicuous object, being visible
+to passing ships at considerable distances from the island. Orefa
+Jökul is the highest mountain in Iceland. Skaptar Jökul is one of the
+active volcanoes of Iceland.
+
+There can be no doubt that Iceland has been formed entirely by lava
+thrown up from the bottom of a submarine plateau, until it extended
+above the surface of the waters. To make an island entirely of lava
+with an area of 40,000 square miles, must, of course, have required
+many cones or craters that continued to pour forth lava for periods of
+time much longer than those during which man has lived on the earth.
+
+The surface of Iceland is far from attractive. The interior is
+practically a vast lava desert, covered with snow-clad mountains or
+Jökuls. There is no plant life except in marshy lands near the coasts,
+and even here scarcely enough grass is raised to feed the few cattle
+and horses owned by the inhabitants. There is no agriculture, owing
+to the very short summers, so that all grain is brought from Europe.
+Every now and then the grass crop is destroyed by accumulation of
+Polar ice on the northern and western coasts. Such failures are always
+attended by great famines, when many of the people die.
+
+Should you ever visit Iceland you would probably be surprised to hear
+the people speaking about their forests. You might go over all the
+coasts of the island without seeing anything larger than a birch bush,
+not much higher than six feet. These are what the Icelanders like to
+speak of as their forest trees, and I suppose there is no harm done,
+if one only understands just what they mean by "trees."
+
+While, however, Iceland has practically no trees, yet it has no
+difficulty in obtaining a plentiful supply of timber, since in the
+deep fiords or bays on the western and southern coasts there can
+always be found much drift timber brought there by the ocean currents
+from the forests of America.
+
+The principal town or settlement in Iceland is Reykjavik, the capital
+of the island, on the southwestern coast; this is the chief trading
+place on the island. Thingvalla is also an important town.
+
+The lavas that form the entire mass of Iceland were thrown out both
+before and since the glacial age. It is the opinion of Geikie that
+these outflows have continued uninterruptedly since that age to the
+present time. It is known that the lavas of Iceland were thrown out
+both before and after the glacial age, because during the glacial age,
+deep cuttings or groovings were made on the surface of the earth by
+the glaciers as they slowly moved over it. Now lava beds containing
+the glacial scratches have been found and resting on them are other
+lava streams. The scratched lavas must, therefore, have been thrown
+out before the glacial age, and the second lavas after that age.
+
+Let us now examine some of the more active volcanoes of Iceland and
+their eruptions. We will begin with the well-known volcano of Skaptar
+Jökul.
+
+The following description of this volcano has been taken from a book
+on Iceland by E. Henderson, published in Boston, 1831. Skaptar Jökul
+lies in the south central part of Iceland about forty odd miles from
+the coast. It takes its name from the Skaptar River, down whose
+channel the lava flowed its entire distance of forty miles from the
+ocean. Skaptar Jökul consists of about twenty conical hills lying
+along one of the fissures that extends from northeast to southwest.
+
+It appears from Henderson's account that people living in the
+neighborhood of Skaptar Jökul were greatly alarmed by repeated
+earthquakes that were felt at different times from the first to the
+eighth of June, 1783. These earthquake shocks increased in number and
+violence, so that the people left their homes and awaited in terror
+the coming catastrophe. On the morning of the eighth a prodigious
+cloud of dense smoke darkened the air, and the surrounding land soon
+became covered with ashes, pumice, and brimstone. As is common with
+eruptions in Iceland, that have been preceded by long periods of rest,
+the heat produced by the escaping lava and the sulphurous gases,
+melted such quantities of ice that great floods were produced in the
+rivers.
+
+On the 10th of June vast torrents of lava that had been escaping
+from the craters entered the valley of the Skaptar River, and
+commenced flowing through its channel. Immense quantities of steam
+were produced, and, in less than twenty-four hours, the river was
+completely dried up, for the lava had collected in the channel,
+which in many places flows between high rocks from 400 to 600 feet
+in height and nearly 200 feet in breadth, and had not only filled
+the river to its brink, but had overflowed the adjacent fields to a
+considerable extent, and flowing along the cultivated banks of the
+river destroyed all the farms in its path.
+
+On gaining the outlet, where the channel of the Skaptar emerged
+into the plain, it might have been supposed that the burning flood
+would have at once spread over the low fields, which lay immediately
+before it, but, contrary to all expectations, this flow was for a
+time stopped by an immense unfathomed abyss in the river's bed, into
+which it emptied itself with great noise. When this chasm was at
+last filled, the lava increased by fresh flows, rose to a prodigious
+height, and breaking over the cooled mass, proceeded south towards the
+plain.
+
+In the meantime the thunder and lightning, together with subterranean
+roars, continued with little or no intermission.
+
+On the 18th of June, 1783, another dreadful eruption of red hot lava
+came from the volcano. This flowed with great velocity and force over
+the surface of the cooling stream that had been thrown out principally
+on the tenth of the month. Floating islands consisting of masses of
+flaming rock were seen on the surface of the lava stream, and the
+water that had been banked up on both sides of the stream was thrown
+into violent boiling.
+
+In the meantime people living along the Hverfisfloit, the next largest
+river to the east of the Skaptar, had not yet been visited by the
+lava streams. It is true that their vegetation had been destroyed by
+showers of red hot stone and ashes, and that both atmosphere and water
+were filled with poisonous substances. The land had also been plunged
+in utter darkness, so that it was scarcely possible at noonday to
+distinguish a sheet of white paper held up at the window from the
+blackness of the wall on either side. But the molten lava streams had
+not yet reached the people of this valley and they hoped that the
+eruption would soon be over, and that the lava flow would continue to
+follow the Skaptar. On the 3d of August, however, they were alarmed by
+seeing steam escaping from the River Hverfisfloit, and soon all its
+water was dried up, and a fresh lava flow poured down upon them. As in
+the case of the Skaptar, the melted rock completely filled the empty
+channel to the brink, and then overflowing, covered the low grounds on
+both sides, so that by the ninth of August it had reached the open and
+level country near its mouth and in the course of a few hours spread
+itself for a distance of nearly six miles across the plain. This flow
+continued after the end of August, and, indeed, even as late as the
+month of February, 1784, when a new eruption took place in this part
+of the country.
+
+Hecla, another well-known volcano in Iceland, situated about thirty
+miles from the southern coast, consists of three peaks, the central of
+which is the highest. Its craters form vast hollows on the sides of
+these peaks, and at the time of the eruption in 1766 were covered with
+snow. Hecla is believed to have been an active volcano long before
+Iceland was inhabited. No less than twenty-three eruptions have been
+recorded between A. D. 1004 and the great eruption of 1766-68.
+
+Volcanic history frequently repeats itself. There had been no great
+eruption of Hecla for a period of about twelve years, and the people
+living in the neighborhood were congratulating themselves on the
+belief that the mountain was becoming actually extinct, and that
+therefore they need not trouble themselves about eruptions. Others,
+however, more farseeing, pointed out the fact that the lakes and
+rivers in the vicinity did not freeze, and that the amount of water
+they contained was greatly decreased.
+
+The following description of the great eruption of Hecla that was
+remarkable both for its violence, as well as for the time during which
+it continued, is taken from Symington's "Sketches of Faroe Islands and
+Iceland":
+
+      "On the 4th of April, 1766, there were some slight shocks
+      of an earthquake, and early next morning a pillar of sand,
+      mingled with fire and red hot stones, burst with a loud
+      thundering noise from its summit. Masses of pumice, six
+      feet in circumference, were thrown to the distance of ten
+      or fifteen miles, together with heavy magnetic stones,
+      one of which, eight pounds weight, fell fourteen miles
+      off, and sank into ground still hardened by the frost. The
+      sand was carried towards the northwest, covering the land,
+      150 miles round, four inches deep, impeding the fishing
+      boats along the coast, and darkening the air, so that at
+      Thingore, 140 miles distant, it was impossible to know
+      whether a sheet of paper was white or black. At Holum, 155
+      miles to the north, some persons thought they saw the stars
+      shining through the sand-cloud. About mid-day, the wind
+      veering round to the southeast, conveyed the dust into the
+      central desert, and prevented it from totally destroying
+      the pastures. On the 9th of April, the lava first appeared,
+      spreading about five miles towards the southwest, and on
+      the 23d of May, a column of water was seen shooting up in
+      the midst of the sand. The last violent eruption was on the
+      5th of July, the mountains, in the interval, often ceasing
+      to eject any matter; and the large stones thrown into the
+      air were compared to a swarm of bees clustering around the
+      mountain-top; the noise was heard like loud thunder forty
+      miles distant, and the accompanying earthquakes were more
+      severe at Krisuvik, eighty miles westward, than at half the
+      distance on the opposite side. The eruptions are said to
+      be in general more violent during a north or west wind than
+      when it blows from the south or east, and on this occasion
+      more matter was thrown out in mild than in stormy weather.
+      Where the ashes were not too thick, it was observed that
+      they increased the fertility of the grass fields, and
+      some of them were carried even to the Orkney Islands, the
+      inhabitants of which were at first terrified by what they
+      considered showers of black snow."
+
+The largest volcano in Iceland is Dyngjufjoll. This has on its summit
+the gigantic crater of Askja, some twenty-five square miles in area.
+This crater is of the intermediate form; the most general form of
+volcanoes on the island consisting of a number of craters that closely
+follow fissures.
+
+Professor Johnstrup, in a report to the Danish Government, on this
+volcano, states that the valley of Askja has been gradually filled
+by repeated flows of lava from enormous craters on the edge of the
+mountain. In many places the surface of the earth is covered with
+bright red pumice stone that was thrown out during an eruption March
+29th, 1875. Some of these craters are filled with steam that escapes
+with an almost deafening roar. The surprising feature of this eruption
+was the immense quantity of pumice stone that escaped.
+
+The volcanoes in the Nyvatus Oraefi are entirely different. This
+barren plain is thirty-five miles in length and thirteen miles in
+breadth. Suddenly on the 18th of February, 1875, a volcano appeared in
+the centre, and four other craters were formed at subsequent dates.
+The mass of lava that was thrown out of these openings has been
+estimated at 10,000,000,000,000 cubic feet, or eighteen times the
+estimated mass of lava that has been emitted from Vesuvius between
+1794 and 1855. This lava is basalt.
+
+
+
+
+CHAPTER V
+
+VESUVIUS
+
+
+The old Greeks and Romans had but little knowledge of volcanoes. They
+only knew the volcanic mountains in the Mediterranean Sea. Here there
+are three volcanic regions:--one in the neighborhood of Naples; one
+including Sicily and the neighboring islands, and the other that of
+the Grecian Archipelago.
+
+Some idea can be had of these three regions from a map of the
+Mediterranean shown in Fig. 12. The principal volcanoes are Vesuvius,
+Etna, Stromboli, and Vulcano, a mountain, by the way, that gave its
+name to all volcanic mountains. In this chapter we will describe the
+volcano of Vesuvius, the most active, though by no means the largest
+of the volcanoes of the Mediterranean.
+
+But, before doing this, it will be well first to describe briefly the
+volcanic districts surrounding Vesuvius.
+
+As shown in Fig. 13, this district includes Vesuvius, Procida, and
+Ischia.
+
+[Illustration: FIG. 12. THE MEDITERRANEAN]
+
+Ischia is a small island measuring about five miles from east to west,
+and three miles from north to south. There were such terrific volcanic
+eruptions on this island long before the Christian Era, that several
+Greek colonies were forced to abandon it. A colony established long
+afterwards, about 380 B. C., by the king of Syracuse also
+had to depart. Strabo, the Grecian geographer (born about 63 B.
+C.), states that, according to tradition, terrific earthquakes
+occurred on the island a little before his time, and its principal
+mountain threw out large quantities of molten rock, which flowed into
+the sea. At the time of this eruption there were earthquake waves in
+the sea, the waters of which slowly receded, leaving large portions
+of the bottom uncovered, and rushing, afterwards, violently over
+the land, caused great destruction. It was during this disturbance,
+so Strabo asserts, that the island of Procida was formed by being
+violently torn from Ischia.
+
+[Illustration: FIG. 13. THE VOLCANIC DISTRICT AROUND VESUVIUS]
+
+The Phlegræan Fields was a name given by the ancients to some of the
+lowlands in the neighborhood of Naples; they were believed to be under
+the special protection of the Roman gods. When the frequent earthquake
+shocks shook these fields, the Roman people believed that conflicts
+were taking place between their gods and slumbering giants confined in
+the regions below the surface.
+
+It is more than probable that Mt. Vesuvius has always been the centre
+of these volcanic disturbances. Long before the Christian Era,
+however, Vesuvius, or Somma, the name given to the old crater that
+then occupied the summit of the mountain, had been an extinct crater.
+Indeed, it had been so quiet that the people who lived on its slopes
+did not appear to know they were living on the slopes of a slumbering
+volcano. Their knowledge of volcanic mountains must have been very
+limited, for this mountain with the huge pit at its summit had all
+the appearance of a volcanic crater. When they climbed to the top of
+the mountain, which, of course, they frequently did to look after the
+vineyards they were cultivating on the slopes, and looked down into
+the deep pit from the rocks on its edge, they could see at the bottom
+of a great central pit three miles in diameter, a lake, with room here
+and there to enable one to walk along its borders. The walls of the
+precipice were covered with luxuriant vines.
+
+When we say that none of the people even suspected that Vesuvius had
+ever been in a state of eruption, we must except some of their learned
+men. For both Diodorus Siculus, a native of Sicily, who lived about
+10 B. C., and wrote an Universal History, containing some
+forty volumes, of which only about one-third remain, and Strabo, the
+Geographer, pointed out in a general manner, that Vesuvius, and much
+of the surrounding country, looked as if it had been eaten by fire.
+Then, too, a Roman philosopher who lived between A. D. 1 and
+A. D. 64, spoke of Vesuvius being "a channel for the eternal
+fire!"
+
+Let us now endeavor to obtain some idea of the appearance of this
+region a short time before A. D. 79, when Vesuvius burst
+forth in a terrific eruption. The slopes of the mountain were covered
+with the rich vegetation that characterizes this part of Italy.
+When most volcanic ashes and lava have been exposed for some time to
+the atmosphere they make a very fertile soil. Now, this soil on the
+slopes of Vesuvius made the vineyards that covered the mountain slopes
+and the fields for miles around its base, bear very plentifully,
+so that the people lived very comfortably. Here and there on the
+slopes of the mountain large towns like Herculaneum and Pompeii had
+long been established, while, in the distance, was the large city of
+Naples. Besides these there were numerous populous towns and villages
+scattered here and there over the plain or on the lower mountain slope.
+
+You have all probably read of the Roman gladiator, Spartacus.
+Spartacus was a Thracian by birth, and while a shepherd had been taken
+prisoner by the Romans and sold to a trainer of gladiators at Capua.
+Chaffing under the tyranny of the Romans, who forced him to fight in
+the arena with men and beasts, he revolted against his masters, and
+with a band of some seventy followers, fled to a mountain fastness in
+the crater of Vesuvius. Proud Rome sent a few men to recapture him,
+with scourges for his punishment, but they were beaten by Spartacus.
+Every day dissatisfied men like himself escaped from the Romans and
+joined his ranks. Rome sent a larger body of men against Spartacus,
+but they also were beaten. At last, recognizing the gravity of the
+position, the Roman Prætor, Clodius, was sent against Spartacus with
+an army of some three thousand men. Clodius caught Spartacus in the
+crater and guarded the only space by which it seemed possible for
+Spartacus to escape. Using the vines that covered the precipitous
+walls of the crater, Spartacus did escape, and falling unexpectedly
+on the armies of Clodius, routed them. After this victory, Spartacus
+with an army of over 100,000 men overran southern Italy, and sacked
+many of the cities of the Roman Campania. During this time Spartacus
+defeated one Roman army after another, until finally, in the year 71
+B. C., Crassus was sent against him and vainly endeavored
+to conquer him. Being unsuccessful, Crassus urged the Roman Senate
+to recall Lucullis from Asia and Pompey from Spain, and finally poor
+Spartacus was cut down in a fight he made against Crassus and Lucullis.
+
+But let us come to the great eruption of Vesuvius in A. D.
+79. The people living on the slopes of Vesuvius were not without
+plenty of warnings of the dreadful catastrophe that was coming. As
+early as A. D. 63 there was a great earthquake that shook the
+country far beyond Naples. In Pompeii, then a flourishing city, the
+Temple of Isis was so much damaged that it had to be rebuilt.
+
+Even if the earthquake shocks had not foretold the coming eruption,
+there were other signs. The height of water in the wells decreased.
+Springs that had never before been known to fail, dried up completely.
+These changes, as we well know, were due to the red hot lava being
+slowly forced up from great depths into the tube connected with the
+crater.
+
+The earthquake shocks continued at irregular intervals for sixteen
+years, until, on the 25th of August, A. D. 79, about one
+o'clock in the afternoon, Vesuvius burst forth in the terrible
+eruption that destroyed the towns of Pompeii and Herculaneum. Pompeii
+was a seaport town situated near the mouth of the River Sarno,
+about fifteen miles southeast of Naples. It was a beautiful place,
+containing many splendid temples. Its people for the greater part
+lived luxuriously, for Pompeii was the summer resort of the richer
+people of Naples, some of whom lived there during the hottest months
+of the year.
+
+Herculaneum, the other town, was nearer Naples, only five miles from
+the city. It was also, like Pompeii, a beautiful town, and contained
+many splendid buildings. In each town there were magnificent baths and
+a large theatre. The inhabitants spent so much of their time in the
+open air, or in the baths, that it was not necessary for them to build
+very large houses. The houses, however, were well built, and though
+generally consisting of practically a single story, were provided with
+all the luxuries that great wealth could command.
+
+On August 25th, A. D. 79, severe earthquake shocks again
+visited this part of the world and Vesuvius suddenly threw up from
+its crater an immense column of black smoke, which, rising high in
+the air, spread out in the form of a huge mushroom, or, perhaps, more
+like the umbrella pine tree of the neighborhood. Rapidly spreading on
+all sides, the smoke soon completely shut out the light of the sun,
+and wrapped the earth in an inky darkness, except for a red glare from
+columns of molten rock that rushed out of the crater.
+
+From the dark cloud immense quantities of red hot stones, pumice, and
+volcanic ashes descended on the earth. At the same time there fell
+a deluge of rain, caused by the sudden condensation of the enormous
+amount of water vapor that was thrown out from the crater during the
+eruption. Fortunately, very few of the people were killed in either of
+the cities of Pompeii and Herculaneum, although some bodies were found
+in the ruins. Most of the people escaped through the darkness and
+gloom, continuing to flee from the city for at least three days.
+
+Both cities were covered so deep with ashes or mud that the tops of
+the tallest buildings were no longer visible. Pompeii was buried by
+showers of ashes or volcanic cinders, and Herculaneum mainly by vast
+floods of aqueous lava.
+
+So completely were these cities covered that their very existence was
+at last forgotten. It is true that Titus, who was then Emperor of
+Rome, endeavored to clear away the ashes and rebuild Pompeii, but the
+task was so great that he finally abandoned it.
+
+During the year 1592, the architect Fontana, while superintending the
+building of an aqueduct, came across some ancient buildings. At a much
+later date, in 1713, some workmen, while digging a well in the village
+of Portici, uncovered three marvellously beautiful marble statues. In
+the year 1738, the same well was dug deeper, when traces of the old
+theatre of Herculaneum were discovered. Some effort was then made to
+excavate the city and many of the public buildings and private houses
+were uncovered, and statues, mosaics, wall paintings, and charred
+manuscripts of papyrus were found. A few of these have been unrolled
+and deciphered, but owing to the difficulty of doing this, without
+destroying them, the greatest number still remain unread.
+
+In 1860, the Italian Government began a systematic excavation of the
+buried cities, and now both Pompeii and Herculaneum are thrown open to
+the sunlight so that one can walk through the old streets, and look
+into the houses, in which, before A. D. 79, the people lived
+so happily.
+
+Many interesting stories are told about the discoveries that were
+made during the government excavations. The skeleton of one of the
+inhabitants was found grasping a money bag. He might have escaped,
+but had gone back to get his money. He got it, but remained with it.
+In another place, the skeletons of a number of people were found in
+an underground room or cellar of a house, where were also found some
+mouldy bread and empty water flasks. Instead of leaving the city,
+which they might have done, they had retreated to the underground
+room for safety, but the fine volcanic dust drifted in and suffocated
+them.
+
+The younger Pliny, the historian, has given an excellent account of
+some features of this great eruption. It appears that his uncle was
+stationed with the Roman fleet, in the Bay of Naples, at the time of
+the eruption. He describes the dark cloud of ashes that was formed
+over Vesuvius. He refers to the rapidity with which it spread, and
+to the showers of ashes, cinders, and stones that it rained down on
+the earth. His uncle, the elder Pliny, landed on the coast, and was
+afterwards killed by a cloud of sulphurous vapor that swept down the
+side of the mountain.
+
+The following letter from the younger Pliny, describing his flight
+with his mother from Misenum, is quoted from Dana's "Characteristics
+of Volcanoes."
+
+      "It was now seven o'clock [on the morning of August 25th],
+      but the light was still faint and doubtful. The surrounding
+      buildings had been badly shaken, and although we were in
+      an open spot [a little yard between his uncle's house and
+      the sea], the space was so small that the danger of a
+      catastrophe from falling walls was great and certain. Not
+      till then did we make up our minds to go from the town....
+      When we were free from the buildings we stopped. There we
+      saw many wonders and endured many terrors. The vehicles we
+      had ordered to be brought out kept running backward and
+      forward, though on level ground; and even when blocked
+      with stones they would not keep still. Besides this, we
+      saw the sea sucked down and, as it were, driven back by
+      the earthquake. There can be no doubt that the shore had
+      advanced on the sea, and many marine animals were left high
+      and dry. On the other side was a dark and dreadful cloud,
+      which was broken by zigzag and rapidly vibrating flashes of
+      fire, and yawning showed long shapes of flame. These were
+      like lightning, only of greater extent....
+
+      "Pretty soon the cloud began to descend over the earth
+      and cover the sea. It enfolded Capreæ and hid also the
+      promontory of Misenum." ... The flight was continued.
+      "Ashes now fell, yet still in small amount. I looked
+      back. A thick mist was close at our heels, which followed
+      us, spreading out over the country, like an inundation."
+      ... Turning from the roar in order to avoid the fleeing,
+      terror-stricken throng, they rested. "Hardly had we sat
+      down when night was over us--not such a night as when there
+      is no moon and clouds cover the sky, but such darkness as
+      one finds in close-shut rooms. One heard the screams of
+      women, the fretting cries of babes, and shouts of men....
+
+      "Little by little it grew light again. We did not think
+      it the light of day, but a proof that the fire was coming
+      nearer. It was indeed fire, but it stopped afar off; and
+      then there was darkness again, and again a rain of ashes,
+      abundant and heavy, and again we rose and shook them off,
+      else we had been covered and even crushed by the weight....
+      At last the murky vapor rolled away, in disappearing smoke
+      or fog. Soon the real daylight appeared; the sun shone out,
+      of a lurid hue, to be sure, as in an eclipse. The whole
+      world which met our frightened eyes was transformed. It was
+      covered with ashes white as snow."
+
+Young Pliny and his mother returned to Misenum, and survived the
+perils to which they were exposed.
+
+It was during this eruption that a large part of the old crater was
+blown off the mountain by the tremendous force at work.
+
+There have been many eruptions of Vesuvius since the great eruption
+of A. D. 79. One of these occurred during the reign of Severus,
+A. D. 203. It was during this eruption that an additional part of the
+old crater of Somma was blown away.
+
+Another great eruption occurred A. D. 472. Then great
+quantities of volcanic dust were thrown up into the air, and falling,
+covered practically all parts of Europe, producing darkening of the
+sun and great fear as far as the city of Constantinople.
+
+But what was perhaps a still greater eruption occurred during December
+of 1631. This eruption spread great quantities of ashes over the
+country for hundreds of miles around, and great streams of mud rushed
+down the slopes of the mountain. Buccini gives the following account
+of this eruption:
+
+      "The crater was five miles in circumference, and about
+      1,000 paces deep. Its sides were covered with brushwood,
+      and at the bottom there was a plain on which cattle grazed.
+      In the woody parts wild boars frequently harbored. In one
+      part of the plain, covered with ashes, were three small
+      pools, one filled with hot but bitter water; another with
+      water saltier than the sea, and a third with water that
+      was hot but tasteless. But at length these forests and
+      grassy plains were consumed, being suddenly blown into the
+      air and their ashes scattered to the winds. In December,
+      1631, seven streams of lava poured at once from the crater
+      and overflowed several villages, on its flanks, and at the
+      foot of the mountain. Reisna, partly built over the ancient
+      city of Herculaneum, was consumed by the fiery torrent.
+      Great floods of mud were as destructive as lava. This is
+      no unusual occurrence during these catastrophes for such
+      is the violence of the rains produced by the evolution of
+      aqueous vapors that torrents of water descend the cone and
+      become charged with impalpable volcanic dust, and rolling
+      among ashes, acquire sufficient consistency to deserve the
+      ordinary appellation of aqueous lava."
+
+Of course, you will understand that we have given only a few of
+the most notable of the eruptions of Mt. Vesuvius. Since the yea
+A. D. 1500 there have been no less than fifty-six recorded
+eruptions, that of the year 1857 being especially violent.
+
+Omitting these eruptions we at last come to the great recent eruption
+of 1872.
+
+Fortunately, the eruption of 1872, as well as still more recent
+eruptions that have occurred, have been more accurately described than
+have most volcanic eruptions, for the Italian Government, recognizing
+the value to the natives of Italy of a knowledge of what was going on
+at the crater of Vesuvius, has maintained for the past thirty years
+an observatory on the western part of the mountain. This observatory
+has been placed in charge of Prof. Luigi Palmieri, a well-known
+student of volcanoes and earthquakes. At this place records are kept
+of the behavior of the volcano, of all earthquake disturbances, as
+well as other phenomena. At the same time, by the use of photography,
+excellent pictures have been obtained showing the appearance of the
+sky during an eruption.
+
+Vesuvius had been in a quiet state from November, 1848, to the year
+1871, when small quantities of lava flowed continuously for several
+months. Again, early in 1872, other quiet eruptions of lava continued
+for weeks at a time. Finally, on April 26th, of that year, a violent
+explosive eruption occurred. The following account has been taken from
+Palmieri's report, entitled, "The Eruption of Vesuvius in 1872."
+
+On April 23d the recording earthquake instruments, the seismographs,
+were greatly affected. On the evening of the 24th lava streams flowed
+down the cone in various directions. These streams were continued
+on the 25th and the 26th, so that on the night of the 26th the
+observatory lay between two streams of molten lava that threw out so
+much heat that the glass windows in the observatory were cracked,
+and a scorching smell was quite perceptible in the rooms. The cone
+of the mountain was deeply fissured, lava escaping freely from all
+the fissures, so that the molten rock appeared to ooze from over its
+entire surface, or as Palmieri expressed it, "Vesuvius sweated fire."
+
+This great cracking or fissuring of the cone was accompanied by the
+opening of two large craters at the summit, that discharged, with a
+great noise, immense clouds of steam, dust, lapilli, and volcanic
+bombs. These latter are very curious and consist of masses of soft
+lava that are thrown high into the air by the outrushing columns of
+steam. Being rotated or spun, as they rise in the air, they assume a
+spherical shape. Some of these volcanic bombs were thrown to a height
+estimated by Palmieri to have been nearly 4,000 feet above the top of
+the mountain. When the height of a projectile is known, the velocity
+with which it left the opening from which it was projected or thrown
+can be estimated, so that the volcanic bombs must have left the crater
+at a velocity of about 600 feet per second.
+
+On the 27th, in the evening, the lava streams ceased flowing, but the
+dust and lapilli continued to fall during the 28th and the 29th. On
+the 30th the detonations decreased and by the 1st of May the eruption
+was entirely over.
+
+Palmieri calculated that the quantity of molten rock thrown out during
+this eruption was sufficient to cover an area of about 1.8 square
+miles to an average depth of about thirteen feet.
+
+As we can see from the above descriptions, the volcanic activity of
+Vesuvius is characterized by long periods of rest followed by periods
+of activity. The periods of rest are measured by years, and often by
+centuries; the periods of activity by days or hours.
+
+But Vesuvius was not to have a long period of rest after its eruption
+of 1872. On the contrary, shortly after the great disaster of
+Martinique in 1906, it again became active, and on the 5th of April,
+1906, began throwing large blocks of lava out of its central cone, and
+on the next day began to throw out large streams of lava, which, on
+April 7th, destroyed a village in the neighborhood. At the same time
+rumbling sounds were heard, and violent earthquake shocks shattered
+the windows of the houses.
+
+Professor Matteucci, the present director of the Vesuvius Observatory,
+made the following report on April the 8th.
+
+      "The eruption of Vesuvius has assumed extraordinary
+      proportions. Yesterday and last night the activity of the
+      crater was terrific, and is increasing. The neighborhood
+      of the observatory is completely covered with lava.
+      Incandescent rocks are being thrown up by the thousands, to
+      a height of 2,400 feet or even 3,000 feet, and falling back
+      form a large cone. Another stream of lava has appeared....
+      The noise of the explosion and of the rocks striking
+      together is deafening. The ground is shaken by strong and
+      continuous seismic movements, and the seismic instruments
+      [instruments employed to record the time, direction, and
+      intensity of earthquake movements] threaten to break. It
+      will probably be necessary to abandon the observatory,
+      which is very much exposed to the shocks. The telegraph is
+      interrupted, and it is believed the Funicular railroad has
+      been destroyed."
+
+On April 9th Matteucci made the following report:
+
+      "The explosive activity of Vesuvius, which was so great
+      yesterday, and was accompanied by very powerful electric
+      discharges, diminished yesterday afternoon. During the
+      night the expulsion of rocks ceased, but the emission of
+      sand increased, completely enveloping me and forming a
+      red mass from six to ten centimeters deep, which carried
+      desolation into these elevated regions. Masses of sand
+      gliding along the earth, created complete darkness until
+      seven o'clock. Several blocks of stone broke windows in the
+      observatory. Last night the earthquake shocks were stronger
+      and more frequent than yesterday, and displaced the seismic
+      apparatus. Yesterday afternoon and this morning, torrents
+      of sand fell."
+
+On April 10th Matteucci sent the following report:
+
+      "Last night was calm, except for a few explosions of
+      considerable force from time to time. At four o'clock this
+      morning the explosions became more violent. The seismic
+      instruments recorded strong disturbances."
+
+The eruption of Vesuvius of 1906 was especially noted for the great
+quantities of sand and ashes thrown out of the crater. The amount
+of sand that fell on the roof of the market house at Monti Olivetto
+was so great that the roof fell in. In this eruption there were some
+six lava streams that poured down the mountain. The most formidable
+of these was that which descended towards Torre Annunziata. Here it
+stopped just short of the wall of the cemetery outside of the town.
+
+During this eruption of Vesuvius, as in previous eruptions, clouds of
+volcanic dust collected in the air, shutting off the light of the sun.
+Naples was in a state of semi-darkness. The roofs of the houses were
+covered to a depth of several inches with an exceedingly fine reddish
+dust. In some places this dust had drifted into heaps fully a yard in
+depth.
+
+
+
+
+CHAPTER VI
+
+OTHER VOLCANOES OF THE MEDITERRANEAN
+
+
+The relative positions of the other volcanic mountains of the
+Mediterranean Sea; i. e., Etna, Stromboli, and the volcanoes of the
+Santorin group of the Grecian Archipelago, are shown in the map, Fig.
+12.
+
+We will begin with the volcanic mountain of Etna, under which,
+according to mythology, the angry gods had buried the rebellious
+Typhoon.
+
+Etna is situated on the island of Sicily, immediately southwest of
+Italy. It is a much larger mountain than Vesuvius, rising, as it
+does, from a circular base about eighty-seven miles around, to a
+height of 10,840 feet above the level of the Mediterranean. It forms
+a conspicuous object when seen either from the Mediterranean, or from
+distant parts of Italy.
+
+The height of Etna is so great that its slopes can be divided into
+three distinct climatic zones or belts. The lowest of these lies
+between the sea and a height of 2,500 feet. In this zone the mountain
+slopes are covered with cultivated fields, olive groves, orchards,
+and vineyards. The middle zone lies between 2,500 feet and 6,270
+feet. This zone is covered with forests of chestnuts, oaks, beeches,
+and cork trees. The third and highest zone includes the rest of the
+mountain, and may be called the desert zone, since it is a sterile
+region, covered with huge blocks of lava and scoriæ, and terminating,
+in the higher portions, in a snow-covered plain, from which the
+central cone rises.
+
+Etna is continually sending up columns of steam and sulphur vapor.
+Every now and then it starts in eruption, throwing out large
+quantities of lava either from the crater on its summit, or from
+some of the 200 smaller cones or craters that occupy portions of its
+slopes. On account, probably, of its height the eruptions are most
+frequently on the sides. Etna affords a magnificent example of a huge
+volcanic pile of the Vesuvian type, which has been slowly built up
+by the gradual accumulation of materials that have escaped from its
+craters.
+
+One of the most interesting features of the higher regions of Etna is
+an immense chasm rent in a side of the cone near the summit, and known
+as the Val del Bove. This chasm forms a vast amphitheater.
+
+The great force that removed such an immense mass of matter from
+the cone could not have been the eroding power of water, since the
+materials of the cone are too porous to permit streams of any size to
+rush down the slopes. The force is most probably to be found in some
+explosive eruption of the mountain, when a portion of the crater was
+suddenly blown off, just as was done in Vesuvius when a large part of
+the old crater of Somma was blown away. What is especially interesting
+about the Val del Bove is the opportunity it affords for studying the
+interior structure of the mountain, for it practically enables one to
+enter to almost the heart of this great volcano.
+
+The Val del Bove has the shape of a great pit five miles in diameter.
+It has almost vertical walls, the height of which varies with their
+position. Those which reach highest up the mountain vary from 3,000 to
+4,000 feet in height.
+
+Like Vesuvius, Etna has been split or fissured into great crevices
+that have been filled with lava during the many eruptions of its
+central crater. On hardening, these lava streams form what are known
+as dikes. As the sides of the mountain are worn away by erosion, the
+dikes, being harder than the rest of the cone, project from its sides
+like huge walls. An excellent opportunity for seeing them is afforded
+in the walls of the Val del Bove.
+
+Sir Charles Lyell, the English geologist, who has carefully studied
+Mt. Etna, asserts that this mountain began to be formed during a
+geological period known as the Tertiary Age, through a crater that
+opened on the floor of the Mediterranean Sea. The material thus
+thrown out, collected around the crater and produced a mountainous
+pile that gradually emerged above the level of the sea, and on fresh
+materials continuing to be thrown out, at length reached its present
+height. It would appear that at some former time in its history, there
+were two vents near the top of the mountain, the second crater being
+formed immediately under the Val del Bove. Soon, however, the second
+and lower crater was closed, the upper one alone remaining active.
+The mountain, therefore, continued to be slowly raised in the air by
+the materials brought out through this opening. Then came the great
+explosive eruption during which the side of the mountain was blown off
+to form the great chasm of the Val del Bove.
+
+Because of its almost constant activity, Mt. Etna must have been
+well known to the ancients, who described some of its most violent
+eruptions. The following brief notes concerning these eruptions have
+been taken from Lyell.
+
+According to Diodorus Siculus, an eruption that occurred before the
+Trojan war, caused the people living in districts near the mountain to
+seek new homes. Thucididies, the Greek historian, states that in the
+sixth year of the Peloponnesian war, which would be about the spring
+of 425 B. C., a lava stream caused great destruction in the
+neighborhood of Campania, this being the third eruption that had
+occurred in Sicily since it had been settled by the Greeks.
+
+Seneca, during the first century of the Christian Era, calls the
+attention of Lucullus to the fact that during his time Mt. Etna had
+lost so much of its height that it could no longer be seen by boatmen
+from points at which it had before been readily visible.
+
+But passing by these very early eruptions of Etna we come to the great
+eruption of 1669. This eruption was preceded by an earthquake that
+destroyed many houses in a town situated in the lower part of the
+forest zone, about twenty-five miles below the summit of the mountain,
+and ten miles from the sea at Catania. During this eruption two deep
+fissures were opened near Catania. From these such quantities of sand
+and scoriæ were thrown out, that, in the course of three or four
+months, a double cone was formed 450 feet high, which is now known as
+Monte Rosso. But what was most curious was the sudden opening, with
+a loud crash, of a fissure six feet broad reaching down to unknown
+depths that extended in a somewhat crooked course to within a mile
+of the summit of Etna. This great fissure was twelve miles in length
+and emitted a most vivid light. Five other parallel fissures of
+considerable length opened, one after another, throwing out vapor,
+and emitting bellowing sounds which were heard at a distance of forty
+miles. These fissures were afterwards filled with molten rock, and in
+this manner were formed the long dikes of porphyry and other rocks
+that are seen to be passing through some of the older lavas of Mt.
+Etna.
+
+[Illustration: FIG. 14. MT. ETNA _From Map of State and
+Government_]
+
+The great lava streams which flowed down the side of the mountain
+during this eruption, destroyed fourteen towns and villages, and
+at length reached Catania. A great wall had been raised around this
+city to prevent the lava from entering it. The molten rock, however,
+accumulated, until it rose to the top of the wall, which was sixty
+feet high, and then pouring over it in a fiery cascade, overwhelmed
+part of the city. It is said that during the first part of its
+journey, the lava streams moved over thirteen miles in twenty days,
+or at the rate of 162 feet an hour. Beyond this, after the lava had
+thickened by cooling, it had a velocity of only twenty-two feet per
+hour.
+
+Fig. 14 represents a plan of Mt. Etna reduced from a map by the
+Italian Government. During the eruption of 1865, a rent was made in
+the mountain extending from Mount Frumento (B in the preceding map)
+for one and one-half miles, and six cones from 300 to 350 feet in
+height were formed along the fissure.
+
+During the eruption of 1874, great fissures three miles in length were
+formed in the mountain.
+
+There exists on the slopes of Mt. Etna vast subterranean grottoes
+formed by the sudden conversion into steam of great quantities of
+water that were overwhelmed by the molten mass. These immense volumes
+of steam produced enormous bubbles in the molten lava. When the lava
+hardened irregular grottoes were left. Lyell describes one of these as
+follows:
+
+      "Near Nicolosi, not far from Monte Rosso, one of these
+      great openings may be seen, called the _Fossa della
+      Palomba_, 625 feet in circumference at its mouth and
+      seventy-eight deep. After reaching the bottom of this, we
+      enter another dark cavity, and then others in succession,
+      sometimes descending precipices by means of ladders. At
+      length, the vaults terminate in a great gallery ninety feet
+      long, and from fifteen to fifty broad, beyond which there
+      is still a passage, never yet explored, so that the extent
+      of these caverns remains unknown. The walls and roofs of
+      these great vaults are composed of rough bristling scoriæ
+      of the most fantastic forms."
+
+Besides the eruptions mentioned there have been many others, such as
+those of 1811, 1819, and 1852. The last of these was greater than any
+eruption except that of 1669. It began in August, 1852, and continued
+until May, 1853, and was remarkable for the immense quantity of lava
+thrown out.
+
+[Illustration: FIG. 15. STROMBOLI, VIEWED FROM THE NORTHWEST,
+APRIL, 1874]
+
+We come now to the volcano of Stromboli. Stromboli, one of the Lipari
+islands, is situated about sixteen miles west of the Straits of
+Messina. Its general appearance is shown in Fig. 15. The form of the
+mountain is that of an irregular four-sided pyramid, which rises about
+3,090 feet above the level of the Mediterranean, and stands on the
+bottom of the sea in water about 3,000 feet deep.
+
+If you carefully examine the appearance of Stromboli, as shown in the
+preceding figure, you will notice that the flat cloud which hangs over
+the island is made up of a number of globular masses of vapor, formed
+during the peculiar action of the volcano.
+
+When examined by night Stromboli presents a still more curious
+appearance. Since the mountain stands alone, its height permits it to
+be seen readily at sea for distances of at least a hundred miles. At
+night a curious glow of red light may be seen on the lower surfaces of
+the cloud. This light is not continuous, but increases in intensity
+from a faint glow to a fairly bright red light, then gradually
+decreases, and finally dies away completely. After awhile the light
+again appears, again gradually decreases, and disappears, and this
+continues until the rising sun prevents the red glow from being any
+longer visible. Stromboli, therefore, acts not unlike the flashing
+lighthouses so common on the sea coasts of all parts of the world.
+Indeed, it is actually used by sailors in the Mediterranean for the
+purpose of showing them their direction. For this reason Stromboli is
+commonly called "The Lighthouse of the Mediterranean."
+
+As Judd remarks, from whom much of the information concerning some of
+the volcanic districts of the Mediterranean has been obtained, the
+flashing light of Stromboli differs from that of the ordinary flashing
+light in two important respects; viz., in the intervals that elapse
+between the successive flashes, and in the intensity of the light
+emitted. As you know, it is necessary that the different lighthouses
+placed near one another on a coast must have their lights of such a
+nature that they can be readily distinguished. In order to do this,
+the flashing light has been devised. In flashing lighthouses, the
+lights only appear at intervals, one lighthouse being distinguished
+from another in its neighborhood by the intervals between successive
+flashes, or, sometimes, indeed, by the color of some of the flashes.
+Now, in the case of Stromboli, the intervals between the successive
+glowings of the red lights are very irregular, varying between one and
+twenty flashes per second. Moreover, the intensity of the light also
+varies greatly from time to time.
+
+You naturally inquire as to the cause of these flashes of light that
+are emitted by Stromboli. If, as Judd suggests, you should climb to
+the summit of the mountain, during the daytime, and look down the
+inside of the crater, you could see its black slag bottom crossed by
+many cracks and fissures. From most of the smaller fissures the vapor
+of water is quietly escaping. This vapor rises in the air in which it
+soon disappears. There are, however, larger cracks on the bottom of
+the crater from which, at more or less regular intervals, masses of
+steam are emitted with loud snorting puffs not unlike those produced
+by a locomotive. From some of the openings molten matter is seen
+slowly oozing out, collecting in parts of the crater and moving up and
+down in a heaving motion. Every now and then a bubble is formed on
+the surface of this liquid. The bubble swells to a gigantic size, and
+suddenly bursts. The steam it contained escapes, carrying fragments of
+scum which are thrown high into the air. The masses of steam, formed
+below the surface of the sticky, boiling, lava, in endeavoring to
+escape, force their way through the mass, blow huge bubbles, which,
+on bursting, produce the roaring sounds that are heard, and throwing
+great columns of vapor in the air, produce the rounded masses of
+clouds you can see floating high up in the air over the mountain. At
+the same time the scum is partially removed from the red hot surface,
+its light illumines the lower surface of the overhanging cloud, which
+flings it back again to the earth. With the bursting of each bubble,
+and the clearing of the scum from the surface of the red hot mass,
+the light begins, increases in intensity, and then as the scum again
+begins to collect on the surface, decreases, and finally disappears,
+and not until the bursting of the next bubble is it again visible.
+
+But let us make a study of some of the peculiarities of Vulcano,
+another of the Lipari islands, which lies north of Sicily.
+
+Vulcano affords a curious example of a volcano that has been harnessed
+by man, or made to do work for him. All volcanoes bring from inside
+of the earth different kinds of chemical substances, in the form of
+vapors, gases, or molten materials. Now, these materials acting on
+one another, produce chemical substances some of which, such as sal
+ammoniac, sulphur, and boracic acid, possess commercial value. This is
+especially true in the case of Vulcano, and since the eruptions are
+not generally violent, a chemical works has actually been erected by
+a Scotch firm on the side of the mountain, where the materials are
+collected from the crevices.
+
+This effort to harness a volcano was for a time so successful that
+the same people contemplated the building of great leaden chambers
+over the principal fissure at the bottom of the crater, so that the
+large volumes of ejected vapors might be condensed and collected. But
+Vulcano, like all other volcanoes, could not be relied on continually
+to keep the peace. One day it suddenly burst forth more fiercely than
+usual, so that the workmen were compelled to abandon the factory and
+fly down the mountain for their lives, but not, however, before some
+of them were severely injured by the explosions.
+
+Vulcano is an instance of a volcano in an almost exhausted or dormant
+condition. It has had, however, many eruptions during the past few
+centuries, some of which have been very violent, for example, that of
+1783, and that of 1786.
+
+There still remains to be considered the volcanic region of the
+Santorin group of the Grecian Archipelago. The island of Santorin
+or Thera, is the southernmost of the Cyclades. It is an exceedingly
+curious island, being a submerged volcano, with most of the top of the
+crater remaining above the waters, so that the entire island has the
+shape of an irregular circle or crescent broken at several points.
+Its formation is, probably, due to the gradual sinking of a volcanic
+mountain until its crater has been almost completely submerged, only
+the higher parts of the edges of the crater being left above the
+surface of the waters. Suppose, for example, a mountain like Vesuvius
+at the time the crater Somma existed, was sunk below the level of the
+Mediterranean until only the highest parts of the crater remained
+above the waters. If, now, one or more volcanic eruptions occurred,
+producing craters or volcanic islands inside the submerged rim, you
+would have a condition of affairs seen in the island of Santorin.
+
+
+
+
+CHAPTER VII
+
+ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND OTHER VOLCANOES OF MEXICO
+
+
+While some of the volcanoes of Mexico are still in an active
+condition, most of them are either only slightly active or are dormant
+or extinct. Humboldt, the celebrated traveller and geographer, states
+that there are only four active volcanic mountains in Mexico; namely,
+Popocatepetl, Tuxtula, Colima, and Jorullo. But there are many others,
+among which may be mentioned Orizaba, Ixtaccihuatl, Xinantecatl,
+Tuxtula, Cofre de Perote, and Colima.
+
+Of course, you can understand that, since extinct volcanoes may at any
+time become active, in parts of the world where communication with the
+interior is not good, many volcanic mountains that have been regarded
+as extinct may have broken out temporarily, during historical times,
+without their eruptions having been recorded.
+
+It was at one time thought that Popocatepetl was the highest mountain
+in North America. More recent measurements, however, have shown that
+there are at least three other mountains in this part of the world,
+that are much higher. One of these is the active volcano of Orizaba
+that we will now briefly describe.
+
+[Illustration: FIG. 16. MEXICO AND CENTRAL AMERICA]
+
+Orizaba is situated in the north central part of Mexico, about
+seventy-five miles west of Vera Cruz. Its ancient Aztec name was
+Cittaltepetl, or _Star Mountain_. The height of the mountain is
+18,200 feet. Like all high tropical mountains whose summits are
+snow-clad, one would pass through the same changes in climate, in
+going from its base to its summit, as in going along the earth's
+surface from the equator to the poles. Near the base of the mountain
+will be found a tropical climate, above that a temperate climate,
+while in still higher regions, the climate of the Arctic region.
+
+According to Russell, from whose work on the volcanoes of North
+America much of the information concerning the volcanoes of Mexico
+and Central America has been condensed, Orizaba has three craters on
+its summit. The last recorded eruption took place about the middle of
+the Eighteenth Century. The mountain is now in a dormant or extinct
+condition, as may be seen from the fact that its three craters are for
+the greater part filled with snow.
+
+Orizaba, like Etna, and many other volcanoes, has deep fissures
+extending through its sides. Through these, lava streams have flowed
+during times when it was active. There are also found on the slopes
+of this mountain many cones of a type known as _parasitic cones_.
+These cones are not caused by materials that have been brought to the
+surface during an eruption, but have been formed by the steam passing
+through lava streams that have come out of the crater during other
+eruptions.
+
+Popocatepetl, or, as the word means, _The Smoking Mountain_, is the
+second highest mountain in Mexico. According to recent measurements
+made by the Mexican Government, its height is 17,876 feet.
+Popocatepetl is situated on the edge of the great plateau of Mexico,
+forty miles southeast of the City of Mexico. It is a conical mountain,
+and is a magnificent object when seen from the City of Mexico, rising,
+as it does, fully 10,000 feet from the elevation of the city, while on
+the east it towers for nearly 18,000 feet above the level of the sea.
+This splendid mountain is poetically described by Russell:
+
+      "Seen from the basal plains, it sweeps up in one grand
+      curve to nearly its full height,--a collossus of three and
+      a quarter miles in elevation, white with everlasting frost
+      on its summit, and bathed in the green of palms, bananas,
+      oranges, and mangoes, at its base. Evergreen oaks and
+      pines encircle its middle height, and above them, before
+      the ice itself is reached, occur broad areas of loose sand
+      into which the lavas have been changed by weathering. Soft
+      wreaths of sulphurous vapor may at times be seen curling
+      over the crest of the summit crater,--gentle reminders that
+      the days of volcanic activity are not yet necessarily over."
+
+Popocatepetl takes its name, _The Smoking Mountain_ from the fact that
+gases and vapor are continually being emitted from its summit crater.
+It has a conical peak with a depression or crater on its summit.
+The bottom of the crater is crossed by fissures from which small
+quantities of steam escape, not, however, sufficient to melt all the
+snow which covers the slopes of the mountain to a depth of from eight
+to ten feet. A small lake of hot water has collected in the crater
+from the water derived from the melting snow. This water, sinking
+through the porous materials in the cone, is the source of a great
+number of large hot springs that occur around the base of the mountain.
+
+Reclus states that the first to climb to the top of Popocatepetl was
+one of Cortez' officers, 1519.
+
+Another snow-capped volcano, which rising from the plain of Mexico is
+in clear view of the city, is Ixtaccihuatl (Ets-tak'-se-wat-el), or as
+the word means in the ancient Aztec, _The White Woman_. This mountain,
+as measured by Heilprin, is 16,960 feet in height. Ixtaccihuatl is
+now in so dormant a condition that many who have climbed to the top
+assert that it is not a volcano at all, since they find no crater on
+its summit. Nor are there any signs of volcanic heat, the summit being
+snow clad during summer. The conical form of the mountain, however,
+and the fact that the entire mountain is formed of volcanic rocks,
+show beyond doubt that it is an extinct volcano, whose crater has most
+probably been completely filled in by the washing away of its sides.
+
+Xinantecatl is another extinct volcanic mountain situated about forty
+miles southwest of the City of Mexico. It is about 16,500 feet high.
+Its name means in the ancient Aztec language, _The Naked Lord_. It is
+also sometimes known as the Nevado de Toluca, or _The Snow of Toluca_.
+On the top of the peak are two craters filled with lakes of fresh
+water. Russell states that the larger of these lakes is about thirty
+feet in depth and contain a peculiar species of fish.
+
+Tuxtula is another volcano of Mexico, situated on the western coast
+of the Gulf of Mexico, about eighty miles southeast of Vera Cruz. It
+was an active volcano in 1664, when it threw out molten lava. It then
+became dormant until March, 1793, when its long rest was broken by one
+of the grandest explosive eruptions of modern times. This eruption
+rivalled in energy the great explosive eruption which blew off the
+summit of Coseguina, in Central America, in 1835. As is common in the
+case of explosive eruptions, volcanic dust and scoriæ were blown high
+into the air, and, being carried by the winds, fell on the roofs of
+houses and on the land at a distance of 150 miles.
+
+There have been a number of less violent eruptions of Tuxtula since
+1835. Tuxtula is a comparatively low mountain, being only 4,960 feet
+high, because much of the mountain was blown away by the eruption of
+1793.
+
+As Russell points out, it is not safe to infer that because an eroded
+mountain is not lofty it cannot be young or energetic, since the very
+energy of some of its eruptions may, as in the case of Tuxtula, blow
+away a large part of the mountain. A low mountain, with an unusually
+large crater, generally means a mountain that has been visited by a
+great explosive eruption.
+
+Another extinct volcano known as the Cofre de Perote is situated on
+the eastern coast of Mexico, east of Ixtaccihuatl, about thirty miles
+north of Orizaba. It takes its name Cofre de Perote which means the
+Coffin of Perote, from its peculiar box-like shape. It was called in
+the Aztec language "Nauhcampatepetl," or the _Four-Ridged Mountain_.
+Cofre de Perote is in a dormant or extinct condition.
+
+We will conclude this brief description of the volcanoes of Mexico
+with the volcano of Colima, a mountain about 5,500 feet high situated
+on the western coast of Mexico.
+
+Colima has been active of recent years, eruptions having occurred in
+1869, 1872, 1873, and 1885. During these eruptions lava escaped from
+lateral openings in the sides of the mountain, these openings being
+termed by the natives the _Sons of Colima_.
+
+
+
+
+CHAPTER VIII
+
+COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA
+
+
+Central America has a great number of volcanoes extending along nearly
+all its western coast, or on the Pacific side of the country.
+
+Central America consists of a high plain or table-land sloping gently
+towards the northeast, but terminating abruptly on the southwest. In
+the opinion of geologists this table-land consists of the surface of a
+huge tilted block of the earth's crust, or, perhaps, more probably, of
+a series of such blocks, that are limited on the southwest by a narrow
+belt of intersecting fractures. It is in these fractures that scores
+of volcanoes are situated, together with active craters, solfataras,
+and hot springs. The volcanoes are mainly of the Vesuvian type. There
+are so many volcanoes in this part of the world that it will be
+possible to describe but a few of them.
+
+We will begin with the volcano of Coseguina, situated on the Pacific
+coast of Nicaragua. Its appearance is that of a conical mountain with
+the top cut off, and suggests that it is most probably an explosive
+volcano which has had the top blown away during some of its great
+eruptions.
+
+Coseguina is celebrated by reason of its tremendous eruption of 1835.
+Before the still more tremendous explosive eruption of Krakatoa in
+1883, described in the first two chapters of this book, Coseguina
+shared with Sombawa, on the island of Sumatra, as being the foremost
+of explosive volcanoes.
+
+It had been estimated that before its eruption of 1835, Coseguina had
+a height of perhaps 10,000 feet, but so much of it was blown away by
+this eruption that it now is a little less than 4,000 feet.
+
+The following description of the great eruption of Coseguina in 1835
+has been condensed from an account prepared by Squier, published in
+1850.
+
+You will note in reading this brief account how closely many of the
+phenomena resemble those that occurred during the eruption of Krakatoa
+in 1833.
+
+The eruption of Coseguina was heralded on the morning of January 20th,
+1835, by several loud explosions that were heard for a distance of
+some 300 miles around the crater of the volcano. Then followed an ink
+black cloud formed directly over the mountain, which gradually spread
+on all sides shutting off the light of the sun, except for a sickly
+yellowish light. Fine sand was thrown from this cloud, which made it
+both difficult and painful to breathe. For two whole days the cloud
+continued to grow denser, the explosions louder and more frequent,
+and the rain of sand thicker. On the third day the explosions were
+strongest and the darkness greatest.
+
+The amount of sand that fell from the cloud was so great that people
+left their houses, fearing the roofs would be crushed in by the great
+weight. This sand fell in large quantities over an area more than
+1,500 miles in diameter, or, quoting the language of Squier:
+
+      "The noise of the explosions was heard nearly as far"
+      (1,500 miles). "And the Superintendent of Belize, eight
+      hundred miles distant, mustered his troops, under the
+      impression that there was a naval action off the harbor.
+      All nature seemed overawed; the birds deserted the
+      air, and the wild beasts their fastnesses, crouching,
+      terror-stricken and harmless, in the dwellings of men.
+      The people for a hundred leagues grouped, dumb with
+      terror, amidst the thick darkness, bearing crosses on
+      their shoulders and stones on their heads in penitential
+      abasement and dismay. Many believed that the day of doom
+      had come, and crowded in the tottering churches, where, in
+      the pauses of the explosions, the voices of the priests
+      were heard in solemn invocation to Heaven. The brightest
+      lights were invisible at the distance of a few feet; and
+      to heighten the terror of the scene, occasional lightnings
+      traversed the darkness, shedding a lurid glare over the
+      earth. This continued for forty-three hours, and then
+      gradually passed away."
+
+It appears that the eruption of Coseguina was followed by violent
+earthquake shocks and other evidences of volcanic energy over extended
+regions. For example, there were fearful earthquakes along the Andes,
+the worst of which occurred on February 20th, and continued at the
+rate of three or four a day up to March 6th, and, less frequently,
+to March 17th. It was during one of these earthquakes that the city
+of Concepcion, Chile, was so completely destroyed, that but a single
+house remained.
+
+The same brilliant sunsets and sunrises occurred in different parts
+of the world after the eruption of Coseguina, due to the presence of
+large quantities of volcanic dust that followed the great eruption of
+Krakatoa.
+
+The cause of this great explosive eruption of Coseguina was most
+probably the same as that which is believed to have caused the
+eruption of Krakatoa, namely, a large volume of water suddenly gaining
+access to a mass of liquid lava.
+
+Volcán del Fuego is another of the many volcanoes of Central America.
+It is situated as one of a group of volcanoes on the highest summit
+of the Isthmus. This volcanic mountain has a regular cone with
+regular slopes on all sides, except on the north, where a table-like
+projection, about 1,000 feet below the summit, is all that remains of
+a vast cone, the summit of which was blown away, according to Russell,
+in prehistoric times, just as was the crater of Somma on Vesuvius.
+
+There have been in Central America, since the time of the Spanish
+conquest, some fifty volcanic eruptions sufficiently great to have
+been recorded. Some idea of the activity of Fuego during this time
+may be had from the fact that of all these eruptions some twenty were
+those of Fuego. At the present time, however, the volcano is dormant
+and apparently almost extinct.
+
+The recorded eruptions of Fuego are nearly all of the explosive type.
+Among the most violent were those that occurred during 1526, 1541,
+and 1581. During 1582, 1585, and 1586, there were eruptions nearly
+every month, the most terrible being near Christmas day in 1586. Other
+memorable eruptions occurred in 1614, 1623, 1686, and 1705, and at
+other dates down to August 17th, 1860, from which date to the present
+time the volcano has been quiet.
+
+We will conclude this brief description of the volcanoes of Central
+America with that of Volcán de Agua, or, as the word means, _The Water
+Volcano_. It is situated in Guatemala near the coast, and is one of
+the mountains that occupies the plateau on which Fuego is situated.
+
+The Volcán de Agua is one of the most remarkable volcanoes in Central
+America, standing, as it does, nearly alone, and rising to an
+elevation of 3,350 metres (10,988 ft.), above the level of the sea. It
+has been extinct for a long time.
+
+It has been supposed by some, from its name, that this is a volcano
+that throws out water. Others believe that the name comes from the
+water produced by the melting of the snow that is collected on the
+sides of the mountain. Now there almost always escapes from the
+craters of volcanoes during violent eruptions immense quantities of
+water vapor, which, condensing, fall as vast showers of rain that
+often deluge the surrounding country. In snow-clad mountains, the
+escape of lava is often attended by floods caused by the rapid melting
+of the snow. The water volcano did not, however, take its name from
+either of these facts, but rather because at the time of the Spanish
+invasion, the crater of the mountain was occupied by a large lake, and
+that during an earthquake in 1541 the wall of the crater was broken,
+when the lake was poured as an immense stream of water down the side
+of the mountain, overwhelming a village which was situated on this
+slope. That this was the correct origin of the same may be seen from
+the fact that the crater at the present time still shows the remains
+of its former lake basin, and that on the sides of the broken rim an
+immense ravine can be seen through which the water poured down on the
+village below.
+
+Daubeny describes this volcano as follows:
+
+      "The Volcán de Agua (Water-Volcano) is of enormous height,
+      being covered with eternal snow, in the latitude of 14°.
+      Captain Basil Hall estimates it at more than 14,000 feet,
+      but a recent traveller states it at 12,600. It has the form
+      of a blunted cone clothed with perpetual verdure to its
+      summit. The crater is from forty to sixty yards in depth,
+      and about 150 in diameter,--the sides and bottom strewed
+      with masses of rock, apparently showing the effects of
+      boiling water or of fire.
+
+      "By a deluge of water from this volcano in 1527, the
+      original city of Guatemala was overwhelmed; and the next
+      built, called the Old City, _La Antiqua_, was ruined by an
+      earthquake in 1773. The present capital is situated at a
+      distance of eight leagues from the mountain."
+
+Another volcano in this part of the country is described by Daubeny as
+follows:
+
+      "Massaya, near the lake of that name, was one of the most
+      active vents at the time of the first discovery of the
+      country. Its flames were visible twenty-five miles off. Its
+      crater was only twenty or thirty paces in diameter; but
+      the melted lava 'seethed and rolled in waves as high as
+      towers.' A story is told of a Dominican who imagined the
+      fluid lava was melted gold, and descended into the crater
+      with an iron ladle to carry some away; but the ladle, it is
+      said, melted, and the monk escaped with difficulty."
+
+
+
+
+CHAPTER IX
+
+THE VOLCANIC MOUNTAINS OF SOUTH AMERICA
+
+
+The volcanoes of South America are limited to the Andes Mountain
+System that stretches like a huge wall along the entire western side
+of the continent. The names of the more important of these volcanoes
+are marked on the map of South America, shown in Fig. 17. As will be
+seen, this huge mountain wall reaches from Patagonia on the south to
+the Isthmus of Panama on the north. The arrangement of the volcanoes
+in South America is of the linear type. The craters follow one another
+in more or less straight lines, or are situated along the lines of
+great fissures that lie near the ocean. You must not, however, suppose
+that there is a continuous chain of active volcanic mountains from the
+Isthmus of Panama to the southern part of the continent. According to
+Lyell, from lat. 2° N., or from the north of Quito, to lat. 43° S. or
+south of Chile, a total distance including 45° of latitude, there is a
+succession of districts with active and extinct volcanoes, or at least
+with volcanoes that have been quiet during the last three centuries.
+
+[Illustration: FIG. 17. SOUTH AMERICA]
+
+Lyell traces the volcanoes of South America as follows:
+
+      "The principal line of active vents which have been seen in
+      eruption in the Andes extends from lat. 43° 28' S., ... to
+      lat. 30° S.; to these thirteen degrees of latitude succeed
+      more than eight degrees, in which no recent volcanic
+      eruptions have been observed. We then come to the volcanoes
+      of Bolivia and Peru, extending six degrees from S. to N.,
+      or from lat. 21° S. to lat. 15° S. Between the Peruvian
+      volcanoes and those of Quito another space intervenes of no
+      less than fourteen degrees of latitude, in which there is
+      said to be but few active volcanoes as far as is yet known.
+      The volcanoes of Quito then succeed, beginning about 100
+      geographical miles south of the equator, and continuing
+      for about 150 miles north of it, when there occurs another
+      undisturbed region of more than six degrees of latitude,
+      after which we arrive at the volcanoes of Guatemala, or
+      Central America, north of the Isthmus of Panama."
+
+Of course, you must not understand that there are no extinct volcanoes
+in these gaps. On the contrary, according to Daubeny, we find,
+beginning on the north in the United States of Colombia, the lofty
+volcano of Tolima. According to Daubeny's book published in 1848,
+Tolima was then constantly emitting steam and sulphur gases from its
+summit. Tolima is situated in the easternmost of the three mountain
+ranges that extend through this section of the country. It is,
+therefore, at a comparatively great distance from the ocean. Tolima
+was in eruption in 1595. It again burst out in 1826.
+
+Coming now to Ecuador we find that this, the smallest of the South
+American Republics, contains numerous great volcanic mountains.
+
+Some of the principal volcanic mountains are Chimborazo, 20,498 feet
+above the sea; Antisana, 18,880 feet; Cotopaxi, 19,660 feet; Pichincha
+(17,644 feet in 1848, Daubeny), El Altar, 16,383 feet.
+
+These all lie in South America on the plateau of Quito. As Baron
+Alexander von Humboldt has pointed out, the volcanic mountains of
+Quito are arranged in two parallel chains that extend side by side
+for a distance of over 500 miles north into the State of Colombia,
+including between them the high plateaus of Quito and Lacumbia.
+According to Whymper, however, who has recently studied this part of
+South America, there is a succession of basins between the mountains,
+but there is no such thing as a single valley in the interior of
+Ecuador. The extinct volcanoes of Cayamba, Antisana, and Chimborazo
+are the most important. On all three mountains there are old lava
+streams on their sides. Although no craters can be seen on their
+summits, yet it is almost certain they once had craters. There is
+plenty of room on the summit of Antisana for a cone as great as that
+of Cotopaxi. Whymper is of the opinion that the snow domes that form
+the summit of Chimborazo were at one time two of the highest points of
+the rim of the old crater.
+
+Nearly due south of Quito is the great volcanic cone of El Altar.
+Like all the peaks of this high plateau, El Altar rises to a great
+height above the sea, being at the present time 16,383 feet above the
+sea. This mountain has an enormous crater that appears to be dormant
+or extinct, and is covered with snow. According to the traditions of
+Indians, El Altar, or, as they call it, _Capac Urcu_ or _The Chief_,
+was the highest mountain near the equator, being much higher than
+Chimborazo. But during a prodigious eruption that occurred before the
+discovery of America, and continued uninterruptedly for eight years,
+the height of the mountain was considerably reduced. According to
+Boussingault, the fragments of the cone of this celebrated mountain
+are now spread for great distances around the mountain on the
+surrounding lowlands.
+
+Pichincha in Ecuador, an extinct volcano, is situated almost
+immediately on the equator. It has a height as measured by Whymper by
+the barometer, of 15,918 feet above the Pacific. The summit is covered
+by blocks of pumice. Several species of lichens are found at this
+elevation. According to Daubeny, Pichincha was extinct prior to 1539,
+when it became active. There were also eruptions in 1577, 1587, and
+1668. It was also in activity during 1831.
+
+Cayamba, another volcanic mountain of Ecuador, lies to the east of
+Pichincha, a short distance north of the equator. Its height is 19,186
+feet. It is nearly extinct.
+
+Cotopaxi, 19,680 feet, is another volcanic mountain of the high
+plateau of Quito. Cotopaxi is still active. Its slopes are covered
+with snow down to a height of about 14,800 feet. Between the lower
+edge of this snow line and the lower slopes of the mountain, there
+lies a zone of naked rock.
+
+According to Whymper, the eruption of Cotopaxi, in 1877, was preceded
+by an unusual degree of activity in the earlier parts of the year.
+This, however, did not cause any alarm until June 25th, 1877, when,
+shortly after midday, an eruption, attended by tremendous subterranean
+roars, began, and an immense black column shot up into the air for
+about twice the height of the cone. This eruption was clearly visible
+at Quito, for the wind blew the ashes towards the Pacific. At this
+time the summit had not changed its appearance, but towards 6:30
+A. M., on the next day, another enormous column of ashes
+rose from the crater. The ashes and cinders were first carried due
+north by the winds, and then, spreading out in all directions, were
+subsequently distributed through the air all over the country. At
+Quito, as early as 8 A. M., the sky assumed the appearance it
+generally has at twilight, and the darkness increased until midday,
+when it became as dark as at midnight. Indeed, it was so dark that one
+could not see his hand before his face.
+
+During this eruption, as is very common in the eruptions of the
+snow-clad mountains of South America, a flood of water, due to the
+rapid melting of the snow and ice on the summit, rushed down the
+mountain slopes at 10 o'clock A. M., on the 26th of the
+month, almost immediately after the appearance of a stream of lava
+that began to flow down the mountain. In a few moments the mountain
+was completely shut off from view by immense columns of steam and
+smoke. At first, a low, moaning sound was heard, which rapidly
+increased to a roar, when a deluge of mud, mingled with huge blocks of
+ice and stones, swept down the mountain, leaving a desert in its path.
+It is estimated that at some places this stream moved with a velocity
+of fifty miles per hour.
+
+The general appearance of Cotopaxi is shown in the accompanying
+reproduction from the painting by Frederick E. Church in the Lenox
+Library, New York.
+
+According to Whymper, who made an ascent of Cotopaxi in 1880, the
+crater on the summit has the form of an immense amphitheatre, 2,300
+feet across from north to south, and 1,650 feet from east to west.
+Its crest is irregular and notched. The crater is surrounded by
+perpendicular cliffs. The western side of the volcano is irregular.
+Barometric measurements gave the height of this volcano at 19,498
+feet. Its height as taken by La Condamine, during the early parts of
+the last century, was 19,605 feet, so that, according to Whymper,
+assuming as would seem probable, that this difference in height has
+not all been due to errors in measurements, the volcano has grown or
+increased in height during the last century and a half.
+
+Chimborazo, 20,498 feet, is another lofty mountain on the plateau of
+Quito. This volcano is situated in lat. 1° 30' S., and is not at the
+present time in an active condition. It is, however, formed entirely
+of volcanic material. Its upper portions are covered with a layer of
+snow to a level of some 2,600 feet below the summit.
+
+[Illustration: COTOPAXI _From a Painting by Frederick E.
+Church in the Lenox Collection of the New York Public Library. By
+Permission_]
+
+Chimborazo has an enormous volcanic summit, which, when seen from the
+Pacific, when the air is especially clear after the long rains of
+winter, is a most splendid sight. Whymper, who ascended the mountain,
+says:
+
+      "When the transparency of the air is increased and its
+      enormous circular summit is seen projected upon the deep
+      azure of blue of the Equatorial sky, it represents a
+      magnificent sight. The great rarity of the air through
+      which the top of the Andes is seen adds much to the
+      splendor."
+
+Whymper says, that as far as records are concerned, there have been no
+eruptions of Chimborazo, which has apparently been an extinct volcano
+for many years. Its crater has been completely buried by a thick cap
+of ice on its summit, while what lava streams exist on the mountain
+are either covered by large glaciers, or have been removed by erosion,
+or hidden by vegetation.
+
+Chimborazo possesses less of the conical outline than Cotopaxi. There
+are steep cliffs towards the summit that have been named by Whymper
+"the northern and southern walls." They seem to him to have been
+formed by the violent upheavals of the explosive eruptions that have
+blown away portions of the cone.
+
+There are other volcanoes in this district, but the above are all we
+have space for describing.
+
+According to Lyell, the volcano of Rancagua, in Chile, lat. 34° 15'
+S., is continually throwing up ashes and vapors like Stromboli.
+Indeed, a year seldom passes in Chile without some earthquake shocks.
+Of these shocks those which came from the side nearest the sea are
+most violent. The town of Copiapo was laid waste by these shocks
+during the years 1773, 1796, and 1819, in both instances after
+intervals of twenty-three years.
+
+Since the volcanic mountains of South America are snow-covered the
+occurrences of volcanic eruptions are apt to be attended by great
+floods caused by the rapid melting of the snow, as well as sometimes
+by the breaking of huge subterranean cavities that are filled with
+water.
+
+According to Lyell, the volcanoes of Peru rise from a plateau from
+17,000 to 20,000 feet above the sea. One of the principal volcanoes
+of Peru is Arequipa, whose summit is 18,877 feet above the level of
+the sea. The mountain takes its name from the city of Arequipa, which
+is situated not far from its base. It is an active volcano. Another
+volcano, Viejo, is found in lat. 16° 55' S.
+
+According to Lyell, there are active vents extending through Chile to
+the island of Chiloe to lat. 30° N.
+
+Aconcagua, west of Valparaiso, in lat. 32° 39' S., 23,000 feet in
+height, the highest mountain in South America, is still in an active
+condition. According to Scrope, when the city of Mendoza was destroyed
+by an earthquake, that killed 10,000 people, in March, 1861, it is
+probable that Aconcagua was in eruption.
+
+There are many other active volcanoes in Chile, extending as far south
+as the volcanoes of Patagonia, north of the Straits of Magellan as
+well as others of Tierra del Fuego.
+
+
+
+
+CHAPTER X
+
+VOLCANOES OF THE UNITED STATES
+
+
+For some readers this may be a surprising chapter heading, for it is a
+general impression that there are no volcanoes in the United States.
+It is true that practically all of the volcanoes of this country are
+dormant or extinct. They have, however, at one time been exceedingly
+active, and, if reports are correct, some of them were active during
+comparatively recent times.
+
+Nearly all of the volcanoes of the United States lie west of the
+meridian of Denver. These volcanoes belong to two distinct types,
+either the Vesuvian type with built up cones, or the plateau or
+fissure type already referred to.
+
+The following brief description of the volcanoes of the United States
+has been collated, for the greater part, from Wallace's excellent book
+on the volcanoes of North America.
+
+Crossing the United States on the Southern Pacific Railroad one's
+attention is caught, in Arizona, by a magnificent group of mountains
+known as the San Francisco Mountains. The highest peak of these
+mountains reaches 12,562 feet above the level of the sea, and 5,700
+feet above the surface of the plateau on which the mountains stand.
+
+[Illustration: FIG. 18. THE UNITED STATES]
+
+According to G. K. Gilbert, the San Francisco Mountain group is formed
+of a variety of lava known as trachyte, that is of comparatively
+recent ejection, possibly of a geological age called the Tertiary. The
+lava forming the mountains escaped through a number of crater cones,
+some of which can still be seen in the neighborhood. Some of these
+craters are now in almost as perfect a condition as the day they were
+formed. Indeed, to one looking at them from a neighboring elevation,
+they appear so fresh, and so little affected by the climate, that one
+might almost believe that the lava had just flowed out of the craters,
+and has not yet hardened. Nevertheless, geologists are sure they have
+been formed long before man appeared on the earth. In one of these
+craters a lake of fresh water has collected.
+
+Another extinct volcano of the United States is Mt. Taylor in New
+Mexico, nearly east of the San Francisco Mountains. This mountain
+rises from the surface of a high table-land, or, as it is called
+in this part of the world, a _mesa_. The surface of the plateau is
+covered with a thick lava stream from which Mt. Taylor rises to
+a height of 11,390 feet above the level of the ocean. This mesa,
+or table-land, is forty-seven miles in length from northwest to
+southeast, and about twenty-three miles in breadth. Its general
+elevation is about 8,200 feet. The plateau rises about 2,000 feet
+above the surface of the level land that surrounds it. All these
+2,000 feet have been removed by erosion. The table-land from which
+Mt. Taylor rises has not been eroded by the action of the rain,
+rivers, and other weathering agencies like the surface of the country
+surrounding it, because of a covering of lava that has been spread
+over its surface to a depth of about 300 feet.
+
+Mt. Taylor is formed almost entirely of lava that has escaped through
+a single opening and has built up a high cone around it. The volcano
+is now quite extinct, so that the original form of the mountain has
+been greatly changed by erosion.
+
+You will remember, when we were discussing the general subject of
+volcanoes, in the beginning of this book, that we spoke of volcanic
+mountains being bottled up after an eruption, by the hardening of
+the lava which remained in the crater and the tube that connects the
+crater with the place from which the lava had been derived. We then
+spoke of this hardened mass being known as a _volcanic plug_, or
+stopper, explaining how the volcano could never again erupt through
+its old crater unless it could develop sufficient force to blow out or
+remove this stopper.
+
+Now besides the crater at the top of Mt. Taylor there were several
+others in the eroded region surrounding the mesa, or high table-land,
+from which Mt. Taylor rises. When, therefore, the erosion which
+removed the 2,000 feet of rocks on all portions of the old mesa that
+were not protected by the coating of lava, these old mountain plugs
+were too hard to be worn away or eroded, and were, therefore, left
+projecting into the air like vast pyramids.
+
+If you should ever visit Mt. Taylor and should go to the eastern
+border of this mesa, and look over the eroded plain, you would see in
+the lowlands a part of the places from which the 2,000 feet of matter
+have been slowly eroded. Dutton describes the beautiful panorama that
+is to be seen as follows:
+
+      "The edge of the mesa suddenly descends by a succession of
+      ledges and slopes, nearly 2,000 feet into the rugged and
+      highly diversified valley-plain below. The country beneath
+      is a medley of low cliffs and bluffs, showing the browns
+      and pale yellows of the Cretaceous sandstones and shales.
+      Out of this confused patchwork of bright colors rise
+      several objects of remarkable aspect. They are apparently
+      inaccessible eyries of black rock, and at a rough guess, by
+      comparison with the known altitudes of surrounding objects,
+      their heights above the mean level of the adjoining plain
+      may range from 800 to 1,500 feet. The blackness of their
+      shade may be exaggerated by contrast with the brilliant
+      colors of the rocks and soil out of which they rise, but
+      their forms are even more striking."
+
+These black piles are the _necks_ or lava plugs of extinct volcanoes.
+They rise above the level of the plain because, being harder than
+the surrounding rocks, they have resisted erosion. In some cases
+these necks or plugs have been converted by shrinkage, on cooling,
+into beautiful columns, somewhat of the type of the basaltic columns
+of the Giant's Causeway. It would be difficult to count the number
+of volcanic necks that can be seen near the edge of the mesa. One's
+attention is at once attracted to some dozen of these piles, which are
+especially striking on account of their great size, and ominous black
+color, but the number is by no means limited to this dozen. There are
+hundreds of them.
+
+Fig. 19 gives some idea of a part of the view from the edge of the
+mesa, and Fig. 20 the appearance of two of these volcanic necks.
+
+But besides high volcanic mountains such as the San Francisco
+Mountains and Mt. Taylor, there are, in different parts of the United
+States, to be found fragments of huge craters from which, in the
+geological past, immense quantities of lava have escaped. In some
+instances these craters are but fragments of huge craters, that, like
+the crater of Mt. Somma, in Vesuvius, have been nearly completely
+blown away by some unrecorded explosion during the far past.
+
+[Illustration: FIG. 19. PANORAMA FROM THE MESA AT THE EDGE OF MT.
+TAYLOR _From U. S. Geological Survey_]
+
+A crater of this type, known as Ice Springs Crater, is situated in the
+desert valley west of the Wahsatch Mountains, some 125 miles south
+of Salt Lake City, Utah. This crater is especially interesting from
+the fact that it occupies a position on a plain that was formed by
+the deposition of sediment in an immense lake that covered this part
+of the United States very long before man lived on the earth. We
+are alluding to Lake Bonneville, a lake that existed in a geological
+time known as the Glacial Epoch. This lake occupied the territory now
+filled by the Great Salt Lake of Utah, but towards the close of the
+Glacial Epoch it was immensely larger than it is now. This can be
+shown not only by the presence of shore lines, that are clearly marked
+on the sides of the surrounding mountains, but also by the ancient
+lake beaches, and deltas, that are common in the district, so that
+instead of there being the comparatively limited area of Great Salt
+Lake as marked on the maps of to-day there was a lake that had an area
+of 19,750 square miles, that covered an area on which at least 200,000
+people dwell.
+
+[Illustration: FIG. 20. VOLCANIC NECKS, EDGE OF MESA AT MT.
+TAYLOR _From U. S. Geological Survey_]
+
+A similar lake, known as Lake Lehontan, existed at the same time,
+covering large areas in the western parts of Nevada.
+
+Coming now to Ice Springs Craters in Utah, we find here three small
+craters formed of scoriæ and lapilli (volcanic ashes consisting of
+small angular stony fragments). Near them lies a fragment of a much
+larger crater known as the Crescent. In some respects this crater was
+not unlike the crater of Somma that surrounded Mt. Vesuvius. It was
+not, however, as large, having a diameter of only 2,200 feet. From
+these craters streams of basalt flowed until they covered considerable
+areas.
+
+A still more recent crater known as Tabernacle Crater is situated
+four miles south of the Ice Springs Crater. Tabernacle Crater takes
+its name from the building known in Salt Lake City as the Tabernacle.
+According to Gilbert, this crater was formed at a time when Lake
+Bonneville stood at a comparatively low level, or when the water was
+only from fifty to seventy-five feet above the bottom of the valley
+on which the crater now stands. At that time an explosive volcanic
+eruption occurred on the bottom of the lake, and the rim of the
+crater, built up by this explosion, was gradually pushed above the
+surface of the lake, so as to shut out its waters.
+
+Extinct volcanic craters, not unlike those of Utah, occur also near
+Ragtown, in Nevada, in a district known as the Carson Valley Desert,
+in one of the broadest areas of what was once Lake Lahontan. Ragtown
+is twenty-two miles southwest of Wadsworth on the Central Pacific
+Railroad. At the present time there are two circular depressions or
+volcanic craters filled with pools of strongly alkaline water known
+as the Ragtown Pond, or Soda Lake. The large lake covers an area of
+268-1/2 acres. Its greatest diameter is over 4,000 feet. Without going
+into a detailed description it will suffice to say that the larger
+crater probably was destroyed by an explosive volcanic eruption.
+
+Another intensely alkaline lake that fills an extinct volcanic crater
+is the Mono Lake, situated in Mono Valley in California at the eastern
+base of the Sierra Nevadas. It has an area of about 200 square miles.
+The centre of the lake has two small islands named Pacha and Negit.
+Immediately south of Mono Lake are a number of craters that occupy
+portions of what was once apparently a fissure extending in a general
+north and south direction. The highest of these craters are in the
+neighborhood of 2,500 feet.
+
+But leaving these inconspicuous craters, let us briefly examine some
+of the higher mountain peaks of the United States that are of volcanic
+origin. One of the most conspicuous of these is Mt. Shasta. This
+mountain is situated in California, at the northern end of the Sierra
+Nevadas. It has a height of 14,350 feet. It is a snow-clad mountain of
+a conical form, and is a conspicuous object in the landscape, because
+it stands alone.
+
+Mt. Shasta is a double-coned mountain. Besides the cone on its summit
+there is a well-developed cone known as Shastina on the western side
+of the mountain, 2,000 feet lower than the main summit.
+
+There are well-defined lava streams on the slopes of Mt. Shasta. One
+of these, which issued from the southern side of the mountain at
+an elevation of 5,500 feet, divided into two streams. One of these
+streams is twelve miles in length. The other entered the canyon of the
+Sacramento River, thus displacing the water.
+
+Coming now to the Cascade Mountains, in Oregon and Washington, we
+will find in them a number of giant peaks of volcanic origin. The
+most important of these are in regular order from south to north, as
+follows: Mt. Pitt, 9,760 feet; Mt. Mazana, 8,223; Mt. Union, 7,881;
+Mt. Scott, 7,123; Three Sisters, Mt. Jefferson, 10,200, and Mt. Hood,
+11,225, in Oregon; Mt. Adams, 9,570; Mt. St. Helen's, 9,750; Mt.
+Rainier, 14,525, and Mt. Baker in Washington, 10,877.
+
+Nearly all these mountains have craters either on their summits or on
+their sides. They are extinct volcanic mountains, that were, for the
+most part, thrown up during the Tertiary Geological Period, so that
+they have all been greatly affected by erosion.
+
+One of the most remarkable of the above volcanic mountains is Mt.
+Mazana, in Oregon. This mountain has on its summit an approximately
+circular cavity from five to six miles in diameter, that is occupied
+by a lake of water known as Crater Lake. This lake is 6,239 feet above
+the level of the sea, and has a depth of 1,975 feet. It is surrounded
+by nearly vertical walls ranging from 900 to 2,200 feet deep, so that
+the vast caldera of which this great depression consists has a depth
+of at least 4,000 feet.
+
+Mt. Pitt, situated about sixty miles north of Mt. Shasta, in southern
+Oregon, has a regularly shaped volcanic cone, and the remnant of a
+crater at its summit. The Three Sisters and Mt. Jefferson lie to
+the north of Mt. Pitt. Like the others they are ancient volcanic
+mountains. But little is accurately known concerning them.
+
+Mt. Hood, 11,225 feet high, rises from the crest of the Cascade
+range in Northwest Oregon, about twenty-five miles south of the
+Columbia River. Mt. Hood is an exceedingly majestic mountain. At its
+summit there are only portions of the walls of the original crater.
+When ascended in 1888, streams of sulphur vapor were escaping from
+fumaroles on its northeastern slopes, at an elevation of 8,500 feet
+above the sea.
+
+Mt. Adams and Mt. St. Helen's lie to the north of Mt. Hood. Mt. Adams
+about sixty miles to the north, and beyond this, Mt. St. Helen's.
+Accurate information concerning the summit of Mt. Adams is still
+lacking. Mt. St. Helen's in Washington has more of a conical summit.
+Russell states that according to frontiersmen, St. Helen's has been
+in a state of activity within the past fifty years. A French-Canadian
+asserts that the mountain was in actual eruption during the winter of
+1841-43, that at this date the light from the volcano was sufficiently
+bright to enable one to see and pick up a pin in the grass at midnight
+near his cabin some twenty miles distant. Mt. St. Helen's was ascended
+in 1889, when fumaroles were found on the northeast side.
+
+Mt. Rainier in Washington is plainly visible from Puget Sound. It is
+a most magnificent mountain. The summit has a bowl-shaped crater, of
+an almost perfectly circular form. The inside of the crater, when
+last ascended, was filled to within thirty or thirty-five feet of its
+rim with ice and snow. There was, however, evidences of heat, since
+numerous jets of steam were seen issuing from its interior rim.
+
+Mt. Baker, Washington, is the northernmost of the volcanoes of the
+Cascade Mountains, south of the boundary line between the United
+States and Canada. But little is known of this mountain. The summit
+appears as a conical peak from Puget Sound, so that its form would
+seem to show that it is of volcanic origin. According to Gibbs,
+officers of the Hudson Bay Company, as well as the Indians, declared
+that Mt. Baker was in eruption in 1843, when it broke out at the same
+time as Mt. St. Helen's, covering the country with ashes.
+
+There are but few volcanoes in the Rocky Mountains which extend from
+north to south through the United States at a considerable distance to
+the east of the Sierra Nevadas and Cascade Ranges. The Spanish Peaks,
+situated in the southeastern part of Colorado about sixty miles south
+of Pueblo, are the remains of ancient volcanoes. Two of the most
+prominent of these peaks rise from 12,720 to 13,620 feet above the sea.
+
+We shall make no effort to attempt to describe the volcanic mountains
+that may exist in those portions of the Rocky Mountain Ranges or the
+Cascade Range lying in Canada. Comparatively little is known of them,
+but inasmuch as volcanic activity has been manifested in Alaska, it
+would seem highly improbable, as Russell remarks, that volcanoes
+should suddenly cease at the northern boundaries of the United States
+and then begin again at the most southern part of Alaska. It will be
+sufficient to say that Mt. Edgecome, situated on an island in the
+neighborhood of Sitka, is of volcanic origin, and that the Aleutian
+Islands, beginning at Alaska on the east at the head of Cook's Inlet,
+extend westward through the Peninsula of Alaska to the Peninsula of
+Kamtschatka for a distance of nearly 1,600 miles. This belt, which
+is called by Russell "the Aleutian Volcanic Belt," contains numerous
+volcanoes that are known to have been active in historical times.
+
+Mt. Wrangell, on the Copper River, 200 miles northeast of the head
+of Cook's Inlet, is a lofty volcanic mountain that is said to have
+been in eruption in 1819, and at the time of last report was still
+throwing out columns of steam. While much remains to be ascertained
+about the volcanoes of the Aleutian Islands, it would appear that
+there are active volcanoes on twenty-five of these islands, on which
+some forty-eight craters have been found. Eruptions are common in the
+district.
+
+
+
+
+CHAPTER XI
+
+THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC ISLANDS OF THE LESSER
+ANTILLES
+
+
+The West Indies Island chain consists of two groups of islands; i. e.,
+the Greater Antilles, including Cuba, Jamaica, Hayti, and Porto Rico,
+on the west, and the chain of the Lesser Antilles on the east.
+
+The Lesser Antilles consists of two parallel chains, the westernmost
+of which is for the greater part mountainous with peaks several
+thousand feet in height. All these islands are volcanic. The chain
+on the east consists of low, calcareous rocks, or rocks consisting
+largely of lime.
+
+In the western chain the islands beginning on the south are, Grenada,
+St. Vincent, St. Lucia, Martinique, Dominica, Guadeloupe, Montserrat,
+Nevis, and St. Eustace, while in the calcareous chain are found the
+Tobago, Barbadoes, and others.
+
+Prior to 1902, the greatest volcanic eruption in this part of the
+world occurred on the island of St. Vincent, with the volcano of
+Soufrière. Although the forces displayed were exceedingly great, yet
+they become insignificant when compared with the appalling eruption
+that took place in Martinique only a short time ago; namely, May the
+8th, 1902, when the volcano of Mt. Pelée, situated on the northwestern
+part of the island, burst into an eruption so terrible that in
+destruction of life it far exceeded the eruption of Krakatoa, although
+the amount of energy causing the eruption was much smaller.
+
+[Illustration: FIG. 21. THE LESSER ANTILLES]
+
+Heilprin, in a book called "Mt. Pelée and the Tragedy of Martinique,"
+from whom most of the information of this chapter has been obtained,
+calls attention to the fact that before the eruption of Pelée there
+were plenty of warnings for those intelligent enough to note them. For
+two or three weeks prior to May 8th, 1902, the volcanic activity of
+Pelée had been rapidly increasing, the mountain throwing out clouds
+of ashes and sulphurous vapors from its crater. By April 25th the
+sulphurous vapors had so increased in quantity as to make breathing
+difficult in St. Pierre. The ashes fell on the surrounding country and
+by the 2d of May had so covered the streets of St. Pierre as to stop
+traffic.
+
+Three days later, May 6th, shortly before noon, an avalanche of mud
+poured down the slopes of the mountain with the rapidity of an express
+train. These torrents of mud and water deluged the towns and villages
+in the neighborhood. The activity of Mt. Pelée increased until the
+morning of May 8th, 1902, when, almost at exactly 8 A. M., an
+eruption occurred, so terrible in its effects that in two minutes the
+city of St. Pierre was almost completely destroyed.
+
+St. Pierre, the principal town of Martinique, is situated on the
+island of Martinique, on the northwestern coast, about ten miles
+southwest of Mt. Pelée. St. Pierre was settled as far back as 1635. It
+is situated on an open roadstead without any harbor.
+
+That there were many points of resemblance between the position of St.
+Pierre and the destroyed city of Pompeii will be recognized as the
+description of the catastrophe is given.
+
+St. Pierre was a beautiful city, and formed the natural outlet to one
+of the richest districts in Martinique for the production of sugar
+cane and cocoa. It contained many fine houses, the homes of planters,
+wealthy bankers, merchants, and shippers, who, besides their regular
+houses in the city, had constructed handsome villas on heights on the
+outskirts of the city. The houses were to a great extent one or two
+stories in height, and were in many cases surrounded by fine gardens.
+The city extended along the coast for about two miles. The streets
+were well lighted.
+
+The eruption of Mt. Pelée on May 8th, 1902, was of a very unusual
+character, containing a feature that--with the exception of a volcanic
+eruption of Soufrière, a volcanic mountain on the neighboring island
+of St. Vincent, and an eruption of Kilauea in Hawaii--so far as I am
+aware, never before occurred. This was a blast of highly heated air,
+mingled with white hot or incandescent dust, that swept down the side
+of the mountain with a velocity of one or two miles per minute, or
+possibly more.
+
+Nearly all of the people in St. Pierre were killed. From the
+appearance of the bodies it seemed that death was practically
+instantaneous, and was due either to scorching or burning, or
+asphyxiation by the breathing of highly heated air. The number of
+people so killed, including almost the entire population of St.
+Pierre, as well as a number of adjoining settlements, was not less
+than 30,000.
+
+The zone of absolute destruction was limited to an area the extent
+of which did not greatly exceed eight or nine square miles. On the
+outskirts of this zone the destruction, though considerable, was less
+complete.
+
+There was almost an entire absence of great earthquake shocks during
+the eruption.
+
+Following the terrible eruption of May 8th were a number of less
+violent eruptions on May 20th, 26th, June 6th, July 9th, and August
+31st. According to Heilprin these eruptions were of the same character
+as that of May 8th.
+
+There has been considerable discussion as to the exact causes of the
+tornadic incandescent blast that caused the awful destruction of life.
+Without entering this discussion it is sufficient to say that it is
+now generally considered that the blast consisted of highly heated
+air, and super-heated steam loaded with great quantities of finely
+divided red hot or even white hot dust particles.
+
+While, perhaps, the force producing the awful eruption of Mt. Pelée
+was greatly excelled in the case of many other volcanic eruptions;
+such as Papandayang, in 1772; Asamayama, in 1783; Skaptar Jökul, in
+1783; Tomboro, in 1815; Coseguina, in 1835; and Krakatoa, in 1883;
+yet, in the words of Heilprin, "in intensity and swiftness of its
+death-dealing blast ... the eruption of May 8th, and of later dates,
+stands unique in records of volcanic manifestations."
+
+While the amount of ashes that accompanied the blast of white hot
+steam and air was comparatively small, yet during the time between
+this and the subsequent eruptions, the amount of ashes that were
+thrown from the surface of Mt. Pelée was exceedingly great.
+
+According to Russell, in a paper on the volcanic eruptions of
+Martinique and St. Vincent, in 1902, the amount of ashes and solid
+matter generally thrown out from the crater of Mt. Pelée would be
+equal to 40,000,000 cubic feet every minute, or one and a half times
+the sediments discharged by the Mississippi in the course of a whole
+year.
+
+According to Heilprin, however, the actual amount of dust thrown from
+the crater of Mt. Pelée was, probably, 500 times greater than the
+amount discharged by the Mississippi River in the course of a year,
+and, consequently, considerably greater than that of all the rivers of
+the world combined, or, as he says:
+
+      "Mont Pelée has now been in a condition of forceful
+      activity for upwards of two hundred days; can we assume
+      that during this time it may have thrown out a mass of
+      material whose cubical contents are hardly less than
+      a quarter of the area of Martinique as it now appears
+      above the waters? One is, indeed, almost appalled by the
+      magnitude of this work, and yet the work may even be very
+      much greater than is here stated. We ask ourselves the
+      questions, what becomes of the void that is being formed in
+      the interior? What form of new catastrophe does it invite?
+      There can be no answer to a question of this kind--except
+      in the future happening that may be associated with this
+      special condition. But geologists must take count of the
+      force as being one of greatest potential energy, whose
+      relation to the modelling and the shaping of the destinies
+      of the globe is of far greater significance than has
+      generally been conceived."
+
+A curious circumstance connected with the eruption of Mt. Pelée was
+the most pronounced electric and magnetic disturbances. Moreover, as
+in the case of the eruption of Krakatoa, there were the same after
+glows or red sunsets and sunrises due to the presence of fine volcanic
+dust in the higher regions of the air. These phenomena were observed
+over widely separated areas.
+
+It appears that this great eruption in Martinique was preceded by
+severe earthquakes in the northern part of South America, especially
+in Colombia and Venezuela. The most marked was the great earthquake
+which on April 18th destroyed the city of Guatamaula; this was,
+perhaps, the most destructive earthquake that has occurred in the
+Western Hemisphere since the great earthquake of 1812, that destroyed
+the city of Caracas. Indeed, Professor Milne suggests that it was this
+earthquake that brought about the eruption of Mt. Pelée.
+
+Soufrière, on the island of St. Vincent, had a great eruption on May
+7th, 1902, one day before the awful eruption of Mt. Pelée. No lava
+flowed during this eruption. There were, however, great discharges
+of mud, due to a lake that before the eruption filled the top of
+a depression known as the old crater which lay southwest of a new
+crater, or the crater that was formed during the eruption of 1812. The
+old crater was nine-tenths of a mile across from east to west, and
+eight-tenths of a mile from north to south. The depth to the crater
+floor was from 1,000 to 2,400 feet. The surface of the new and shallow
+boiling lake which occupied the deepest part of the floor during the
+latter part of May, and from June to August, was estimated to be
+only 1,200 feet above the level of the sea. The sheet of water that
+occupied it before the eruption being several hundred feet higher.
+
+Soufrière did not fail to give warnings of its coming eruption.
+Rumblings were heard two days before the explosion. On May 5th, 1902,
+fishermen who crossed the lake noticed that the water was disturbed
+and agitated. On the Tuesday following, May 6th, great clouds were
+thrown out during the afternoon, and the volcano was illumined by a
+reddish glare of fire. The first explosion was heard shortly before
+two o'clock on the following day and the volcano burst into activity.
+The explosions, together with great discharges of pumice, ashes, and
+boulders, followed one another rapidly. A column of steam was shot up
+into the air for a height of 30,000 feet. The severest paroxysm came
+shortly after ten A. M., and was succeeded by others nearly
+as violent during the next few hours. By this time a reddish curtain
+of clouds nearly shut out the island from view, and rapidly advanced
+over the land and descended on the sea. This eruption caused a loss of
+life of about 1,350.
+
+This eruption of Mt. Soufrière was accompanied by the same tornadic
+blast of glowing air. There was not, however, any single blast quite
+as severe as that which attended the eruption of Pelée on May 8th,
+1902.
+
+
+
+
+CHAPTER XII
+
+SOME OTHER NOTED VOLCANIC MOUNTAINS
+
+
+Since the limits of our book will prevent any further description
+of volcanic districts or regions, we must content ourselves with
+descriptions of some of the noted of the remaining volcanoes, although
+many we will thus omit contain great wonders.
+
+As we have already seen from the description of Krakatoa, the island
+of Java near which Krakatoa is situated is especially noted not only
+for the great number of its volcanic mountains, but also for the
+frequency and severity of their eruptions.
+
+Perhaps the most destructive eruption of any of the volcanic mountains
+of Java was of a volcanic mountain called Papandayang. This volcano,
+situated on the southern coast of the island, is 7,034 feet in
+height, and was in eruption in 1772. According to Scrope, from whom
+the details of this eruption have been obtained, two others of the
+many volcanoes on Java, situated at 184 and 352 geographical miles
+respectively from Papandayang, broke out at the same time into active
+eruption, although several intervening cones were undisturbed.
+
+The eruption of Papandayang was of the explosive type, a large part
+of the mountain being broken off by the great force of the eruption,
+and its materials scattered far and wide over the surrounding country.
+During this eruption forty villages with their inhabitants were
+buried by great showers of ashes. An area of fifteen by six miles was
+left in the shape of a huge pit by the great eruption. It was at
+first believed by some that this pit was due to the actual sinking
+in of the ground, but a more careful study has shown that it was in
+reality caused by the great force of the eruption, being, in point
+of fact, a vast explosive crater that was formed by the expulsion of
+the materials that formerly filled it. Some idea of the great extent
+of this eruption of Papandayang may be had by the size of this huge
+crater that was six by fifteen miles in diameter.
+
+Another great volcanic mountain in Java that had a terrific eruption
+was Galungoon, or Galung Gung. According to Lyell, from whom the facts
+of this eruption have been obtained, prior to this eruption the slopes
+of the mountain were highly cultivated and densely populated. There
+was a circular pit or crater on the summit of the mountain, but there
+had been no traditions of any eruptions prior to 1822.
+
+In July, 1822, the waters of the Kunir River, one of the small rivers
+that flow down the slopes of the mountain, were observed to become
+hot and turbid. On the 8th of October, 1822, a terrific explosion was
+suddenly heard, accompanied by great earthquake shocks, when immense
+columns of hot water and boiling mud, mixed with burning brimstone,
+ashes, and lapilli, were thrown violently like a great waterspout from
+the opening in the mountain, with such enormous violence that great
+quantities fell across the River Tandoi, forty miles distant, while
+the valleys in the neighborhood were filled with a burning torrent.
+The rivers overflowed their banks and produced great destruction by
+floods of burning and boiling materials that washed away all the
+villages and cultivated fields in their path. During this eruption an
+extended area was covered with boiling mud in which were completely
+buried the bodies of many of those who perished.
+
+So great was the violence with which the boiling mud, cinders, etc.,
+were thrown out of the mountain that they entirely failed to fall on
+many of the villages in the immediate neighborhood, while the more
+remote villages were completely destroyed and buried out of sight
+under the mud.
+
+The first eruption continued for nearly five hours. During several
+days following the eruption, torrents of rain fell, which produced
+floods in the rivers that covered the country far and wide with thick
+layers of mud.
+
+Four days after the great eruption, that is, on the 12th of October,
+1822, a second and still more violent eruption occurred, when immense
+quantities of hot mud were again thrown out of the crater. Great
+blocks of hardened lava called basalt were thrown a distance of seven
+miles from the volcano. This eruption was accompanied by a violent
+earthquake. It was during this eruption that a huge piece of the side
+of the cone was blown out, not unlike the case of the Val del Bove on
+Mt. Etna. The surrounding country was covered with mud. The immense
+quantity of materials thus thrown out of the side of the mountain
+produced changes in the courses of several rivers, thus causing great
+floods which in the single night of October 12th drowned 2,000 people.
+During these eruptions there were 114 villages destroyed, with a total
+loss of life of about 4,000.
+
+There is a volcanic mountain on the island of Sumbawa that is noted
+for the very destructive eruption that occurred on it in April, 1815.
+If you examine the map of the Sunda Islands chain, you will see that
+the island of Sumbawa lies immediately east of a little island called
+Lombock, about 200 miles east of Java.
+
+This eruption of Sumbawa was of the most frightful violence, and,
+indeed, with the exception of Krakatoa and Pelée, was one of the
+greatest eruptions in historic times.
+
+Like all great eruptions, that of Sumbawa gave plenty of signs of
+its coming. During April, 1814, the volcano manifested considerable
+increase in its activity, and ashes fell on the decks of vessels
+sailing past the island.
+
+The eruption began on April 5th, 1815, but reached its greatest
+violence on the 11th and 12th of April. According to Lyell, the sound
+of the explosion was heard at the island of Sumatra at a distance of
+970 geographical miles towards the west, and in the opposite direction
+it was heard for a distance of 720 miles. The destruction of life was
+terrible. Out of a population of 12,000 in the province of Tomboro,
+only twenty-six people escaped with their lives.
+
+Like many other great eruptions the shooting upwards of the great
+column of matter from the crater produced a violent whirlwind that
+carried people, horses, cattle, and almost every movable object high
+into the air, and tore up huge trees by their roots.
+
+Immense quantities of ashes fell over the surrounding country, or were
+carried towards Java to the west a distance of 300 miles, while on the
+north they were carried towards Celebes for a distance of 217 miles.
+Cinders covered the ocean towards the west two feet thick and several
+miles in length, so that ships could hardly make their way through
+them.
+
+The darkness in Java produced by the dense ash cloud was greater than
+had ever before been experienced with the single exception of the
+great eruption of Krakatoa. A considerable quantity of this volcanic
+dust was carried to the islands of Amboyna and Banda, the last named
+island being at a distance of 800 miles east of the volcano.
+
+This eruption of Sumbawa was attended by great lava streams that
+covered vast areas of the land and afterwards poured into the sea.
+
+As in the case of the explosive eruption of Krakatoa great waves were
+produced in the ocean all along the coasts of Sumbawa, and surrounding
+islands. The sea suddenly rose from two to twelve feet. A great wave
+rushed up the mouths of the rivers, and at the town of Tomboro, on
+the west side of Sumbawa, an area of land was sunk in the waters and
+remained permanently covered by eighteen feet of water.
+
+The most important of the still active volcanoes of Japan is
+Assamayna. This mountain was in terrible eruption during the autumn of
+1783, when dense showers of ashes thrown out of the crater darkened
+the sky, turning the day into night, and, falling on the cultivated
+fields around the mountain, changed them into deserts. During the
+eruption some forty-eight villages were destroyed by showers of ashes
+and red hot stones and thousands of the inhabitants were either killed
+directly by the stones and ashes, or died from starvation, since their
+fields were covered with ashes for miles around to a depth of from two
+and a half to five feet.
+
+Another terrible eruption in Japan was in the volcanic mountain of
+Wunzen, or Onzen-Gatake. This occurred during 1791-93. During the last
+eruption of this volcano, 53,000 people lost their lives, either by
+reason of the eruption of the volcano, or by huge waves set up in the
+ocean by an earthquake.
+
+
+
+
+CHAPTER XIII
+
+JORULLO, A YOUNG VOLCANIC MOUNTAIN
+
+
+You must not suppose that when we speak of Jorullo as a young volcanic
+mountain that we mean young in the sense that you or I might be called
+young, but young as regards mountains; for Jorullo, now a great
+mountain range, had no existence before the year 1759, and that would
+make the mountain a little less than 150 years old, which so far as
+mountains are concerned may properly be regarded as quite young.
+
+The story of Jorullo is very interesting, and affords an excellent
+example of the great scale on which modern volcanic eruptions take
+place during historical times.
+
+If you examine the map of Mexico on page 86 you will see that Jorullo
+lies 170 miles southwest of the city of Mexico, and 108 miles from the
+Pacific Ocean, which is the nearest large body of water. This mountain
+is of especial interest because, if old traditions are to be believed,
+it was thrown up during practically a single night. This wonderful
+event took place on an elevated plain or plateau, called the Plain of
+Malpais, that lies between 2,000 and 3,000 feet above the level of the
+ocean. The plain was situated in a part of Mexico that was celebrated
+for the growth of the finest cotton and indigo in the world. It
+formed the large estate of a wealthy planter, Señor Pedro de Jorullo,
+who lived at his ease as a wealthy planter is apt to do in tropical
+countries like Mexico.
+
+Jorullo's plantation was covered by an especially fertile soil, since
+it was formed by the deposits of volcanic ashes, dust, tufa, etc.,
+produced, most probably, by neighboring volcanoes long before man
+appeared on the earth, for the plain of Malpais was bounded by hills
+that were composed of volcanic materials. There had, however, been no
+signs of volcanic activity in the neighborhood. It had indeed been
+quiet, so far as volcanic eruptions were concerned, since the time of
+the discovery of America by Columbus, until the middle of the last
+century. The fertile fields of the Jorullo plantation were watered by
+two rivers, or as we would probably call them, brooks, the Cuitamba
+and the San Pedro.
+
+Signs were not wanting of the coming calamity. During June, 1759,
+subterranean sounds were heard of a low rumbling character, which
+every now and then increased until they resembled in intensity the
+sounds produced by the firing of large guns. These sounds were
+accompanied by earthquake shocks that greatly terrified the people
+and caused them to flee from their homes. Nothing, however, occurred,
+so, becoming accustomed to the noises, the people returned to their
+houses. The noises and tremblings ceased for over two months, until,
+on the 29th of September, 1759, they were again heard, and a terrible
+eruption began. A long fissure opened in the earth, extending
+generally from northeast to southwest. From this fissure flames
+burst out, fragments of burning rock and stone, together with large
+quantities of ashes were thrown to great heights in the air, and were
+followed by streams of molten rock. Six volcanic cones were formed
+along the fissure. The highest of these cones is what now constitutes
+the volcanic mountain of Jorullo, which then reached a height of at
+least 1,600 feet above the level of the plain. From its cone were
+thrown out great quantities of lava of the same type as that which
+escaped from the craters of many volcanic islands such as Hawaii and
+Iceland, namely, basaltic lavas. This eruption, which began on the
+29th of September, 1759, continued until the month of February, 1760.
+
+The account as above given was obtained by Humboldt, who visited the
+country some fifty-six years after the eruption. This story was told
+him by the Indians, but was also recorded in verse by a Jesuit priest,
+Raphael Landiva, a native of Guatemala. According to the account given
+Humboldt by the Indians, it appears that when a long time after the
+eruptions had quieted down, they had returned to their old homes with
+the hope of cultivating part of the grounds, they found the plains
+still too hot to permit their living on them.
+
+According to Lyell, there was around the base of the cone, spreading
+from them as a centre over an area of some four square miles, a convex
+mass, about 550 feet in height, most of the surface of which was
+covered with thousands of small flattish conical mounds from six to
+nine feet in height. These, together with numerous large fissures that
+crossed the plain in different directions, served as points for the
+escape of sulphur vapors, as well as for the vapors of hot water.
+
+During the escape of lava from the craters in 1759, the molten rock,
+spreading over the plain, ran into the channels of the river or brooks
+before named, driving out the water. This water reappeared at the base
+of the mountain in numerous hot springs.
+
+Humboldt thought that the conical mountains had been lifted or raised
+by the formation of huge bubbles formed under the lava, thus causing
+it to assume a shape not unlike that of a huge bladder. This opinion,
+however, has not been accepted by geologists at the present time.
+Scrope points out that this was probably the origin of the little
+conical mounds that covered the surface of the principal conical
+mounds but was not, in all probability, the cause of the mound itself.
+He says:
+
+      "With regard to the disputed question as to the origin
+      of the raised plain of the Malpais, M. de Saussure, the
+      last and most trustworthy visitor, entirely confirms the
+      opinion which I ventured to proclaim in 1825, that Humboldt
+      was mistaken in supposing it to have been 'blown up from
+      beneath like a bladder,' and that it is merely an ordinary
+      current of lava, which, owing to its very imperfect
+      liquidity at the time of its issue from the volcanic vent,
+      as well as to the overflow of one sheet or stream upon
+      another, had acquired great thickness about its source,
+      gradually thinning off towards the outer limit of the
+      elliptical area it covered."
+
+If you have been able to follow the above you will see that Mr. Scrope
+means that in his opinion the cone of Jorullo is a lava cone like
+that we have already studied on Mt. Loa or Mt. Kilauea, or, in other
+words, that the lava as it came out from the opening on the top of
+Jorullo, flowed in all directions around the opening, thus building up
+a mountain in the form of a flat lava cone.
+
+Perhaps one of the reasons Humboldt had for believing the entire
+elevation of Jorullo to be due to the formation of a huge bladder was
+the fact that the plain on which the cone is situated, when struck,
+gave out a sound as though there was a vast hollow space below it.
+This was especially the case when the hoofs of the horses driven over
+its surface produced sounds as though they were moving over the summit
+of a hollow dome-like space below. But, as Lyell points out, this was
+probably only due to the fact that the materials forming the cone were
+very light and porous.
+
+According to Burkhardt, a German mining engineer who visited Jorullo
+in 1827, there appears to have been no other eruptions of the volcano
+since the time of Humboldt's visit. Mr. Burkhardt descended to the
+bottom of the crater and observed that small quantities of sulphurous
+vapors were still escaping. The small cones or _hornitos_, however, on
+the slopes had entirely ceased emitting steam. It appeared, too, that
+the twenty-four years that had passed since the time of Humboldt's
+visit, the rich soil of the surrounding country had permitted the
+successful cultivation of some crops of sugar cane and indigo.
+
+Russell appears to doubt the reliability of the information obtained
+by Humboldt concerning Jorullo. He suggests that a poetical account
+by the Jesuit missionary from whom Humboldt obtained much of his
+information was not apt to possess marked scientific accuracy. While,
+however, this may be true, yet to a certain extent it seems entirely
+probable that the principal facts were as above given. The following
+account as given by Humboldt, is taken from a translation made in the
+early part of 1800:
+
+      "The affrighted inhabitants fled to the mountains of
+      Aguasarco. A tract of ground from three to four square
+      miles in extent, which goes by the name of Malpays, rose up
+      in the shape of a bladder. The bounds of this convulsion
+      are still distinguishable in the fractural strata. The
+      Malpays, near its edge, is only twelve metres above the
+      old level of the plain called the Playas de Jorullo; but
+      the convexity of the ground thus thrown up increases
+      progressively towards the centre, to an elevation of 160
+      metres (524.8 ft.).
+
+      "Those who witnessed this catastrophe from the top of
+      Aguasarco assert that flames were seen to issue forth
+      for an extent of more than half a square league, that
+      fragments of burning rocks were thrown up to prodigious
+      heights, and that through a thick cloud of ashes,
+      illuminated by the volcanic fire, the softened surface
+      of the earth was seen to swell up like an agitated
+      sea. The rivers of Cuitamba and San Pedro precipitated
+      themselves into the burning chasms. The decomposition of
+      the water contributed to invigorate the flames, which were
+      distinguishable at the city of Pascuaro, though situated on
+      very extensive table-land 1,400 metres (4,592 ft.) elevated
+      above the plains of Las Playas de Jorullo. Eruptions of
+      mud, and especially of strata of clay enveloping balls
+      of decomposed basalt in concentrical layers, appeared to
+      indicate that subterranean water had no small share in
+      producing this extraordinary revolution. Thousands of small
+      cones, from two to three metres in height, called by the
+      indigenes ovens, issued forth from the Malpays....
+
+      "In the midst of the ovens, six large masses, elevated from
+      400 to 500 metres each above the old level of the plain,
+      sprung up from a chasm, of which the direction is from
+      N. N. E. to the S. S. E. This is the phenomenon of the
+      Montenovo of Naples, several times repeated in a range of
+      volcanic hills. The most elevated of these enormous masses,
+      which bears some resemblance to the puys de l'Auvergne, is
+      the great Volcan de Jorullo. It is continually burning,
+      and has thrown up from the north side an immense quantity
+      of scorified and basaltic lavas containing fragments of
+      primitive rocks. These great eruptions of the central
+      volcano continued till the month of February, 1760. In the
+      following years they became gradually less frequent.... The
+      roofs of the houses of Queretaro were then covered with
+      ashes at a distance of more than forty-eight leagues in a
+      straight line from the scene of the explosion. Although
+      the subterranean fire now appears far from violent, and
+      the Malpays and the great volcano begin to be covered with
+      vegetation, we nevertheless found the ambient air heated to
+      such a degree by the action of the small ovens, that the
+      thermometer at a great distance from the surface and in the
+      shade rose as high as 43° C." (109° 4' F.).
+
+
+
+
+CHAPTER XIV
+
+MID-OCEAN VOLCANIC ISLANDS
+
+
+Besides the volcanoes we have already described, there are many others
+situated in mid-ocean far from any continent. A brief description will
+be given of a few of these.
+
+All the three great central oceans, the Pacific, the Atlantic, and the
+Indian, contain numerous volcanic islands, some of which rise many
+thousands of feet above the general level.
+
+We will begin with a description of some of the more important
+volcanic islands of the Pacific. It was first pointed out by Kotzebue,
+and afterwards by Darwin, that all the islands of the Pacific Ocean
+can be divided into two great classes, the _high islands_ and the
+_low islands_. All the high islands are of volcanic origin, while
+the low islands are of coral formation. It is the opinion of Dana,
+who has made a careful study of coral formations, especially in the
+Pacific, that in all probability even the low islands of the Pacific
+were originally volcanic, and that the deposits of coral had been made
+along their shores after their volcanoes had become extinct.
+
+The islands of the Pacific, like the shores of the continents and
+most of their mountain ranges, extend in two great lines of trend, or
+general direction, which intersect each other nearly at right angles.
+These lines extend from the southeast to the northwest, and from the
+northeast to the southwest respectively, those extending in a general
+direction from southeast to northwest being the most common in the
+Pacific.
+
+Now, perhaps, the greatest number of the earth's volcanoes are
+arranged along fissures, or cracks in the earth's crust. The craters
+are situated along the cracks, the openings being kept clear at the
+crater, and gradually closing elsewhere, probably by pressure. In
+other words, most of the volcanoes follow one another along more or
+less straight lines. For example, in the western part of South America
+they follow the Andes Mountains. A similar arrangement exists in the
+volcanoes of Central America, Mexico, and the United States. Now, this
+is especially true of mid-ocean volcanoes of the Pacific which lie
+along lines extending from southeast to northwest, or from northeast
+to southwest, though mainly along the former.
+
+Some of the volcanic islands of the Pacific have already been
+described or referred to, as, for example, the Aleutian Islands,
+which stretch in a curved line from the southwestern extremity of
+the peninsula of Alaska to Kamtschatka on the coast of Asia. We have
+already described the island of Hawaii, the great volcanoes of the
+Sandwich Islands chain, and besides these there are in the North
+Pacific the Ladrone Islands, lying east of the Philippines.
+
+Some of the principal remaining islands are: the Fejee Islands, which
+are volcanic, with numerous hot springs and craters. The Friendly
+Islands, with the peak of Tafua, 2,138 feet high, an active volcano
+with a large crater always burning, and two other volcanoes, Apia,
+and Upala. Tahiti, to the east, is at present extinct. One of its
+mountains, Orobena, said to be 10,000 feet high, has a crater on its
+summit. The Marquesas, still further to the east, are also volcanic.
+All of these islands lie generally in the lines of the northeast
+trend.
+
+The Tongan or New Zealand Island chain extends in the direction of
+the northeast trend. This, as you will see, is the direction in which
+the two islands of New Zealand extend. The Tongan Island chain is
+continued to the south through Auckland and the Macquaire Islands to
+58° S. Towards the north, in almost the same line, are the Kermadec
+Islands near 30° S.
+
+There are several active volcanoes in New Zealand. An explosive
+eruption of Tarawera, in New Zealand, in 1883, continued for several
+days, and was followed, three days afterwards, by an outburst in an
+active volcano in the Bay of Plenty, and two months afterwards, by a
+violent outburst in a volcano on the island of Ninafou in the Tongan
+Islands.
+
+Coming now to the Atlantic Ocean we find a number of volcanic
+mountains in the deep waters near mid-ocean. The principal of these,
+besides Iceland, are the Azores, the Canaries, Cape Verde Islands,
+Ascension Island, St. Helena Island, and Tristan d'Acunha. The Peak
+of Pico, in the Azores, rises to a height of 7,016 feet. The Peak
+of Teneriffe, in the Canaries, reaches the height of 12,225 feet.
+Teneriffe is a snow-capped mountain. It has a cone on its summit with
+precipitous walls like Vesuvius. Sulphurous vapors are continually
+formed at its summit, but no flames can be seen.
+
+In the Cape Verde Islands is to be found the active volcanic mountain
+of Fuego, rising 7,000 feet above the sea. It has a central cone that
+has been broken down on one side like that of Somma on Vesuvius. Fuego
+was in eruption in 1785, and also in 1799.
+
+Ascension Island, south of the equator, is formed entirely of volcanic
+materials. This island rises from an apparently granite floor on the
+bed of the ocean, in water 12,000 feet deep.
+
+St. Helena lies further to the south. It is an extinct volcano, and
+has the remains of a crater on its summit with lava dikes in various
+parts of the island.
+
+Tristan d'Acunha is an isolated mountain that lies in the South
+Atlantic, south of St. Helena, 1,500 miles from Africa, the nearest
+land. It is an extinct volcano that rises from a depth of 12,150 feet
+to a height of 7,000 feet above the sea. It has a truncated cone on
+its summit and a lake of pure water in its old crater.
+
+There are only a few volcanic islands in the Indian Ocean. Kerguelen
+Island lies in the southern waters. St. Paul and Amsterdam to the
+north, lying near 40° S. lat., as well as the Crozet Islands, are
+extinct volcanoes.
+
+In the Arctic Ocean is the volcanic island of Jan Mayen. In the
+Antarctic Ocean, as far as is known, there are only two volcanoes,
+Mt. Erebus and Mt. Terror. Mt. Erebus, 12,400 feet high, is an active
+volcano. Mt. Terror, 10,990 feet high, is an extinct volcano.
+
+
+
+
+CHAPTER XV
+
+SUBMARINE VOLCANOES
+
+
+A submarine volcano is a volcano that erupts on the bed of the ocean
+with its crater covered by the waters. Many of the great volcanic
+mountains of the world began as submarine volcanoes. A crater first
+opened on the floor of the ocean, and lava escaping, was heaped up
+around the opening, until it emerged above the surface as an island.
+As we have seen, the island of Iceland is believed to have begun in
+this way. Such, too, in all probability, was the origin of Hawaii,
+Vesuvius, Etna, and Santorin.
+
+But besides the volcanic mountains that were thrown up during the
+geological past, there are others that have been called into existence
+while man has been living on the earth. We will now describe a few
+islands that have been formed in this manner by submarine volcanic
+eruptions.
+
+That volcanic eruptions, or at least something that greatly resembles
+eruptions, occur on the bed of the ocean too far below the surface to
+permit them to be directly seen from above, has been shown in a number
+of cases where the captains of vessels have reported that in certain
+parts of the ocean, jets of water, or steam, and pillars of flame have
+been seen rising to great heights from the surface of the water, and
+that in certain regions sulphurous smoke has also been seen. During
+such occurrences, the water is agitated, as if it were being violently
+boiled. Moreover, these parts of the ocean are shaken by severe
+earthquake shocks.
+
+Another evidence of submarine volcanic eruptions is to be found in
+great quantities of ashes, scoriæ, or pumice stone, that are seen
+spread out over the surface of the ocean after the commotions referred
+to in the preceding paragraph. Still another proof is that parts of
+the ocean whose waters were previously very deep are found to have
+suddenly shoaled.
+
+Of course, the best proof is the appearance of rocky reefs or small
+islands thrown up above the surface of the water, especially where
+volcanic cones appear. While in many cases the new islands thus thrown
+up are subsequently washed away by the waves, yet some have continued
+above the water.
+
+One of the most noted instances of the formation of an island by a
+submarine volcano was Sabrina, which was thrown up in 1811, in the
+Atlantic Ocean, off the shores of St. Michael in the Azores Islands.
+Sabrina had a cone that was 300 feet in height. It did not long remain
+above the waters, however, being soon washed away by the waves. It is
+interesting to note that in the same part of the ocean where Sabrina
+appeared, other islands have appeared and disappeared, at times long
+before 1811; that is, during the year 1691, as well as during 1720.
+
+Another instance of a submarine island is Graham's Island, that was
+thrown up in 1831, in the Mediterranean Sea, between the west coast
+of Sicily and the nearest part of Africa, on which ancient Carthage
+was situated. The part of the sea where the island was thrown up had
+previously a depth of 600 feet.
+
+The general appearance of Graham's Island is represented in Fig. 22.
+
+Graham's Island was formed by accumulations of loose scoria and
+cinders, together with blocks of lava and fragments of limestone. It
+reached a height of 200 feet above the water, but only remained above
+the surface for a few months, when it was washed away, leaving a
+submarine bank some twelve miles in width, that was covered by water
+of about 150 feet, but which, however, increased rapidly in depth
+towards the edge until depths of from 1,200 to 2,000 feet were reached.
+
+[Illustration: FIG. 22. GRAHAM'S ISLAND--A RECENT VOLCANIC
+ISLAND]
+
+According to Lyell, on the 28th of June, 1831, before Graham's Island
+appeared, a ship passing over this portion of the sea felt severe
+earthquake shocks. On July 10th of the same year, the captain of a
+vessel from Sicily reported that as he passed near this part of the
+Mediterranean, a column of water, 800 yards in circumference, was seen
+to rise from the sea to a height of sixty feet, and that afterwards a
+column of steam rising to a height of 1,800 feet was seen in the same
+place. On again passing the same region on July 18th, this captain
+found a small island about twelve feet in height, with a crater in
+its centre, that was throwing out volcanic materials, together with
+immense masses of vapor.
+
+The island thus formed grew rapidly, both in size and height. When
+visited at the end of July, it had attained a height of from fifty to
+ninety feet, and was three-quarters of a mile in circumference. By
+August 4th, it had reached a height of 200 feet, and was then some
+three miles in circumference. From this time, however, the island
+began to decrease in size, as the waves began to wash it away. By
+August 25th, it was only two miles in circumference. On September
+3d, it had decreased to three-fifths of a mile in circumference, and
+continued to decrease until it entirely disappeared, so that in the
+year 1832, there were, according to measurements, some 150 feet of
+water over its former site.
+
+The Mediterranean Sea between Sicily and Greece is also especially
+liable to submarine activity. New islands appear and disappear so
+frequently that in this region they are almost regarded as common
+phenomena.
+
+There are many other parts of the ocean where submarine volcanic
+eruptions are common. This is especially the case in the narrowest
+part of the Atlantic Ocean between Africa and South America. Here
+there is a region situated partly above the equator, though for the
+greater part south of the equator, frequently visited by submarine
+eruptions, that are accompanied by earthquakes, by the agitation of
+the water, by the appearance of floating masses of ashes and scoriæ,
+as well as by columns of steam or smoke. Floating masses of ashes and
+scoriæ sometimes occur so thick as to retard the progress of vessels.
+
+But what forms, perhaps, one of the best instances of a large island
+formed by submarine eruptions during historical times, is Bogosloff
+Island in Behring Sea, some forty miles west of Unalaska Island. This
+island, the position of which is seen on the accompanying map, is
+known to the Russians as Ioanna Bogoslova, or St. John the Theologian.
+It is situated in lat. 53° 58' N., long. 168° west. It is said that
+during the year 1795, some of the natives of Unalaska Island saw what
+they thought was a fog in the neighborhood of a small rock, which they
+had known for a long time to project above the sea in these waters.
+This rock was marked on some Russian chart dated 1768-69. It was seen
+by Captain Cooke, in 1778, and was named by him Ship Rock.
+
+But it was not a fog that the Unalaskans had seen in the neighborhood
+of Ship Rock; for, to their great surprise, the fog continued in sight
+although everywhere else the air was quite clear. Of course, this
+was a great mystery to the people. During the spring of 1796, one of
+them, who possessed either greater curiosity than the rest, or greater
+courage, or both, visited the rock. He returned, telling the strange
+story that all the ocean around the rock was boiling, and that the
+mist or fog was caused by the rising steam. What was taking place was
+a submarine eruption. During May, 1796, sufficient matter had been
+brought up from below to increase greatly the area of the small rock.
+
+[Illustration: FIG. 23. ALEUTIAN ISLANDS]
+
+During later years several attempts have been made to visit Bogosloff
+Island. For example, the island was visited during 1872 and 1873,
+when it was found to have increased in height to 850 feet. But no
+appearance of any volcanic crater was to be seen.
+
+During October, 1883, a great volcanic eruption occurred there.
+Considerable changes were produced in its shape, as well as in the
+depth of the surrounding water. During this eruption, clouds of steam
+completely hid the island. Great quantities of ashes obscured the
+light of the sun. After the eruption, a new island was thrown up near
+the old one, in a place where the water had previously been deep
+enough for the ready passage of ships. The new island was about half a
+mile from the old one. It was conical in form, from 500 to 800 feet in
+height, and about three-quarters of a mile in diameter.
+
+The new island was visited in 1884 by the U. S. Revenue Marine Steamer
+_Corwin_. Lieutenant Cartwell, who visited the island at this time,
+described it as follows:
+
+      "The sides of New Bogosloff rise with a gentle slope to the
+      crater. The ascent at first appears easy, but a thin layer
+      of ashes, formed into a crust by the action of rain and
+      moisture, is not strong enough to sustain a man's weight.
+      At every step my feet crushed through the outer covering
+      and I sank at first ankle-deep and later on knee-deep into
+      a soft, almost impalpable dust which arose in clouds and
+      nearly suffocated me. As the summit was reached, the heat
+      of the ashes become almost unbearable, and I was forced
+      to continue the ascent by picking my way over rocks whose
+      surfaces being exposed to the air, were somewhat cooled and
+      afforded a more secure foothold.
+
+      "On all sides of the cone there are openings through
+      which steam escaped with more or less energy. I observed
+      from some vents the steam was emitted at regular
+      intervals, while from others it issued with no perceptible
+      intermission. Around each vent there was a thick deposit of
+      sulphur, which gave off suffocating vapors."
+
+
+
+
+CHAPTER XVI
+
+DISTRIBUTION OF THE EARTH'S VOLCANOES
+
+
+Having now considered at some length the principal volcanoes of the
+earth, and endeavored to obtain some idea of the many wonders they
+exhibit, especially as regards the vast quantities of material they
+bring from the inside of the earth, as well as the great force with
+which they sometimes throw these materials out of their craters, it
+will be well to point out where such volcanoes are to be found.
+
+It may have seemed to you, when you have carefully followed what has
+been said about the earth's volcanoes, that they are to be found
+pretty nearly everywhere, at least so far as latitude is concerned;
+and in this supposition you are correct; for there are volcanoes in
+the Arctic Ocean, as in the volcanic island of Jan Mayen between
+Iceland and Spitzbergen, there are Mt. Erebus and Mt. Terror in the
+Antarctic Ocean, besides very numerous volcanoes in the Atlantic,
+Pacific, and Indian Oceans, and their shores in both the temperate and
+the torrid zones.
+
+There is, however, one thing that you have probably especially
+noticed and that is that volcanoes are seldom found at very great
+distances from the ocean, except on some of its arms or seas, such
+as the Mediterranean Sea. I do not mean by this that all the earth's
+volcanoes are either situated directly on the coast of the continents
+or on islands, since, in such a large body as the earth, a distance of
+a few hundred miles from the ocean is hardly to be regarded as being
+very far from it. But it is true that all the earth's volcanoes are
+either situated on the coasts of the continents, or on islands, and,
+moreover, they are situated to a greater or less extent along lines,
+which, as we have already pointed out, are believed to mark weak
+portions of the earth's crust that have been fissured or fractured.
+
+In order that you may have some idea of this distribution, I think it
+will be well to give you a number of interesting facts that have been
+pointed out by Dana. According to this authority, there are something
+in the neighborhood of 300 active volcanoes on the earth. Of these,
+no less than five-sixths, or 250, lie either on the borders of the
+Pacific Ocean, or on some of its many islands. Thirty-nine either
+lie within or on the borders of the Atlantic, of which thirteen are
+in Iceland, or near the Arctic Circle, three in the Canaries, seven
+in the Mediterranean Sea, six in the Lesser Antilles, and ten in
+the Atlantic Oceanic Islands. The Indian Ocean contains only a few
+active volcanoes. There are, however, a much greater number of extinct
+volcanoes, which may at any time again become active.
+
+The following is the distribution of the earth's volcanoes as given
+by Dana. As you will see, from an inspection of Fig. 24, all of the
+regions of volcanoes lie either on the borders of the continents, or
+on islands in the oceans. The districts are as follows:
+
+1. _Scattered Over the Pacific Ocean._--This district includes the
+following active volcanoes; i. e., the Hawaiian Islands, nearly in
+mid-ocean, almost directly below the Tropic of Cancer; in the west
+central parts of the South Pacific; in the New Hebrides; in the
+Friendly Islands, the Tongan or New Zealand Islands, in the Santa Cruz
+Islands, and in the Ladrones.
+
+[Illustration: FIG. 24. MAP OF THE WORLD, SHOWING LOCATION OF
+ACTIVE AND RECENTLY EXTINCT VOLCANOES]
+
+2. _On the Borders of the Pacific._--This district includes the
+volcanoes that extend from the southern part of South America
+at intervals along the Andes Mountain range. Of these there are
+thirty-two in Chile, seven or eight in Bolivia and Southern Peru;
+about twenty in the neighborhood of Quito. Further north there are
+thirty-nine in Central America, and seven in Mexico. Proceeding
+northwards through the United States, there are a number of volcanic
+mountains, generally extinct, in portions of the Sierra Nevadas
+and Cascade Ranges. Probably a number of volcanic mountains exist
+in portions of Canada lying between the northern boundaries of the
+United States and Alaska, and a number in Alaska; some twenty-one
+volcanic mountains in the Aleutian Islands; some fifteen or twenty
+in Kamtschatka; thirteen in the Kuriles; some twenty-five or thirty
+in Japan and the neighboring islands; some fifteen or twenty in the
+Philippines; several along the northern coasts of New Guinea; a number
+in New Zealand and south of Cape Horn; the volcanoes of the Deception
+Island with its hot springs, and also in the South Shetlands 62° 30' S.
+
+3. _In the Indian Ocean._--On the western border of the Indian Ocean
+there are a few volcanoes in Madagascar; in the Island of Bourbon;
+Mauritius; the Comoro Islands; and in Kerguelen Land on the south.
+There are also volcanoes on the western border of the Indian Ocean
+where the lofty peak of Kilima Ndjro, 18,000 feet, is volcanic.
+
+4. _Over the Seas that Separate the Northern and the Southern
+Continents and in their Vicinity._--This is an especially active
+region of volcanoes. For the sake of convenience the continents of the
+world are sometimes divided into three pairs or double continents;
+namely, North and South America, connected by the Isthmus of Panama;
+Europe and Africa, connected by the Isthmus of Suez; and Australia and
+Asia, completely separated by a sunken isthmus, the summits of which
+form the Sunda Island chain. In the first of these regions we have the
+very active group of the West Indies, where there are ten volcanic
+islands. In the second pair of double continents we have the volcanoes
+of the Mediterranean and Red Seas, and their borders, such as Sicily,
+Vesuvius, and other parts of Italy, Spain, Germany, the Grecian
+Archipelago, Asia Minor, and extending eastward through the Caspian,
+Mt. Ararat, Demavend, on the south shores of the Caspian, Mt. Ararat,
+and some few others along the borders of the Red Sea.
+
+In the East Indies we find the most intense centre of volcanic
+activity in the world. Here there are some 200 volcanoes of which
+there are nearly fifty in Java alone, more than half of which are
+still active. There are nearly as many volcanoes in Sumatra, and many
+in the small islands near Borneo, the Philippines, etc.
+
+5. _On the Borders of the Atlantic and Elsewhere._--It is an
+interesting fact that there are no volcanoes on the eastern borders
+of the Atlantic north of the West Indies Island chain. In the South
+Atlantic the only volcano on the borders is one of the Cameroons
+Mountains. In the Atlantic Ocean we have Iceland, the Azores, the
+Canaries, Cape Verde, Ascension, St. Helena, and Tristan d'Acunha.
+
+This curious distribution of the volcanoes of the world near the
+oceanic waters appears to be dependent rather on the very early shapes
+of the continents and the ocean beds than on their present shapes.
+
+
+
+
+CHAPTER XVII
+
+VOLCANOES OF THE GEOLOGICAL PAST
+
+
+The question is often asked whether the volcanic eruptions of the
+geological past were not much more violent and destructive than the
+volcanoes of the present time. Now, while this is a matter that
+properly belongs to the subject of geology, and will be treated at
+greater length in the Wonder Book on Geology, yet a short mention
+should be made of it here.
+
+It is the opinion of Dana that while there have been volcanoes during
+the different geological ages, yet volcanic activity has increased
+through the geological past until the age that immediately preceded
+the appearance of man on the earth. He thinks there is no reason for
+believing that there were any very great volcanic eruptions during the
+earliest geological time known as the Archæic. Dana speaks as follows
+concerning this:
+
+      "In this connection it is an instructive fact that in
+      eastern North America, at epochs when there was the
+      greatest amount of friction and crushing ... those of the
+      making of the Green Mountains and the Appalachians ... no
+      volcanoes were made, and little took place in the way of
+      eruptions through fissures."
+
+On the other hand, Prestwich seems inclined to think that the absence
+of well-marked cones of volcanic material in the rock of the older
+geological ages is not to be regarded as proof that no eruptions then
+took place, since the very great amount of erosion that occurred
+between that time and the Tertiary Age before the appearance of man,
+would, probably, have completely obliterated any cones, and even the
+volcanic materials would have undergone such changes as completely to
+alter their general character. He agrees, however, with Dana that,
+probably, the most violent and explosive volcanoes of the geological
+ages have been those of the Tertiary Age.
+
+Without, however, attempting anything more than a brief reference to
+the volcanoes of the geological past, it may be said that many of the
+more important of the active volcanoes of the earth's present time
+were begun in the Tertiary Age. Mt. Etna, Vesuvius, and Mt. Hecla are
+believed to have commenced at this time.
+
+There is an interesting region of geological volcanoes in the
+neighborhood of Auvergne in Central France. Here they occur in three
+separate groups that extend over a high granite platform from north
+to south for a distance of about 100 miles, and from twenty to eighty
+miles from east to west. The eruptions began in the earlier portions
+of the Tertiary Age, and continued down to the latter periods of
+prehistoric times. Some of these volcanic craters remain to-day almost
+as unaffected by erosion as if they had been formed but recently.
+
+Other regions of geological volcanoes are to be found in parts of
+Spain near the foot of the Pyrenees Mountains, in parts of Italy and
+Germany, as well as in regions in the Caucasus Mountains.
+
+In Asia Minor there exists a group of almost thirty extinct volcanoes
+in the neighborhood of the Gulf of Smyrna. Both Little and Great
+Ararat contain volcanic cones: that in the latter mountain was active
+during historical times. There are also extensive volcanic districts
+in the Taurus Mountains. In addition to these there are groups of
+extinct volcanoes in portions of Central Asia.
+
+Aden, on the Red Sea, is the centre of an extensive volcanic district.
+Indeed, on both shores of the Red Sea there are a few volcanoes that
+are still active, while in Sinai, and in the districts of the south,
+there are several extinct craters.
+
+But it is in the New World, especially on the Pacific coast of
+North America, that volcanic activity was especially great during
+the geological past. There is a district containing volcanic rocks
+that extends through various parts of western North America, from
+New Mexico and North California, to Oregon and British Columbia.
+This district has a width of from eighty to 200 miles, and a length
+of not quite 800 miles. This great area of nearly 150,000 square
+miles is covered with great sheets of volcanic rocks except where
+mountain ranges rise from them, or where the rivers have cut deep
+valleys through them. In portions of California and New Mexico these
+plateaus rise to heights of from 8,000 to 10,000 feet, while in parts
+of Colorado, where they form huge dome-like mountains, they reach a
+thickness of 14,000 feet. In Oregon the sheet of lava is 2,000 feet
+thick, and, indeed, in some places, is estimated to have a depth of
+7,000 feet.
+
+In the opinion of nearly all American geologists these great lava
+flows in western North America were not of the type known as crater
+eruptions, but were what are called fissure eruptions. Some of them
+are believed to have occurred during geological times as early as the
+Eocene. Prestwich, however, is of the opinion that the eruptions of
+the past in these portions of the world were not confined to fissure
+eruptions, but that crater eruptions also occurred; and that it was
+towards the close of the Tertiary Age that crater eruptions occurred
+with great lava flows. Indeed, as we have seen, in portions of Utah
+and the neighborhood the remains of true craters can be found.
+
+Besides the above there are evidences of geological volcanoes of still
+older times. In portions of Deccan, in southern Hindostan, there is an
+immense plateau formed of trap rock, that extends from east to west
+for a distance of 400 miles, and from north to south through from 700
+to 800 miles. This district, with an area of almost 200,000 square
+miles, is covered with a vast lava sheet. It was, in the opinion of
+Prestwich, from whom many of the facts of the geological volcanic
+eruptions have been obtained, probably still more extensive. The
+plateau of Deccan rises gradually from the east to the west, where, in
+some parts of the Ghauts Mountains, it reaches a height of from 4,000
+to 5,000 feet.
+
+One of the greatest of these prehistoric volcanoes of Scotland was a
+volcano in the Isle of Mull in the Hebrides. This volcano was probably
+nearly thirty miles across at its base, and was from 10,000 to 12,000
+feet high. It is now only 3,172 feet in height.
+
+According to Judd the Island of Skye in Inverness-shire is the remains
+of a volcano that was active in Tertiary times, probably many millions
+of years ago. This volcano was very large, probably about thirty miles
+across at its base, with a height of perhaps as great as 12,000 or
+15,000 feet. Now there are only left some granite and other similar
+rocks that form the Red Mountains and Coolim Hills of Skye that reach
+about 3,000 feet above the sea level.
+
+There are many other parts of the world containing volcanoes that were
+active during the geological past. The above, however, is as far as we
+can describe such volcanoes in this book.
+
+
+
+
+CHAPTER XVIII
+
+LAPLACE'S NEBULAR HYPOTHESIS
+
+
+LaPlace's nebular hypothesis is the name given to an ingenious
+hypothesis proposed by LaPlace, a celebrated French astronomer, in an
+endeavor to explain how the solar system has been evolved.
+
+You will notice that this is called a hypothesis and not a theory.
+The word hypothesis is properly applied to a more or less intelligent
+guess or assumption, that has been made for the purpose of trying
+to find out in the cause of any natural phenomenon. A theory is an
+expression of a physical truth based on natural laws and principles
+that have been independently established. A theory, therefore, is much
+more complete than a hypothesis. A hypothesis, as Silliman remarks,
+bears the same relation to a theory or law, that a scaffolding does to
+a completed building, since it forms a convenient means for erecting
+the building. LaPlace's work is properly called a hypothesis, because
+it is not to be considered as any more than a means for enabling one
+intelligently to inquire into the probable manner in which the solar
+system has reached its present condition, by gradual steps or stages
+during the almost inconceivable length of time since its creation.
+
+Before describing LaPlace's hypothesis it will be necessary to give
+you some ideas concerning what is known by astronomers as the solar
+system.
+
+The solar system consists of the sun, and the eight large bodies
+called planets that revolve around the sun. It also includes a number
+of moons or satellites revolving around the planets, a number of small
+bodies, called planetoids or asteroids, together with numerous comets
+and meteorites. Besides these there is probably a system of meteoric
+bodies that are believed to revolve around the sun, and to produce, by
+the reflection of the light from their surfaces, what is known as the
+_zodiacal light_.
+
+The principal bodies of the solar system are the planets. These
+constitute eight large bodies named in their order from the sun,
+beginning with the nearest: Mercury, Venus, Earth, Mars, Jupiter,
+Saturn, Uranus, and Neptune. The last four planets, Jupiter, Saturn,
+Uranus, and Neptune are much larger than the others, and are therefore
+known as the _major planets_ in order to distinguish them from
+Mercury, Venus, Earth, and Mars, which are called the _minor planets_.
+You can remember the order in which the last three planets come by
+their initial letter, S-aturn, U-ranus, and N-eptune, spelling the
+word SUN, around which they all revolve.
+
+It may be interesting to state here that the ancients knew of seven
+only of these planets. Since, as they asserted, there were only seven
+days in the week, and seven openings into the head; i. e., two for the
+eyes, two for the nostrils, two for the ears, and one for the mouth,
+it was natural that there should be but seven planets. During later
+years, however, an eighth planet was discovered and named Neptune. It
+would be interesting to explain to you how the position of this planet
+was reasoned out by mathematical calculations, that is, in other
+words, how, as a result of such calculations, an astronomer was told
+that if he would point his telescope to a certain part of the heavens
+he would discover a new planet. He did this and located the planet
+Neptune. However interesting this story may be it belongs properly
+to astronomy, and will be described in full in the Wonder Book of
+Astronomy.
+
+In the opinion of some astronomers it is quite probable that a ninth
+planet will be found far beyond the orbit of Neptune. There may also
+be some additional planets discovered between Mercury and the Sun.
+
+Besides the eight known planets there exist, somewhere between the
+orbits of Mars and Jupiter, many smaller planets called _asteroids_,
+or _minor planets_. A long time ago it was pointed out by Bode that
+a curious relation exists between the distances of the planets from
+the sun. This relation or law is generally known, after the name of
+the astronomer who first called attention to it, as _Bode's Law_.
+No reason has been discovered for this arrangement of the planets,
+so that Bode's Law may be regarded as empirical. It may, however,
+be mentioned here that the distances of all the planets from the
+sun agrees with the law very closely, with the single exception of
+Neptune, which is quite at variance with the law.
+
+It was noticed at an early date, that a gap existed between Mars
+and Jupiter, so that astronomers began to believe that there was
+probably a missing planet in that space, and this belief was greatly
+strengthened when Neptune was discovered in 1781. Without going any
+further into this story in this book, it may be said that it is the
+general opinion of astronomers that the planetoids or asteroids were
+formed possibly from the fragments of the missing planet, or, more
+probably, from the breaking up of some of the outer rings on the
+planet Mars.
+
+The distances of the planets from the central sun vary from the
+nearest planet, Mercury, which is about 36,000,000 miles from the sun,
+to the furthest, or Neptune, which is 2,766,000,000 miles from the sun.
+
+All the major planets have a single moon, or more, revolving around
+them. For example, Jupiter has four moons; Uranus, six; Saturn, eight;
+Neptune, one. As to the minor planets, Mars has two moons; and, as far
+as is known, neither Mercury or Venus has a moon. Our earth has one
+moon, but, as we shall afterwards see, this is not to be regarded as
+a moon or satellite of the earth, but rather as a twin planet to the
+earth.
+
+LaPlace's nebular hypothesis was proposed by LaPlace during the year
+1796. While there are many objections that can be brought against
+it, since it fails to account for all of the phenomena of the solar
+system, yet it is a significant fact now, in the year 1907, nearly a
+century and a quarter after the hypothesis was first announced, that
+although modified in many respects, there has not been any hypothesis
+proposed to entirely replace it.
+
+While the nebular hypothesis of LaPlace is necessarily a matter that
+belongs to astronomy, yet it will be advisable to consider it here,
+since it explains the source of the original heat of both the earth
+and the moon, which we believe is the true cause of volcanoes.
+
+In his nebular hypothesis, LaPlace assumes that all the materials of
+which the solar system is formed, were originally scattered throughout
+space in the shape of an exceedingly rare form of matter known as
+nebulous matter. He points out that if it be granted that this medium
+began to accumulate around a common centre, so as to form a huge globe
+or sphere, and if a motion of rotation on its axis from west to east
+were given to this sphere that, on strictly mechanical principles, a
+system of heavenly bodies corresponding to the solar system might have
+been evolved. Let us, therefore, try to understand how this might have
+been brought about.
+
+The nebulous matter that LaPlace assumed originally constituted all
+the matter in the solar system, was highly heated gaseous matter. In
+other words, it consisted of ordinary matter raised to a very high
+temperature; LaPlace thought at a temperature very much hotter than
+that of the sun.
+
+As this great mass of matter commenced to cool, it began to collect
+around a centre and slowly rotate. Its contraction or shrinkage, while
+cooling, must have caused an increase in the speed with which it spun
+around or rotated on its axis. At first it spun but sluggishly, but as
+it cooled and began to shrink this rate of rotation began slowly to
+increase.
+
+Now you must bear in mind that the huge rotating mass, as imagined
+by LaPlace, was very many times larger than the size of our present
+sun. Indeed, instead of having a diameter of only 866,500 miles, its
+temperature was so high that the nebulous matter of which it was
+composed had expanded it so much that it extended far beyond the orbit
+of Neptune, or had a diameter twice as great as 2,766,000,000 miles.
+
+As the huge mass continued to shrink or contract, its rotation
+began to gradually increase until at last its centrifugal force was
+sufficiently great to cause it to bulge out at the equator, so as
+at last to separate a ring of gaseous matter. This ring was left
+behind by the sun, as it continued cooling, and formed the first
+planet that was born into the solar system. The ring might have
+continued to revolve around the sun for a time, and would, of course,
+revolve in the same direction as that in which the sun was rotating,
+that is, from west to east. Eventually, however, it broke up into
+smaller fragments, that afterwards collected in a single body, and,
+assuming a globe-like shape of the planet, formed the planet Neptune.
+Necessarily, too, the planet so formed not only would revolve in its
+orbit from west to east in the same direction in which the sun was
+revolving on its axis, but would also rotate or spin on its axis in
+the same direction.
+
+After, in this way, throwing off the first planet, the central sun
+continued to cool and grow smaller, until the increase in the rate
+of its rotation was again such as to permit its centrifugal force to
+form a second ring around its equator, which being left as the sun
+continued to contract, gave rise to another planet, or to Uranus, and
+so on until the four major planets and the four minor planets were
+born.
+
+According to this hypothesis, the planet that was first born was the
+planet that is farthest from the sun, that is, Neptune, and the planet
+last born must have been the nearest planet, Mercury.
+
+But while all this planet forming was going on, the separate planets
+also continued to shrink, and, therefore, began to rotate more rapidly
+on their axes. Under the influence of the centrifugal force, ring-like
+masses began to form around their equators, and these masses left by
+the planet constituted their moons or satellites. As you can see,
+according to this hypothesis, just as the planets would all revolve in
+their orbits from west to east, and rotate on their axes in the same
+direction as the sun, so, too, the moons or satellites of the planets
+would also rotate on their axes, from east to west, and revolve in
+their orbits in the same direction.
+
+In order to show the extent to which LaPlace's nebular hypothesis
+explains the peculiarities of the solar system, we must inquire what
+are the most important of these peculiarities. We will take these from
+Young's general book on Astronomy, from which most of the facts in
+this chapter have been condensed. They are as follows:
+
+The orbits of nearly all the planets and their satellites are nearly
+circular; they are all in the same plane; and all revolve in the same
+direction. They are, moreover, with the single exception of Neptune,
+arranged at distances from the sun in accordance with Bode's Law.
+
+All the planets increase in both directions, towards and from the sun,
+in density from Saturn, the least dense.
+
+All the planets, with the exception probably of Uranus, rotate in a
+plane that is nearly the same as the plane of the orbit in which they
+revolve. Moreover, with the exception of probably both Uranus and
+Neptune, all the planets rotate in the same direction as that in which
+they revolve.
+
+The satellites revolve in orbits whose planes nearly coincide with the
+plane of the planets' rotation, while the direction of the revolution
+of the satellites is the same as that in which their planets revolve.
+
+Finally, the largest planets rotate most swiftly.
+
+Now, LaPlace's nebular hypothesis explains nearly all of the above
+facts. The following modifications of the hypothesis, however, are
+necessary. Let us briefly examine some of these modifications.
+
+In the first place it can be shown that the original nebulous mass
+instead of being at a higher temperature than that of the sun was
+probably at a much lower temperature, since the condensation of
+the gaseous matter must have increased the temperature. Instead,
+therefore, of the original nebulous mass being purely gaseous it was,
+as Young expressed it: "Rather a cloud of ice cold meteoric dust than
+an incandescent gas or a fire mist." Or in other words, the original
+nebulous mass from which the solar system was evolved, consisted of
+finely divided particles of solid or liquid matter surrounded by an
+envelope of permanent gaseous matter.
+
+A doubt, too, has been raised as regards the manner in which the
+planets were liberated from the central sun. Instead of separating in
+the form of a regular ring, it has been thought that probably in most
+cases this separation assumed the shape of a lump. It might, however,
+have occurred at times in the ring-like form as may be seen in the
+case of the planet Saturn.
+
+Again, instead of the outer rings being separated first, and the
+others in regular order, so that the outer planets are much the older,
+it would seem possible, or, as Young states, even probable, that
+several of the planets may be of the same or nearly the same age, as
+they would be if more than one ring had been separated at one time,
+or, indeed, several planets may have been formed from different zones
+of a single ring.
+
+As you will see, LaPlace's nebular hypothesis assumes that both
+sun and moon were in a highly heated condition when they were
+separated from the nebulous sun, so that we can understand that the
+former molten condition of their interiors was due to the heat they
+originally possessed.
+
+
+
+
+CHAPTER XIX
+
+THE EARTH'S HEATED INTERIOR, THE CAUSE OF VOLCANOES
+
+
+As we have already seen, the nebular hypothesis of LaPlace would seem
+to make it more than probable that the earth was originally in a
+highly heated condition, and only reached its present state after long
+cooling. While this cooling has gone on for probably millions upon
+millions of years both before and during the geological past, yet in
+the opinion of perhaps the best geologists the interior of the earth
+is still very hot, only the outer portions or crust having hardened by
+loss of heat.
+
+That there is a very hot region somewhere inside the earth is evident,
+since from some place or places below the surface there come out
+the immense streams of lava that, continuing to flow at irregular
+intervals, have at last built up such great masses of land as the
+island of Hawaii, the still greater island of Iceland, the even
+greater lava fields of the western United States, and the great
+plateau of the Deccan in southern Hindustan.
+
+It certainly must have required a great quantity of lava to build up
+an island like Hawaii with its area of fully 40,000 square miles, for
+the highest point on the summit of Mt. Kea reaches 13,805 feet above
+the level of the sea, and, moreover, stands on the bed of the Pacific
+Ocean in water fully 12,000 feet deep.
+
+But Iceland is only one of many similar cases. Volcanoes are to
+be found in practically all parts of the earth, not only in the
+equatorial regions, where they are especially numerous, but also in
+the frigid and temperate zones. We must also remember the immense lava
+streams that are known to have come from the interior during the great
+fissure eruptions of the geological past. When all these facts are
+taken into consideration, it would certainly seem that there is only
+one source sufficiently great to supply this wonderful demand, and
+that is the entire inside of the earth.
+
+But entirely apart from volcanic phenomena there are other proofs that
+the entire interior of the earth is in a highly heated condition. The
+differences of temperature caused by the sun during day and night
+do not affect the earth much below a depth of three feet, while the
+differences of temperature between summer and winter do not extend
+much further below the surface than forty feet. Below these depths, in
+all parts of the earth, the temperature of the crust rises at a rate,
+which, although not uniform, yet is not far from an increase of one
+degree of the Fahrenheit thermometer scale for every fifty or sixty
+feet of descent.
+
+If the above rate of increase continues uniform the temperature of
+the crust would be sufficiently hot to boil water at a distance of
+about 8,000 feet below the surface, while at a depth of about thirty
+miles the temperature would be sufficiently high to melt all known
+substances at ordinary conditions of atmospheric pressure; that is, to
+melt all known substances if they were subjected to such a temperature
+at the level of the sea.
+
+In considering the above we must not lose sight of the fact that this
+increase in temperature with descent below the surface of the earth's
+crust occurs, not only in places where there are volcanoes, but over
+all parts of the earth, thus seeming to point out that there is
+something hot below the surface which fills the entire inside of the
+earth.
+
+It is true the greatest distance to which man has actually gone down
+through the earth's crust is but a few miles. We do not, therefore,
+know by actual experience that the interior is anywhere in a fused
+condition, yet the escape of lava or molten rocks in all latitudes,
+and in the enormous quantities referred to above, seems to show that
+the entire inside of the earth is at a temperature sufficiently high
+to melt all known substances under ordinary conditions.
+
+It may be interesting in this connection to examine some of the proofs
+of this increase in temperature with descent below the surface. The
+following figures are given by Dana:
+
+Borings to great depths have been made in various parts of the earth,
+both for artesian wells as well as for the shafts of mines. After
+passing the line of invariable temperature, the rate of increase for a
+total distance of 4,000 feet below the surface is in the neighborhood
+of from one degree for fifty-five to sixty feet, or an average of
+fifty-seven and a half feet for each degree of heat. In the case of
+the deep artesian well bored at Grenelle, Paris, where a temperature
+of eighty-five degrees Fahrenheit was reached at a distance of 2,000
+feet, the rate of increase was somewhat more rapid, being one degree
+Fahrenheit for every sixty feet.
+
+In a deep well bored in a salt mine at Neusalzwerk, Prussia, a depth
+of 2,200 feet showed a temperature of ninety-one degrees Fahrenheit at
+the bottom. This was at the rate of one degree for every fifty feet of
+descent. At Schladenbach, in Prussia, a well has been dug to the depth
+of 5,735 feet with a temperature of 134° F. A boring at Wheeling, in
+West Virginia, reached a depth of 4,500 feet, 3,700 feet below the
+level of the sea. Here the rate of increase of temperature in the
+upper half was one degree Fahrenheit for every eighty feet, and in
+the lower half of one degree for every sixty feet.
+
+It must not be supposed because the rate of increase of temperature is
+not uniform that the argument of a highly heated interior is weakened.
+On the contrary, it would be very surprising if the rate continued
+uniform; for it is evident that the conducting power of different
+materials in the earth's crust for heat must necessarily make a great
+difference in the rate at which heat should increase, as we go farther
+down into the earth. This is so important a matter that I will explain
+it at somewhat greater length.
+
+Let us suppose that instead of the highly heated interior of the
+earth, we consider the simple case of a hot stove, the doors or other
+openings into which are closed so that it is impossible to see the
+red hot coals inside. Now, suppose holes were bored in the sides of
+this stove not deep enough to reach the red hot mass within, and that
+tightly fitting rods or plugs all of the same length and thickness,
+but of different kinds of materials such as wood, earthenware, glass,
+iron, copper, silver, and gold, etc., were so placed in the holes as
+to tightly fit them. Now, under these circumstances the end of all
+the plugs would be at the same distance from the heated inside. They
+would not, however, by any means show the same temperatures, the
+metallic rods would be too hot to touch, while the end of the piece
+of wood would hardly be hot enough to burn the hand when held against
+it. The piece of glass and earthenware though less cool would be much
+less hot than the different rods of metals. Their temperatures would
+be necessarily affected by their conducting power for heat. The wood,
+the glass, and the earthenware being poorer conductors than the metals
+would show much lower temperatures.
+
+Now, the same thing is true with the different materials that
+constitute the rocks of the earth's crust. Some of these are much
+better conductors of heat than others, so that the rate of increase of
+temperature with descent below the surface must necessarily vary with
+the kind of materials that form the crust of different parts of the
+earth.
+
+You may, therefore, safely conclude that the entire interior of the
+earth is in a highly heated condition, and that the source of this
+heat is to be traced to the heat the earth originally possessed when,
+in accordance to the nebular hypothesis of LaPlace, it was separated
+from the sun which gave birth to it, that the present crust of the
+earth has been formed on the outside by the loss of a portion of this
+heat.
+
+The rapidity with which a body cools, depends, among other things,
+on the difference between its temperature and that of the medium in
+which it is placed. The greater this difference of temperature the
+greater the rapidity of cooling. Careful measurements made by Tait,
+the English physicist, show that our earth loses every year from each
+square foot of surface, an amount of heat that would be able to raise
+the temperature of one pound of water from the melting point of ice to
+the boiling point of water, or from 32° F. to 212° F. The rate of loss
+of heat, must, therefore, have been much greater when the earth was
+more highly heated than it is now, and will be much smaller than now
+many years from the present.
+
+Now, let us suppose, what nearly everyone acknowledges to be true,
+that the earth was originally so hot as to be a molten globe, and that
+while in this molten condition, it began to revolve or move around the
+sun. Since the empty space through which the earth moves is very cold,
+something in the neighborhood of 45° below the zero of the Fahrenheit
+thermometer scale, the loss of heat would take place very rapidly and
+a thin crust of hardened materials would be formed on the outside. Now
+all the time the earth is cooling, it is shrinking or growing smaller.
+
+A very little thought will convince you that this cooling or shrinkage
+could not go on uninterruptedly; for, while the earth was cooling it
+was contracting, or growing smaller, and in this way a great pressure,
+or as it is generally called in science, a great stress was being
+produced. Every now and then this stress became so great that the
+crust of the earth was fractured or broken.
+
+At first these fractures would not require a very great amount of
+stress or force, since the crust of lava was then very thin. After
+great periods of time, however, the crust grew thicker and thicker,
+and the amount of force required to break it continually increased, so
+that the fractures of the crust produced a greater disturbance.
+
+Whenever the earth's crust was fractured in this way the earth was
+shaken by what are called earthquakes, while a part of the molten
+interior would run out or escape, making volcanoes. In the very early
+times neither the earthquakes or the volcanoes were as energetic as
+they were at later periods when the thickness of the earth's crust
+increased.
+
+Now, having as we believe correctly come to the conclusion that the
+entire interior of the earth is in a highly heated condition, the
+next question that arises is as to the present condition of this
+interior. A long time ago it was believed that the interior of the
+earth is still melted, and that a cooled portion or crust surrounds
+a great molten mass that fills all the inside; that it is this mass
+which supplies the immense quantities of molten rock or lava that
+escape through the craters of volcanoes or through the fissures in
+the crust. Without going into this question thoroughly, since it is a
+very difficult question to understand, it will be sufficient to say
+that there are many reasons why it is impossible to believe that the
+interior is still melted.
+
+You will understand that if the interior of the earth were melted like
+a huge central sea of fire that each volcano would necessarily affect
+all the others. Now, as we have seen, this is never the case, so that
+this is one reason we cannot believe in the existence of a melted
+interior.
+
+Another reason we cannot believe in a molten interior is an
+astronomical consideration. It can be shown that under the attraction
+of the sun and moon the earth could not possibly behave as it does
+if it were still liquid in the interior. That, on the contrary, the
+behavior of the earth to the attraction of the sun and moon is such as
+to make it necessary for us to believe that it is as rigid throughout
+as would be a globe of steel of the same size.
+
+I can easily understand that you find it very difficult to see how it
+can be believed that the interior of the earth is solid and yet at the
+same time be sufficiently hot to melt. I can imagine hearing you ask
+if it is hot enough in the inside to melt any known materials, why it
+is not melted. The reason, however, is very simple when you come to
+think it over. For a solid to fuse or become melted, it is not only
+necessary for it to be heated to a temperature which is different for
+different substances, but that at the same time it is heated it shall
+have plenty of room in which to expand or grow bigger. In other words,
+the temperature required to fuse any substance increases very rapidly
+with the pressure to which that substance is exposed.
+
+Now, try to think of the pressure to which the materials that fill
+the inside of the earth are subjected at great distances below the
+surface. This pressure is enormous, not only by reason of the weight
+of the many miles of rocks that are pressing down, but also by reason
+of the enormous stress or pressure caused by contraction or shrinkage.
+When we say that the interior of the earth is hot enough to melt all
+known substances we mean hot enough to melt them if they could be
+brought from great depths to the level of the sea, but not hot enough
+to melt them when subjected to the great pressure that exists in
+regions far below the surface of the earth.
+
+Briefly, the condition of things is believed to be as follows: The
+entire interior is filled with rock hot enough to melt at the level
+of the sea, but under too great pressure to melt. If this be granted,
+as it is by perhaps the greatest number of men who are competent to
+judge, the phenomena of earthquakes can be readily explained, as can,
+indeed, the phenomena of those great movements whereby great changes
+of level take place in different parts of the earth.
+
+Now let us see how volcanoes can be explained on the assumption that
+the interior of the earth is hot enough to melt, but remains solid
+only because there is no room for the heated mass to expand in. Such
+a heated interior as we have imagined, must be constantly losing its
+heat and, therefore, shrinking. Every now and then this shrinkage must
+produce great fissures or cracks in the solid crust of the earth.
+Now should such cracks or fissures extend downwards to the heated
+interior, there must result a decrease in the pressure. The rocks
+would, therefore, begin to expand and would be forced by the great
+pressure to rise slowly in such cracks or fissures. The further they
+rise the greater the relief of pressure, until they at last assume a
+molten condition in which they are forced out through the craters of
+volcanoes as molten rocks or lava.
+
+But it is not only volcanoes that seem to indicate a highly heated
+plastic condition as existing in the earth's interior. As geologists
+well know, there are to be found in the various strata of the earth
+places where great fissures have been made at various times during the
+geological past. These fissures vary in width from a few inches to
+many hundreds of feet, and are frequently scores of miles in length.
+Lava either flows out of them, and covers adjoining sections of the
+country, or simply rises in them and, afterwards cooling, forms dikes.
+In many instances, however, the lava is forced in between more or less
+horizontal layers and in some cases has caused these layers to assume
+the shape of what geologists know as _subtruderant mountains_. Some
+of the eastern ranges of the Rocky Mountains have been formed in this
+manner.
+
+We can, therefore, picture to ourselves the following as the manner
+of formation of an ordinary volcano. A fissure is first formed in the
+solid crust of the earth, extending downwards to the regions of great
+heat. There is thus produced a relief of pressure, so that at this
+point the highly heated rocks begin to be slowly forced up through the
+fissure. As they rise higher and higher they become less solid and
+finally expand into fused masses that can flow out of the crater or
+opening in the earth's surface. In this way a volcano is started.
+
+But for this volcano to continue in eruption, it is necessary that
+the conditions shall continue that force the molten rock upwards from
+great depths. It is not enough for the lava to fill the crevice that
+exists upwards to the surface, it must continue to be forced upwards
+until it escapes. If it is permitted to remain in the fissure for any
+time, it hardens, and only great dikes are formed. It would seem,
+therefore, that some other force must be called into action to keep
+the fissure open or, in other words, to prevent the chilling of the
+lava. Now, this force is generally believed to be the expansive force
+of steam or the vapor of water.
+
+As Dana points out, by far the greater part of the vapor which escapes
+from the craters of volcanoes consists of steam or the vapor of water.
+Indeed, it can be shown that for every hundred parts of different
+vapors, at least ninety-nine of such parts consist of water vapor. It
+is for the greater part, to the pressure of steam or water vapor that
+the escape of lava from the tube near the top of the crater is due.
+
+Of course, the question arises as to where the water comes from that
+produces this steam. There are three possible sources. From the rains;
+from leakage at the bed of the ocean; and from vapors existing at
+great depths below the surface.
+
+It is not probable that either rain water, or water from the ocean,
+penetrates through the earth's crust for distances much greater than a
+few thousand feet. It is, however, very well known that in all parts
+of the earth, except in desert regions, whether they are near or far
+from the ocean, the rocks are always found fully charged with water.
+When, therefore, the slowly rising lava passes through the moist rocks
+that everywhere form the crust of the earth, there must be formed in
+them great quantities of steam under very high pressure. Moreover,
+many substances, especially those forming lava, possess the power of
+absorbing large quantities of steam and other gases. Therefore, as
+the molten material reaches the moist rocks in the earth's crust, it
+becomes highly charged with steam, and as the lava rises towards the
+surface this steam expands.
+
+Where the lava is in a very fluid condition the steam quietly escapes,
+as does the steam from the surface of boiling water. But where the
+lava is viscous, like tar or pitch, great bubbles are formed, which,
+on their explosion, throw the lava upwards for great distances into
+the air.
+
+We can, therefore, account in this manner for both the non-explosive
+as well as the explosive type of volcanoes.
+
+It must not be supposed, however, that it is the explosive power of
+steam which is the principal cause of the lava rising upwards from
+great depths. This is caused by the great pressure or stress set up
+by the contraction of a cooling crust. The pressure of this steam is
+added to this pressure which keeps the lava flowing upwards from great
+depths below.
+
+The objection has sometimes been urged that it is impossible to
+believe the lava comes from a highly heated interior, because, as is
+well known, lavas are of different types even when coming from the
+same volcano at different times of eruption. While such an objection
+would have weight were it believed that the interior of the earth is
+still in a molten condition, it loses its weight when one believes
+that the interior is solid. It must, however, be acknowledged that
+the largest part of the interior of the earth would probably have the
+same chemical composition if it had ever been in a completely melted
+condition throughout.
+
+I do not doubt you have already concluded that the reason the earth's
+volcanoes are practically limited to the borders of continents,
+or to the shores of islands, is the leakage of the ocean waters
+into the crust at these parts. This was at one time believed by
+most geologists. That sea water has much to do with such volcanoes
+as Vesuvius there is no doubt, but it is now generally recognized
+that it is not so much the present outlines of the earth, or the
+present arrangement of its land and water areas, that determines the
+distribution of the world's volcanoes. It is rather believed that the
+location of the lines of fractures along which the earth's volcanoes
+are found were determined by conditions that occurred long before the
+earth assumed its present outlines.
+
+But there is another explanation that has been suggested as regards
+the condition of the interior of the earth. Judd refers to this
+explanation as follows:
+
+      "Some physicists have asserted that a globe of liquid
+      matter radiating its heat into space, would tend to
+      solidify both at the surface and the centre at the
+      same time. The consequence of this action would be the
+      production of a sphere with a solid external shell and a
+      solid central nucleus, but with an interposed layer in a
+      fluid or semi-fluid condition. It has been pointed out that
+      if we suppose the solidification to have gone so far as
+      to have caused the partial union of the interior nucleus
+      and the external shell, we may conceive a condition of
+      things in which the stability and rigidity is sufficient to
+      satisfy both geologists and astronomers, but that in still
+      unsolidified pockets or reservoirs, filled with liquefied
+      rock, between the nucleus and the shell, we should have
+      a competent cause for the production of the volcanic
+      phenomena of the globe. In this hypothesis, however, it is
+      assumed that the cooling at the centre and the surface of
+      the globe would go on at such rate that the reservoirs of
+      liquid material would be left at a moderate depth from the
+      surface, so that easy communication could be opened between
+      them and volcanic vents."
+
+I must caution you, however, not to think that the above theory of
+volcanoes is accepted by all scientific men. On the contrary, there
+are many who believe that the earth is solid throughout because it
+has completely lost its original heat; that it is only comparatively
+small areas that are to be found filled with molten or at least highly
+heated material. But these opinions are held largely by those who have
+given their attention almost entirely to the phenomena of earthquakes,
+or who base their reasonings on mathematical grounds only and have not
+sufficiently considered the phenomena of volcanoes. Since, however,
+they can be better understood after we have explained the phenomena of
+earthquakes, we will defer their discussion to the last chapters of
+this book.
+
+
+
+
+CHAPTER XX
+
+SOME FORMS OF LAVA
+
+
+In describing the wonders of volcanoes, we must not fail to say
+something of the many remarkable forms that lava is capable of
+assuming.
+
+All volcanic lavas contain large quantities of an acid substance known
+as _silica_, or what is known better as _quartz sand_. This material
+exists in lava combined chemically with various substances called
+bases, the principal of which are alumina, magnesia, lime, iron,
+potash, and soda.
+
+Although there are many kinds of lava, yet all lavas can be arranged
+under three great classes according to the quantity of silica they
+contain.
+
+_Acid lavas_ are those in which the quantity of silica is greatest.
+In these lavas the silica, which varies from 66 to 80%, is combined
+with small quantities of lime or magnesia, and comparatively large
+quantities of potash or soda. Some of the most important varieties of
+acid lavas are known as _trachytes_, _andesites_, _rhyolites_, and
+_obsidians_.
+
+_Basic lavas_ are those containing from 45 to 55% of silica. They
+are rich in lime and magnesia, but poor in soda or potash. Some of
+the most important of basic lavas are the _dolerites_ and _basalts_.
+Generally speaking, basic lavas are of a darker color than acid lavas,
+and fuse at much lower temperatures.
+
+_Intermediate lavas_ are those containing silica in the proportion of
+from 55 to 66%.
+
+While the temperature of liquid lava has not been very accurately
+determined, yet, since we know that molten lava is able to melt silver
+or copper, its temperature must be somewhere between 2,500° F. and
+3,000° F., the melting point varying with the chemical composition.
+
+According to Dana lavas can be divided into the following classes
+according to their fusibility; i. e., _lavas of easy fusibility_, such
+as _basalts_; these lavas fuse at about 2,250° F.; _lavas of medium
+fusibility_, including andesites; these lavas fuse at about 2,520° F.;
+_lavas of difficult fusibility_, such as trachytes; these lavas fuse
+at about 2,700° F.
+
+But what is, perhaps, most curious about lavas is that when the
+surface of a freshly broken piece of cold lava is carefully examined,
+it is found to contain a number of small crystals of such mineral
+substances as quartz, feldspar, hornblende, mica, magnetite, etc.
+
+The best way to study the different forms of lava crystals is to
+prepare a thin transparent slice of hardened lava and then examine it
+with a good magnifying glass. It will be found that the slice consists
+of a mass of a glass-like material through which the crystals are
+irregularly distributed, not unlike the raisins and currants in a
+slice of not over rich plumcake.
+
+When examined by a more powerful glass, such as a microscope, cloudy
+patches can be seen distributed irregularly through the glass-like
+mass. When these patches are examined by a higher power of the
+microscope they are seen to consist of small solid particles of
+definite forms known as _microliths_ and _crystallites_. It has been
+shown by a careful study of these minute objects that they form the
+exceedingly small particles of which crystals are built up.
+
+If we fuse a small quantity of lava and then let it slowly cool, the
+glassy mass will be found to contain numerous crystallites. On the
+other hand, when fused lava is permitted to cool quickly, it takes on
+the form of a black, glass-like mass known as _obsidian_ or _volcanic_
+glass, a very common form of lava in some parts of the world.
+
+In some lavas there are found larger crystals that appear to have been
+separated from the glassy mass, under the great pressure that exists
+in the subterranean reservoirs at great depths below the volcanic
+crater, and then floated to the surface surrounded by the glass-like
+material. Now when we examine these crystals with a higher power of
+the microscope, we frequently find in them minute cavities containing
+a small quantity of liquid and a bubble of gas, thus causing them to
+resemble small spirit levels. The liquid in such cavities has been
+examined chemically and in most cases has been found to consist of
+water containing several salts in solution. Sometimes, however, the
+liquid consists of liquefied carbonic acid gas. These wonderful things
+will be discussed at greater length in the Wonder Book of Light.
+
+When the mass of molten rock or lava that comes out of the crater
+of a volcano is thrown upwards in the air the condition it assumes
+by the time it falls back again to the earth depends on the height
+it reaches. If this height is great the lava chills or hardens
+before reaching the earth, and assumes various forms according to
+the size of the fragments. The largest of these fragments are called
+_cinders_; the finer particles _volcanic dust_; while most of those
+of intermediate particles are known among other things as _volcanic
+ashes_.
+
+We have already seen that when an explosive volcanic eruption occurs
+there is suddenly thrown out of the crater of the volcano a huge
+column of various substances that rises sometimes as high as 30,000
+feet or even more. The smaller fragments of lava are quickly cooled
+and form volcanic ashes, sand, cinders, or dust. These are rapidly
+spread out by the wind in the form of a black cloud, that not only
+covers the mountain but reaches out over the surrounding country,
+completely shutting off the light of the sun. From this cloud
+particles of red hot ashes, cinders, sand, etc., begin to fall, the
+largest particles near the crater of the volcano, and the smaller
+particles at much greater distances. In very powerful explosive
+volcanic eruptions such as Krakatoa, the finer dust may be carried to
+practically all parts of the world.
+
+Volcanic ashes consist of a fine, light, gray powder. These particles
+take the name ashes from their resemblance to the ashes left after the
+burning of pieces of wood or coal in an open fire. The name, however,
+as Geicke points out, is unfortunate, since it is apt to lead one to
+suppose that volcanic ashes consist of some burned material. Such an
+idea is erroneous, however, since ashes do not consist of anything
+that is left after burning, but merely of fine particles of molten
+rock that have hardened by cooling. When in the shape of what is known
+as volcanic dust these particles are so exceedingly small that they
+can readily make their way through the smallest openings in a closed
+room just as does the finest dust in the rooms of our houses when
+they are shut up. There are cases on record where people have been
+suffocated by the entrance of volcanic dust in closed rooms to which
+they have fled for safety during volcanic eruptions.
+
+_Volcanic sand_ consists of the coarser particles of chilled lava that
+are partly round and partly angular. They are of various sizes up to
+that of an ordinary pea. Volcanic sand is formed by the breaking up of
+the lava by the explosion of the vapors as they escape from the lava
+on relief from pressure. Volcanic dust when examined by the microscope
+is found to consist of very small particles that are more or less
+crystalline.
+
+But besides the above there are larger fragments known as _lapilli_,
+consisting of rounded or angular bits of lava varying in size from
+that of a pea to an ordinary black walnut. These sometimes consist of
+solid fragments, but are usually porous, sometimes so much so that
+they readily float on water.
+
+A curious form sometimes assumed by lava consists of what are called
+_volcanic bombs_. These are formed during explosive eruptions,
+when masses of liquid lava are hurled high up into the air. During
+their flight they take on a rotary motion, which tends to make them
+globular, so that cooling, while still revolving, they assume the
+form of a more or less spherical mass. At times, however, they are
+still sufficiently soft when they strike the earth to be flattened out
+in the form of flat cakes. When of a spherical form these are very
+properly called volcanic bombs.
+
+That volcanic bombs have actually been subjected to a spinning motion
+while in the air can sometimes be shown by the fact that masses of
+scoriæ are frequently found in the interior with air cells largest at
+the centre of the bomb.
+
+Volcanic bombs are sometimes thrown from the crater to great
+distances. During one of its recent eruptions, Cotopaxi threw out
+bombs that fell at a distance of nine miles from the crater.
+
+According to Dana another form of lava bombs is sometimes found on the
+slopes of the active volcanoes of Hawaii, where masses of lava acquire
+a ball-like shape while rolling down an inclination.
+
+What are sometimes called volcanic bombs, but which are more properly
+_volcanic vesicles_, are produced by small fragments of lava which
+are thrown up in the air for only a moderate height and, on cooling,
+assume pear-like forms. Fig. 25 represents the appearance of volcanic
+vesicles. The direction in which these vesicles moved through the air
+while in a molten state is indicated by their shape, the blunt end
+being the end towards which the particles were projected.
+
+[Illustration: FIG. 25. VOLCANIC VESICLES _From Dana's Manual
+of Geology_]
+
+But by far the greater portion of the hardened lava; i. e., the
+coarser, heavier particles, fall back on the mountain, and collecting
+around the crater build up volcanic cones, as already described in the
+case of mountains of the Vesuvian type.
+
+There are two different ways in which the melted lava is broken up
+into fine particles when it is thrown upwards from the crater of the
+volcano. Nearly all lava contains large quantities of steam that are
+shut up, or occluded in the mass, being prevented from escaping by
+reason of the pressure to which the lava is subjected. The lava is
+released from this pressure as it is thrown out of the crater. The
+steam or gases escape explosively and thus break the lava into fine
+liquid spray, which rapidly hardens.
+
+There is another way in which small particles of lava are formed.
+Sometimes large pieces of hardened lava are shot upwards into the air
+with a velocity as great as that with which a heavy projectile leaves
+the muzzle of a large gun. These heavy particles striking against
+one another, either while rising or falling, are broken into smaller
+fragments. Sometimes, indeed, these fragments fall back again into
+the crater from which they are again violently thrown out, and are
+again broken into smaller fragments either while rising or falling.
+
+You will, probably, remember several instances of volcanic eruptions
+where masses of rock were thrown violently up into the air out of
+the crater. These larger masses are known as _volcanic blocks_. They
+probably consist of masses of hardened lava that have collected in
+the tube of the volcano during some of its periods of inactivity.
+Sometimes, however, they consist of fragments of rocks that are not
+of volcanic origin. Cases are on record where volcanic blocks have
+been thrown out of the craters in so great quantities as to cover the
+surface of many square miles of land with fragments hundreds of feet
+deep.
+
+There is sometimes formed on the surface of a pool of lava as it
+collects in the craters of such volcanoes as Mt. Loa or Kilauea, when
+the volcanoes are not in eruption, a material resembling froth or
+scum. The same thing sometimes occurs on the surface of some kinds
+of lava as it runs down the side of the mountain. In this way a very
+light variety of highly cellular lava known as _pumice stone_ is
+produced. The action which thus takes place is not unlike that which
+occurs during the raising of a lot of the dough from which bread is
+made, where the carbonic acid gas which is formed during the raising
+of the dough expands, and produces the well-known open cellular
+structure of well-raised bread. In the case of pumice stone, however,
+this raising goes on to such an extent that the mass consists often of
+less than 2% of solid matter, the remainder being a tangled mass of
+air.
+
+[Illustration: THE LAVA FLOW OF THE CRATER OF KILAUEA, HAWAIIAN
+ISLANDS _From a Stereograph, Copyright, by Underwood & Underwood_]
+
+Fragments of lava that possess a cellular structure form what are
+known as _scoriæ_. The lightest of all kinds of scoriæ is what is
+known as _thread-lace scoriæ_. Here the thin walls consist of mere
+threads. Figs. 26 and 27 represent the appearance of thread-lace
+scoriæ from Kilauea. The separate threads are very fine, being only
+from one-thirtieth to one-fortieth of an inch in thickness. As can be
+seen, this form of scoriæ have six-sided or hexagonal shapes. You can
+form some idea of the great lightness of such scoriæ when you learn
+that they contain only 1.7% of rocky material. Indeed, they contain
+so little solid material that a layer of volcanic glass only one inch
+thick, if blown out into scoriæ, would be able to produce a layer
+sixty inches thick.
+
+[Illustration: FIG. 26. THREAD-LACE SCORIÆ FROM KILAUEA _From
+Dana's Manual of Geology_]
+
+Another curious form sometimes assumed by lava, especially in the
+case of Kilauea, is where the lava is spun out in the form of long
+silk-like hairs. This is called by the natives _Pele's hair_, after
+the name of their goddess. Inasmuch as the origin of this form of lava
+was at one time generally attributed to the action of the wind in
+drawing out thread-like pieces from the jets of lava thrown upwards
+from the pool, it will be interesting if its true cause is explained.
+
+[Illustration: FIG. 27. THREAD-LACE SCORIÆ FROM KILAUEA _From
+Dana's Manual of Geology_]
+
+Dutton, in his report on the Hawaiian volcanoes, refers to the
+formation of Pele's hair as follows:
+
+      "The phenomenon of Pele's hair is often spoken of in the
+      school books, and receives its name from this locality.
+      It has generally been explained as the result of the
+      action of the wind upon minute threads of lava drawn out
+      by the spurting up of boiling lava. Nothing of the sort
+      was seen here, and yet Pele's hair was seen forming in
+      great abundance. Whenever the surface of the liquid lava
+      was exposed during the break-up the air above the lake was
+      filled with these cobwebs, but there was no spurting or
+      apparent boiling on the exposed surface. The explanation of
+      the phenomenon which I would offer is as follows: Liquid
+      lava coming up from the depths always contains more or
+      less water, which it gives off slowly and by degrees, in
+      much the same way as champagne gives off carbonic acid
+      when the bottle is uncorked. Water-vapor is held in the
+      liquid lava by some affinity similar to chemical affinity,
+      and though it escapes ultimately, yet it is surrendered
+      by the lava with reluctance so long as the lava remains
+      liquid. But when the lava solidifies the water is expelled
+      much more energetically, and the water-vapor separates
+      in the form of minute vesicles. Since the congelation of
+      all siliceous compounds is a passage free from a liquid
+      condition through an intermediate state of viscosity to
+      final solidity, the walls of these vesicles are capable of
+      being drawn out as in the case of glass. The commotion set
+      up by the descending crust produces eddies and numberless
+      currents in the surface of the lava. These vesicles are
+      drawn out on the surface of the current with exceeding
+      tenuity, producing myriads of minute filaments, and the
+      air, agitated by the intense heat at the surface of the
+      pool, readily lifts them and wafts them away. It forms
+      almost wholly at the time of the break-up. The air is then
+      full of it. Yet I saw no spouting or sputtering, but only
+      the eddying of the lava like water in the wake of a ship.
+      The country to the leeward of Kilauea shows an abundance
+      of Pele's hair, and it may be gathered by the barrelful. A
+      bunch of it is much like finely shredded asbestos."
+
+You have probably often seen the beautiful frost pictures that collect
+on the panes of glass in a room where the ventilation has been
+neglected. These pictures consist of groupings of ice crystals that
+collect on the surface of the windows, when the moist vapor-laden
+air in the room is chilled by contact with their cold surfaces. Now
+the crystals formed in cooling lavas are sometimes grouped in forms
+closely resembling frost pictures. A few of such forms are represented
+in Figs. 28 and 29 in lava from Mt. Loa and Mt. Kea.
+
+[Illustration: FIG. 28. FROST-LIKE LAVA CRYSTALS _From Dana's
+Manual of Geology_]
+
+[Illustration: FIG. 29. FROST-LIKE LAVA CRYSTALS _From Dana's
+Manual of Geology_]
+
+Certain varieties of lava, especially that which is found in dikes,
+form cool, beautiful columns called basaltic columns. They are due to
+the contraction that occurs on the cooling of the material. Instances
+of basaltic columns are seen in the Giant's Causeway, on the northern
+coast of Ireland, as well as in the Isle of Cyclops on the coast of
+Italy. The general appearance of the latter is represented in Fig. 30.
+
+[Illustration: FIG. 30. BASALTIC COLUMNS, ISLE OF CYCLOPS,
+ITALY]
+
+It is a curious fact that the entire mass of basalt does not generally
+take the columnous form but only certain layers which terminate
+suddenly above and below at structureless masses of basalt, as shown
+in Fig. 31. These columns, however, are always found at right angles
+to the cooling surfaces as seen in the figures. They may, therefore,
+be inclined at all angles to the horizon.
+
+[Illustration: FIG. 31. COLUMNAR AND NON-COLUMNAR BASALT]
+
+When molten lava is only thrown up a short distance into the air
+from a crater it is still partially molten when on falling it again
+reaches the earth, and therefore clings to any surface on which it
+falls. There are thus built up curious cones known as _driblet cones_,
+in which the separate drops covering the sides of the cone can be
+distinctly traced. Driblet cones are represented in Figs. 32 and 33.
+Here, as can be seen, the separate drops can be readily traced as they
+run down a short distance before cooling.
+
+[Illustration: FIGS. 32, 33. DRIBLET CONES _From Dana's
+Manual of Geology_]
+
+We have already referred briefly to the _lava caves_ or _grottoes_,
+that are formed in some of the lava streams issuing from Vesuvius,
+Etna, or Hawaii. These caves consist either of a number of
+communicating huge bubbles, or of the tunnels that are formed in the
+lava by the hardening of the outside of the lava streams as they flow
+down the sides of the mountain, and towards the close of the eruption
+are afterwards emptied by the molten lava within continuing to flow to
+a lower level before solidifying. Now, in the interior of these caves,
+there are often found on the walls, as well as on the portions of the
+floors of the caves, immediately below them, curious pendants, like
+icicles, or, more correctly, like the _stalactites of limestone_ that
+are seen hanging to the walls of caves in limestone districts, where
+they are formed as follows: as the rain water sinks through limestone
+strata it dissolves some of the lime, when, slowly falling, drop after
+drop, from the roofs of the caverns, small particles of lime are
+deposited on the roof, and in this manner a pendant of limestone is
+formed. The water that falls to the floor of the causeway immediately
+below, also builds up a dome-like hillock called a stalagmite. In due
+time the pillar reaches downwards, and the opposite hillock upwards
+until the two meet, thus forming great natural pillars that appear
+to hold up the roof of the vast cave in which they have been slowly
+formed. A number of _lava stalactites_ are represented in Fig. 34.
+
+[Illustration: FIG. 34. LAVA STALACTITES _From Dana's Manual
+of Geology_]
+
+Now, in a similar manner these lava stalactites, formed in the lava
+caves or grottoes, are caused by the stream as it escapes from the
+walls of the caves depositing on them stalactites of various lava
+minerals it has dissolved as it slowly passed through them.
+
+But the most important of all volcanic products is _volcanic dust_.
+This, as we have seen, is so light that it remains longest in the air,
+and is often carried by the winds to great distances from the volcano
+from which it escaped. It may interest you to know that some of the
+most fruitful of the great wheat fields of the western parts of the
+United States owe their extraordinary fertility to immense deposits
+of volcanic dust that have been thrown out from some of the great
+volcanoes of the geological past, now found in an extinct condition in
+these parts of the United States.
+
+According to Russell, immense deposits of volcanic dust are spread
+over vast areas in Montana, Southern Dakota, Nebraska, and Kansas, as
+well as over parts of Oregon, and Washington, and, indeed, over large
+areas of southwestern Canada and Alaska.
+
+It is practically certain that many of the eruptions producing this
+dust occurred within historic times. There must, therefore, have been
+many times in these parts of our country when the dense ash clouds
+hiding the sun turned the day into night and destroyed the forests and
+other vegetation by showers of red hot ashes. There were produced,
+too, the same great dread, and possibly loss of life as common during
+historical eruptions. It is pleasing, however, to think that while
+these great catastrophes brought suffering and dread to the people who
+then lived on the earth, they were, nevertheless, but the forerunners
+of those fruitful fields that at a much later age were to bless the
+people who afterwards lived on them.
+
+
+
+
+CHAPTER XXI
+
+MUD VOLCANOES AND HOT SPRINGS
+
+
+Mud volcanoes are the more or less conical hillocks from which, under
+certain conditions, mud is thrown out through the crust of the earth.
+
+Geikie defines mud volcanoes as follows:
+
+      "Conical hills formed by the accumulation of fine and
+      usually saline (salty) mud, which, with various gases, is
+      continuously or intermittently given out from the orifice
+      or crater in the centre. They occur in groups, each hillock
+      being sometimes less than a yard in height, but ranging up
+      to elevations of 100 feet or more. Like true volcanoes,
+      they have their periods of repose, when either no discharge
+      takes place at all, or mud oozes out tranquilly from the
+      crater, and their periods of activity, when large volumes
+      of gas, and sometimes columns of flame, rush out with
+      considerable violence and explosion, and throw up mud and
+      stones to a height of several hundred feet."
+
+There are two kinds of mud volcanoes: those in which the mud is thrown
+out by the action of different kinds of gases, and those in which the
+mud is thrown out by the action of steam.
+
+Mud volcanoes may or not be volcanic phenomena. Those which occur in
+the neighborhood of volcanoes whether active, dormant, or extinct, are
+probably of volcanic origin. There are others, however, which occur
+in regions far removed from volcanoes. These are probably due not to
+volcanoes, but to chemical action and the eruptions are caused by the
+action of gases.
+
+The gases producing these eruptions are either carbonic acid gas
+(the gas that is given off from soda water); carburetted hydrogen
+(the gas that is sometimes seen escaping from the bottom of marshy
+ground); sulphuretted hydrogen (a gas that is given off from rotten or
+decomposing eggs, and possessing the characteristic odor of decayed
+eggs) and nitrogen gas derived from the atmosphere. In mud volcanoes
+of the gaseous type the mud is generally cold, and the water salty. In
+this latter case the mud volcanoes are also called _salses_. Daubeny
+has pointed out that the mud volcanoes of this class that occur in the
+neighborhood of Sicily are due to the slow burning or oxidation of
+beds of sulphur.
+
+Mud volcanoes which eject hot mud by the force of eruption of steam,
+which occur in volcanic districts, are of volcanic origin. They are
+caused by the passage of hot water and steam through beds of volcanic
+rock such as tufa, or hardened volcanic mud and other volcanic
+products. The hot water or steam raises the temperature of the mud
+through which it passes to the boiling point. As Dana remarks, the mud
+varies in consistency from very liquid muddy water to a thick mass
+like boiling soap, or in some cases like masses of mud or paint, and,
+in still other cases, to material like soft mortar, the consistency of
+the mud varying with the dryness of the season.
+
+There are three regions where mud volcanoes are especially common.
+One of the best known is in the Yellowstone National Park, four miles
+north of Yellowstone Lake, and six miles from Crater Hill. Some of
+these mud volcanoes have circular craters about ten feet in depth
+around which they have built mounds, the rims of which are several
+feet above the general level.
+
+There are well-known regions of mud volcanoes in different parts of
+Iceland. Here, according to Lyell, they occur in many of the valleys
+where sulphur vapor and steam bursts from fissures in the ground with
+a loud hissing noise. In these regions there are pools of boiling
+water filled with a bluish black clay-like paste, that is kept
+violently boiling. Huge bubbles, fifteen feet or more in diameter,
+rise from the surface of the boiling mass. The volcanoes pile up the
+mud around the sides of their craters or basins.
+
+Another part of the world where mud volcanoes are especially numerous
+is on the western shores of the Caspian Sea at a place called Baku.
+These are of the gaseous type and are attended by flames that blaze
+up to great heights often for several hours. These flames are due to
+the presence of natural gas and petroleum vapor that pass out through
+the water. Large quantities of mud are thrown out from the craters of
+these mud volcanoes.
+
+There are also many mud volcanoes in a district in India about 120
+miles northwest of Cutch near the mouth of the Indus. In this region
+the cone built up around the crater is sometimes as high as 400 feet.
+
+The following description of mud volcanoes on Java is quoted from
+Daubeny's book on volcanoes.
+
+      "It would appear likewise from Dr. Horsfield's description,
+      that Java exhibits phenomena of a similar kind to those
+      noticed in Sicily and at the foot of the Apennines, and
+      there known under the name of 'Salses.' In the calcareous
+      district (which I suspect to belong to the same class
+      of formations as the blue clay and tertiary limestone
+      of Sicily) occur a number of hot springs, containing in
+      solution a large quantity of calcareous earth, which
+      incrusts the surface of the ground near it. Of these, some
+      are much mixed with petroleum, and others highly saline.
+
+      "The latter are dispersed through a district of country
+      consisting of limestone, several miles in circumference.
+      They are of considerable number, and force themselves
+      upwards through apertures in the rocks with some violence
+      and ebullition. The waters are strongly impregnated with
+      muriate of soda, and yield upon evaporation very good salt
+      for culinary purposes (not less than 200 tons in the year).
+
+      "About the centre of this limestone district is found an
+      extraordinary volcanic phenomenon. On approaching the
+      spot from a distance, it is first discovered by a large
+      volume of smoke rising and disappearing at intervals of a
+      few seconds, resembling the vapors arising from a violent
+      surf, whilst a dull noise is heard like that of distant
+      thunder. Having advanced so near that the vision was no
+      longer impeded by the smoke, a large hemispherical mass was
+      observed, consisting of black earth mixed with water, about
+      sixteen feet in diameter, rising to the height of twenty or
+      thirty feet in a perfectly regular manner, and, as it were,
+      pushed up by a force beneath, which suddenly exploded with
+      a dull noise, and scattered about a volume of black mud
+      in every direction. After an interval of two or three, or
+      sometimes four or five seconds, the hemispherical body of
+      mud or earth rose and exploded again.
+
+      "In the same manner this volcanic ebullition goes on
+      without interruption, throwing up a globular mass of mud,
+      and dispersing it with violence through the neighboring
+      places. The spot where the ebullition occurs is nearly
+      circular and perfectly level; it is covered with only the
+      earthy particles impregnated with salt water, which are
+      thrown up from below; its circumference may be estimated
+      at about half an English mile. In order to conduct the
+      salt water to the circumference, small passages or gutters
+      are made in the loose muddy earth, which lead it to the
+      borders, where it is collected in holes dug in the ground
+      for the purpose of evaporation.
+
+      "A strong, pungent, sulphurous smell, somewhat resembling
+      that of earth-oil (naphtha), is perceived on standing near
+      the site of the explosion, and the mud recently thrown
+      up possesses a degree of heat greater than that of the
+      surrounding atmosphere. During the rainy season these
+      explosions are more violent, the mud is thrown up much
+      higher, and the noise is heard at a greater distance.
+
+      "This volcanic phenomenon is situated near the centre of
+      the large plain, which interrupts the great series of
+      volcanoes, and owes its origin to the same general cause as
+      that of the numerous eruptions met with in this island."
+
+There are, in many parts of the world, springs, whose waters issue
+from their reservoirs at temperatures either at or near the boiling
+point of water. These are called _hot_ or _thermal springs_. Hot
+springs are found both in volcanic regions, as well as in regions
+where there are no volcanoes, but where there are lines of deep
+fissures or faults. According to Dana, in both of these classes, the
+cause is to be traced to heat of volcanic or deep subterranean origin.
+Hot springs are also found in regions where there are no volcanoes.
+In these cases the heat is due to the gradual oxidation of various
+sulphide ores, or to some other chemical action.
+
+The waters of hot or thermal springs almost always contain various
+mineral substances in solution. All spring water contains some little
+dissolved mineral matter, but in hot springs the quantity of this
+matter is greater than in cold springs, because hot water can dissolve
+mineral substances much better than can cold water.
+
+It might surprise you to hear that one of the commonest substances
+that is found in solution in the waters of many hot springs is silica;
+for silica is practically sand, and sand does not easily dissolve in
+water as does sugar. The very hot water, however, which comes from
+the hot spring, whose temperature below the earth's surface is very
+much higher than it is when it comes out of the spring, possesses
+the power of readily dissolving silica from the rocks over which it
+flows. When the waters of such springs reach the surface the silica
+is deposited in a solid condition around the outlets of the springs.
+In this way there are built up craters or mounds, or, more correctly,
+crater-shaped basins.
+
+Sometimes the hot water contains calcareous substances dissolved in
+it, the solution being caused not only by reason of the hot water, but
+also by means of the carbonic gas it contains. When this water flows
+from the springs, it builds up the same crater-shaped mounds, only in
+this case the mounds are of lime instead of silica.
+
+There are peculiar kinds of hot springs called _geysers_, that possess
+the power of throwing huge streams of water up into the air at more or
+less regular intervals. The word geyser is an Icelandic word meaning
+to rage, or snort, or gush, the name being given by reason of the
+manner in which the waters rush violently out during an eruption.
+
+As Dana points out, when the water in a basin of a hot spring merely
+boils, whether this boiling is nearly continuous, or the water is
+alternately boiling and quiet, the spring is called a hot or thermal
+spring, but where the water is thrown violently out at more or less
+regular intervals, it is called a geyser.
+
+The cause of the eruption of a geyser was discovered by Professor
+Bunsen, the celebrated German chemist, after a careful study of
+the geyser regions in Iceland. The waters of geysers contain large
+quantities of either silica or lime in solution. Bunsen traced the
+cause of these curious eruptions to be the manner in which the hot
+springs pile up cones of silica or limestone around their mouths.
+
+The water of a geyser generally issues from the top of a more or less
+conical hillock, reaching the surface through a funnel-shaped tube.
+Both the tube and the basin are covered with a smooth coating of
+silica or limestone. In the case of the Great Geyser in Iceland, the
+basin is over fifty feet high and seventy-five feet deep. Both the
+tube and the basin have been slowly deposited by the hot water of the
+geyser.
+
+It is only when the tube of a geyser has reached a certain depth that
+the geyser is able to erupt. Moreover, as soon as this tube passes a
+certain depth the geyser can no longer erupt and forever afterwards
+becomes an ordinary hot spring. There are, therefore, to be found in
+most geyser regions, a number of what might be called young geysers or
+merely hot springs, that are not yet deep enough to erupt; others that
+have just commenced eruption, others that have reached their prime,
+while others that, old and decrepit, have again merely become hot
+springs.
+
+Let us now try to understand the cause of the eruption of a geyser.
+Bunsen's explanation, which is now generally accepted, is as follows:
+
+The heat of the volcanic strata through which the tube of the geyser
+extends, gradually raises the temperature of the water that fills
+the geyser tube. Since the boiling point of a liquid increases with
+the pressure to which it is subjected, far down in the tube of a
+geyser, the pressure arising from the weight of the water above it is
+sufficiently great to prevent the water from beginning to boil until
+it reaches a temperature far higher than that at which it would boil
+in the upper parts of the tube. Suppose now, when the water in the
+funnel-shaped tube is nearly filled to the top, the water at last
+grows hot enough to begin boiling at some point near the middle of
+the tube. The pressure of the steam driven off from this portion of
+the water raises the column of water above it in the tube and begins
+to empty it out of the top of the geyser. All the water below this
+point being thus suddenly relieved of its pressure, and being now much
+hotter than is necessary to boil the water at that decreased pressure,
+suddenly flashes into steam, and violently shoots out all the water
+above it to a height that in some cases may be as great as 100 to 200
+feet. The steam causes this eruption, then rushes out with a roar, and
+the geyser eruption is over.
+
+Professor Tyndall in his charming book entitled "Heat as a Mode of
+Motion" speaks as follows concerning Professor Bunsen's discovery:
+
+      "Previous to an eruption, both the tube and basin are
+      filled with hot water; detonations which shake the ground,
+      are heard at intervals, and each is succeeded by a violent
+      agitation of the water in the basin. The water in the
+      pipe is lifted up so as to form an eminence in the middle
+      of the basin, and an overflow is the consequence. These
+      detonations are evidently due to the production of steam in
+      the ducts which feed the geyser tube, which steam escaping
+      into the cooler water of the tube is there suddenly
+      condensed, and produces the explosions. Professor Bunsen
+      succeeded in determining the temperature of the geyser
+      tube, from top to bottom, a few minutes before a great
+      eruption; and these observations revealed the extraordinary
+      fact that at no part of the tube did the water reach its
+      boiling point. In the sketch [not reproduced] I have given
+      on one side the temperatures actually observed, and on
+      the other side the temperatures at which water would boil,
+      taking into account both the pressure of the atmosphere and
+      the pressure of the superincumbent column of water. The
+      nearest approach to the boiling point is at A, a height of
+      30 feet from the bottom; but even here the water is 2° C.,
+      or more than 3-1/2° F., below the temperature at which it
+      could boil. How then is it possible that an eruption could
+      occur under such circumstances?
+
+      "Fix your attention upon the water at the point A, where
+      the temperature is within 2° C. of the boiling point. Call
+      to mind the lifting of the column when the detonations
+      are heard. Let us suppose that by the entrance of steam
+      from the ducts near the bottom of the tube, the geyser
+      column is elevated six feet, a height quite within the
+      limits of actual observation; the water at A is thereby
+      transferred to B. Its boiling point at A is 123.8°, and
+      its actual temperature 121.8°; but at B its boiling point
+      is only 120.8°, hence, when transferred from A to B the
+      heat which it possesses is in excess of that necessary to
+      make it boil. This excess of heat is instantly applied to
+      the generation of steam: the column is thus lifted higher,
+      and the water below is further relieved. More steam is
+      generated; from the middle downwards the mass suddenly
+      bursts into ebullition, the water above, mixed with steam
+      clouds, is projected into the atmosphere, and we have the
+      geyser eruption in all its grandeur.
+
+      "By its contact with the air the water is cooled, falls
+      back into the basin, partially refills the tube, in which
+      it gradually rises, and finally fills the basin as before.
+      Detonations are heard at intervals, and risings of the
+      water in the basin. These are so many futile attempts at
+      an eruption, for not until the water in the tube comes
+      sufficiently near its boiling temperature, to make the
+      lifting of the column effective, can we have a true
+      eruption."
+
+The principal geyser regions of the world are in Iceland, in New
+Zealand, and in the Yellowstone National Park in the United States.
+
+There are several geyser regions in Iceland. The best known lies in
+the neighborhood of Mt. Hecla. Here is a great geyser that shoots up
+a column of water to a height of about 100 feet every thirty hours.
+Fig. 35 represents the appearance of the crater of the great geyser in
+Iceland.
+
+[Illustration: FIG. 35. CRATER OF THE GREAT GEYSER OF ICELAND]
+
+It is a well-known fact that in geyser regions generally, the throwing
+of stones or other materials into the tube will frequently hasten an
+eruption. This is probably due to the fact that the throwing in of
+these things results in the raising of the water in the tube, thus
+hastening the eruption.
+
+The New Zealand region is in the neighborhood of Lake Rotomahama in
+the northern island.
+
+The geyser region in the Yellowstone Park is by far the most
+interesting of all geyser regions. This region is situated principally
+around Fire-Hole Fork of the Madison, and near Shoshone Lake at the
+head of Lake Fork of the Snake River. There are many geysers in this
+region, as well as simple hot springs. The temperature of their
+waters varies from between 160° and 200° F. to the boiling point of
+water at this elevation. As you are probably aware, water boils at
+the temperature of 212° F. only under the condition of the ordinary
+atmospheric pressure that exists at the level of the sea. At higher
+elevations, such as on the slopes of mountains, or on high plateaus,
+water boils at a lower temperature. The height of the country in which
+the Yellowstone Park is situated is so great that the water boils at
+temperatures of from 198° to 199° F.
+
+The conical hillock of geyser cones from which the waters flow assume
+various shapes, two of which are shown in Figs. 36 and 37.
+
+[Illustration: FIG. 36. GIANT GEYSER _From Dana's Manual of
+Geology_]
+
+
+[Illustration: FIG. 37. BEE HIVE _From Dana's Manual of
+Geology_]
+
+That shown in Fig. 36 represents the shape of the cone of the giant
+geyser in the upper geyser basin of the Fire-Hole, Yellowstone
+National Park. This cone is about ten feet in height, and twenty-four
+feet in diameter. As shown in the figure it is broken on one of its
+sides. It throws out, at long intervals, a column of water the height
+of which varies from ninety to 200 feet.
+
+Fig. 38 represents the crater of a cone known as the Bee Hive in
+eruption.
+
+Besides the above named geyser regions there is another region on the
+shores of Celebes, and a small region on San Miguel, in the Azores
+Islands, in the Atlantic Ocean.
+
+Besides hot springs and mud volcanoes there are two other phenomena
+connected with volcanic action that we will now briefly describe.
+
+When eruptions take place and the lava begins to flow down the side
+of a mountain, the different vapors and gases with which the lava is
+charged begin to escape or pass out from the boiling or fused mass.
+When these substances are of such a character that they produce fumes,
+or the vapors of various chemical substances, that become solid on
+cooling, they form what are called _fumaroles_, a word derived from
+a Latin word meaning "to smoke." For the greater part, fumaroles are
+found on the edge of craters, but sometimes are found in cavernous
+places either in the crater or in the lava streams.
+
+There is, still, another class of openings through which only
+sulphurous vapors escape. These are called _solfataras_, a word
+derived from the Italian word _solfo_, or sulphur. Solfataras are
+generally found in regions distant from volcanic action. In the
+materials that escape from recently ejected lava, or molten lava,
+the temperature is high enough to volatilize many of the solid
+ingredients. But where the temperature is low, only sulphur vapors are
+driven off. It is for this reason that fumaroles are only found around
+the craters of active volcanoes, or on the lines of cracks or crevices
+of the lava stream where the temperature is very high.
+
+[Illustration: FIG. 38. BEE HIVE GEYSER OF ICELAND _From
+Dana's Manual of Geology_]
+
+Besides water vapor and sulphurous vapors there are other substances
+that escape from the earth in volcanic districts. Sulphurous acid,
+together with hydrogen and nitrogen escape from nearly all lava. At
+Vesuvius chlorine gas is given off. This, however, as soon as it
+passes into the atmosphere becomes changed into hydrochloric acid.
+Sulphurous acid is frequently changed into sulphuric acid, which,
+combining with various substances, forms such materials as _gypsum_,
+or sulphate of lime, the chemical name for plaster of Paris; sulphate
+of soda or _Glauber's salt_; sodium chloride or _common table salt_;
+and _sal ammoniac_. You will remember in reading the description of
+Vulcano, in the Grecian Archipelago, that some of these products were
+collected at the chemical works that had been established on the
+volcano.
+
+When a volcanic mountain is for the time being passing from an active
+to an extinct condition, it is sometimes said to be in the _fumarole
+stage_, since the presence of the fumaroles are the only indication
+of its activity. The volcanic heat is still great. When it reaches a
+still greater decline, the fumaroles disappear, and only solfataras
+are left. The amount of heat is now only sufficient to produce sulphur
+vapors and the vapor of water. This is called the _solfatara stage_.
+
+Of course, as we have already pointed out, fumaroles and solfataras
+may occur in the neighborhood of a volcano at different distances from
+its crater.
+
+
+
+
+CHAPTER XXII
+
+THE VOLCANOES OF THE MOON
+
+
+There can be no doubt that the moon was once the seat of very great
+volcanic activity. It was formerly believed that the very many
+volcanic craters which can be seen on its surface when it is examined
+by a comparatively small telescope, were all extinct. While this
+is nearly true, yet recent investigations have shown that in all
+probability a feeble volcanic activity still exists in a few of these
+craters.
+
+The distinctness with which the surface of the moon is seen does not
+depend so much on the size of the telescope employed, as it does
+on the steadiness of the atmosphere when the telescope is being
+used. When one wishes to examine a very distant body like a star,
+it is necessary to use a powerful telescope, but in the case of a
+comparatively near body, like one of the planets or the moon, a big
+telescope is not necessary. It is, however, necessary to make the
+observations at some time of the year, or in some part of the world,
+when the air is apt to be free from winds.
+
+A person on the earth's surface looking at the heavenly bodies through
+a telescope is practically in the position in which he would be were
+he at the bottom of the water in a large lake looking up through the
+water at some body in the heavens. He would have no difficulty in
+seeing such a body distinctly as long as the upper surface of the
+water remained quiet, and unruffled by waves. As soon, however, as
+waves were set up, the images seen in the telescope are so distorted
+as to become practically worthless. It is for this reason that it is
+customary to build great astronomical observatories in parts of the
+world where there are apt to be many days in the year when the air is
+almost entirely free from wind.
+
+Since the atmosphere is apt to be disturbed by winds in both the
+temperate and the polar latitudes, these parts of the world are
+not very satisfactory as sites for astronomical observatories. The
+conditions are more favorable near the equator, since, although at
+certain seasons of the year there are very severe storms in these
+regions, yet there are quite long periods when the air is almost
+entirely free from winds.
+
+It is for this reason that Harvard University has erected an
+astronomical observatory at Arequipa, Peru, at an elevation of 8,000
+feet above the level of the Pacific Ocean. Here, with a comparatively
+small object glass, of about twelve inches aperture, magnificent
+photographs have been obtained not only of the moon but also of the
+planet Mars.
+
+According to Professor Pickering, from whose magnificent work,
+entitled, "The Moon," much of the information in this chapter has been
+obtained, the moon, which is generally spoken of as a satellite of the
+earth, ought rather to be called the earth's twin planet. Although the
+moon appears to revolve in a small elliptical orbit around the earth
+it should properly be said to revolve around the sun; for, together
+with the earth, it revolves around the sun once every year. As seen
+from any of the planets that lie near the earth the earth and moon
+would appear as a very beautiful double star.
+
+In order the more readily to understand what will be said shortly
+concerning the origin of the moon, it may be mentioned that the
+moon's diameter is 2,163 miles, or a little more than one-fourth the
+diameter of our earth.
+
+You will, most probably, be surprised to learn that the origin of the
+moon is believed to be very different from the origin of the moons
+or satellites of Jupiter, Saturn, and the other planets. As we have
+already seen, according to the nebular hypothesis, all the planets
+except the earth probably had their moons formed from the rings that
+were left surrounding them when they shrunk on cooling to their
+present dimensions. Such a ring is still to be seen surrounding Saturn.
+
+Now it is believed that our moon was formed in a different manner.
+It was not thrown off from the earth while the latter was in a
+highly fluid or gaseous condition, but after the earth had shrunken
+to nearly its present size and, most probably, after a solid crust
+had been formed on its surface. In order that our earth should be
+able to violently throw off a large portion of its mass, it is only
+necessary that at the time this separation occurred, its motion of
+rotation on its axis was sufficiently great to enable it to make one
+complete revolution in rather less than three hours instead of in
+the twenty-four hours it now requires. At this velocity of rotation,
+objects would fly off the earth in the neighborhood of the equator,
+under the influence of the high centrifugal force. Let us, then,
+endeavor to see if it was at all probable that the earth ever did turn
+so rapidly on its axis.
+
+You all probably know that it is principally the attraction of the
+moon that produces the earth's tides. Of course, the sun also produces
+tides on the earth, but it is so far off from the earth that not
+withstanding its greater mass the tides it forms are much smaller
+than those produced by the moon. You also know that the moon produces
+at the same time two tides in every twenty-four hours, on directly
+opposite sides of the earth; one on the side immediately under the
+moon, and the other on the side furthest from the moon. As the earth
+rotates between these two tides, they act as a break which serves to
+impede its motion. Every high tide, therefore, tends to make the earth
+rotate more slowly, and thus to slowly increase the length of the day.
+For this reason to-day is a trifle longer than yesterday, and still
+longer than a day a hundred years ago.
+
+You must not suppose for a moment that this increase in the length of
+the day is large. On the contrary, it is so small that since the year
+A. D. 1, up to the present time, the day is only a very small
+fraction of a second longer.
+
+But it was very different in the earth's geological past, when the
+inside of the earth was in a molten condition; for then great tides
+were set up in the melted interior of the earth that not only greatly
+changed the shape of the earth, but decreased the rate of rotation
+much more rapidly than it does when the earth's tides are limited as
+they are now to the waters on the earth's surfaces.
+
+There was, however, at the same time, something going on that tended
+greatly to make the earth turn more rapidly on its axis. While the
+originally melted earth was cooling and shrinking, the rate of
+its rotation was necessarily increasing. As you know, the time of
+vibration of a pendulum, that is, the time it requires to make one
+complete to-and-fro motion, is shorter the shorter the length of the
+pendulum. A pendulum two feet long moves to and fro more slowly than
+a pendulum one foot in length. In the same way a rotating sphere will
+make one complete rotation in a shorter time when its radius, which
+corresponds to the length of a pendulum, is shorter. Therefore, as the
+earth shrunk, it rotated more and more rapidly, and at last reached a
+rapidity of motion at which an immense quantity of matter flew off
+its surface nearest the equator and went out into space, never again
+to return. It was this mass that constituted the earth's moon.
+
+Necessarily such a tremendous catastrophe was attended by an
+earthquake as well as by the most fearful volcanic phenomena that
+the earth has ever witnessed. The terrible catastrophe produced by
+the explosive eruption of Krakatoa was but as a small drop of rain
+falling on the earth, when compared with the catastrophe produced when
+the "five thousand million cubic miles of material left the earth's
+surface, never again to return to it."
+
+It is not known whether this matter was torn off the earth at a single
+time or during successive times, but quoting the beautiful language of
+Professor Pickering:
+
+      "We may try in vain to imagine the awful uproar and fearful
+      volcanic phenomena exhibited when a planet was cleft in
+      twain, and a new planet was born into the solar system."
+
+This terrible catastrophe took place at a time not when the earth was
+a gaseous mass, but when it had condensed into a comparatively small
+mass not much larger than it is at its present time, and possibly
+even after it had hardened sufficiently to form a solid crust on its
+outside.
+
+If you look at a map of the earth on a Mercator's projection, such,
+for example, as that employed in illustrating the distribution of the
+world's volcanoes in Fig. 24, you can see, even without any very close
+examination, that the great water area of the Atlantic Ocean has its
+eastern and western shores almost parallel to each other, so that
+if you conceive the Eastern and Western Continents as being pushed
+together, they would, except at the south, almost completely fit
+together, and the same thing is true, if Greenland is pushed towards
+the northeastern coast of North America. Of course, some portions of
+the coast would not fit exactly, but then these portions might either
+have been worn away, or, as is more probable, have been changed in
+shape by the deposit of immense beds of sedimentary rocks spread over
+the borders of the Atlantic by the great rivers that empty into it.
+This is so remarkable a fact that it will be well worth your while to
+turn to the map mentioned and convince yourself of the proof of what
+I have just said. As you will see, Europe and Africa would almost
+exactly fit against South America and North America, while Greenland
+would even more closely fit against the northeastern coast of North
+America.
+
+Now, while we do not say that it was so, it has been suggested as just
+possible that the great depression of the Pacific Ocean represents the
+spot that was once filled by the moon. That the Eastern and Western
+Continents, then torn asunder by the great force of the convulsion,
+were left floating on the surface of a sea of molten matter, a greatly
+widened crack marking positions they assumed at the end of this
+cataclysm.
+
+Of course, you must understand that all this is a mere supposition,
+and that we do not know whether the earth was actually cooled on the
+outside when this occurred, since it might have still been in a liquid
+condition throughout. It would seem, however, to have occurred rather
+recently, since it could not have occurred until the earth shrunk so
+much that it became so small in radius as to acquire a very rapid rate
+of motion on its axis.
+
+It is an interesting fact that we are, perhaps, better acquainted with
+that side of the moon which is turned towards us than we are with the
+surface of the earth on which we live. Of course, I do not mean in the
+small details of the moon's surface, but with such portions as can be
+seen through a good telescope when the air is quiet. While there are
+no parts of the moon's surface that have not been carefully examined
+in detail probably thousands of times by acute astronomers, there are
+still comparatively large areas of the earth that have never been once
+trodden by civilized man.
+
+When I speak of all parts of the moon's surface, I only mean those
+parts that are turned towards us. You may possibly be ignorant of the
+fact that the moon always turns exactly the same face towards the
+earth. Not only has no man ever seen the opposite side of the moon,
+but he never can hope to see it while he remains on the earth. This is
+because the moon turns or rotates on its axis in exactly the same time
+that it revolves in its orbit.
+
+When I say that the time of rotation is the same as the time of
+revolution of the moon, I do not mean that it is almost the same, but
+that it is exactly the same. If it differed even but a small fraction
+of a second, a time would come when we would be able to see the other
+side of the moon. Now, since astronomers have made careful pictures
+of the moon, many, many years ago, we can see by comparing them
+with photographs taken at the present time there has been no change
+whatever in that face of the moon which is turned towards us, and
+this, of course, proves beyond question, that the time of the moon's
+rotation during this great period has remained exactly the same as the
+time of its revolution.
+
+It may possibly seem to you that it cannot be a matter of great
+importance in a book like this on the Wonders of Volcanoes and
+Earthquakes, whether or not the moon always turns its face towards
+the earth; on the contrary, it is a matter of the greatest importance
+since by it we can prove positively that the moon was at one time at
+least in a partly fluid condition. It was the presence of this partly
+fluid interior that resulted in the time of the moon's rotation
+agreeing exactly with the time of its revolution. The tides of the
+earth set up in the moon's molten interior, tides, that instead of
+reaching twice every day the height of a few feet only, were set up
+in the molten mass in the moon's interior, probably reaching miles in
+height, rapidly decreased the time of the moon's rotation until the
+moon rotated once only during every complete revolution.
+
+Even now that the moon is probably solid throughout, the time of its
+rotation and revolution exactly agree because, while in a molten
+condition, the action of the earth changed its shape from that of an
+exact sphere to a spheroid, with its longest axis in the direction of
+the earth. Even, therefore, if the moon at any time began to rotate
+faster than the earth, the earth acting on its projecting surface
+retarded it until the time of its rotation agreed exactly with the
+time of its revolution.
+
+It was at one time believed that the moon had no atmosphere. It is
+now known, however, that it has an atmosphere. It is true this is a
+rare atmosphere, probably not greater in density than the one-ten
+thousandth of the earth's atmosphere. This important question was
+settled once for all on August 12th, 1892, at the Harvard Observatory
+at Arequipa, Peru, when a photograph was taken of an object on the
+moon. It could be readily seen on examining this photograph that the
+light coming from the moon experienced a bending, known as refraction,
+in passing from the space outside the moon to its atmosphere on to its
+surface.
+
+Of course, when the moon was thrown off from the earth by reason of
+its great centrifugal force, it carried along with it a portion of the
+earth's atmosphere. But since the quantity of matter in the moon is
+only about one-eightieth of that of the earth, the force of gravity
+on the moon is much smaller than that on the earth, being almost
+exactly one-sixth that of the earth's gravity. In other words, if you
+could succeed in reaching the moon's surface, you would only weigh
+one-sixth of what you weigh on the earth, but then you could carry a
+weight six times heavier with no greater effort, and, as for running,
+jumping, and other athletic exercises, the surface of the moon would,
+indeed, be a great place on which to break records, since one could
+readily jump six times higher, put the shot six times further, than
+on the earth, or go through most other athletic exercises with a
+corresponding increase.
+
+Without going any further into this question it will be sufficient
+to say that the moon's present atmosphere is believed to consist of
+carbonic acid gas, and that while on the general surface of the moon
+this atmosphere must be very rare, yet, at the bottom of the great
+fissures that cross the moon's surface, it may possess a fairly great
+density, especially if the moon still possesses feeble volcanic
+activity; that carbonic acid gas is still being given off from the
+inside of the moon as we know it is being given off from inside the
+earth.
+
+Under the best conditions of atmosphere and telescope, we can see the
+moon's surface as it would appear at a distance varying from 800 miles
+to 300 miles from the earth. With a fifteen-inch telescope, under
+perfect conditions of vision, objects can be seen as if they were at
+a distance of 800 miles from the earth, and with the most powerful
+glasses, and the best conditions of atmosphere this distance can be
+reduced to about 300 miles. This would enable us to clearly see large
+objects like rivers, lakes, seas, or forests, if they existed, but
+would not be sufficient to enable us to see houses, buildings, or
+roads.
+
+When we come to examine the surface of the moon under the most
+favorable conditions, we find that it is extremely irregular. There
+are plenty of high mountains. These mountains are not collected
+in ranges as they are on the earth's surface, but are completely
+separated from each other, and are scattered in great numbers over the
+moon's surface.
+
+You may form some idea of the number of volcanoes that have been
+observed on the moon when I tell you that as many as 32,000 have been
+seen on that side of the moon that is turned towards the earth.
+
+Now it is an interesting fact that almost all these mountains possess
+great craters that are not unlike some of the volcanic craters we see
+on the earth. The volcanic craters of the moon, however, are of very
+much greater size than those on the earth, many being from fifty to
+sixty miles in diameter, while some of them are more than 100 miles
+in diameter. Smaller craters, say from twenty to twenty-five miles in
+diameter, can be counted by the hundreds.
+
+Like most of the moon's craters, the largest crater more closely
+resembles one of the pit-craters or calderas on the island of Hawaii.
+This volcanic crater consists of a huge circular ring with a small
+irregular peak that rises inside the ring. This peak, by the way,
+might at first appear to resemble the crater of Vesuvius, which after
+a long period of inactivity of the mountain during the eruption that
+destroyed Pompeii and Herculaneum was thrown up inside of what had
+been left standing of the old crater of Somma. But it has no crater
+at its summit, and, therefore, resembles rather the irregular pile or
+rock that rises from the surface of a lava lake in the craters of Mt.
+Loa or Mt. Kilauea in Hawaii.
+
+Besides the numerous craters to be seen on the moon's surface there
+are many lines of deep, crooked valleys, known as _rills_, that may
+at one time have been the beds of rivers. Besides the rills, there are
+many straight clefts about half a mile in width, that extend down into
+the surface of the moon for unknown depths. These clefts can be seen
+passing directly through mountains and valleys. They are believed to
+be cracks or fissures in the moon's surface.
+
+On the moon is a great crater called Tycho. It is situated near the
+moon's south pole. The great crater of Tycho is by far the most
+prominent object on the moon's surface. It has a system of rays that
+extend for great distances around its craters.
+
+You will also see if you examine the moon's surface by a powerful
+glass that there are immense plains called _oceans_ or _seas_. By an
+appropriate custom the names of the different craters on the moon are
+the same as the names of the great astronomers and philosophers that
+have long since passed from their labors, such as Tycho, Copernicus,
+Kepler, Plato, etc.
+
+Various explanations have been given as to the origin of the craters
+on the moon's surface, but without going into a discussion it may be
+said that they are now generally regarded as having been formed in the
+main just as were the craters of the earth's volcanoes.
+
+The tremendous size of the moon's craters is of course due to the
+great decrease in the force of gravity. This would make the craters,
+approximately, six times as great as the craters on the earth.
+Professor Pickering points out that while the moon's craters resemble
+more closely those of Hawaii than those of any other of the earth's
+volcanoes, yet there is this difference in them: that while the
+earth's crater floors are generally considerably higher than the level
+of the sea, the moon's crater floors are generally below the level of
+the surrounding country. Still, taking them all in all, the craters
+of the moon's volcanoes resemble those of the island of Hawaii, or
+again quoting from Pickering:--
+
+      "There seems, indeed, to be no feature found upon the moon
+      which is not presented by these Hawaiian volcanoes, there
+      is no feature of the volcanoes that does not also have its
+      counterpart in the moon."
+
+
+
+
+CHAPTER XXIII
+
+EARTHQUAKES
+
+
+An _earthquake_ is a shaking of the earth. It may vary in intensity
+from a shaking so feeble that it requires the use of a delicate
+instrument to detect it, to a shaking violent enough to overthrow
+heavy buildings, and even to make great rents or fissures in the crust.
+
+An earthquake then is an _earth-shake_. It may be caused by anything
+capable of shaking the earth; for example, as the falling of a heavy
+weight on its surface. Now, a shaking so caused is only felt in the
+immediate neighborhood of the place the weight strikes the earth. On
+the contrary, in an earthquake, the shaking spreads in all directions
+through the earth's crust, until, in the case of very violent
+earthquakes, it reaches portions that may be situated many thousands
+of miles away from where the shock started. This spreading of the
+earthquake waves through the solid earth is not unlike the spreading
+of the circular waves that are set up in a still water surface when a
+stone is tossed in.
+
+Any shaking of the earth's crust produces what may be called an
+earth-shake or earthquake. The mere falling of a raindrop on the earth
+produces a slight shaking. The falling of a heavy stone produces a
+stronger shaking, and sets up a series of minute waves, generally
+called vibrations, that spread around the place in all directions from
+where the stone struck. These movements, however, while they spread
+in all directions, just as they do in a surface of a lake, when a
+stone is thrown into it, are of course much more quickly stopped by
+the solid earth than similar movements are by the more readily movable
+water.
+
+But, while any shaking of the earth's crust constitutes an earthquake,
+yet, strictly speaking, an earthquake is produced only by some force
+that acts suddenly on the earth, _at a point below its surface_, and,
+therefore, out of sight. This, of course, would rule out all such
+shakings as are caused by bodies striking the outer surface of the
+earth.
+
+Earthquakes may occur in any part of the world, and at any time of the
+day or year. They do occur, however, most frequently in certain parts
+of the world, at certain seasons of the year and at certain hours of
+the day.
+
+Earthquakes are far from being unusual occurrences. In some parts of
+the world, such as the island of Java, they are very common, and in
+Japan, under certain circumstances, scarcely a day passes without one
+or more shocks in some part of that little empire.
+
+Professor Mallet, who has made a very extensive study of earthquakes,
+published in 1850 to 1858, in the Philosophical Transactions, brief
+abstracts or descriptions of all the more important earthquakes he
+could find records of during the past 3,456 years. The number of
+earthquakes thus recorded during this period reached 6,830. Of this
+great number nearly one-half occurred during the last fifty years.
+
+It should not be inferred from the above figures that the number of
+earthquakes has really increased so greatly in the past half-century.
+The explanation of the apparent increase is that greater care has
+been taken recently in recording earthquakes, and that an apparatus
+called a _seismometer_, or _earthquake-recorder_, has been invented
+which automatically produces a record of the smallest shocks; so that
+a great many have been recorded that would otherwise have passed
+undetected.
+
+It is the opinion of Le Conte that if the records of all the
+earthquakes of 3,456 years had been thus made there would have been
+found during the entire time of Mallet's researches to have occurred
+no less than 200,000, while during the last four years of Mallet's
+records, the number would have probably reached two earthquakes per
+week.
+
+Since Mallet's time, Prof. Alexis Perry published (1876) a much larger
+list of earthquakes. Perry finds that from 1843 to 1872 there have
+been 17,249 earthquakes, or 575 every year. Perry's list, however,
+is incomplete, since it fails to record earthquakes that occurred in
+mid-ocean, and in the unexplored and uncivilized parts of the world.
+So it seems likely that earthquakes are so common that our earth, at
+some part or other of its surface, is continually shaking or quaking.
+
+Earthquakes are such tremendous phenomena that they were necessarily
+observed by the ancients. We find more or less complete accounts of
+them in various writings. Lucretius (Titus Carus Lucretius, a great
+Roman poet) speaks as follows, in his De Rerum Natura (On the Nature
+of Things). We use Munro's translation here:
+
+      "Now mark and learn what the law of earthquakes is. And
+      first of all take for granted that the earth below us as
+      well as above is filled in all parts with windy caverns,
+      and bears within its bosom many lakes and many chasms,
+      cliffs and craggy rocks; and you must suppose that many
+      rivers hidden beneath the crust of the earth roll on with
+      violent waves and submerged stones; for the very nature
+      of the case requires it to be throughout like to itself.
+      With such things then attached and placed below, the
+      earth quakes above from the shock of great falling masses,
+      when underneath, time has undermined vast caverns. Whole
+      mountains, indeed, fall in, and in an instant from the
+      mighty shock tremblings spread themselves far and wide from
+      that centre. And with good cause, since buildings beside
+      a road tremble throughout, when shaken by a wagon of not
+      such very great weight; and they rock no less, where any
+      sharp pebble on the road jolts up the iron tires of the
+      wheels on both sides. Sometimes, too, when an enormous mass
+      of soil through age rolls down from the land into great
+      and extensive pools of water, the earth rocks and sways
+      with the undulation of the water just as a vessel at times
+      cannot rest, until the liquid within has ceased to sway
+      about in unsteady undulations....
+
+      "The same great quaking likewise arises from this cause,
+      when on a sudden the wind and some enormous force of air
+      gathering either from without or within the earth have
+      flung themselves into the hollow of the earth and there
+      chafe at first with much uproar among the great caverns
+      and are carried on with a whirling motion, and when their
+      force, afterwards stirred and lashed into fury, bursts
+      abroad and at the same moment cleaves the deep earth and
+      opens up a great yawning chasm. This fell out in Syrian
+      Sidon and took place at Ægium in the Peloponnese, two towns
+      which an outbreak of wind of this sort and the ensuing
+      earthquake threw down. And many walled places besides fell
+      down by great commotions on land and many towns sank down
+      engulfed in the sea together with their burghers. And if
+      they do not break out, still the impetuous fury of the
+      air and the fierce violence of the wind spread over the
+      numerous passages of the earth like a shivering-fit and
+      thereby cause a trembling."
+
+Of course, no one at the present time believes this ridiculous
+explanation as to the cause of earthquakes.
+
+Aristotle, a Greek philosopher, speaks thus concerning earthquakes. We
+quote the translation employed by Mallet:
+
+      "Three theories on the subject have been handed down to
+      us by three different persons; namely, Anaxagoras of
+      Klazomene, before him Anaximenes the Milesian, and later
+      than these Democritus of Abdera.
+
+      "Anaxagoras says that the ether of nature rises upward, but
+      that when it falls into hollow places in the lower parts
+      of the earth it moves it (the earth); because the parts
+      above are cemented or closed up by rain, all parts being by
+      nature equally spongy or full of cavities, both those which
+      are above (where we live) and those which are below. Of
+      this opinion it may perhaps be unnecessary to say anything,
+      as being foolish, for it is absurd to suppose that things
+      would thus exist above and beneath, and that the parts of
+      bodies which have weight would not on every side be borne
+      to the earth, and those which are light, and fiery, rise;
+      especially since we see the surface of the earth to be
+      convex and spherical, the horizon constantly changing as
+      we change our place, at least as far as we know. And it is
+      also foolish to assert on the one hand that it remains in
+      the air on account of its great size, and on the other to
+      say that it is shaken, when struck from beneath upwards.
+      And besides these objections, it is to be remarked that
+      he has not treated of the attendant circumstances of
+      earthquakes, for neither every time nor place is subject to
+      these convulsions.
+
+      "But Democritus says, that the earth being full of water,
+      and receiving much also by means of rain, is moved by
+      this. For when the water increases in bulk, because the
+      cavities cannot contain it, in its struggles it causes an
+      earthquake. And when the earth becomes partially dried up,
+      the water being drawn from the full reservoirs into those
+      which are empty, in passing from one to the other, by its
+      movements it causes an earthquake also.
+
+      "Anaximenes, however, says that the earth, when parched up
+      and again moistened, cracks, and by the masses thus broken
+      off falling on it, is shaken; wherefore earthquakes occur
+      in drouths and again in times of rain; in drouths, because,
+      as we have said, it cracks, when highly dried, and then,
+      when moistened over again, it cracks and falls to pieces.
+      Were this the case, however, the earth ought to appear
+      in many places subsiding. Why then is it that hitherto
+      many places have been very subject to these convulsions
+      which do not present any such remarkable differences from
+      others? Yet such ought to be the case. And, moreover, those
+      who think thus must assert that earthquakes constantly
+      become less and less, and at last cease altogether. For
+      the continual condensation of the earth would cause this.
+      Wherefore, if this be not the fact, it is plain that this
+      is not the correct explanation."
+
+Besides the above, there are numerous references to earthquakes in the
+works of other writers. Thales, Seneca, and Pliny all speak of these
+phenomena and appear to describe correctly the movement of the earth
+in waves both in the solid land, as well as on the sea.
+
+Coming down to less ancient writers, Mallet refers to a book by
+Fromondi, published in Antwerp, in 1527, that contains much valuable
+and interesting information. Among other things Fromondi declares
+that in the year 369, in the reign of Valentinian, there was a great
+earthquake that shook nearly the entire world and that another
+earthquake of almost equal severity occurred in 1116. He also states
+that in 1601 an earthquake continued for nearly forty days; that a
+great earthquake in Italy, in 1538, lasted fifteen days, and that
+another, in Spain, lasted for nearly three years.
+
+This does not mean that these earthquakes actually continued to shake
+the earth violently for the times mentioned. These are only the times
+during which, at intervals of greater or less length, successive
+shocks were felt in these localities.
+
+Another of the less ancient writers referred to by Mallet is
+Travagini, who published a book in Venice in 1683. This book contains
+a description of a terrible earthquake occurring in Italy on the 6th
+of April, 1667, which affected large portions of the country adjacent
+to Ragusa.
+
+Without attempting at present to discuss the various theories of
+earthquakes, it will suffice to say that earthquakes can be divided,
+according to their origin, into two classes: _volcanic earthquakes_,
+or earthquakes that are caused by practically the same forces that
+cause volcanoes, and _tectonic[3] earthquakes_, or those produced by
+the slipping of a large mass of rock lying along the lines of old or
+new fractures.
+
+Earthquakes of the first class are found especially in volcanic
+districts, while those of the second class are found in all parts
+of the world, whether in volcanic districts or elsewhere. According
+to Dana, earthquakes of the second class generally start in the
+neighborhood of mountains, where old lines of fractures are especially
+abundant.
+
+As regards the direction of the shaking movements of the earth,
+earthquakes can be divided into three different classes: _explosive
+earthquakes_, or those in which the force acts vertically upwards;
+_horizontal earthquakes_, or those in which the force moves in a more
+or less horizontal direction, or parallel to the general surface
+of the earth, and _rotary earthquakes_, or those in which the earth
+rotates or moves in great eddies or whirls.
+
+When the earthquake wave is started below the earth's surface, it
+spreads through the crust in all directions. The direction these waves
+will have on emerging, or coming out of the surface, will depend on
+the distance of this point from the place the waves started. When a
+place is situated directly over where the wave started, the waves will
+emerge so as to move vertically upwards, so that the earth at this
+point will be shaken by an explosive earthquake. As the point where
+the waves pass out is situated further and further from the place
+where the waves start, the waves will emerge more nearly horizontally,
+the greater the distance from the source.
+
+In explosive earthquakes, which, as just explained, occur at areas
+almost immediately above the point where the disturbance starts,
+the force is, generally speaking, the greatest. In earthquakes of
+this character the force is sometimes sufficiently great to throw
+large bodies high up into the air. In the case of the great Riobamba
+earthquake of 1797, the force was not only sufficiently great to
+fracture the earth in various places, but also to throw bodies lying
+on the surface great distances into the air. Bodies of men were thrown
+several hundred feet into the air and were afterwards found on the
+other side of a broad river or high up on the side of a hill.
+
+It is possible that Humboldt did not inquire with as much care as
+he should have done into these reports. They were probably greatly
+exaggerated, since it is difficult to understand how a force great as
+this would have failed to detach the soil at these places, and hurl it
+after the people. This much, however, can be accepted, that the upward
+force was very great.
+
+In the great Calabria earthquake of March, 1783, Dolomieu states that
+the tops of the granite hills of Calabria were distinctly seen to rise
+and fall. In some cases houses were suddenly raised a great distance
+in the air, and were afterwards brought down again to a position of
+rest, at a higher level without any damage occurring to them. In a
+similar manner during the Caracas earthquake of March, 1812, the
+ground was seen to rise and fall in a nearly vertical direction. But,
+perhaps, one of the most terrible earthquakes of this character was
+the earthquake that destroyed the greater part of Jamaica in June,
+1793. During this earthquake the entire surface of the ground at Port
+Royal assumed the appearance of a rolling sea. Houses were shifted
+from their old sites. Many of the inhabitants who had succeeded in
+escaping from the city to the neighboring country were thrown great
+distances into the air. Some of these, by good fortune, fell into the
+harbor, from which, in some cases, they escaped with their lives. Here
+again the projectile force was probably greatly exaggerated.
+
+Vertical movements characterized the great earthquake of Lisbon, on
+November 1st, 1755, the city appearing to have been not far from the
+point of origin.
+
+The commonest type of earthquakes is the horizontal, where the waves
+emerge at the surface in a direction either horizontal or parallel
+to the general surface, or at least inclined to it at a very small
+angle. Where the materials of the earth's crust, through which the
+waves spread, are of the same kind and of the same density in all
+directions, the area shaken is approximately circular, but where the
+materials of the crust are more or less dense in some directions than
+in others, the area of disturbance is of course oblong or elliptical.
+
+In some cases earthquakes of the horizontal type are limited almost
+entirely to a single direction. This is especially the case with
+earthquakes that occur in mountainous districts. These earthquakes are
+known as _linear earthquakes_, since they spread almost in a single
+line.
+
+When earthquake waves pass from one medium to another, that is, from
+one kind of rock to another, the greater portion of the waves is
+refracted or bent out of their straight direction as they pass into
+the new medium; a part of the waves, however, are reflected. It is
+these reflected waves that probably cause rotary earthquakes.
+
+The speed with which the surface waves move outwards in all
+directions, varies not only with the force of the wave, but also with
+the kind of material through which they pass. This velocity may be
+in the neighborhood of twenty miles per second, while in others the
+velocity is as great as 140 miles per second.
+
+Naturally, one would suppose that the most severe earthquakes are
+those in which the waves move the most rapidly. On the contrary,
+however, the comparatively feeble shocks are sent through the earth
+with greater velocity.
+
+In rotary earthquakes, as the name indicates, the ground is whirled
+or twisted in the manner of a violent eddy, and is often left in
+this twisted condition. In the great Calabria earthquake, huge
+blocks of stone forming obelisks were twisted on one another in a
+manner represented in Fig. 39. In this case the pedestals remained
+unaffected, but the separate blocks of stone were partially turned
+around, as shown. During this earthquake the earth was so twisted that
+trees, which had been planted in straight lines before the earthquake,
+were left standing in zigzags. During the great Charleston earthquake,
+South Carolina, the chimney-tops of the houses were separated at
+places where they joined the roof and were twisted around these places
+without being overthrown. In some of the houses wardrobes or bureaus
+were turned at right angles to their former positions, and in some
+cases were even found with their faces turned towards the wall.
+
+[Illustration: FIG. 39. HEAVY STONE OBELISKS TWISTED BY CALABRIAN
+EARTHQUAKE OF 1783]
+
+Mallet suggests that in some cases the rotary motion is more apparent
+than real, being due only to a to-and-fro motion without any twisting,
+the apparent turning being due to the greater freedom of motion of the
+object in one direction than in another. A twisting motion, however,
+has actually taken place in some earthquakes.
+
+While separate shocks, in a given locality, may follow one another
+at intervals for fairly long times, yet the principal shock or shake
+that produces the greatest damage is generally of exceedingly short
+duration. In the Caracas earthquake the greatest destruction was
+accomplished in about one minute. There were three distinct shocks,
+each of which lasted but three or four seconds. The great Calabria
+earthquake, of 1783, lasted but two minutes. The earthquake of Lisbon,
+in 1755, lasted five minutes, but the first, and worst, shock, was
+only from five to six seconds.
+
+
+
+
+CHAPTER XXIV
+
+SOME OF THE PHENOMENA OF EARTHQUAKES
+
+
+The nature of an earthquake and the movements of its waves from
+their starting place having now been briefly described, it remains
+to explain some of the strange phenomena that precede, accompany, or
+follow one.
+
+Next to the violent shaking of the earth's crust, perhaps the most
+wonderful and impressive thing is the great variety of sounds and
+noises. These occur not only while the earth-waves are passing through
+the crust at any place, but also long before the principal shocks
+reach the place, as well as long after they have passed.
+
+Earthquake sounds vary almost infinitely, both in intensity and
+character. Some are like the gentle sighings of the wind, or resemble
+faint mysterious whisperings; some are not unlike the confused
+murmurings of a crowded room; some resemble the sounds of a busy
+street. Some sounds are full and strong, like the deep bass notes
+of a large organ. Others resemble the din of a great battle with
+the reports of the large guns. Still others reach the intensity of
+continuous peals of thunder. But we can better understand the nature
+of earthquake sounds from an actual description of them in a number of
+great earthquakes, and by inquiring at the same time into any of the
+peculiar facts connected.
+
+Humboldt in his great work, "Cosmos," thus describes the varied voice
+of the earthquake:
+
+      "It is either rolling or rustling, or clanking, like
+      chains being moved, or like near thunder, or clear and
+      ringing, as if obsidian or some other vitrified masses were
+      struck in subterranean cavities."
+
+That the sounds produced during earthquakes are carried through the
+ground faster than through the air appears clear from the fact that
+such sounds are sometimes heard in deep mines when they are not at all
+heard on the earth's surface.
+
+In describing the earthquake that occurred in Kamtschatka, in 1759,
+Krashenikoff of St. Petersburg states that noises were heard like the
+rushing of a strong underground wind, accompanied by a hissing sound,
+which resembled the sizzlings heard when red hot coals are thrown in
+water.
+
+In an earthquake that occurred in Lincolnshire, England, February
+6th, 1817, a noise was heard closely resembling the sounds of wagons
+running away on a road. So complete and convincing was the resemblance
+that several wagoners on one of the roads drew their teams to one side
+so as to permit the runaway to pass safely.
+
+Another kind of noise heard during earthquakes is a loud hollow
+bellowing. Sometimes, however, the sounds are more musical in their
+nature, being not unlike those produced by a very large organ pipe. At
+other times they resemble the noises produced when steam is blown into
+cold water.
+
+The following account of earthquake sounds is given by Daubeny,
+in his book on volcanoes. It appears that during March, 1822, the
+people living on the island of Melida, opposite Ragusa, in Dalmatia,
+were greatly alarmed by sounds that at first they believed due to
+cannonading either at sea or on the neighboring coast. They afterwards
+found that these sounds were due to something that was taking place
+under the ground. The noises continued at intervals until August
+23d, 1823, when a great earthquake occurred, during which one of the
+highest mountains on the island was cleft or split in one place. The
+underground noises continued from time to time and so frightened
+the people that they were about to leave the island permanently and
+emigrate to the mainland of Dalmatia. They were dissuaded from doing
+so by the government, and while the noises continued at intervals it
+so happened that no damage came to them. It is said, however, that
+twenty years after an active volcano broke out on the island.
+
+There are various causes that produce earthquake sounds. A very slight
+rubbing or grinding together of rock surfaces may produce fairly
+loud noises, the volume of the sound being increased by transmission
+through the rock masses that lie in the path of the waves. An example
+of such an increase in the loudness of sounds is seen in the case of
+several of the large blocks of stone used for some of the piers of
+Kingston Harbor, in Ireland. When these rocks are moved together by
+blows of the waves they produce loud and appalling sounds, as if the
+whole island were being washed away. The same rocks, however, when
+left high and dry on the falling of the tide, can be caused to rub
+together, when moved by the hand. Under these circumstances, they
+produce but feeble sounds that can only be heard in their immediate
+neighborhood.
+
+No doubt, some find it difficult to understand how it is possible for
+comparatively feeble sound-waves to be strengthened by their passage
+through large masses of solids. This is important and should be made
+clear. As everyone well knows, the ticking of a watch can only be
+heard at a short distance when the watch is held in the hand, because
+the sound-waves cannot readily pass through the body of the person
+holding the watch to the earth, the materials of the body not being
+sufficiently elastic. If, however, the watch be placed on the bare
+surface of a large wooden table from which the tablecloth has been
+removed, so that the watch can come directly in contact with the wood,
+and nothing else is placed on the table but the watch, the sound-waves
+are transmitted to the mass of the table and its entire surface sends
+them out into the air. The ticking of the watch can then be heard
+distinctly in almost any part of a large room.
+
+Mallet states that in nearly all great earthquakes sounds are heard
+before the principal shock, and in his description of the Calabrian
+earthquake Hamilton says:
+
+      "All agreed that every shock seemed to come with a rumbling
+      noise from the westward, beginning with the horizontal and
+      ending with the vorticose (rotary) motion."
+
+According to Dolomieu, during the Lisbon earthquake, the shocks were
+preceded "by a loud subterranean noise like thunder, which was renewed
+for every shock.... This great shock," he says, referring to one of
+the great upward shocks, "occurred without the prelude of any slight
+shocks, without any notice whatever as suddenly as the blowing up of
+a mine.... Some, however, pretend that a muffled interior noise was
+heard almost at the same moment."
+
+The noises do not generally continue long after the earthquake shocks.
+In some cases, however, a very loud noise is heard at intervals for a
+considerable length of time after the principal shock. This was the
+case at Quito and Ibarra, in which a great noise was heard for from
+eighteen to twenty minutes after the principal shock. In a similar
+manner during the earthquake of October, 1746, at Lima, and Callao,
+South America, peals of underground thunder were heard at Truxillo
+for fifteen minutes after the principal shock. In such cases it
+seems probable that the noises were not caused by the same impulses
+that caused the original shock, but by the forces that caused the
+subsequent shock.
+
+Humboldt relates that in 1784 there were noises heard at Guanajuato,
+from the 9th to the 12th of February. They were not, however, followed
+by an earthquake.
+
+Humboldt also states that in an earthquake which occurred on the 30th
+of April, 1812, on the banks of the Orinoco River, in South America,
+a loud thundering noise was heard, without, however, any shock, but
+at this time a volcano on the island of St. Vincent, in the Lesser
+Antilles, although some 632 miles to the northeast, was pouring out
+streams of lava. Again in the great eruption of Cotopaxi, in 1734,
+underground noises were heard as if cannon were being fired. These
+sounds were distinctly heard at as great a distance as Honda on the
+banks of the Magdalena River. Now, bearing in mind that the crater of
+Cotopaxi is situated on the high plateau of Quito, in a region full
+of valleys and fissures, it would seem that for the sounds to have
+been sent through the 436 miles between the mountains and the valley
+of the Magdalena River, the waves must, for the greater part, have
+been transmitted through the solid earth at some considerable distance
+below the surface.
+
+Mallet states that the underground noises which continued for more
+than a month from the midnight of January 9th, 1784, at Guanajuato,
+were not followed by any earthquake shocks, that it was if as thunder
+clouds occupied the space below the surface at that part of the earth
+and from these clouds there came the slow rolling sounds like short,
+quick, snaps of thunder.
+
+Major Dutton in his book entitled "Earthquakes in the Light of the
+New Seismology" gives the following as the principal signs that herald
+the coming earthquake in the open country.
+
+      "The first sensation is the sound. It is wholly unlike
+      anything we have ever heard before, unless we have already
+      had a similar experience. It is a strange murmur. Some
+      liken it to the sighing of pine-trees in the wind, or to
+      falling rain; others to the distant roar of the surf;
+      others to the far-off rumble of the railway train; others
+      to distant thunder. It grows louder. The earth begins to
+      quiver, then to shake rudely. Soon the ground begins to
+      heave. Then it is actually seen to be traversed by visible
+      waves somewhat likes waves at sea, but of less height and
+      moving much more swiftly. The sound becomes a roar. It is
+      difficult to stand, and at length it becomes impossible to
+      do so. The victim flings himself to the ground to avoid
+      being dashed to it, or he clings to a convenient sapling,
+      or fence-post, to avoid being overthrown. The trees are
+      seen to sway sometimes through large arcs, and are said,
+      doubtless with exaggeration, to touch the ground with
+      their branches, first on one side, then on the other. As
+      the waves rush past, the ground on the crests opens in
+      cracks which close again in the troughs. As they close, the
+      squeezed-out air blows forth sand and gravel, and sometimes
+      sand and water are spurted high in air. The roar becomes
+      appalling. Through its din are heard loud, deep, solemn
+      booms that seem like the voice of the Eternal One, speaking
+      out of the depths of the universe. Suddenly this storm
+      subsides, the earth comes speedily to rest and all is over."
+
+There are many other curious phenomena besides earthquake sounds or
+noises. Among some of the more interesting are the fire and smoke that
+are seen to come out of fissures that have been rent in the ground.
+
+It is possible that in many cases these flashes of fire are in reality
+produced by electric discharges that momentarily light the clouds of
+dust thrown up out of the fissure. But sometimes true flames are seen
+escaping from the fissures. This was the case during the earthquake of
+Lisbon, in 1755, when fire burst through fissures at several places,
+burning with a lambent flame for some hours.
+
+The clouds of dust that follow the rending of mountain masses by
+earthquakes are probably to be traced to the fracture of the rock
+masses, the dust so formed being violently thrown forth by the air
+squeezed out of the fissures, when they are suddenly closed. The
+violent compression of this air may raise this dust to incandescence.
+
+Mallet asserts that in many cases the clouds of smoke observed do
+not consist of true smoke like that produced when wood or vegetable
+matters are incompletely burned, but is only ordinary air mixed with
+sulphurous acid gas, and various other gases.
+
+But not only fire and smoke are seen at times coming out of fissures
+in the earth. A thing still more frequently thrown out is water, which
+often spouts forth along with great quantities of mud, sand, and the
+finely ground fragments of earthy materials generally. Among many
+other instances where the emission of water from the crevices was
+particularly noticeable, may be mentioned the earthquakes at Jamaica
+in 1687 and 1692. Here the water, in some places, was thrown out of
+the ground to considerable heights in the air.
+
+Mallet calls attention to the fact that the waters of springs collect
+in reservoirs consisting either of fissures or crevices of the rocks,
+of small width but great depth, which are vertical or inclined to the
+horizon, or in reservoirs that are formed of extended beds of sand or
+gravel.
+
+Now, when the earthquake waves moving horizontally over the surface
+produce movements that squeeze these fissures together, the water in
+the fissures is spurted out in high jets, and carries with it the
+finely divided rock or sand formed by the rubbing together of the rock
+surfaces. In the case of the reservoirs consisting of beds of sand
+or gravel, lying between impervious layers, if, during an earthquake
+motion, the land areas are suddenly lowered, the water rushing into
+the cavity thus left will afterwards be shot out with considerable
+force, when the land is suddenly raised again.
+
+Where there are no direct openings in the ground the water will burst
+through the crust in the shape of great vertical jets, thus forming a
+circular hole, broken or fractured at its edges. Water jets of this
+character were especially numerous during the earthquake of Calabria
+in 1783. In a swampy plain, known as Rosarno, many of these circular
+wells or openings about the size of an ordinary carriage wheel, though
+in some cases much larger, were to be seen crowded together. The
+appearance of the openings are represented in Fig. 40.
+
+Some of these were filled with water, but the greater number were dry
+and filled with loose sand. These latter, when examined by digging,
+were shown to be funnel-shaped, as seen in Fig. 41. As seen, the
+margins of the wells exhibit a series of cracks or crevices extending
+radially outward from the centre. Their origin is evident. As the
+water was violently expelled by the squeezing motion of the upper
+and lower impervious strata, it shot upwards, thus producing the
+funnel-shaped tube. At the same time the force of the eruption was
+sufficiently great to produce the radial fissures or fractures at the
+sides.
+
+[Illustration: FIG. 40. CIRCULAR HOLLOW FORMED BY CALABRIAN
+EARTHQUAKE]
+
+[Illustration: FIG. 41. SECTION OF CIRCULAR HOLLOW FORMED BY
+CALABRIAN EARTHQUAKE]
+
+But greater fissures than these have been formed by earthquakes,
+especially those of the class created by a slipping of the earth's
+strata. In the case of an earthquake on the South Island of New
+Zealand, in 1848, a fissure having an average width of eighteen
+inches could be clearly seen extending in a direction parallel to
+the mountain chain for a distance of sixty miles, and during a later
+earthquake in the same region, in 1855, a fracture was formed that
+could be clearly traced for a distance of nearly ninety miles.
+
+In some cases these fissures or fractured parts of the crust are left
+with one of their sides at a higher level than the opposite side. This
+was the case of the great Japanese earthquake of October 28th, 1891.
+
+There are three kinds of waves produced by earthquakes; namely, the
+earthquake waves proper through the earth; the sound waves in the air,
+and great forced waves in the sea.
+
+The sound waves of course reach the air from the point of origin below
+the earth's surface through the solid materials of the crust, and take
+on the curious varieties already described in connection with the
+sounds accompanying earthquakes.
+
+We have already briefly described the manner in which the earthquake
+waves travel through the materials of the earth's crust. There remain
+to be discussed the great waves that are rolled up in the ocean
+during an earthquake shock. These waves are, perhaps, among the most
+destructive phenomena of great earthquakes. The following are only
+some of the more remarkable of such waves, and have been taken from
+Mallet's collection of earthquake data.
+
+During some of the great earthquakes on the coasts of Chile and Peru,
+huge waves from the ocean did great damage when they reached the land.
+In the earthquake of 1590, ocean waves rushed for several leagues
+inland over the coast of Chile, carrying with them ships that were
+left high and dry as the wave receded. In the earthquake of 1687,
+Callao was inundated by a great wave from the Pacific Ocean, and ships
+were carried a full league into the country. During the earthquake of
+1746, Callao was again swept away by a huge ocean wave. At later times
+earthquake waves have caused great damage to several other parts of
+the coast of South America.
+
+Ocean waves of this character are formed by successive upward and
+downward movements at the bottom of the ocean, following each other at
+very brief intervals. Le Conte points out that the sudden upheaval of
+the bed of the ocean forms a huge mound in the surface of the water
+which results in a large wave that spreads rapidly in all directions.
+Waves produced in this manner sometimes reach a height of fifty to
+sixty feet. They are not readily observed in the deep ocean, but
+as soon as they reach the shallow waters near the shore they rush
+forward, forming waves from fifty to sixty feet in height and, rushing
+over the land, sweep everything before them.
+
+During the great Lisbon earthquake of 1755 a huge wave started at a
+point fifty miles off the coast of Portugal. Half an hour after the
+earthquake was over several waves, the largest of which was sixty
+feet in height, rushed over a part of the city and greatly increased
+the ruin already wrought by the earthquake. According to Le Conte the
+great waves so formed moved in all directions across the Atlantic
+Ocean. They were thirty feet high when they reached Cadiz, eighteen
+feet in height at Madeira, and five feet on the coast of Ireland. They
+even crossed the Atlantic, being observed on the coasts of the West
+Indies.
+
+A great ocean wave accompanied the Japanese earthquake in 1854. As in
+the case of the Lisbon earthquake this wave started in the bed of the
+ocean off the coast of Japan and only reached the island half an hour
+afterwards. It was thirty feet in height, and completely swept away
+the town of Simoda.
+
+Owing to water's greater freedom of motion earthquake waves travel
+greater distances through the water than they do on land.
+
+Of course, great earthquake shocks as a rule cause a very large loss
+of life. The following figures from Mallet give some idea of the
+extent of this loss, which is generally a matter of a few moments.
+
+In the Lisbon earthquake, where the worst shock lasted a few seconds,
+60,000 people were killed. During other earthquakes the losses have
+been as follows: 10,000 at Morocco; 40,000 in Calabria; 50,000 in
+Syria, and probably 120,000 in earthquakes that occurred in Syria in
+A. D. 19 and in A. D. 526.
+
+But even these figures give only a meagre idea of the vast loss of
+life that has occurred during the past. It is said that during the
+reign of Justinian, earthquakes repeatedly shook the whole Roman
+world. The city of Constantinople was visited by earthquake shocks
+that continued at intervals for forty days. Deep chasms were opened in
+the earth and huge masses were thrown into the air. Enormous sea-waves
+were formed. At Antioch, during the earthquake of May 20th, A.
+D. 526, 250,000 people are believed to have been killed.
+
+On the 31st of July, A. D. 365, in the second year of
+Valentinian, a dreadful earthquake shook the Roman world, and a great
+wave rolled in from the Mediterranean and swept two miles inland,
+carrying ships over the tops of houses. During this earthquake 50,000
+people lost their lives at Alexandria.
+
+In the earthquake of Messina in 1692, 74,000 people are said to have
+been killed; and, according to other accounts, 100,000. In the year
+A. D. 602, another earthquake at Antioch killed 60,000 people.
+
+During the earthquake of Quito, in 1797, Humboldt estimates that
+40,000 natives were either buried in crevices in the earth, under
+the ruins of buildings, or were drowned in lakes and ponds that were
+temporarily formed.
+
+In this connection Mallet writes as follows:
+
+      "Such are the numbers to be met with in narratives, and
+      if we suppose that there occurs one great earthquake in
+      three years over the whole earth and that this involves the
+      entombment of only 10,000 human beings, and that such has
+      been the economy of our system for the last 4,000 years, we
+      shall have a number representing above 13,000,000 men thus
+      suddenly swallowed up, with countless bodies of animals of
+      every lower class. Sir Charles Lyell then with good reason
+      suggests that even in our own time we may yet find the
+      remains of men and of their habitations and implements thus
+      buried deep and embalmed, as it were, by earthquakes that
+      occurred in the days of Moses and the Ptolemies."
+
+Necessarily the progress of a great earthquake wave will produce great
+changes in the earth's surface features; for example, landslides,
+where immense layers of clay or other material slip or slide to a
+lower level and are thrown across the course of a river, causing its
+waters to be dammed up and then by spreading to form great lakes.
+
+Sometimes, after vast bodies of water have been collected in this
+manner, disastrous floods result later from a sudden giving way of the
+barrier, and the loss thus caused is occasionally far greater than
+that directly due to the earthquake.
+
+Permanent changes of level are frequently caused by earthquakes, as,
+for example, the coast of Chile during the earthquake of November
+19th, 1822, where the coast for many miles was raised from three to
+four feet above its former plane.
+
+In other cases the level of the ground is permanently lowered. This
+occurred in the Bengal earthquake in 1762, when an area of some sixty
+square miles suddenly sank, leaving only the tops of the higher points
+above water.
+
+In some cases of changes in the level of the ground, large areas being
+raised in one place and lowered in another, rivers take new courses,
+and their old courses are completely obliterated.
+
+
+
+
+CHAPTER XXV
+
+THE EARTHQUAKE OF CALABRIA IN 1783
+
+
+All students of elementary geography are quick to notice that the
+extreme southeastern part of Italy is shaped something like a boot,
+which appears to be kicking at the island of Sicily. This part of the
+Mediterranean Sea has for very many years been the arena or storm
+centre of more or less intense volcanic activity. To the northwest is
+the active volcano of Vesuvius, as well as the volcanic regions of the
+Phlegræan Fields. Immediately opposite the point of Italy, near the
+toe of the foot, is the active volcanic mountain, Etna, while not far
+from this point is the volcano of Stromboli.
+
+In 1783 this part of the world was visited by a very severe
+earthquake. Since at that time the country was divided into two
+parts, known as Upper Calabria and Lower Calabria, this earthquake is
+sometimes spoken of as the earthquake of the Calabrias, or more simply
+as the Calabrian earthquake.
+
+The great mountain range of the Apennines, mainly of granite
+formation, extends through the central part of Italy. The lands
+adjoining the mountains on each side are flat and marshy, and
+consequently unhealthy.
+
+Numerous observers have compiled excellent accounts of the Calabrian
+earthquake. These, having been made by educated persons, are, to a
+large extent free from the inconsistencies and exaggerations apt to
+characterize descriptions by ignorant persons, especially when in
+a condition of excitement or alarm. Among reliable writers was Sir
+William Hamilton, who made a personal examination of the region, soon
+after the first severe shock, and collected much valuable information
+for a paper which was afterwards published in the Philosophical
+Transactions of the Royal Society. Then, too, Dolomieu, another
+scientific man of high ability, made a careful study of the effects
+produced by the earthquake.
+
+[Illustration: FIG. 42. MAP OF THE CALABRIAN EARTHQUAKE OF
+1783]
+
+As can be seen by an examination of the map presented in Fig. 42, the
+part of Italy included in the Calabrias covers an area from north to
+south almost equal to two degrees of latitude. Although the shock
+extended beyond the limits of Calabria, since it reached as far north
+as Naples, as well as over a great part of the Island of Sicily, the
+territory in which the greatest damage was done did not exceed in area
+about 500 square miles.
+
+The southern part of Italy is subject to frequent earthquake shocks.
+Pignatari, an Italian physician, asserts that this region was visited
+during 1783 by no less than 949 earthquakes, of which 501 were of the
+first class, or degree of intensity, while in 1784, there were 151
+earthquakes, of which ninety-eight were of the first class.
+
+It seems that the city of Oppido, marked on the above map as midway
+between the two coasts, was the point from which the severe earthquake
+of 1783 started. If one draws a circle, with a radius of twenty-two
+miles, around Oppido as a centre, the portions of the Calabrias that
+were the most affected will all lie within this circle.
+
+The great Calabrian earthquake was attended by numerous shocks. The
+first and the most severe shock, that of February 5th, 1783, was only
+two minutes in destroying most of the houses in all cities, towns, and
+villages on the western side of the Apennines in this part of Italy.
+
+Another severe shock occurred on the 28th of March. This shock was
+almost as severe as that of February 5th.
+
+In order to understand many of the effects produced by this
+earthquake, inquiry must be made into the geological character of the
+region. According to Dolomieu, the flat country at the slopes of the
+Apennines, known as the Plain of Calabria, is covered with sand and
+clay mixed with sea shells. These strata have been deposited by the
+sea from materials that have been obtained by the decomposition of the
+granite mountain ranges in the Apennines. The plain is quite level
+except where it is crossed by deep valleys or ravines, which have
+been eroded or cut by the swift mountain torrents. In many cases,
+these ravines or valleys have depths as great as 600 feet. Their sides
+are generally almost perpendicular. Consequently, as Lyell remarks,
+throughout the length of the mountain chain, the soil, which adheres
+but loosely to the granite base of the mountain chain, could therefore
+be easily separated from the mountain, and sliding over the solid
+steeps of the mountain could readily move, especially through the
+ravines or gorges, to distances in some cases as great as from nine to
+ten miles.
+
+This peculiarity of the country must be thoroughly understood, since,
+otherwise, it would seem impossible that lands could be carried
+several miles from their former position, and often bear along
+with them almost undisturbed houses, olive groves, vineyards, and
+cultivated fields.
+
+The heaving of the surface of the earth like the waters of the sea,
+so common in severe earthquakes, occurred during the Calabrian
+earthquake. In some places this heaving so shook the trees that they
+bent until their tops touched the ground near their base.
+
+Parts of the ground were violently thrown upwards into the air as in
+the explosive type of earthquakes. In many instances the large paving
+stones were thrown into the air and afterwards found with their lower
+portions upwards.
+
+During the earthquake deep fissures were made in the earth at various
+localities and there were, moreover, marked changes of level. At
+Messina in Sicily the shore was fissured and rent and while before the
+convulsion the surface had been level, it was afterwards found to be
+inclined toward the sea.
+
+According to Dolomieu the following curious incident occurred during
+the passage of the earthquake waves. A well in the ground of one of
+the convents of the Augustines, lined on the inside with stones, was
+so affected by the upward thrust given to the land that its stone
+lining was left projecting above the level of the earth in the form of
+a small tower some eight or nine feet in height.
+
+Frequent instances occurred of deep fissures in the surface of the
+earth. Many of these remained open after the earthquake, although in
+other cases they were firmly closed together before the earthquake
+shocks ceased.
+
+[Illustration: FIG. 43. FISSURES CAUSED BY THE CALABRIAN
+EARTHQUAKE]
+
+Fig. 43 represents the appearance of certain fissures in a part of
+Calabria during this earthquake. These cracks, it will be noticed,
+radiate or pass outward in all directions from a central point, just
+like the cracks that are formed in a glass window pane when it is
+fractured by a stone thrown against it.
+
+Of course, the most violent effects were near the origin of the
+earthquake at Oppido. Here the formation of deep fissures was common.
+In another part of the country a number of buildings were suddenly
+swallowed up in a central chasm, which almost immediately closed,
+thus permanently burying all these objects.
+
+Some idea of the force with which the fissures were afterwards closed
+can be formed by reflecting on a case where, in order to recover some
+of the buried articles, the ground was dug up at these points, and it
+was found that the materials, human bodies and other objects, were so
+jammed together as to make one compact mass.
+
+To Sir William Hamilton a place was shown where the fissures, though,
+when he saw them, they were not more than a foot in width, had opened
+sufficiently wide during the shock to swallow up a hundred goats as
+well as an ox.
+
+An earthquake that caused such marked changes in the appearance of the
+earth's surface, naturally made great changes in the direction of the
+rivers. In one case the end of a small valley was so completely filled
+with stones and dirt that the water was dammed up, producing a lake
+two miles in length and one mile in breadth. In a similar manner no
+less than 215 lakes were formed in different portions of Calabria.
+
+Of course, in the flat country at the base of the Apennines,
+frequent landslides occurred, the land sliding into great chasms and
+continuing to move down them for considerable distances, so that in
+many places pieces of land containing olive trees, vineyards, and
+green fields, were bodily transported for distances of several miles.
+This, moreover, was done so quietly as to leave the houses entirely
+uninjured, and the trees and other vegetation continuing to grow up
+with apparently no marked decrease in vitality.
+
+As is usual in such cases, the sudden and strong blows acting on the
+waters of the sea, killed great numbers of fish just as does the
+explosion of dynamite at a point below the surface of the water; and
+in a similar way the fish that usually live at the bottom of the sea
+in the soft mud, being disturbed by the earthquake shocks, came near
+the surface where they were caught in vast numbers.
+
+It is an interesting fact that during this earthquake the volcano of
+Stromboli showed a marked decrease in the volume of smoke it gave out.
+Etna, however, was observed to emit large quantities of vapor during
+the convulsion.
+
+Lyell tells the following story of the Prince of Scilla, who with
+many of his vassals sought safety in their fishing boats. Suddenly,
+on the night of February 5th, while some of the people were sleeping
+in the boat, and others were resting on a low plain near the sea,
+in the neighborhood, another shock occurred, a great mass was torn
+from a neighboring mountain and hurled with a crash on the plain, and
+immediately afterwards a wave, twenty feet or more in height, rolled
+over the level plain, sweeping away the people. It then retreated, but
+soon rushed back again, bringing with it many of the bodies of the
+people who had perished. At the same time all the boats were either
+sunk or dashed against the beach, and the Prince with 1,430 of his
+people was destroyed.
+
+The total number of deaths caused by this earthquake in the Calabrias
+and Sicily were estimated by Hamilton at 40,000. Besides these about
+20,000 more perished in epidemics that followed the earthquake, or
+died for lack of proper food.
+
+
+
+
+CHAPTER XXVI
+
+THE GREAT LISBON EARTHQUAKE OF 1755
+
+
+Lisbon, the capital of Portugal, on the Tagus River, is built along
+both banks for five miles, and on several small neighboring hills. It
+is supplied with water by means of an aqueduct, called the Alcantara,
+which brings the water from springs about nine miles to the northwest.
+For portions of its length the aqueduct is placed underground, but
+where it crosses the deep valley of the Alcantara it is supported,
+for a distance of 2,400 feet, by a number of marble arches, which
+in one place are 260 feet in height. This fact is put forward not
+merely for the sake of its artistic interest, but because, strange to
+relate, this part of the aqueduct remained uninjured during that great
+earthquake, the greatest of modern times.
+
+On the 1st of November, 1755, this frightful catastrophe, according to
+Lyell, from whose excellent account much of the information contained
+in this chapter has been obtained, struck the beautiful city almost
+without any warning. Terrible sounds came suddenly from underground;
+almost instantly afterward a violent shock threw down the greater
+portion of the city; in less than six minutes 60,000 people were
+killed.
+
+The place from which this earthquake started must have been situated
+on the bed of the ocean at some distance from the coast; for the great
+wave thus raised in the Atlantic Ocean did not reach the mouth of the
+Tagus River until about half an hour after the most severe shocks
+were over. The arrival of this wave at the mouth of the Tagus was
+announced by the sea retiring to such an extent as to leave the bar
+dry. Then a huge wave, sixty feet in height, rolled in from the ocean
+and completed the work of destruction that had been commenced by the
+earthquake.
+
+So great was the shock that the mountains in the neighborhood were
+violently shaken and some of them split or fractured in a most
+wonderful manner.
+
+Particularly large was the loss of life in the churches whither
+hundreds hastened for refuge when the shakings of the earth began,
+for most of these buildings fell and buried the worshippers. Another
+immense loss of life was caused by the destruction of a large marble
+quay or wharf that was suddenly swallowed up by the sea. While the
+buildings in the city were being overthrown by the violent shakings
+of the earth, a multitude sought the quay as a flat place where they
+could not be injured by the falling buildings. Suddenly, however,
+this structure sank into the water and not only were all the people
+drowned, but none of the bodies was ever afterwards found.
+
+Failure to find any remnants of the pier or any of the people who
+perished on it has been attributed to the formation of eddies or
+whirls that were sufficiently strong to carry down vessels by suction
+similar to that of the famous maelstrom off the coast of Norway. Of
+course, in a time of boundless excitement like that of the Lisbon
+earthquake, accounts are apt to be highly exaggerated. For example,
+assertions are made in many books that the water left in the harbor
+after the sinking of the quay was unfathomable. Now, in point of fact,
+the depth of this place has been measured and found to be less than
+100 fathoms.
+
+When it is remembered that not one of the bodies of the people on that
+quay was ever again seen, it is possible, as Lyell suggests, that a
+deep fissure or chasm opened immediately on the ground on which the
+quay stood, so that it, together with all on it, were dropped into the
+chasm, which, closing, buried them deep in the earth.
+
+The Lisbon earthquake was especially noted for the extent of country
+affected by it. Humboldt estimated this area as being more than four
+times the size of Europe. In parts of this area immense mountain
+ranges, such as the Pyrenees, Alps, etc., were violently shaken. When
+the size of these mountains is considered one realizes that it must
+have required a mighty force to shake them. These shakings were so
+severe that they produced a deep fissure in the ground in France.
+Continuing towards the north the solid earth was shaken as far as
+the shores of the Baltic and Norway and Sweden, generally. This, of
+course, included the flat country of Northern Germany. The hot springs
+of Toplitz disappeared for a time, but, breaking out afterwards,
+discharged such quantities of muddy water that the surrounding country
+was inundated.
+
+The waves crossed the Atlantic, causing high tides on the island of
+Antigua, Barbadoes, and Martinique, of the Lesser Antilles, where,
+instead of the usual tides of two feet, tides of twenty feet high were
+observed. Further to the north the waves reached the eastern shores of
+North America, and shook the continent as far west as the Great Lakes,
+and spread in the North Atlantic as far as Iceland.
+
+Toward the south the waves affected parts of northwestern Africa,
+where much loss of life occurred in the villages some eight leagues
+distant from the city of Morocco. Here from 8,000 to 10,000 people
+were killed, being swallowed up by deep fissures in the earth, which
+afterwards closed on their bodies.
+
+Severe shocks were in many cases felt on vessels at sea. In one
+instance, although the vessels were at considerable distances from
+where the waves started, the captains reported that the shocks were so
+great that on several occasions it was believed the vessel had struck
+a rock, till, on heaving the lead, they found that they were in very
+deep water. In another instance, such was the shock to the vessel that
+the planks on the deck had their seams opened. In still another case
+several of the sailors were thrown into the air for a distance of
+about one and a half feet.
+
+It has been frequently observed that when great earthquakes happen,
+curious changes take place in the level of the waters of lakes
+entirely disconnected with the ocean; for example, mountain lakes,
+far above the level of the sea, the water suddenly rising and then
+resuming its original level. Sometimes the waters of such lakes have
+suddenly disappeared, probably being drained off through a fissure
+formed in the bed of the lake. In such event the lake generally
+remains dry after the passage of the earthquake.
+
+At the time of the Lisbon earthquake it was observed that the water of
+Loch Lomond in Scotland first rose above its ordinary, then sank again
+to its usual level. This difference of level is explained by Lyell as
+follows: when the earthquake waves reached the lake, the water being
+unable to take the sudden shove given to it by the earthquake waves,
+dashed over that side of the basin which first received the shock.
+Assuming this to be the case, since the rise of the level in the water
+of Loch Lomond was two feet and four inches, it is comparatively easy
+to calculate the speed of movement that the earthquake waves had,
+when they reached this body of water. Calculated in this way it would
+seem that the waves had a speed of about twenty miles a minute.
+
+But what especially characterized the Lisbon earthquake were the great
+waves that were produced in the ocean. Besides the huge wave that
+entered the Tagus, a wave of the same height swept eastward along the
+southern coast of Spain, and the northwestern coast of Africa. At
+Tangier in Africa it swept the coast as a very high wave no less than
+eighteen times, or, in other words, eighteen huge waves rolled in from
+the ocean. At Funchal, on the Madeira Islands, this wave rose fifteen
+feet above the high water mark.
+
+Many attempts have been made to explain the manner in which the great
+sea waves are started in earthquake movements. Some believe that they
+are due to the sudden raising or heaving up of the water, far above
+ordinary level. But, as Lyell points out, this explanation would not
+be satisfactory for the waves produced in the case of the Lisbon
+earthquake, since it would fail to account for the fact that both on
+the coasts of Portugal as well as on the island of Madeira the high
+wave was preceded by a movement of the water toward the point of
+origin; that is, the waters moved away from Lisbon and the Madeira
+Islands, so as to leave the water very low at those points, when
+shortly afterwards a huge wave rushed in from the sea and swept over
+the land.
+
+Earthquake waves move much more rapidly through the solid rocks of
+the earth's crust than through the waters of the ocean. The shock
+transmitted through the solid earth from Lisbon to the Madeira Islands
+took only twenty-five minutes to reach the islands, while the waves in
+the ocean took about two and a half hours to cover the same distance.
+
+
+
+
+CHAPTER XXVII
+
+THE EARTHQUAKE OF CUTCH, INDIA, IN 1819
+
+
+Cutch is one of the Provinces of India lying on the western coast of
+Hindostan, east of the delta of the Indus River.
+
+A great earthquake occurred in this region on June 16th, 1819. As
+indicated by the map presented in Fig. 44, by Lyell, the district
+of Cutch lies on the coast of the Arabian Sea. Cutch is at times a
+peninsula, being washed on the south and east by the Arabian Sea and
+the Gulf of Cutch, and on the north by a depression known as the Runn
+of Cutch which, during unusual tides, is overflowed by the waters of
+the sea, but for the rest of the year is dry.
+
+The earthquake of Cutch was apparently central at the town of Bhooj,
+where the destruction was extreme, hardly a house being left standing.
+The shock extended over a radius of about 1,000 miles from Bhooj,
+reaching to Khatmandoo, Calcutta, and Pondicherry.
+
+At Anjar the fort, together with its tower and guns, were completely
+ruined. The shocks continued at intervals after the principal shock
+until June 20th, when the volcano of Denodur is said by some to have
+emitted flames, although this is denied by others.
+
+Great changes were produced in the eastern channel of the Indus,
+which forms the western boundary of the Province of Cutch. The water
+in this inlet had become so low that it was readily fordable at low
+tide at Luckput, and was only covered with six feet of water at high
+tide. After the earthquake it deepened at the port of Luckput to over
+eighteen feet at low tide, while in other parts of the channel the
+water had deepened from four to ten feet at high tide, where before
+the earthquake shock it had never been deeper than from one to two
+feet. Indeed, after these changes the inland navigation of the country
+again became possible after having been closed for many centuries.
+
+[Illustration: FIG. 44. MAP SHOWING DISTRICT VISITED BY THE
+EARTHQUAKE OF CUTCH OF 1819]
+
+The Cutch earthquake resulted in a marked depression of the country,
+especially north of Luckput, where the fort and village of Sindree
+were so quietly sunk that the fort, with its tower and walls, was left
+projecting slightly above a body of water that not only completely
+covered the old site but also formed a large lake marked on the
+preceding map, at Sindree, by the dark shading. It was this change of
+level that deepened the eastern channel of the Indus, just mentioned.
+
+[Illustration: FIG 45.. SINDREE BEFORE THE EARTHQUAKE OF
+1819]
+
+Fig. 45, from Lyell, gives an idea of the appearance of the fort at
+Sindree before the earthquake. The appearance of the fort after its
+submergence is represented in Fig. 46, where, as will be noticed, only
+the top of the tower and the walls remain above the surface of the
+water. That the masonry was not affected either by the earthquake, or
+by the inrush of waters, is evident from the fact that the ruins were
+still standing in March, 1838, as represented in the figure.
+
+In heavy shading on the map in Fig. 44 is a large area lying in the
+northern part of the province known as the Runn of Cutch. This is a
+flat region of about 7,000 square miles. It owes its level surface to
+its being the deserted or dried-up bed of a sea. For the greater part
+of the year its bottom is dry and hard, and is covered with a crust of
+salt half an inch or so in thickness.
+
+[Illustration: FIG. 46. SINDREE AFTER THE EARTHQUAKE OF 1819]
+
+According to Lyell, from whom most of the facts concerning this
+earthquake have been obtained, the Runn of Cutch is connected with
+a vast inland sea, not only by the water driven into it through the
+Gulf of Cutch, but also through the eastern channel of the Indus at
+Luckput. These changes occur especially during the monsoon, when the
+seas are high, and especially after the heavy rains that come with
+these winds, when the wet condition of the soil permits the sea water
+to spread rapidly.
+
+Traditions of the natives tend to confirm belief that Cutch a long
+time ago was a true peninsula, and that the Runn of Cutch was then an
+arm of the sea.
+
+That a change of this character did occur in the Runn of Cutch seems
+to be proved by the ruins of old towns now far inland that are said to
+have been ancient seaports, and as apparent evidences of this many
+pieces of wrought iron and ships' nails have been found in parts of
+the Runn.
+
+At the same time that the sinking of the land around the fort and
+village of Sindree took place a considerable elevation occurred in the
+neighborhood. Immediately after the earthquake, the people in Sindree
+saw that a low hill or mound had been thrown up in a place that before
+had been a low and perfectly level plain. They named this elevation
+the Ullah Bund, or _the Mound of God_, in order to distinguish it
+from several embankments that had been built directly across the
+eastern mouth of the Indus; for the Ullah Bund had been raised by the
+earthquake across the same branch of the Indus.
+
+For several years after the earthquake of 1819 marked changes kept
+developing in the channels of the Indus. During 1826 a large body of
+water entered into the eastern branch of the Indus above the Ullah
+Bund and finally forced its way through the mound, thus establishing
+a direct course to the sea. The Ullah Bund, being thus cut in two,
+an opportunity was afforded of seeing the materials of which it was
+composed. These were found to consist principally of clay filled with
+shells.
+
+The opening of the river resulted in throwing such large quantities of
+fresh water into Lake Sindree that its waters were rendered fresh for
+several months, but at last regained their saltiness.
+
+Dana states that in 1845 another earthquake occurred in this district
+which converted Sindree Lake into a salt marsh.
+
+
+
+
+CHAPTER XXVIII
+
+THE SAN FRANCISCO EARTHQUAKE OF APRIL 18, 1906
+
+
+About twelve minutes past five o'clock on the morning of the 18th of
+April, 1906, the inhabitants of San Francisco were rudely awakened by
+a few frightful earthquake shocks. Their houses were violently shaken
+to and fro, and on all sides were heard the awful crashings of falling
+walls, chimneys, and buildings, together with the death-shrieks of
+those caught in the ruins. Rushing madly into the streets they could
+see on every side evidences of destruction; for, in almost every
+direction, were heaps of fallen buildings, still being violently
+shaken by the earthquake waves that rapidly passed through the solid
+earth. Huge cracks or crevices had been formed in the streets, while
+the heavy rails of the trolley tracks had been bent and twisted by the
+mighty forces.
+
+Before describing in detail the great San Francisco earthquake, the
+location of the city and its surroundings demand consideration.
+
+As can be seen from the map, Fig. 47, San Francisco is situated on the
+western coast of California, at the northern end of a peninsula, some
+twenty miles in length and about six miles in width. This peninsula
+is formed by the magnificent Bay of San Francisco on the east, a
+navigable strait called the Golden Gate on the north, and the Pacific
+Ocean on the west.
+
+[Illustration: FIG. 47. MAP OF WESTERN COAST OF CALIFORNIA SHOWING
+POSITION OF SAN FRANCISCO]
+
+San Francisco Bay, accessible by the Golden Gate, is the principal
+harbor on the Pacific Coast, and is, indeed, one of the most
+magnificent harbors in the world. It is land-locked, that is,
+surrounded by a continuous land border except at its entrance through
+the Golden Gate. Including San Pablo Bay, it has a length of about
+fifty-five miles, and varies in breadth from three to twelve miles.
+The entrance to the harbor, however, is impeded by a bar across the
+mouth of the Golden Gate, over which there is a depth of but thirty
+feet of water at low tide.
+
+San Francisco has over 750 miles of streets, 200 miles of which are
+paved. The city is lighted by both electricity and gas, and has an
+extensive system of water-works, the water being brought from the
+Pilarcitos and Calaveras Creeks, situated from twenty to forty miles
+respectively from the city.
+
+San Francisco is in a region where earthquakes are common. It might,
+therefore, be visited at any time by a great catastrophe. There have
+occurred between 1850 and 1888, no less than 254 earthquake shocks in
+the State of California, these shocks having been especially frequent
+in the country surrounding San Francisco Bay. The most severe were
+the earthquake of 1868, which injured San Francisco; the Owens Valley
+earthquake of 1872; the Vacaville earthquake of 1892; the Mare Island
+earthquake of 1898; and a smaller earthquake in 1900. Since 1900 there
+was a period of rest until the 18th of April, 1906.
+
+As in the case of practically all severe earthquakes, that which
+destroyed San Francisco consisted of a few momentary shocks: then all
+was over. According to a preliminary report of the State Earthquake
+Commission, appointed by the Governor of California, April 21st, 1906,
+these shocks, as recorded in the observatory at Berkeley, began at
+twelve minutes and six seconds after five A. M., Pacific
+Standard Time. Their entire duration was only one minute and fifty
+seconds, but, as frequently happens, there were a number of minor
+shocks, following at regular intervals during the next few hours as
+well as the next few days.
+
+While the most severe shocks were in the neighborhood of the Peninsula
+of San Francisco, yet minor disturbances were felt as far north
+as Coos Bay, Oregon, and as far south as Los Angeles, California.
+As shown by recording instruments at the seismograph station at
+Washington, D. C., Sitka, Alaska; Potsdam, Germany; and Tokio, Japan,
+a series of waves were propagated through the earth, as well as over
+its periphery.
+
+The damage done within the city limits was wide-reaching. Among the
+buildings almost completely destroyed were the City Hall, on which
+about $7,000,000 had been expended, the United States Post Office,
+besides many business blocks, hotels, department stores, theatres,
+banks, churches, and dwelling houses.
+
+Amid the terrors of such a calamity it is difficult to obtain
+observations possessing any scientific value. Fortunately, however,
+there was in the city a physicist trained to observe phenomena of this
+character, Professor George Davidson of the University of California.
+Like others, he had been awakened by the first severe shock. At once
+recognizing the nature of the phenomenon, and desirous of obtaining
+the exact time of its occurrence, he counted seconds while he ran
+towards the table on which he had placed his watch, and in this way
+estimated that the shock occurred at twelve minutes past five in
+the morning. The closeness of this observation is emphasized by the
+fact that it differed from the recorded time by only six seconds. He
+states that the motion, at the time of its greatest intensity, closely
+resembled that of a rat vigorously shaken by a terrier.
+
+The destruction caused by the earthquake was, however, but a small
+part of the total loss to the city. Fires were almost immediately
+started in the ruined houses by the fires in the kitchens and other
+parts of the houses, by the ignited jets of the illuminating gas,
+and, perhaps, especially, by the crossing of numerous electric light
+wires.
+
+The manner in which the woodwork and other combustible materials of
+the buildings were loosely tossed together by the shocks helped the
+quick spread of the fires, and this, too, was probably greatly aided
+by the illuminating gas from the broken gas pipes and mains. Eight
+severe conflagrations were, therefore, soon raging in different parts
+of the doomed city. What made these fires especially dangerous was the
+fact that the earthquake shocks had destroyed the water pipes. Thus
+the firemen were handicapped in their heroic endeavors to extinguish
+the flames.
+
+At the time of the fire a strong wind was blowing from the northeast.
+Since the firemen were unable to check the flames, the fire line
+rapidly advanced. Its path led towards the best residential parts of
+the city through portions of the mission section containing a dense
+population of poor people. The dwellings in this latter section
+consisted of frame houses, through which the flames rapidly spread.
+
+There was but one way to save the city from total destruction--a free
+use of dynamite! This was intelligently employed until the supply gave
+out, when it seemed that the city was doomed to utter destruction.
+But at the last moment, as it were, came a lucky change in the
+direction of the wind. Instead of blowing from the northeast, the
+steady southwest winds set in, and beat back the fire on itself, so by
+Friday, the 18th being Wednesday, it was under complete control and
+the rest of the city was saved.
+
+[Illustration: A SAN FRANCISCO PAVEMENT TORN BY THE
+EARTHQUAKE _From a Stereograph, Copyright, 1906, by Underwood &
+Underwood_]
+
+The extent of the fire is thus described in an article in the
+"Outlook," for Saturday, April 28th, 1906, as follows:
+
+      "The turn in the direction of the fire endangered for a
+      time the great Ferry House, at the foot of Market Street.
+      While the section actually destroyed is not, geographically
+      speaking, much more than one-third of the city limits,
+      yet it is in the heart of San Francisco, and includes the
+      chief business streets and the Mission District, inhabited
+      by poor people, and a large part of the so-called Nob Hill
+      Quarter, where were the finest and costliest residences of
+      the city. Another fine residence section, Civic Heights,
+      escaped, together with that known as the Western District.
+
+      "The unburned district, though large in extent, was in
+      the nature of suburbs, and was not closely built up, so
+      that estimates made, as late as Saturday, declared that
+      three-fourths of San Francisco's improvements in real
+      estate had been destroyed."
+
+The burnt district was about two miles from east to west and from two
+to four miles from north to south, with, of course, very irregular
+outlines.
+
+Naturally, the great destruction wrought by the earthquake of April
+18th, 1906, attracted the almost universal attention of scientific men
+especially interested in earthquake phenomena. We are, therefore, able
+to speak authoritatively about the probable causes.
+
+The great San Francisco earthquake of April 18th, 1906, appears to
+have been a _tectonic_ quake. Ransome, in an article entitled, "The
+Probable Cause of the San Francisco Earthquake," says:
+
+      "The region thus amply fulfils the conditions under which
+      tectonic earthquakes arise. It is in unstable equilibrium,
+      and it is cut by long northwest faults into narrow blocks
+      which are in turn traversed by many minor dislocations.
+      Under the operation of the unknown forces of elevation and
+      subsidence, stresses are set up which finally overcome the
+      adhesion of the opposing walls of one or more of the fault
+      fissures; an abrupt slip of a few inches, or a few feet,
+      takes place and an earthquake results. The region extending
+      for some hundreds of miles north and south of the Bay of
+      San Francisco may be considered as particularly susceptible
+      to shocks on account of the number and magnitude of the
+      faults and the evidences that these furnish of very recent
+      slippings and the marked subsidence in the vicinity of the
+      Golden Gate."
+
+
+
+
+CHAPTER XXIX
+
+SOME OTHER NOTABLE EARTHQUAKES
+
+
+It would, of course, be impossible within the limits of this book to
+attempt a description of all the remarkable earthquakes in the annals
+of science; but before leaving this part of the theme a brief account
+of a few more among the many may be worth while.
+
+Jamaica, one of the West Indian Islands, about ninety miles south of
+Cuba, suffered a very destructive earthquake in 1692. During this
+earthquake the ground was agitated like the waves of the sea. These
+movements were so violent that numerous fissures were made in the
+ground, as many as 300 being formed at the same time, rapidly opening
+and closing. Many of the inhabitants were swallowed up in these
+fissures. In some cases, however, their bodies were afterward thrown
+out of the fissures, along with quantities of water.
+
+The Jamaican earthquake was characterized by marked sinkings of the
+ground. At the city of Port Royal, which was then the capital, many
+houses on the harbor side sank in from twenty-four to forty-eight
+feet of water. As in the case of the earthquake at Cutch, many of
+these houses were left standing, the chimney tops of some being seen
+above the water, with their foundations and other parts apparently
+uninjured, and some of them were standing at a date as late as 1780.
+At a little later date, 1793, they were mostly ruins.
+
+During the Jamaican quake a tract of land containing at least 1,000
+acres near the town was sunk, and a wave of the sea rolled over it.
+This wave is said by Lyell to have carried a frigate over the roofs of
+the houses and left it stranded on one roof. When the wave rolled back
+to the sea, the weight of the frigate made it fall through the roof.
+
+Perhaps one of the most remarkable things about the Jamaican
+earthquake was the swallowing up of several plantations, which
+disappeared, together with all their inhabitants, their former place
+becoming a lake. But the lake soon disappeared, leaving a mass of sand
+and gravel which obliterated any least sign that dwellings and trees
+had once adorned the spot.
+
+The forces developed during this earthquake were sufficiently powerful
+to make several rents in the Blue Mountains, and the shock of blows on
+the waters of the sea killed fish by the hundred thousands so that the
+silver shine of their dead bodies stretched for miles and was beheld
+for days "on the face of the deep."
+
+Portions of the world that have been frequently visited by mighty
+earthquakes, are the coasts of Chile. On the 24th of May, 1751, a part
+of the Chilian coast near the ancient town of Concepcion, sometimes
+called Penco, was destroyed by an earthquake, and the powerful
+earthquake waves that afterwards rushed in from the sea. So complete
+was this destruction that the ancient harbor was rendered useless and
+the people had to build another town about ten miles from the coast,
+so as to be beyond the reach of earthquake waves from the sea.
+
+Another great earthquake occurred on the coast of Chile on the
+19th of November, 1822. This shock was felt simultaneously over a
+distance of 1,200 miles from north to south. It reached its greatest
+intensity about 100 miles north of Valparaiso. This earthquake caused
+a rising of the coast to a height of from three to five feet. From
+careful examinations it appears that the area over which a permanent
+elevation of the country took place must have been equal to 100,000
+square miles, an area equal to about half of the area of France, and
+five-sixths that of Great Britain and Ireland.
+
+      "If we suppose," says Dana, "the elevation to have been
+      only three feet on an average, it will be seen that the
+      mass of rock added to the continent of America by the
+      movement, or, in other words, the mass previously below the
+      level of the sea, and after the shock, permanently above
+      it, must have contained fifty-seven cubic miles in bulk;
+      which would be sufficient to form a conical mountain two
+      miles high (or about as high as Etna) with a circumference
+      at the base of nearly thirty-three miles.... Assuming the
+      Great Pyramid of Egypt, if solid, to weigh in accordance
+      with the estimate before given 6,000,000 tons, we may
+      state that the rock added to the continent by the Chilian
+      earthquake would have equalled more than 100,000 pyramids.
+
+      "But it must always be borne in mind that the weight of
+      rock here alluded to constituted but an insignificant
+      part of the whole amount which the volcanic forces had to
+      overcome. The thickness of rock between the surface of
+      Chile and the subterranean foci of volcanic action may be
+      many miles or leagues deep. Say that the thickness was only
+      two miles, even then the mass which changed place and rose
+      three feet, being 200,000 cubic miles in volume, must have
+      exceeded in weight 363,000,000 pyramids."
+
+The shocks of this earthquake continued from the time of its
+occurrence, on November 19th, 1822, to the end of September, 1823, and
+even then there were scarcely two days that passed without a shock.
+
+On the 20th of February, 1835, the same part of the world was in the
+throes of an earthquake that was felt nearly 1,000 miles from north to
+south, or from near the town of Concepcion to the Isle of Chiloe, and
+from east to west a distance of about 500 miles, from Mendoza to the
+island of Juan Fernandez, which you probably know better as Robinson
+Crusoe's Island. By this earthquake the new town of Concepcion and
+several other towns were partly destroyed.
+
+There were the same phenomena connected with great sea waves that are
+common in earthquakes of this character. Both this and the preceding
+earthquakes probably began on the bed of the ocean at some distance
+from the coast; for, in the last earthquake, the sea retired from the
+Bay of Concepcion and vessels were grounded that had been anchored
+in seven fathoms of water. Shortly afterwards waves from sixteen to
+twenty feet in height rushed in from the ocean and swept over the land.
+
+It is interesting in this connection to note that the volcanoes of the
+Chilian Andes were in an unusual state of activity before, during, and
+after the earthquake.
+
+Another characteristic of this quake was the great number of severe
+shocks. Between the day of the first great shock; i. e., on February
+20th, 1835, and March 4th, there were more than 300 severe shocks.
+
+In this as in the preceding quake a notable elevation of the land near
+the coast occurred, amounting to from four to five feet, and a part of
+the bed of the ocean near the coast was raised permanently above the
+level of the sea.
+
+In the description of the explosive eruption of Krakatoa in 1883, the
+fact was noted that the island of Java is very frequently visited by
+earthquakes. Here a terribly severe earthquake occurred on the 5th of
+January, 1699. There were no less than 208 shocks of great intensity.
+Considerable property in the city of Batavia was destroyed, and a
+neighboring river, that has its head waters by a volcano near the
+city, ran high and muddy and brought down multitudes of fishes that
+had been killed, together with many buffaloes, tigers, rhinoceroses,
+deer, and other wild beasts. Seven hills bordering on the river sank
+down, damming up the streams of the region and thereby causing wide
+destruction from floods.
+
+During portions of the years 1811 and 1812 an earthquake occurred
+in the United States, in the Mississippi Valley near the town of
+New Madrid, Missouri, at the mouth of the Ohio River. These shocks
+continued almost incessantly for several months, and were accompanied
+by a sinking of the ground over large areas. This depressed area,
+known in the neighborhood as _The Sunk Country_, extended along the
+course of the White Water River and its tributaries for a distance of
+about eighty miles from north to south, and several miles from east
+to west. Most of it was converted into a marshy lake characterized by
+thousands of submerged trees. The area was covered for the greater
+part with water to a depth of about three to four feet.
+
+As the earthquake shocks continued at intervals for several months
+there was an ample opportunity for studying the peculiarities of the
+earth waves. The ground rose and fell like large waves in the sea, and
+after the crest of the waves had reached great heights, the ground
+burst, and threw large quantities of water, sand, and earth into the
+air.
+
+[Illustration: FIG. 48. NEW ZEALAND]
+
+Throughout the disturbed district there were numerous depressions
+known as _sink-holes_, or irregularly shaped pits, varying from ten to
+thirty yards across, and having a depth of about twenty feet. These
+were formed by the forcible ejection of large quantities of water
+mixed with sand.
+
+New Zealand has been subject to earthquake shocks for a long time, the
+years 1826, 1841, 1843, 1848, and 1855 being especially marked by such
+visitations. It is a characteristic of the New Zealand earthquakes
+that they have produced a marked change in the coast line. This was
+particularly the case with those of 1848 and 1855.
+
+The 23d of January, 1855, an earthquake occurred that was most violent
+in the narrowest part of Cook's Strait, a body of water separating
+the two principal islands that constitute New Zealand; or, as they
+are called, the North Island and the South Island. These shocks were
+felt at sea by ships 150 miles from the coast. The entire area shaken,
+including the water, has been estimated at three times the area of
+the British Isles. In the vicinity of the southern shores of the
+North Island a tract of land having an area of 4,600 square miles is
+believed to have been permanently raised from one to nine feet.
+
+The earthquakes in New Zealand are evidently of the tectonic type.
+During that of 1848 a rent or fissure was formed, which, though but
+eighteen inches in average width, yet extended for a distance of sixty
+miles in a direction parallel to one of the mountain chains.
+
+On the 31st of August, 1886, an earthquake of considerable intensity
+occurred in the United States in the neighborhood of the city of
+Charleston, South Carolina. The details of this earthquake were
+carefully studied by Major Dutton of the U. S. A., and published in
+the Ninth Annual Report of the United States Geological Survey of 1888.
+
+Charleston is situated on a narrow tongue of land between the Ashley
+and the Cooper Rivers, about seven miles from the Atlantic Ocean.
+There are in this area numerous creeks connected with the drainage of
+these rivers. As the city limits extended, the creeks were filled in,
+forming "made land," all buildings or structures erected on this land
+being supported by pilings.
+
+It appears that the point at which the earthquakes started was
+situated sixteen or seventeen miles from Charleston.
+
+The earthquake shock affected a large area of the United States. Fig.
+49 shows curved lines called isoseismal connecting places, having the
+same degree of seismic intensity. This map shows that these isoseimals
+are marked by figures or numbers from two to ten. These numbers are
+the numbers of the Rossi-Forel earthquake scale. They indicate varying
+degrees of intensity, beginning from the least intense shock which
+is marked as two and ending with the severest shock marked as ten.
+There is one degree not marked on this map, the least, called the
+micro-seismic shock.
+
+The shocks then increase in intensity as follows: II. Extremely
+feeble shocks; III. Very feeble shocks; IV. Feeble shocks; V. Shocks
+of moderate intensity; VI. Fairly strong shocks; VII. Strong shocks;
+VIII. Very strong shocks; IX. Extremely strong shocks; X. Shocks of
+extreme intensity.
+
+The meaning of the map presented in the accompanying figure will now
+become more apparent in several ways. That portion numbered ten,
+denoting where shocks of greatest intensity have been experienced,
+clearly indicates the region just above the point where the earthquake
+originated.
+
+Beyond this is a region marked nine where the earthquake shock has
+decreased in intensity to the next figure on the Rossi-Forel scale,
+and then to eight and a half, seven, six, five, four, three, and two.
+
+[Illustration: FIG. 49. MAP SHOWING REGION AFFECTED BY THE
+CHARLESTON EARTHQUAKE OF 1886]
+
+The Charleston earthquake damaged property to a considerable extent;
+for, although comparatively few buildings were completely destroyed, a
+considerable number were partially injured, and many, not thrown down
+by the shock, had to be torn down in order to insure public safety.
+The loss of life, fortunately, was comparatively small. During this
+earthquake a number of openings called _craterlets_ were made in the
+ground by the forcible ejection of large quantities of water and sand.
+
+The empire of Japan is another part of the world particularly subject
+to great as well as frequent earthquake shocks. Although Japan is also
+especially noted for its volcanic activity, its earthquakes are almost
+entirely of the tectonic type, or are due to the slipping of the land
+at faults in the earth's crust. Most of these quakes occur on the bed
+of the ocean on the sides of a steep slope that extends down to a very
+deep part of the Pacific known as the _Tuscarora Deep_.
+
+On the 28th of October, 1891, Japan was visited by a great quake,
+generally known as the Mino-Owaro earthquake, from the name of the two
+provinces of Mino and Owaro in which it occurred.
+
+This earthquake is correctly regarded as one of the most severe in
+Japanese records. Originating, as it did, in a densely populated
+section, it caused a great loss of life and property. The deaths
+reached about 7,000, while the number of houses entirely destroyed
+reached about 80,000 and those partly destroyed nearly 200,000. The
+total area markedly affected reached 250,000 square kilometres, while
+the area sensibly affected reached 900,000 square kilometres, or a
+little more than one-half the Empire.
+
+The place at which this earthquake started was situated, not as usual
+on the bed of the ocean, but on the surface of the land. The first
+shock was the strongest and wrought the greatest havoc. Besides the
+loss of life and property, the damage to the system of dikes or levees
+on the river where it passed through the delta plain near the river's
+mouth was heavy, and singular in some of its features. In one case,
+near the city of Nagoya, on the Bay near the southern coast of Niphon,
+one of these levees was lifted and shifted bodily more than sixty feet
+from its original position.
+
+That this quake was of the tectonic type was evident from the great
+fault that was formed. According to Davison this fault was seventy
+miles in length and in places had a breadth of from two to five feet.
+It extended from east to west, crossing the entire width of the island.
+
+Another great earthquake was that which hit northeastern Bengal and
+Assam in India on the 12th of June, 1897. According to the India
+Geological Survey, by whom a careful examination of the effects
+produced by this quake was made, it was, perhaps, the greatest quake
+that ever happened, not even excepting the Lisbon earthquake.
+
+The place where the quake started appears to have been of unusual size
+and irregularity of outline. Its southern boundary was almost in the
+shape of a straight line extending from east to west about 200 miles,
+and covering a total area of nearly 6,000 square miles. Over all this
+vast area the intensity of the shock was exceedingly severe. The total
+area perceptibly shaken by the quake was about equal to 1,750,000
+square miles.
+
+That this quake was of the tectonic type became evident, when several
+faults were found in the ground afterwards. Some of these extended
+twelve miles, with a breadth at places as great as thirty feet.
+
+Valparaiso, or, as the name means, Vale of Paradise, the second
+largest city of Chile and its chief seaport, lies about ninety
+miles east of Santiago, the capital, with which it is connected by a
+railroad.
+
+This beautiful sea city is built at the base of a cluster of hills
+about 1,600 feet above sea level. On August 16th, 1906, it was visited
+by an earthquake. There were two distinct shocks. Contrary to general
+rule it was not the first, but the second shock that did the most
+damage, coming about ten minutes after the first. As you will see from
+the above date the earthquake of Valparaiso occurred shortly after
+the catastrophe of San Francisco. In a general way, its coming was
+predicted by Dr. G. F. Becker of the United States Geological Survey,
+on April 19th, 1906, one day after the San Francisco disaster. Becker
+published an article in the "New York Tribune," in which he argued
+that the severe shock at San Francisco, having occurred on one part
+of the earthquake region extending around the Pacific, would probably
+soon affect other portions of this region along the Pacific coast line
+of this hemisphere.
+
+As at San Francisco fierce fires immediately started in the ruins of
+the houses, but the Valparaisans were more fortunate in having a water
+supply available.
+
+There were very many shocks following the first two of this
+earthquake. Indeed, during August 16th, 17th, 18th, and 19th, no less
+than 380 were noted.
+
+Santiago, situated at the foot of the Andes, was also considerably
+damaged by the same earthquake. Estimates, probably conservative, put
+the total of dead in both cities at 1,000 and the number of people
+rendered homeless temporarily, at 100,000.
+
+
+
+
+CHAPTER XXX
+
+SODOM AND GOMORRAH AND THE CITIES OF THE PLAIN
+
+
+The eastern border of the Mediterranean Sea or Syria, with that part
+of Arabia forming the Sinai Peninsula and which lies between the two
+northern arms of the Red Sea, is a region formerly characterized by
+extreme volcanic activity. This region includes the greater part of
+the land promised, according to the Old Testament, to the Children
+of Israel. Through a large part of this region flows that historic
+river, the Jordan, until it empties into the Dead Sea, also called the
+Salt Sea, the Sea of the Plain, and by some Lake Asphaltites because
+of asphalt or bitumen so abundant on its shores. This river has its
+source in the Mountains of Lebanon, some distance north of the Sea of
+Chinnerth, Tiberius, or the Sea of Galilee, which empties into the
+River Jordan.
+
+As the map in Fig. 50 shows, this famous, though small river, flows
+between ranges of high hills, or low mountains, that lie on both its
+eastern and western boundaries; and these parallel ranges extend
+down to the Gulf of Akaba, which forms the eastern boundary of the
+Sinai Peninsula. The Sea of Galilee, the valley of the Jordan and the
+country between the Dead Sea and the Gulf of Akaba, are all, for the
+most part, considerably below the level of the Mediterranean or the
+Red Sea; the Sea of Galilee being about 626 feet and the Dead Sea 1312
+feet below that line.
+
+[Illustration: FIG. 50. SYRIA]
+
+That this country has been the scene of great volcanic activities is
+evident from the volcanic rocks found over different portions of its
+surface. Moreover, the remains of several craters are still visible.
+On the western banks of the Jordan numerous dikes and streaks of
+basalt occur in the limestone that covers parts of the region. Besides
+there are thermal springs whose waters are at a temperature, according
+to Daubeny, of 114° F. Then, too, in the neighborhood of the Dead
+Sea, as well as in the neighborhood of the adjoining mountain ranges,
+there are quantities of sulphur and asphaltum or bitumen, while on the
+Dead Sea asphaltum is found floating in sufficient quantity to be a
+source of considerable revenue to the boatmen who collect it. It was
+in this region that Sodom, Gomorrah, and other cities of the plain
+were situated; cities so wicked that God utterly destroyed them by
+volcanoes and earthquakes.
+
+Volcanic activity was evidently common in this land of the Bible
+during the times of the prophets of Israel; for in their poetic
+writings are frequent references to such phenomena--beautiful and
+majestic similes and metaphors derived from contemplation of live
+volcanoes.
+
+Jeremiah says:
+
+      "Behold, I am against thee, O devouring mountain, saith the
+      Lord, which destroyeth all the earth; and I will stretch
+      out mine hand upon thee, and roll thee down from the rocks,
+      and will make thee a burnt[4] mountain.
+
+      "And they shall not take of thee a stone for a corner,
+      nor a stone for foundations; but thou shalt be desolate
+      forever, saith the Lord." (Jer. li, 25-26.)
+
+So, too, the prophet Isaiah says:
+
+      "Oh that thou wouldst rend the heavens, that thou wouldst
+      come down, that the mountains might flow down at thy
+      presence!
+
+      "As when the melting fire burneth, the fire causeth the
+      water to boil, to make thy name known to thine adversaries,
+      that the nations may tremble at thy presence!
+
+      "When thou didst terrible things which we look not for,
+      thou cameth down, the mountains flowed down at thy
+      presence." (Is. lxiv, 1-2.)
+
+So, too, the prophet Nahum says:
+
+      "The mountains quake at him, and the hills melt, and the
+      earth is burned at his presence, yea, the world, and all
+      that dwell therein.
+
+      "Who can stand before his indignation? And who can abide in
+      the fierceness of his anger? His fury is poured down like
+      fire, and the rocks are thrown down by him." (Nahum, i,
+      5-6.)
+
+Let us now examine briefly the description Moses gives of the
+destruction of Sodom, Gomorrah, and other cities of the plain. This
+destruction occurred during the life time of Abraham and his nephew
+Lot. The record says that God told Abraham He intended to destroy
+them because of their wickedness. Then follows in the 18th chapter
+of Genesis the eloquent pleading of Abraham for one of the doomed
+cities. At Abraham's earnest plea God promises to spare Sodom if
+fifty righteous men can be found therein. Obtaining this respite,
+Abraham repeatedly asks further mercy for the city, and at last
+receives the sacred promise that the city shall not be destroyed, if
+but ten righteous people can be found there. An evidence of the great
+wickedness of the city is seen in the fact that not even ten could be
+found. Whereupon the Lord gives notice to Lot that the cities were
+doomed and commands Lot to leave at once with his family.
+
+      "Escape for thy life; look not behind thee, neither stay
+      thou in all the plain; escape to the mountain, lest thou be
+      consumed!"
+
+Moses describes what happened as follows:
+
+      "The sun was risen upon the earth, when Lot entered into
+      Zoar.
+
+      "Then the Lord rained upon Sodom and upon Gomorrah
+      brimstone and fire from the Lord out of heaven;
+
+      "And he overthrew those cities and all the plain, and all
+      the inhabitants of the cities, and that which grew upon the
+      ground.
+
+      "But his wife looked back from behind him, and she became a
+      pillar of salt.
+
+      "And Abraham gat up early in the morning to the place where
+      he stood before the Lord:
+
+      "And he looked toward Sodom and Gomorrah, and toward all
+      the land of the plain, and beheld, and lo, the smoke of
+      the country went up as the smoke of a furnace." (Gen. xix,
+      23-28).
+
+This is clearly the description of a volcanic eruption, for throughout
+the Bible things are described as they appear to be. When Moses speaks
+of brimstone and fire being rained upon Sodom and Gomorrah out of
+heaven, he is describing the phenomenon as it would appear to one
+looking at it. Of course, we know that in volcanic eruptions such
+things come to the earth through the crater of the volcano. The lava
+is thrown high into the air, and the hardening, but still red hot,
+ashes, rain down on the earth from the ash cloud that forms over the
+mountain. But, looked at from a distance they appear to fall or be
+rained down from the skies. In exactly the same way, Livy, the Roman
+historian, tells about showers of stones that fell from heaven on
+Mt. Albano near Rome for two whole days during the second Punic War.
+So, too, even Pliny, who had some pretensions to be considered a
+naturalist, in describing the appearance of Mt. Vesuvius during the
+terrible eruption of A. D. 79, when Herculaneum and Pompeii
+were destroyed, speaks of the red hot stones and ashes as falling
+from above. So, in reality, they did, although, as in the case of the
+cities of the plain, the materials forming the cloud came from the
+crater of the volcano below.
+
+As to brimstone falling from the sky, this is by no means an unusual
+occurrence during many volcanic eruptions, since sulphur is a common
+material, often thrown out of the craters of some volcanoes.
+
+Note also the statement that, when Abraham rose early in the morning
+and looked toward the place where Sodom and Gomorrah stood, he saw
+the smoke of the country go up like the smoke of a furnace. This was,
+probably, the smoke caused by the burning of the city, or even by the
+destruction of the crops in their fields, when ignited by the falling
+red hot ashes. It might also have been partly due to the burning of
+asphalt thrown out from the fissures in the ground, or to the showers
+of volcanic ashes that fell from the cloud formed during the eruption.
+
+That the cities there were destroyed by a volcano far in the past
+appears from things outside of the Bible proper; for Strabo,
+the Greek geographer, refers to Jewish traditions that thirteen
+flourishing cities were swallowed up by a volcano, and this finds fair
+corroboration in the ruins along the western borders of the Dead Sea.
+
+A writer referring to these eruptions says:
+
+      "The eruptions themselves have ceased long since, but the
+      effects, which usually succeed them, still continue to be
+      felt at intervals in this country. The coast in general is
+      subject to earthquakes, and history notes several which
+      have changed the face of Antioch, Laodicea, Tripoli,
+      Berytus, Tyre, and Sidon. In 1793 there happened one which
+      spread the greatest ravages. It is said to have destroyed
+      in the valley of Balbec upwards of 20,000 persons."
+
+Attention has already been called to the fact that the valley of the
+Jordan occupies a depressed or sunken region far below the level
+of the Mediterranean and the Red Seas. It is the belief of some
+geologists that this depression was caused by an earthquake which
+accompanied the volcanic eruption that destroyed Sodom and Gomorrah
+and the cities of the plain. Indeed, some contend that the present
+site of the valley of the Jordan, including the Sea of Tiberius and
+the Dead Sea, is a great fissure that was made in the limestone of the
+valley during the time of that earthquake.
+
+It would appear from the peculiar geography of this section of country
+that the Jordan River has not always emptied into the Dead Sea, but
+that before the time of the destruction of the Cities of the Plain the
+greater part of the country now occupied by the Dead Sea was a fertile
+valley, and the Jordan emptied directly into the Red Sea at the Gulf
+of Akaba; that during the disturbance through changes in the valley,
+or possibly by a lava stream flowing across a portion of the bed of
+the lower Jordan, or even by a huge accumulation of stones or ashes
+thrown out from a neighboring volcano, the discharge of the river into
+the Red Sea was cut off, and that in this way the waters of the rivers
+began to accumulate and to flow over the plain, thus forming the basin
+of the Dead Sea.
+
+There is no difficulty in accounting for the saltness of the Dead
+Sea. There are large quantities of salt, and salty matters generally,
+in the volcanic rocks of the region, but, even if this were not so,
+when a river empties into a lake with no outlet to the sea, and
+which therefore loses its water by evaporation only, the water will
+gradually become very salt, since the remaining waters of such a lake
+contain more or less salt, while the water they lose by evaporation
+contains none.
+
+The waters of the Dead Sea are very salt, but not the saltest in
+the world. In every 100 pounds of Dead Sea water twenty-four pounds
+consist of salty matters. The waters of the Great Salt Lake, in Utah,
+contain eighteen per cent of salty matters. Lake Van, in eastern
+Turkey, is, perhaps, the saltest lake on earth, it containing no less
+than thirty-three pounds of salty substances in every 100 pounds of
+water.
+
+Daubeny, an authority on volcanoes, and quite competent to give an
+opinion concerning what is possible in this line, describes what he
+believes took place, as follows:
+
+      "Briefly then to recapitulate the train of phenomena by
+      which the destruction of the cities might have been brought
+      about, I would suppose that the River Jordan, prior to
+      that event, continued its course tranquilly through the
+      great longitudinal valley, called El Arabah, into the
+      Gulf of Akaba; that a shower of stones and sand from some
+      neighboring volcano first overwhelmed these places; and
+      that its eruption was followed by a depression of the whole
+      of the region, from some point apparently intermediate
+      between the lake of Tiberius and the mountains of Lebanon,
+      to the watershed in the parallel of 30°, which occurs in
+      the valley of El Arabah above-mentioned. I would thence
+      infer that the waters of the Jordan, pent-up within the
+      valley by a range of mountains to the east and west, and a
+      barrier of elevated table-land to the south, could find no
+      outlet, and consequently by degrees formed a lake in its
+      most depressed portion, which, however, did not occur at
+      once, and therefore is not recorded by Scripture as a part
+      of the catastrophe, though reference is made in another
+      passage of its existence _in what was before the valley of
+      Siddim_."
+
+As regards the turning of Lot's wife into a pillar of salt, Henderson,
+who has carefully studied this part of the country, remarks: "How
+natural is the incrustation of his wife on this hypothesis! Remaining
+in a lower part of the valley, and looking with a wistful eye towards
+Sodom, she was surrounded, ere she was aware, by the lava, which
+rising and swelling, at length reached her, and (whilst the volcanic
+effluvia deprived her of life) incrusted her where she stood, so that
+being, as it were, embalmed by the salso-bituminous mass, she became a
+conspicuous beacon and admonitory example of future generations."
+
+
+
+
+CHAPTER XXXI
+
+INSTRUMENTS FOR RECORDING AND MEASURING EARTHQUAKE SHOCKS
+
+
+To attempt by the unaided senses a determination of the direction in
+which earthquake shocks reach any certain spot, the velocity with
+which they are travelling, their degree of intensity, their general
+character, whether horizontal or vertical, or any peculiarities which
+might show them to be exceptional would be futile for more reasons
+than one. Even a skilled scientific observer, familiar with what has
+already been discovered and eager to discover more, might in the
+excitement of an earthquake become so excited himself as to make him
+unable to take reliable observations.
+
+But human ingenuity has succeeded in devising delicate instruments
+capable of recording not only the exact time of the arrival of an
+earthquake shock, but also of measuring the different parts of what
+may seem to be a single shock, the direction in which the shocks reach
+the place, as well as the variations of intensity in all the shocks.
+
+Crude instruments to do some of these things have been in use from
+very early times. According to Mallet among the more important
+of these early instruments was the following: the instrument of
+Cacciatore of Palmero. This consisted of a circular wooden dish, about
+ten inches in diameter, placed horizontally, and filled with mercury
+to the brim of eight notches at equal distances apart. Beneath each
+notch was placed a small cup. On the passage of the earthquake waves
+the vessel, being tilted in a direction dependent on the direction in
+which the waves were travelling, would cause some of the mercury to
+spill over into one or more of the cups, thus indicating by its amount
+the intensity of the wave, and by the particular cup or cups that were
+filled, the direction in which the waves reached the place.
+
+Somewhat similar contrivances were of a vessel partly filled with
+molasses, or other sticky liquid; or a cylindrical tub, the sides of
+which were chalked or whitewashed and filled with some colored liquid.
+In either of these cases, on the passage of the earthquake waves,
+the vessels were tilted and showed by the height of the marks the
+intensity of the waves, and by the position of the marks the direction
+in which the waves first reached the instrument.
+
+These instruments, though satisfactory for the study of earthquake
+shocks a long time ago, when an earthquake was regarded as practically
+consisting of but a single shock, or, at the most, of a very few
+shocks, would be worthless for the study of earthquakes now, for it is
+finally known that an earthquake consists of a series of many hundreds
+of vibrations, differing greatly in their rapidity and intensity, and
+following one another in a definite order.
+
+The old forms of earthquake instruments were known as _seismoscopes_.
+The word seismoscope is a compound word from Greek consisting of
+the two words, seism and scope. It means literally any instrument
+capable of seeing, or calling attention to, a seism, or _earth-shake_.
+In other words, a seismoscope is any instrument capable of calling
+attention only to an earth-shake.
+
+Of course, neither of the rude seismoscopes just mentioned would be
+able to give any valuable indications of the successive shakings to
+which the vessel containing the viscid liquid had been subjected,
+since the liquid would simply be splashed a number of times over the
+same parts of the vessel. In order to get a record of the successive
+shocks another form of apparatus must be employed, a form known as a
+_seismograph_.
+
+Concerning the complex character of the apparently single earthquake
+shock, Professor Milne makes this highly interesting and picturesque
+statement:
+
+      "An earthquake disturbance at a station far removed from
+      its origin shows that the main movement has two attendants,
+      one which precedes and the other which follows. The first
+      of these by its characteristics indicates what is to
+      follow, whilst the latter, in a very much more pronounced
+      manner, will often repeat at definite intervals, but with
+      decreasing intensity, the prominent features of what
+      has passed. Inasmuch as these latter rhythmical, but
+      decreasing, impulses of the dying earthquake are more
+      likely to result from reflection than from interference, I
+      have provisionally called them Echoes."
+
+There are many different forms of instruments known as seismographs
+that are capable of recording all of these vibrations, but there is
+this objection to their use: that the records appear in so tangled a
+form that it is practically impossible to decipher or untangle them.
+This fact can be grasped by examining Fig. 51, which represents a
+record of this kind.
+
+[Illustration: FIG. 51. COMPLEX RECORD OF SEISMOGRAPH]
+
+It is necessary, therefore, to employ a modified form of instrument
+called a _seismometer_, able not only to record all the different
+vibrations, but to record them in such a manner that they can be
+easily recognized. Fig. 52, for example, shows results obtained by the
+use of a seismometer, in which the different vibrations are separated,
+and so recorded on a sheet of paper, as to be readily understood. Such
+a record is called a _seismogram_, and represents a _long distance
+seismogram_. Here the large arrow indicates the beginning of the
+record. And herein, as can be clearly seen, what would appear to an
+observer without an instrument only a single shock, lasting but the
+fraction of a minute, in reality consists of the _preliminary shake_
+as represented in ab and bc, the _principal shake_, as represented
+at c, d1, d2, and d3, and the _final portions of the shake_ or the
+"echoes" of Professor Milne, as represented from d3 to e.
+
+[Illustration: FIG. 52. LONG DISTANCE SEISMOGRAM]
+
+Except in a very general way there is for present purposes no need
+of explaining the construction and operation of the seismometer
+and seismograph. Suffice it to say, there are many forms of these
+instruments, any of which are capable of recording the details of a
+passing shock. The most important thing in either a seismograph or a
+seismometer is to obtain what is known as a _steady point_; that is, a
+point consisting of some object or mass that will remain practically
+at rest, while everything around it, even the support which holds it,
+is affected by the earthquake.
+
+It is, of course, not very easy to obtain a steady point, but it can
+be done; and it will be at once comprehended that if a plate or piece
+of paper were attached to such a steady point or mass, and a pencil
+or tracer had one of its ends resting on the plate, and its other end
+attached to the support that vibrates with the earth, a tracing or
+record would be drawn on the plate from which the character of the
+motion of the end of the tracer, and, therefore, of the earth, would
+be marked on the plate.
+
+[Illustration: FIG. 53. VICENTINI VERTICAL PENDULUM]
+
+Various devices have been employed for the steady points. The most
+successful consists of a heavy mass of lead.
+
+Fig. 53 represents a form of instrument invented by Professor
+Vicentini of Italy. Here the steady point consists of a heavy leaden
+bob, of 200, 400, or even 500 kilograms, suspended by three metallic
+rods united above by a brass cap, hung on a steel wire to a bracket
+fixed on the wall. This wire may have a length as great as fifty feet.
+
+[Illustration: FIG. 54. VICENTINI PENDULUM AND RECORDER]
+
+Fig. 54 represents the recording instrument. Here a tracer is provided
+that is capable of multiplying the motion fifty times, or even eighty
+times. A record is traced on a sheet of paper passing over a roller
+which imparts a rapid motion to a sheet so as to make sure that the
+different parts of the shock or vibration will be recorded on separate
+portions of the paper.
+
+
+
+
+CHAPTER XXXII
+
+SEAQUAKES
+
+
+As earthquakes are shakings of the earth's crust in places where it is
+uncovered by the waters of the ocean, so _seaquakes_ are the shakings
+of those portions that lie on the bed of the ocean.
+
+Mallet points out that the earthquake wave may start either in the
+interior of the continent, or on the bed of the ocean; that the latter
+place is the more common, since on the land vents--rude safety-valves,
+as it were,--are provided by the craters of the volcanoes; that, when
+earthquakes start on the ocean bed, the impulses are conveyed in
+different forms of waves, i. e., those through the solid earth, those
+through the water, and those through the air, with varying sounds like
+bellowings and explosions, or like the rolling of wagons over rough
+roads.
+
+To learn when quakes occur on the sea is a much harder task, since on
+the land we can use seismoscopes, seismographs, or seismometers to
+indicate, record, or measure the shakings of the crust, while on the
+sea, where the water is always in more or less motion and the surface
+so far from the ocean's bed this is impossible, or, rather shall it
+be said, has hitherto been found so; for that the mind of man may
+surmount this obstacle is not impossible to conceive.
+
+To detect the wave produced by the quaking of the bed of the ocean
+is exceedingly difficult, since those in very deep water are flat or
+possess but a small height. Indeed, in the deepest parts of the ocean
+this height is probably to be measured only by inches instead of feet.
+When, however, the waves advance towards the shore they increase in
+height, and when they reach the shallows near the coast, they begin
+to curl over and break, thus creating the enormous waves mentioned so
+often as attending great earthquakes in the ocean.
+
+During the great earthquake of Simoda in Japan, 1854, the waters of
+the bay were first greatly agitated, and then retreated, leaving the
+bottom bare in places where the water was formerly thirty feet deep. A
+wave, thirty feet high, then rushed in from the bay and, climbing the
+land, swept away everything in its path, covering the town with water
+to the tops of the houses. This monster wave then receded, but rushed
+back five times.
+
+In 1751, an earthquake wave suddenly entered Callao, the port of Lima,
+Peru, sinking twenty-three vessels and driving a frigate inland, where
+it was left high and dry. This wave extended across the Pacific to the
+Hawaiian Islands, a distance of 6,000 miles.
+
+On the 13th of August, 1866, an earthquake wave, that started a short
+distance from shore, produced a number of earthquake waves sixty feet
+high that reached the coast of Peru half an hour after the principal
+earthquake shock. These waves reached Coquimbo, 800 miles distant,
+in about three hours, and Honolulu, on the Sandwich Islands, 5,520
+miles distant, in twelve hours, and the coast of Japan, more than
+10,000 miles distant, on the next day. Le Conte remarks that these
+waves would have encircled the earth, had it not been for the barrier
+interposed by the Andes.
+
+Another great seaquake, known as the Iquiqui seaquake, during 1868 in
+the same neighborhood damaged severely the towns of north Chile and
+southern Peru.
+
+While, however, there is difficulty in readily observing the
+earthquake waves that form in the deep ocean, yet such is at times the
+violence of an earthquake that there is no difficulty in detecting its
+presence, even in deep water. Dr. Rudolph has made a careful study of
+the evidences of earthquakes produced in the deep sea, from a careful
+examination of a great number of the logs of ships. Logs, as everybody
+knows, are books in which the captain or commanding officer makes
+careful entries of all important happenings to the vessel, conditions
+of the weather and of the sea. From this source Dr. Rudolph obtained
+considerable information of much value concerning these phenomena.
+
+I have already called your attention to portion of the Atlantic Ocean
+lying near the Equator, in the warmest part of the ocean, between
+Africa and South America, as being a region especially liable to
+submarine volcanic showers. While, generally speaking, there is
+nothing in this region to indicate the probability of submarine
+disturbance, yet suddenly, if a vessel happens to pass directly over
+the point of origin of the quake, there ensues a great quaking or
+quivering. Loose objects on the ship begin to shake and clatter.
+Noises arise from some invisible point deep down in the ocean. The
+disturbance grows, the noises begin to resemble distant thunder, the
+ship trembles and staggers as though it had struck rocks, and many
+believe she is about to go down; when, as suddenly as it began, the
+commotion ceases, the noises stop, and the ship shapes her course as
+calmly, and as gallantly, as before.
+
+Rudolph gives two excellent examples of seaquakes in this region, both
+of which were, doubtless, due to submarine eruptions.
+
+On the 25th of January, 1859, as the ship _Florence_ was in lat.
+0° 48' N., long. 29° 16' W., about ten miles N. W. by N. from St.
+Paul's Rock, the people on board felt a sudden shock that began with a
+rumbling sound like distant thunder. This lasted only forty seconds.
+The glass and dishes of the vessel rattled so violently that it was
+feared they would be broken. The shakings were so strong that several
+objects on the vessel were thrown down. Everyone believed the ship
+had struck on rocks. The captain leaned over the taffrail in order to
+see the position of the reef, but soon saw that the vessel had struck
+nothing, and informed his crew "it was only an earthquake shock."
+
+Another of the log books examined by Rudolph was that of a ship in the
+same part of the Atlantic Ocean. This record showed that suddenly on
+a morning, in 1883, strange noises were heard that soon increased and
+became not unlike the firing of great guns or the peals of distant
+thunder. The ship vibrated as if its anchor had been suddenly let go,
+and at the same time a feeling came over all the crew, as if they had
+been electrified.
+
+In some cases the vibrations were sufficiently severe to throw heavy
+objects from the deck, as appears in an account given by a French
+geologist of a quake in the Mediterranean off the shores of Asia Minor.
+
+"Our ship was over the epicentre,"[5] he says, "and was so severely
+shaken that at first the Admiral feared the complete destruction of
+the corvette." He then makes the statement that the shocks which were
+directly upwards were so strong as to throw heavy objects in the air;
+for example, a heavy gun and its carriage. While it is possible, as
+Dutton remarks, that this incident of the heavy gun and carriage was
+grossly exaggerated, yet it should not be forgotten that in the case
+of submarine eruptions such as that which resulted in the production
+of the island of Sabrina, an immense column of water, weighing
+probably many times more than a gun and its carriage, was observed to
+be shot high into the air.
+
+Where the seaquake is produced by a strong submarine volcanic
+eruption, there is a violent commotion of the water itself, so that a
+vessel passing over such a point may be greatly injured, and, indeed,
+even destroyed. Such disasters, however, are fortunately exceedingly
+rare.
+
+Among other common effects of seaquakes is the destruction of fish
+already mentioned by the sudden blow to the water stunning and killing
+them, just as the explosion of dynamite or other high explosives does
+in a lake or pond.
+
+The most marked effect, however, of seaquakes is the starting of the
+great wave on the coasts of continents and islands.
+
+There are certain parts of the ocean that are especially liable to
+seaquakes. Some of the more important of these, as shown by Rudolph's
+researches, are:
+
+The region already referred to in the narrowest parts of the Atlantic
+Ocean between Africa and South America almost immediately under the
+equator. Here there are two well marked regions. One is in lat. 1°
+N., long. 30° W., where there is a submarine ridge, the tops of which
+form what are known as St. Paul's Rock. The ocean here is very deep,
+the slopes of the ridge descending rapidly. It is on these slopes
+that earthquakes are very apt to occur just as they do on the steep
+slopes of mountain ranges. The other region, called by Rudolph the
+_Equatorial District_, lies a little further to the east on both sides
+of the equator in long. 20° W.
+
+It appears from Rudolph's researches that between 1845 and 1893 no
+less than thirty-seven seaquakes were reported in the logs of ships
+in the neighborhood of St. Paul's Rock, and between 1747 and 1890, in
+the equatorial district, there were forty-nine seaquakes. It must not
+be supposed, however, that these were all the quakes in the regions
+during these times, since, of course, many shocks must have happened
+that were not felt even by vessels in the neighborhood and many more,
+when this portion of the ocean was free from any craft.
+
+In the North Atlantic there is a portion of the ocean's bed known as
+the _West Indies Deep_. Here the bed is marked by great depths and by
+many irregularities and is, therefore, a region where seaquakes are
+common.
+
+Still another district is found in the North Atlantic in the
+neighborhood of the Azores. This is the region in which the Lisbon
+earthquake is believed to have started.
+
+Another region where seaquakes are common is in the Pacific along the
+coast of South America from the equator to 45° S. lat. "Here," says
+Dutton, "especially in the vicinity of the angle where the Peruvian
+and Chilian coasts meet have they been most numerous and formidable.
+The harbors of Pisco, Arica, Tacua, Iquiqui, and Pisago have been
+repeatedly subject to these destructive invasions."
+
+There has been considerable discussion as to the exact manner in which
+the earthquake waves are set up. Whatever be the cause or causes,
+the action must be sudden, such as an upheaval of the bottom, or a
+collapse of a large section of the ocean's bed, with a dropping of a
+vast body of water. Or, possibly, a submarine volcanic eruption causes
+the water to lift suddenly under pressure of steam generated by escape
+of the lava and other hot volcanic products.
+
+Dr. Rudolph attributes earthquake waves to submarine volcanic
+eruptions alone. It would seem, however, as if each one of the other
+things above referred to might at times be the direct cause.
+
+
+
+
+CHAPTER XXXIII
+
+THE DISTRIBUTION OF EARTHQUAKES
+
+
+Earthquakes may occur at any part of the earth's surface, at any time
+of the day, or at any season of the year, yet they are more frequent
+at certain parts, certain hours, certain seasons.
+
+Since some earthquakes are unquestionably connected with volcanic
+eruptions, a map or chart of the volcanoes of the earth would also,
+to a certain extent, show the parts of the earth that are likely to
+be visited by earthquakes. Since, however, by far the most severe
+earthquakes are not directly connected with volcanoes, but are due to
+sudden slips of faulted strata, a volcanic chart would necessarily
+fail to indicate accurately the principal earthquake regions.
+
+In the preparation of a map showing the distribution of earthquakes
+over the earth's surface, Mallet adopted the plan of colorings or
+tintings in such a manner that the depth of the colors would represent
+not only the parts shaken, but also the relative number of times
+shaken, as well as the intensity of the shocks. In order to determine
+the depth of tint to be employed, Mallet divided earthquakes into the
+following classes according to their intensity:
+
+_Great earthquakes_, or earthquakes of the first class; or those in
+which the area affected is of great size, in which many cities have
+been overthrown, and many people killed, and parts of the surface
+greatly altered.
+
+_Intermediate earthquakes_, or those in which, although the area
+affected is great, yet the destruction of buildings, or loss of life,
+has been comparatively small.
+
+_Minor earthquakes_, or those which, although capable of producing
+small fissures in the crust, generally leave but few or no traces of
+their occurrence.
+
+The greatest distance to which earthquake waves of the first class
+extend is taken by Mallet as being over a diameter of 1,080 miles;
+those of the second class over a diameter of about 360 miles, and
+those of the third class over a diameter of about 120 miles.
+
+According to the Rossi Forel scale already given, earthquake shocks
+are divided according to their relative intensity into ten separate
+classes, viz.: I. The micro-seismic; II. The extremely feeble; III.
+The very feeble; IV. The feeble; V. The moderately intense; VI.
+The fairly strong; VII. The strong; VIII. The very strong; IX. The
+extremely strong; X. Shocks of extreme intensity.
+
+An earthquake map prepared according to Mallet's scale would show a
+greater depth of color or tint in the neighborhood of the volcanic
+districts of the earth and especially in the neighborhood of the
+mountain regions, where tectonic quakes are most frequent. Oceanic
+areas would be left almost untinted, not because earthquakes do not
+occur on the bed of the ocean, but because of the difficulty of
+observing such earthquakes at great distances from the land. So far
+from earthquakes being absent on the bed of the ocean it is most
+probable that they are more frequent there than elsewhere.
+
+Prepared in this way, Mallet's map would show a preponderance of
+earthquakes along the borders of the continents, especially along the
+"Great Circle of Fire" on the borders of the Pacific Ocean.
+
+Dutton as well as some others assert that the "Great Circle of Fire"
+on the shores of the Pacific has in reality no existence; that,
+instead of there being a continuous region of volcanoes, there is in
+reality nothing more than a considerable number of volcanoes arranged
+in groups along the borders of this ocean, but separated by spaces
+containing no marked volcanic activity. We do not think this a tenable
+position, since it is well known that volcanoes lie along great lines
+of fissures at different points or openings which are kept open
+by subsequent volcanic activity, while the remaining portions are
+closed soon afterwards; and, moreover, in parts of these so-called
+non-volcanic regions, there are probably extended regions of extinct
+volcanoes.
+
+Since the time of Mallet many maps have been made to show the
+distribution of earthquakes. Among the best of such is that by M. de
+Montessus de Ballore.
+
+Some idea of the great amount of work required for the preparation of
+Montessus' map may be formed when one learns that the catalogue of
+earthquakes collected by him for this purpose included for the years
+1880 to 1900, 131,292 quakes.
+
+De Montessus' earthquake map divides the grand divisions of the earth
+into numerous sub-divisions, too numerous, indeed, for even brief
+description in a work of this kind. From the map he thus laboriously
+prepared De Montessus drew the following general conclusions:
+
+1. The parts of the earth that are most apt to be shaken by
+earthquakes are those which possess the greatest differences of relief
+between their highlands and lowlands, and that in such regions the
+most pronounced earthquakes are found on the steepest slopes.
+
+2. Earthquakes are most common along those parts of the crust that are
+thrown up in huge wrinkles, or mountain ranges, whether these masses
+be above the level of the sea or are covered by it.
+
+[Illustration: FIG. 55. DAVISON'S EARTHQUAKE MAP OF JAPAN]
+
+3. Earthquakes are more common in mountainous districts than in
+plains. But not all mountains are characterized by earthquakes nor
+are all plains free from them. Sometimes the plain at the base of
+the mountain appears to be especially liable to shocks, probably by
+reason of slips along faults at these points.
+
+The great mountain ranges of the world are generally characterized
+by unequal slopes, the long gentle slope facing the interior of the
+continents, and the short, abrupt slopes being turned towards the
+coast. Now, Montessus points out that volcanoes are the most frequent
+on the short, abrupt slopes. In some cases, however, where the long
+slopes are the roughest, it is these slopes that are most frequently
+shaken.
+
+The beds of the ocean that lie along rapidly descending lines,
+especially when they lie on the borders of large mountain ranges, are
+especially liable to earthquakes.
+
+Dr. Charles Davison has made a map of the earthquakes of Japan in
+which he had adopted the plan of representing the origin or centres
+of earthquakes by a series of contour lines like those employed on
+topographical maps. The advantage of this type of map over that
+employed by Mallet is just this: Davison's earthquake map of Japan in
+which the active volcanoes are marked by dots, and the earthquakes
+by contour lines surrounding the points of origin, discloses the
+interesting fact that here the positions of the volcanoes and the
+earthquake centres coincide, since the mountainous districts where the
+active volcanoes are numerous are singularly free from earthquakes.
+This can be seen from an inspection of Fig. 55.
+
+
+
+
+CHAPTER XXXIV
+
+THE CAUSES OF EARTHQUAKES
+
+
+Earthquakes occurred long before man appeared on earth. It is natural,
+therefore, that our early ancestors, experiencing these unwelcome
+phenomena, vaguely endeavored to explain their causes. These early
+attempts at explanation have in many cases been of an exceedingly
+fanciful character.
+
+The ancient Mongolians and Hindoos declared that earthquakes are due
+to our earth resting on a huge frog and that they occur whenever the
+frog scratches its head.
+
+In Japan, where earthquakes are very common, the ignorant people even
+at a much later day declared that there exists in the depth of the sea
+an immense fish which, when angry, dashes its head violently against
+the coast of the island, thus making the earth tremble. This is,
+doubtless, the biggest fish-story extant.
+
+Another folk-lore explanation in Japan attributes the cause of the
+tremblings of the earth to a subterranean monster whose head lies in
+the north of the island of Hondo, while his tail lies between the two
+principal cities. The shaking of his tail causes earthquakes.
+
+Fantastic and foolish as these explanations are, it is worthy of
+note that the first of the Japanese explanations shows no little
+observation on the part of the people, since it locates the
+starting-points of earthquakes as being not on the land, but on the
+bottom of the sea. In point of fact, nearly all the great earthquakes
+in Japan seem to start somewhere between the coasts of the islands
+on the sea-bottom that leads down to a very deep part of the Pacific
+known as the Tuscarora Deep.
+
+Many years ago nearly everyone believed that earthquakes were caused
+solely by the forces that produce volcanic eruptions; that all
+earthquakes, whether in the neighborhood of active volcanoes, or at
+great distances therefrom, were to be regarded solely as volcanic in
+their origin.
+
+It is now recognized that the most severe and far-reaching earthquakes
+have no immediate connection with volcanic explosions, but are due to
+the sudden slippings of the earth's strata over lines of faults; or,
+in other words, earthquakes are most frequently of the tectonic type.
+
+At the present time there is unfortunately much difference in
+opinion as to the exact cause of earthquakes. By this is not meant
+the immediate cause, but the ultimate cause. As to the immediate
+cause, practically all are agreed that quakes of volcanic origin are
+to be traced to the same forces that produce volcanic eruptions,
+while quakes of tectonic origin are due directly to the slipping of
+the strata along the faults. But when inquiry is instituted as to
+the nature of the forces that cause the volcanic eruptions, or that
+produce such an alteration of the strata as permits them afterwards to
+slip and thus jar the earth, there is much difference of opinion.
+
+As can be seen from a few quotations of well-known authorities, only
+two kinds of earthquakes exist; namely, volcanic earthquakes and
+tectonic earthquakes.
+
+Dana, for example, while acknowledging that small earthquakes may be
+caused by the sudden falling of large rock masses into cavities in the
+crust of the earth, says:
+
+      "But true earthquakes come, for the most part at least,
+      from one or the other of the following sources of
+      disturbance.
+
+      "1. Vapors suddenly produced, causing ruptures and friction.
+
+      "2. Sudden movements or slips along old or new fractures.
+
+      "Earthquakes due to the former of these methods are common
+      about volcanoes, and at the Hawaiian islands shakings that
+      are destructive over the island of Hawaii at the moment of
+      some of the more violent eruptions, do not often affect the
+      island of Oahu, a depth of 500 fathoms of water, the least
+      depth between the two islands, being sufficient to stop off
+      the vibrations....
+
+      "Earthquakes of the second mode of origin may occur in all
+      regions, volcanic or not. They have their origin mostly in
+      the vicinity of mountain regions, where old fractures most
+      abound. The vibrations may begin in a slip of a few inches,
+      in fact; but where there has been a succession of slips,
+      up and up from 10,000 feet or more, as in the Appalachian,
+      earthquakes of inconceivable volcanic activity must have
+      resulted."
+
+Dana points out that volcanoes stand on lines of fractures in the
+openings of which their existence began and that, during geological
+time, slips up or down these fractures have occurred, producing
+earthquakes and possibly starting eruptions.
+
+Prestwich, a well-known English geologist, speaks very decidedly
+concerning the causes of earthquakes:
+
+      "For my own part, I am disposed to share the belief
+      expressed by Dana that the tension or pressure, by which
+      the great oscillations or plications of the earth's crust
+      have been produced, have not entirely ceased; and that
+      this is generally the most probable cause of earthquakes.
+      The uplifting of the great continental tracts and mountain
+      ranges must have always left the interior of the crust in
+      a state of unstable equilibrium, and any slight slide or
+      settling along an old fracture, or in highly disturbed and
+      distorted strata, would be attended by an earthquake shock.
+
+      "In volcanic areas the removal of the large volumes of
+      molten rock from the interior to the surface must produce
+      settlements and strains which might also result in some of
+      these minor earthquakes to which volcanic districts are
+      so subject. Where we have the two conditions combined, as
+      they are in the Andes in South America, these earthquake
+      phenomena are, as we should expect, developed on the
+      grandest and widest scale."
+
+Geikie, the Scotch geologist, says:
+
+      "Various conceivable causes may, at different times
+      and under different conditions, communicate a shock to
+      the subterranean regions. Such as the sudden flashing
+      into steam of water in the spherodial state, the sudden
+      condensation of steam, the explosion of a volcanic outpour,
+      the falling in of the roof of a subterranean cavity, or the
+      sudden snap of deep-seated rocks subjected to prolonged and
+      intense stress."
+
+Sir Charles Lyell, the great English geologist, holds the following
+views concerning the origin of earthquakes. He speaks as follows in
+his "Principles of Geology":
+
+      "1. The primary cause of the volcanoes and the earthquakes
+      are to a great extent the same, and connected with the
+      development of heat and chemical action at various depths
+      in the interior of the globe.
+
+      "2. Volcanic heat has been supposed by many to be the
+      result of the high temperature which belonged to the
+      whole planet when it was in a state of igneous fusion,
+      a temperature which they suppose to have been always
+      diminishing and still to continue to diminish by radiation
+      into space....
+
+      "The powerful agency of steam or aqueous vapor in volcanic
+      eruptions leads us to compare its power of propelling lava
+      to the surface with that which it exerts in driving up
+      water in the pipe of an Icelandic geyser. Various gases
+      also, rendered liquid by pressure at great depths, may
+      aid in causing volcanic outbursts and in fissuring and
+      convulsing the rocks during earthquakes."
+
+Major Clarence Edward Dutton, U. S. A., an acknowledged authority on
+seismology, speaks as follows:
+
+      "Thus far, then, we have two causes of earthquakes which
+      are apparently well sustained: (1) the downthrows, which
+      have often been observed to be accompanied by earthquakes,
+      and (2) volcanic action. But neither of them have been
+      shown to be connected with more than a comparatively small
+      number. Much the greater part of the earthquakes still
+      require explanation, and the indications are manifold that
+      some of them are produced by some cause yet to be stated."
+
+He acknowledges, however, this unknown cause may be traceable to
+volcanic agency. To quote him in full:
+
+      "It remains now to refer to the possibility that many
+      quakes whose origin is unknown, or extremely doubtful, may,
+      after all, be volcanic. This must be fully admitted, and,
+      indeed, it is in many cases highly probable. Evidences
+      that volcanic action has taken place in the depths of the
+      earth without visible, permanent results on the surface
+      abound in ancient rock exposures. Formations of great
+      geological age, once deeply buried and brought to daylight
+      by secular denudations, show that lavas have penetrated
+      surrounding rock-masses in many astonishing ways. Sometimes
+      they have intruded between strata, lifting or floating up
+      the overlying beds without any indication of escaping to
+      the surface. Sometimes the lava breaks across a series of
+      strata and finds its way into the partings between higher
+      beds. Or it forces its way into a fissure to form a dike
+      which may never reach the surface. In one place a long arm
+      or sheet of lava has in a most surprising and inexplicable
+      manner thrust itself into the enveloping rock-mass, and in
+      the older or metamorphic rocks these offshoots or apophyses
+      cross each other in great numbers and form a tangled
+      network of intrusive dikes. In other places the intruded
+      lava has formed immense lenticular (lense shaped) masses
+      (laccolites), which have domed up the overlying strata
+      into mountain masses. These intrusions, almost infinitely
+      varied in form and condition, are often, in fact usually,
+      inexplicable as mechanical problems, but their reality is
+      vouched for by the evidence of our senses. What concerns
+      us here is the great energy which they suggest and their
+      adequacy to generate in the rocks those sudden, elastic
+      displacements which are the real initiatory impulses of an
+      earthquake. They assure us that a great deal of volcanic
+      action has transpired in past ages far under ground, which
+      makes no other sign at the surface than those vibrations
+      which we call an earthquake."
+
+Koto, the celebrated Japanese student of earthquakes, and a member
+of the Earthquake Investigation Committee appointed by the Japanese
+Government for studying the great Mino-Owaro earthquake, in Japan,
+1891, is properly regarded as an authority on earthquakes. Living, as
+he does, in a country where earthquakes and volcanic eruptions are of
+almost daily occurrence, he has had abundant opportunity for studying
+these phenomena, especially in connection with the Seismological
+Institute of Japan. He speaks as follows:
+
+      "To make clear once for all my own standpoint, I may say
+      plainly that the chain of volcanoes and the system of
+      mountains of the non-volcanic earthquake, appear to me
+      to have very intimate and fundamental relations with the
+      so-called tectonic line."
+
+Mallet regards earthquakes that can be directly traceable to volcanic
+origin as unsuccessful efforts on the part of nature to establish
+volcanoes. He speaks concerning this matter as follows:
+
+      "An earthquake in a non-volcanic region may, in fact, be
+      viewed as an uncompleted effort to establish a volcano.
+      The forces of explosion and impulse are the same in both;
+      they differ only in degree of energy, or in the varying
+      sorts and degrees of resistance opposed to them. There is
+      more than a mere vaguely admitted connection between them,
+      as heretofore commonly acknowledged--one so vague that the
+      earthquake has been often stated to be the cause of the
+      volcano (Johnson, 'Phy. Atlas,' Geology, page 21), and more
+      commonly the volcano the cause of the earthquake, neither
+      view being the expression of the truth of nature. They are
+      not in the relation to each other of cause and effect, but
+      are both unequal manifestations of a common force under
+      different conditions."
+
+Before closing this chapter on the causes of earthquakes it may be
+well to state briefly the explanations that have been suggested by
+those who hold that the earth is solid and cold throughout its entire
+mass, except that in the neighborhood of volcanic districts there
+are limited areas situated only a comparatively few miles below the
+surface where the rocks are highly heated.
+
+Professor Mallet suggested that the source of heat for these local
+areas of melted rocks was to be found in the enormous mechanical force
+that is developed by the crushing of the strata in the earth's crust.
+The principal objection to Mallet's theory is to be found in the
+fact that, for this heat to be available for the melting of rocks,
+it must be produced rapidly, and not spread out over long periods of
+time. Moreover, there would appear to be no other way to account for
+the production of the great force required to effect the crushing of
+the earth's strata save on the assumption of a highly heated interior
+still cooling and contracting.
+
+In his "Aspects of the Earth" Shaler has suggested an hypothesis
+that may be regarded to a certain extent as explaining how heat,
+slowly generated, might be blanketed, or prevented from escaping and
+so possibly reaching a temperature sufficiently high to melt the
+materials in portions of the interior not far below the surface of the
+earth.
+
+      "We thus see that in the water imprisoned in the deposits
+      of the early geological ages and brought to a high
+      temperature by the blanketing action of the more recently
+      deposited beds, we have a sufficient cause for the great
+      generation of steam at high temperatures, and this is the
+      sole essential phenomenon of volcanic eruptions. We see
+      also by this hypothesis why volcanoes do not occur at
+      points remote from the sea, and why they cease to be in
+      action soon after the sea leaves their neighborhood....
+
+      "The foregoing considerations make it tolerably clear that
+      volcanoes are fed from deposits of water contained in
+      ancient rocks which have become greatly heated through the
+      blanketing effects of the strata which have been laid down
+      upon them. The gas which is the only invariable element
+      of volcanic eruptions is steam; moreover, it is the steam
+      of sea-water, as is proven by analysis of the ejections.
+      It breaks its way to the surface only on those parts of
+      the earth which are near to where the deposition of strata
+      is lifting the temperature of water contained in rocks by
+      preventing, in fact, the escape of the earth's heat."
+
+Another very common theory is that of chemical action, or the heat
+produced by the oxidation of various substances inside the earth,
+such, for example, as iron pyrites, a compound of iron and sulphur.
+
+When Sir Humphrey Davy discovered metallic sodium and it was found
+that this material, when thrown on water, possessed the power of
+liberating intense heat, the discovery was welcomed by geologists
+as affording a possible explanation of the cause of volcanoes and
+earthquakes.
+
+It may be said generally concerning chemical action as the source
+of the earth's interior heat, that the chief objection against it
+is the fact that such heat is liberated too slowly to result in the
+production of a very high temperature. This objection does not exist
+in the case of such substances as metallic sodium, since here the
+heat is rapidly developed and is sufficient in amount to fuse the
+substances produced. But in the lava produced in such great quantities
+as it is in volcanic districts there must be liberated at the same
+time large quantities of gaseous hydrogen. Now, although hydrogen
+is, as we have already seen, sometimes given off with the gases that
+escape from volcanic craters, yet the quantity which escapes is so
+small that this theory of volcanic activity has been practically
+abandoned.
+
+Quite recently, however, among the various chemical substances that
+are produced under the extremely high temperatures of the electric
+furnace have been found, or formed, a number of curious substances
+such as _calcium carbide_, _calcium silicide_, _barium silicide_,
+etc., that possess the property of becoming highly heated on coming in
+contact with water.
+
+Now it is an interesting fact that the hydrogen and other gases
+which are given off by the action of water on these substances are
+absorbed in large quantities by the materials themselves, so that the
+objection of the absence of hydrogen and similar gases in the craters
+of the volcanoes would not be quite as objectionable as in the case of
+such substances.
+
+Of course, it is impossible to say whether such substances as calcium
+carbide, etc., actually exist inside the earth's crust, yet, as
+has been pointed out, the principal condition necessary for their
+formation, i. e., a high temperature, existed at times long after
+the earth, assuming the correctness of the nebular hypothesis, was
+separated from the nebulous sun.
+
+There still remains to be discussed the most curious of all possible
+causes that have been suggested for the presence of the local heated
+areas at comparatively short distances below the earth's crust;
+namely, radio-activity.
+
+In 1896, Henri Becquerel, a Frenchman, while investigating the power
+of the X-rays, when passing through certain substances, to produce
+phosphorescence, or causing the substances to shine in the dark,
+made the extraordinary discovery that some of the salts of uranium
+possess the power of emitting a peculiar radiation closely resembling
+the X-rays, that is able to pass through substances opaque to
+ordinary light as well as to affect photographic plates. But the most
+extraordinary part of this discovery was that the salts of uranium
+apparently possess the power of giving out this radiation continuously
+without being exposed to the sun's rays.
+
+This peculiar property was called _radio-activity_, and was shortly
+afterwards found to be present in many other substances besides
+uranium, and notably so in two newly discovered elements known as
+polonium and radium.
+
+Now it has been suggested that if there existed somewhere beneath the
+earth's crust in these locally heated areas, large quantities of
+radio-active substances, these regions would at last become highly
+heated, and in this way likely to produce volcanoes and earthquakes.
+It would not, however, seem that this is probably their true cause.
+
+From what has just been said it is clear how exceedingly difficult it
+has become to explain the source of the earth's interior heat when
+the fact of the earth's original highly heated condition is denied.
+We are, therefore, disposed with Russell to believe, as stated in the
+first part of this volume, that the ultimate cause of both volcanoes
+and earthquakes is to be found in the gradual cooling of an originally
+highly heated globe, and that the greater part of the interior is
+still in a highly heated condition, hot enough to be melted but yet
+in a solid condition by reason of the great pressure to which it is
+subjected.
+
+
+
+
+CHAPTER XXXV
+
+EARTHQUAKES OF THE GEOLOGICAL PAST--CATACLYSMS
+
+
+There were numerous volcanoes in the geological past; therefore, since
+volcanic eruptions are generally attended by earthquake shocks, it
+follows that during that remote past the earth has been violently
+shaken by earthquakes. Indeed, if we assume, as we believe to be the
+case, that the cause of earthquakes is correctly to be traced to an
+originally heated globe which is gradually cooling, it follows that
+the earth was necessarily subject to great earthquakes almost from the
+time when it began to cool.
+
+But to establish as a fact the occurrence of an earthquake at so
+remote a time in the earth's history is far more difficult than to
+detect the occurrence of a volcano at that time. While the earthquake
+shocks may produce fissures in the earth's crust, and may be
+accompanied by great changes of level, yet the great time that has
+elapsed between such occurrences and the present would permit the
+various geological agencies that are at work either to cover these
+fissures completely, or completely to remove by erosion, or in other
+similar ways, the rocks in which they occurred. It is different in
+the case of a volcano; for the volcanic craters are in many cases
+still left standing, and then there are the voluminous sheets of lava
+that have spread over great areas of the earth, as well as numerous
+volcanic cones. Besides, there are thousands of square miles of
+surface that have been covered, often to great depths, by deposits of
+volcanic dust thrown out at one time or another from the craters of
+the then active volcanoes.
+
+I am sure you will acknowledge that any force capable of causing great
+cracks or fissures in the earth's crust, must, while doing this, have
+produced violent shakings of the earth. Great cracks or fissures are
+to be found in the rocks of all the geological formations. These are a
+record of the earthquakes that must have attended these convulsions.
+And there is plenty of evidence to show that the earth's crust has
+been torn into these fissures in places deep down below the present
+surface; for, by the action of water, many of these portions have
+been uncovered so that these great cracks or fissures which have been
+afterwards filled with a molten rock that has hardened can be seen in
+the great dikes that still remain.
+
+But there are still other evidences of the existence of earthquakes
+during the geological past. There are found in the different strata
+of the earth's crust fossil remains of the plants and animals that
+lived on the earth long before the creation of man. By a careful study
+of these fossils we know positively the kinds of animals and plants
+that lived on the earth, in its waters, or in its atmosphere, when
+these strata were being deposited. It is in this way possible for a
+geologist to trace the life of the earth and its development as it
+is written on the great book of which the earth's different strata
+form the separate pages. Now, a careful study of the earth's fauna
+and flora during the geological past, shows, beyond any question,
+that occasionally great changes have occurred in the earth; for, here
+and there, during different times, we find that certain species of
+animals and plants have completely disappeared, to be followed, after
+certain intervals, by entirely different species. It is evident,
+therefore, that changes have occurred that have made it impossible for
+the animals and plants that formerly lived on the earth to exist under
+the changed conditions. These occurrences are known to geologists
+as _exterminations_, _catastrophes_, or _cataclysms_. They are also
+sometimes called _revolutions_, for they mark a more or less complete
+wiping-out of the animals living at the time they occurred.
+
+If you will try to think you will readily understand how great a
+catastrophe must be, that would be able to wipe out or completely
+destroy an entire race of animals.
+
+You have doubtless read with astonishment the terrible catastrophe
+that accompanied the eruption of Krakatoa, especially at the loss of
+life and property caused by the great waves that were set up in the
+ocean, but far reaching as these losses were they have nevertheless
+affected but a limited portion of the earth. The plain truth is even
+more stupendous, for catastrophes of the geological past appear to
+have been so far-reaching and powerful as to affect the whole surface
+of the earth, and to have annihilated entire races of animals and
+plants as if they had never existed.
+
+Geologists are all practically agreed that there are only two ways in
+which such exterminations of the earth's life could have been caused,
+and these are changes in the earth's climate, or the starting of waves
+in the sea by great earthquakes. In the sea; for it must be borne
+in mind that in the geological past the greater part of the earth's
+surface was covered by water, and the land areas were comparatively
+small and low, so that waves created by earthquakes might easily have
+overwhelmed the entire land surface.
+
+Of course, it is fair to suppose that in many cases these
+exterminations may have been caused by sudden changes of climate, such
+as would naturally have resulted from any change in the direction
+of hot ocean currents which formerly flowed from the equator to the
+poles. The appearance of a fairly large mass of land in the central
+parts of the ocean might readily have turned aside the hot ocean
+currents that formerly swept over the polar regions, thus greatly
+lowering the earth's average temperature in these regions.
+
+But it seems probable that the principal cause of the destruction of
+life in the geological past was produced by earthquake waves in the
+sea, sweeping over the continents. Let us, therefore, examine two of
+the earth's principal geological revolutions or cataclysms; namely,
+that which occurred at the close of an early geological time known as
+the Palaeozoic, and that which occurred at the end of a geological
+time intermediate between the Palaeozoic time or the time of ancient
+life, called the Mesozoic time, and the Cenozoic time, or the time
+immediately preceding the present time. These two revolutions are
+called by Dana, _the Post-Palaeozoic_, or _Appalachian Revolution_,
+and the _Post-Mesozoic Revolution_. Both were characterized by the
+making of great mountain systems, and were, therefore, especially
+liable to repetitions of tremendous earthquakes that must have
+produced enormous waves in the ocean.
+
+"Palaeozoic time," says Dana, "closed with the making of one of the
+great mountain ranges of North America--the Appalachian, besides
+ranges in other lands, and in producing one of the most universal and
+abrupt disappearances of life in geological history. So great an event
+is properly styled a revolution."
+
+Towards the close of the Palaeozoic time immense disturbances of
+the earth's crust occurred during the uplifting of the Appalachian
+Mountain System. One may, perhaps, form some faint idea of the
+immensity of the forces at work, from the fact that there were
+great faults produced by the uplifting of the lands attended with
+displacement amounting to 10,000 or 20,000 feet or more; that in parts
+of southwestern Virginia there were flexure faults 100 miles in length.
+
+As to the probability of the extensive exterminations that have
+occurred during these times being produced by earthquake waves, Dana
+speaks thus:
+
+      "The causes of the extermination are two.... (1) a colder
+      climate.... (2) earthquake waves produced by orogenic
+      movements (movements producing mountain ranges). If North
+      America from the west of the Carolinas to the Mississippi
+      Valley can be shaken in consequence of a little slip along
+      a fracture in times of perfect quiet (the allusion here
+      to the Charleston earthquake, in 1886), and ruin mark its
+      movements, incalculable violence and great surgings of
+      the ocean should have occurred and been often repeated
+      during the progress of flexures, miles in height and
+      space, and slips along newly opened fractures that kept up
+      their interrupted progress through thousands of feet of
+      displacements....
+
+      "Under such circumstances the devastation of the sea-border
+      and the low-lying land of the period, the destruction of
+      their animals and plants, would have been a sure result.
+      The survivors within a long distance of the coastline
+      would have been few. The same waves would have swept over
+      European land and seas, and there found coadjutors for new
+      strife in earthquake waves of European origin. These times
+      of catastrophe may have continued in America through half
+      of the following Triassic period; for fully two thirds of
+      the Triassic period are unrepresented by rocks and fossils
+      on the Atlantic border."
+
+Coming now to the Post-Mesozoic revolution this period was marked by
+the making of the greatest of the North American mountain systems.
+
+Dana points out that this revolution affected the summit region of the
+Rocky Mountains over a broad belt probably as long as the western side
+of the continent.
+
+This great belt of mountain-making extended from the Arctic regions
+through North America, probably paralleled by like work, of equal
+extent, in South America, but on a more eastern line.
+
+"The disappearance of species," says Dana, "at the close of Mesozoic
+time was one of the two most noted in all geological history. Probably
+not a tenth part of the animal species of the world disappeared
+at the time, and far less of the vegetable life and terrestrial
+Invertebrates; yet the change was so comprehensive that no Cretaceous
+species of Vertebrate is yet known to occur in the rocks of the
+American Tertiary, and not even a marine Invertebrate."
+
+In tracing the causes of these disappearances, Dana points out that,
+perhaps, the principal cause was a decrease in the temperature of the
+ocean, since the destructions were limited in large measure to marine
+life. He regards, however, the other most probable cause as traceable
+to earthquake waves; for the making of a great mountain range along
+the entire length of the continent resulted in displacements of
+the rock formations along lines hundreds of miles in length. Such
+displacements must have been attended by a succession of earthquakes
+of unusual violence, causing the destruction by sudden shocks beneath,
+and resulting, directly and indirectly, in waves sweeping over the
+continent. Since at this time the land was still low for the greater
+part, the huge waves must have repeatedly swept over the greater part
+of the land, leaving only the smaller species of animals and the
+vegetation.
+
+It is evident, therefore, that during the geological past earthquakes
+occurred that were probably vastly greater than any that have occurred
+on the earth during more recent times.
+
+
+
+
+CHAPTER XXXVI
+
+THE KIMBERLY DIAMOND FIELDS AND THEIR VOLCANIC ORIGIN
+
+
+The elementary substance carbon occurs in three forms, i. e.,
+_charcoal_, _graphite_, and the _diamond_. The commonest form of
+carbon is to be found in charcoal, as well as in bituminous coal,
+anthracite coal, and _lignite_. Graphite, also known as _plumbago_,
+or _black lead_, is the substance you have seen so often in the lead
+of pencils. The diamond, as every one knows, is the highly prized
+precious stone that sparkles so brightly in the light, and is so hard
+that it is capable of scratching almost any other substance.
+
+Diamonds are found in various parts of the world. We are now
+interested in them, however, only as they occur in certain parts of
+the world, as in the great Kimberly diamond fields in Southern Africa.
+
+Dr. Max Bauer in his book on precious stones says that the discovery
+of diamonds in South Africa was made by a traveller named O'Reilly,
+who, in 1867, saw a child sitting in the house of a Boer named Jacobs,
+playing with a shining stone. Jacob's farm was a short distance south
+of the Orange River near Hopetown. This stone proved to be a diamond
+weighing some twenty-one and three-tenths carats and was afterwards
+sold for $2,500. The incident led to the discovery and consequent
+development of the Kimberly diamond fields.
+
+Without going into a description of the different deposits in which
+diamonds are found, it will suffice to say that in the Kimberly
+district the diamonds occur distributed through the materials that
+fill peculiar funnel-shaped depressions called _pipes_ which extend
+vertically downward to unknown depths. The rock that fills a pipe
+consists of an entirely different material from that in which the pipe
+occurs. The upper extremity of the pipe is generally slightly elevated
+above the general surface for a few yards. The pipes vary in diameter
+from twenty to 750 yards, diameters of from 200 to 300 yards being
+quiet common.
+
+In 1892, the diamond-bearing material found in the pipes of the
+Kimberly mines had been excavated vertically downwards a distance of
+1,261 feet, without any signs of its being exhausted.
+
+Now, the materials which fill the pipe of the great Kimberly mine are
+practically the same in all the mines in the neighborhood. At the
+upper part of the pipe the materials show the action of weathering by
+exposure to the air. Here the ground is of a yellowish color. Below,
+the materials have a blue color.
+
+According to Bauer the diamond-bearing material that fills the upper
+part of the pipe consists of a soft, sandy material of a light yellow
+color, known to diamond miners as _yellow ground_, or _yellow stuff_.
+
+In the case of the Kimberly mine, the yellow ground has a thickness of
+about sixty feet. Below it the material has a blue color and is known
+as the _blue ground_. This latter material possesses the character
+of a volcanic _tuff_, which is a hardened clay. It is of a green or
+bluish green color and has the appearance of dried mud that holds
+or binds together numerous irregular, tough, and sometimes rounded
+fragments of a green or bluish black serpentine.
+
+The diamonds are found near the surface in the yellow ground, as
+well as downwards through the blue ground. It was at one time thought
+that most of the diamonds existed in the yellow ground, and that they
+would soon disappear entirely at short distances below where the blue
+ground began. Under this belief some of the most valuable claims
+changed hands at prices far below their true value. It was soon found,
+however, that large and valuable stones existed in the blue ground,
+and, indeed, this ground has never been mined to a depth below where
+valuable diamonds appear.
+
+The diamonds occur in very small quantities spread through the yellow
+and blue grounds. The following statement by Bauer will show this:
+
+      "A striking illustration of their sparing occurrence is
+      furnished by the fact that in the richest part of the
+      richest mine, namely, in the Kimberly mine, they constitute
+      only one part in 2,000,000, or 0.00005% of the blue ground.
+      In other mines the proportion is still lower, namely, one
+      part in 40,000,000, a yield which corresponds to five
+      carats per cubic yard of rock."
+
+Of course, you will desire by this time to know the manner in which
+the pipes of the diamond mines of South Africa have become filled with
+the diamond-bearing rocks, and particularly what diamonds have to do
+with a book on volcanoes and earthquakes.
+
+Dr. Emil Cohen, who has made a study of these regions, regards the
+pipes as volcanic vents or chimneys, and that the materials filling
+the pipes have been brought up from below by volcanic forces. He says:
+
+      "I consider that the diamantiferous ground is a product
+      of volcanic action, and was probably erupted at a
+      comparatively low temperature in the form of an ash
+      saturated with water and comparable to the materials
+      ejected by a mud volcano. Subsequently new minerals were
+      formed in the mass, consequent on alterations induced in
+      the upper part by exposure to atmospheric agencies, and in
+      the lower by the presence of water. Each of the crater-like
+      basins, or, perhaps, more correctly, funnels, in which
+      alone diamonds are now found, was at one time the outlet
+      of an active volcano which became filled up, partly with
+      the products of eruption and partly with ejected material
+      which fell back from the sides of the crater intermingled
+      with various foreign substances, such as small pebbles,
+      or organic remains of local origin, all of which became
+      imbedded in the volcanic tuff. The substance of the tuff
+      was probably mainly derived from deep-seated crystalline
+      rocks, of which isolated remains are now to be found,
+      and which are similar to those which now crop out at the
+      surface, only at a considerable distance from the diamond
+      fields. These crystalline rocks from which the diamonds
+      probably took their origin, were pulverized and forced
+      up into the pipes by the action of volcanic forces, and
+      imbedded in this eruptive material, these diamonds either
+      in perfect crystals or in fragments are now found."
+
+So far as the volcanic origin of the diamonds of the Kimberly diamond
+fields is concerned, Cohen's theory has been generally accepted with
+the following modifications: that the pipes were not filled by a
+single volcanic eruption, but by successive eruptions, and that in
+the case of the Kimberly mine, the pipes contain the results of as
+many as fifteen successive eruptions. There has, however, been another
+and more important modification proposed to Cohen's theory, which is
+far more probable. It will be noticed that Cohen's theory regards the
+action of the volcanic eruption as only serving to bring fragments
+of a deep-seated mother rock that contained the diamonds up from
+below with the material that fills the pipe. Now, Prof. Carvill Lewis
+proposes the following very important change in Cohen's theory: that
+the blue ground does not consist of fragmentary material or tuff, but
+was forced up from below in the pipe in a molten mass and consolidated
+on cooling. In other words, the blue ground is filled with an ordinary
+igneous rock that was solidified in place in the vent or pipe.
+
+In the great Kimberly mines the surface of the pipe is divided into
+numerous separate claims, each consisting of a small square lot. There
+are so many of these claims in the Kimberly mine that its surface is
+honey-combed by numerous square pits. The work is done largely by
+native Kaffirs employed there since the '70's. As the material was
+removed from the pit, the adjoining claims were separated from each
+other by high vertical walls.
+
+At a later date, in order to remove the material and separate the
+lots, high staging provided with ropes and hauling machinery was
+erected. The number of these ropes is now so great that the mine has
+the appearance of a huge cobweb.
+
+A very extensive series of investigations has been made at a
+comparatively recent date by Prof. Henri Moissan of France on various
+chemical products that are obtained under the influence of the high
+temperatures of the electric furnace. When a powerful electric current
+is caused to pass through a highly refractory material, that is to
+say, a material difficult to fuse, such as carbon, it raises it to an
+extremely high temperature. A still higher temperature can be obtained
+by causing a powerful current to flow between two carbon rods that
+are first brought into contact, and then gradually separated from
+each other, just as they are in the ordinary arc lights employed for
+lighting the streets of our cities. In the latter way a temperature
+that is estimated as high as 3,500° C. (6,332° F.), can be readily
+obtained. Under these very high temperatures some very curious
+chemical products have been obtained in electric furnaces. These
+furnaces consist of small chambers made of highly refractory materials
+closely surrounding the incandescent carbon, or the carbon voltaic
+arc. Among some of the most curious of these products are artificially
+produced diamonds.
+
+Moissan, however, was not the first to produce diamonds artificially.
+As soon as Lavoisier had experimentally shown that the chemical
+composition of the diamond and carbon are the same, efforts were made
+to convert charcoal into diamonds, and Despretz, as early as 1849,
+by means of the combined influence of a powerful burning glass, the
+oxyhydrogen blowpipe, and the carbon voltaic arc obtained a very high
+temperature. He claims by this temperature to have been able to change
+carbon into a few microscopic diamonds. It is quite possible, in the
+light of later investigations, that Despretz may have been mistaken
+in his belief that he had actually produced diamonds; but whether
+this be so or not, he was certainly one of the pioneers in this early
+transformation of charcoal.
+
+Theoretically, all that would be required in order to change the
+non-crystalline form of carbon into the diamond, would be to
+subject the carbon to a temperature sufficiently high to fuse it
+and then permit it slowly to crystallize. Could this be done, there
+should be no trouble in transforming any amount of coal into any
+equal amount of diamonds. But the transformation is by no means as
+simple as might be supposed. It is not that the temperature of the
+carbon cannot be raised to its point of fusion, but that as soon
+as a certain temperature has been reached, the carbon, instead of
+fusing or melting, is suddenly volatilized or turned into vapor.
+There is no doubt that this is done. Thousands of feet of carbon
+rods are volatilized every night in the arc lamps of our cities,
+but the trouble is that this carbon vapor so formed, when cooled,
+or condensed, is not converted into the exceedingly hard, clear,
+crystalline diamond, but into the soft, dull black graphite or
+plumbago.
+
+Now the process adopted by Moissan in order to cause volatilized
+carbon, or carbon vapor, to condense in the form of crystalline
+diamonds was practically as follows: he placed pieces of pure carbon
+inside a very strong steel tube, such, for example, as would be formed
+by boring a short cylindrical hole in a piece of strong thick steel,
+and placing a small quantity of carbon inside the tube so formed.
+Closing the open end of the tube by means of a tightly fitting screw
+plug, he volatilized the carbon inside the tube. The steel, tube, and
+plug formed an electric furnace, for, as soon as he passed an electric
+current through it, the temperature at once became high enough to
+volatilize the carbon.
+
+Under these circumstances the carbon vapor was subjected to great
+pressure owing to the limited space in which it was liberated. As soon
+as this mass of dense vapor had been formed, he seized the steel tube
+with a pair of furnace tongs, and plunged it below the surface of cold
+water in a bucket.
+
+Of course, as the hot tube suddenly chilled, there was a great
+shrinking in the walls of the furnace, so that the already compressed
+carbon vapor was subjected to a still greater pressure which possibly
+liquified it. Of that, however, we cannot speak definitely. This,
+however, can safely be asserted, that when the tube was broken open
+a confused mass of small crystals was found inside, some of which,
+on examination with the microscope, were found to consist of small
+crystals of two forms of diamonds, namely, the black diamond, or
+carbonado, and the regular crystallized diamond.
+
+Moissan made a great number of experiments for producing diamonds
+in this way, and succeeded in forming some very beautiful, though
+microscopic, diamonds.
+
+What may be said to characterize especially Moissan's experiments was
+the comparatively great number of diamonds, so small as to be scarcely
+distinguishable under the microscope. The high temperature to which
+the materials inside the tube were exposed resulted in the production
+of numerous minute crystals of different minerals. In order to get rid
+of as many of these as possible Moissan adopted the plan of subjecting
+the material to the action of powerful solvents, such as sulphuric
+acid, aqua regia, or a mixture of sulphuric and nitric acid, and
+hydrofluoric acid. These acids destroyed most of the minute crystals
+of other minerals, but left the minute crystals of diamonds unaffected.
+
+Now it will be observed that the theory proposed by Prof. Carvill
+Lewis as to the probable origin of the diamonds of the Kimberly mines
+bears a wonderfully close resemblance to the method adopted by Moissan
+for the production of artificial diamonds, since it supposes the
+diamonds to have been formed by the sudden cooling or chilling within
+the pipe of various molten materials brought up from great depths by
+the volcanic forces. If this be true, then besides the comparatively
+large crystallized and perfect diamonds found in the blue ground
+of the Kimberly mines, there should also be found large quantities
+of microscopic diamonds, just as are found in Moissan's electric
+furnaces, in which he produced artificial diamonds.
+
+Moissan, considering this, obtained a specimen of the blue ground
+from the Kimberly diamond pipe and on subjecting it to the action of
+the different solvents before named, found in the mass that was left
+undissolved a great number of microscopic diamonds. It would seem,
+therefore, that there is no reasonable doubt but that the Kimberly
+diamond fields had their diamonds produced by the sudden chilling in
+the volcanic pipes of molten materials brought from great depths by
+the force of volcanic eruption.
+
+
+
+
+CHAPTER XXXVII
+
+THE FABLED CONTINENT OF ATLANTIS
+
+
+Besides the sudden changes of level that frequently occur during
+earthquake shocks there are gradual changes of level that take place
+very slowly throughout long periods of time.
+
+These are believed to be due to the warpings produced by the cooling
+of an originally highly heated globe.
+
+It is not true, therefore, that the earth's surface is fixed, or that
+its land and water areas remain always the same. On the contrary, what
+is land at one time is water at another time, and so, too, water areas
+may become changed into land areas.
+
+For the most part these changes go on so slowly as not to be
+noticeable in an ordinary lifetime. Indeed, in some cases, they are so
+extremely gradual that Methuselah himself might have gone to his grave
+in ignorance of their progress.
+
+Let us briefly note a few well-known gradual changes of level.
+
+One of the most extensive of these is the sinking of an immense area,
+over 6,000 miles in diameter, that covers a large part of the bed or
+floor of the Pacific Ocean.
+
+It is an easy matter to observe the gradual changes of level on the
+coasts, since the old water line can be at once found, but it is very
+difficult to detect such changes in the bed of the ocean, hidden as
+it is by a covering of water. Yet many things that seem impossible to
+the uninitiated are readily solved by those familiar with physical
+science. Little signs, meaningless to others, are easily read, and
+these prove beyond doubt the gradual sinking of the ocean's bed.
+
+It was once believed that the coral polyps or animalculæ from the
+hard, bony skeletons of which coral reefs are formed, could live
+at the greatest depths of the ocean. These minute animals were,
+therefore, generally credited with filling up the deep ocean,
+in certain places, and converting it into dry land, and poetic
+philosophers were pleased to point to their indefatigable labors as an
+object lesson to the slothful.
+
+But these charming, though fallacious, ideas were rudely overthrown by
+the sounding line and the drag-net. It had long been known that pieces
+of coral rock were brought up by dredging apparatus from the bottom of
+the ocean at all depths, but it was eventually shown that such pieces
+of coral rock never contained living animalculæ, when brought from
+water at greater depths than from 100 to 120 feet.
+
+It puzzled scientific men no little at first to explain this apparent
+inconsistency. If the coral polyp could not live in water at greater
+depths than from 100 to 120 feet, how could the presence of coral rock
+at a depth of thousands of feet be explained? Happily, however, this
+problem was solved by the great naturalist, Charles Darwin, who showed
+that coral islands can only be formed in parts of the ocean whose beds
+are sinking at the same gradual rate at which the coral rock is being
+deposited. The presence, therefore, of coral islands on the bed of the
+Pacific, as well as along parts of its coasts, are, to scientific men,
+as good indications of its gradual sinking as if such facts had been
+written in the clearest language.
+
+But there are other instances of gradual changes of level besides
+the bed of the Pacific. About 600 miles along the coast of Greenland,
+from Disco Bay, near lat. 69° N., south to the Firth of Igaliko, lat.
+60° 43' N., the bed of the ocean has been slowly sinking through 400
+years. Old buildings and islands have been covered by the waters, so
+that fishermen have been compelled to provide new poles for their
+boats. As Sir Charles Lyell remarks:
+
+      "In one place the Moravian settlers have been obliged more
+      than once to move inland the poles upon which their large
+      boats are set, and the old poles still remain beneath the
+      water as silent witnesses of the change."
+
+Besides these gradual changes of level there are many others, but
+only one more need be cited: the gradual movements of the coasts of
+North America between Labrador and New Jersey that are rising in some
+places, and sinking in other places.
+
+The evidences of these gradual changes of level are sometimes of
+such a character that he who runs may read them. One of the most
+interesting is, perhaps, that of the old Roman temple of Jupiter
+Serapis, at Pozzuli, on the borders of the Mediterranean. This temple,
+when completed, was 124 feet in length and 115 feet in width. Its roof
+was supported by forty-six columns, each forty-two feet in height, and
+five feet in diameter. Only three of these columns are now standing.
+They give, however, unquestionable evidence of having been submerged
+for about half their height. Nor, indeed, is the evidence wanting that
+this submergence continued a considerable time; for, while the lower
+twelve feet of the columns remain smooth and unaffected, yet, for a
+distance of nine feet above this portion, they have been perforated
+by various stone-boring mollusks of a species still living in the
+Mediterranean. This witnesses that the columns, when submerged, were
+buried in mud for twelve feet, and surrounded by water nine feet
+deep. According to Dana, the pavement of the temple is still under
+water. The fact that another pavement exists below it shows that these
+changes of level had occurred before the temple was deserted by the
+Romans. It appears, that, prior to 1845, a gradual sinking of this
+part of the coast had been going on, but that since then there has
+ensued a gradual rising.
+
+The evidences of these gradual changes of level in the land and water
+surfaces of the earth cannot be doubted by even the most skeptical.
+Again and again has the dry land disappeared below the surface of the
+waters of the ocean. Again and again, the ocean's bed has been raised
+to the surface and been converted into dry land. Suppose we attempt to
+follow one of the latter movements.
+
+We will imagine an extensive area to have slowly appeared above the
+ocean. In due process of time this land surface, which we will assume
+to have continental dimensions, gradually becomes covered with plant
+and animal life. If it remains above the water for a sufficient
+length of time, its simple plants and animals acquire more and more
+complex forms, so as to make it difficult to detect any traces of the
+original species from which they have descended, or, more correctly,
+ascended. Moreover, where favorable conditions exist, the continent
+becomes peopled with men, who gradually advance from barbarism to
+semi-barbarism and eventually become a most highly civilized nation,
+sending to different parts of the world colonies, who carry with them
+the language and religious customs of the land of their birth.
+
+But, a sudden or paroxysmal change of level occurs. The highly
+developed and densely populated region is suddenly swept out of
+existence and completely covered by the waters of the ocean until, in
+a few thousand years, all traces of its existence have so completely
+disappeared that but few, if any, can be found willing to acknowledge
+it ever had an existence.
+
+Such, it is claimed, was the fate of the fabled Continent of Atlantis.
+It will, therefore, be interesting to endeavor briefly to review its
+past history and to read some of the things that have been written
+about this part of the world, which appears in the opinion of some of
+the ancients to have actually existed.
+
+References to Atlantis have been made by various early writers. Solon,
+the great Athenian lawgiver, who flourished 600 years B. C.,
+began a description of this place in verse. This description was never
+completed. At a later date one of Solon's descendants, Plato, who
+lived about 400 B. C., prepared a description of Atlantis,
+giving in detail its location, the general character of its surface,
+a description of its principal city, and the civilization of its
+inhabitants, as well as a brief reference to its sudden destruction.
+In another place this record of Plato will be given in full. It will
+suffice now to quote briefly what he says concerning its location.
+
+      "There was an island situated in front of the straits which
+      you call the Columns of Heracles (Straits of Gibraltar).
+      The island was larger than Libya and Asia put together,
+      and was the way to other islands, and from the island you
+      might pass through the whole in the opposite continent,
+      for this sea which is within the Straits of Heracles is
+      only a harbor, having a narrow entrance, but that other is
+      the real sea, and the surrounding land may most truly be
+      called a continent. Now, in the island of Atlantis, there
+      was a great and wonderful empire, which had ruled over the
+      whole island and several others, as well as over part of
+      the continents; and, besides these, they subjected the
+      parts of Libya within the Columns of Heracles as far as
+      Egypt, and of Europe as far as Tyrrhenia. The vast power,
+      thus gathered into one, endeavored to subdue at one blow
+      our country and yours, and the whole of the land which was
+      within the straits, and then, Solon, your country shone
+      forth, in the excellence of her virtues and strength, among
+      all mankind, for she was the first in courage and military
+      skill, and was the leader of the Hellenes. And when the
+      rest fell off from her, being compelled to stand alone,
+      after having undergone the very extremity of danger, she
+      defeated and triumphed over the invaders, and preserved
+      from slavery those who were not yet subjected, and freely
+      liberated all the others who dwelt within the limits of
+      Heracles.
+
+      "But afterwards, there occurred violent earthquakes and
+      floods, and in a single day and night of rain, all your
+      warlike men in a body sunk into the earth, and the island
+      of Atlantis in a like manner disappeared, and was sunk
+      beneath the sea. And that is the reason why the sea in
+      those parts is impassable and impenetrable, because there
+      is such a quantity of shallow mud in the way; and this
+      was caused by the subsidence of the island." ("Plato's
+      Dialogues," ii, 517, Timæus).
+
+But besides Solon and Plato there are other ancient writers who refer
+to the lost island of Atlantis.
+
+Ælian, in his "Varia Historia," lib. iii, chap. xvii, states that
+Theopompos, who flourished 400 B. C., refers to an interview
+between Midas, King of Phrygia, and Sielus, in which the latter speaks
+of a great continent larger than Asia, Europe, and Libya together that
+existed in the Atlantic.
+
+Proclus quotes a statement from an ancient writer, who speaks about
+the islands of the sea beyond the Pillars of Hercules (Straits of
+Gibraltar).
+
+Marcellus, in a book on the Ethiopians, refers to seven islands in
+the Atlantic whose inhabitants preserve legends of a greater island
+(possibly Atlantis), that had dominion over the small islands.
+
+Diodorus Siculus asserts that the Phoenicians discovered a large
+island in the Atlantic beyond the Pillars of Hercules several days'
+sail from the coast of Africa.
+
+Homer, Plutarch, and other ancient writers, refer to several islands
+in the Atlantic situated several thousand stadia from the Pillars of
+Hercules. (A stadium was a Greek measure of length equal to 600 feet.
+It was equal to one-eighth of a Roman mile, or 625 Roman feet.)
+
+Ignatius Donnelly, in his book, called "Atlantis, the Ante-Diluvian
+World," claims that Plato's description of Atlantis which has
+generally been regarded as imaginary, was, on the contrary, historic;
+that the prehistoric continent of Atlantis was the cradle of the human
+race; that here man reached his highest civilization; that Atlantis
+was the site of the Garden of Eden, the Gardens of the Hesperides, the
+Elysian Fields, as well as Olympus; that, under the forms of the gods
+and goddesses of the ancient Greeks, the Phoenicians, the Hindoos,
+and the Scandinavians, are related the stories of the kings, queens,
+and heroes of Atlantis.
+
+Much that has been claimed for the lost continent can hardly be
+regarded in any other light save that of imagination. For example, it
+has been asserted that it was from Atlantis that the colonies were
+sent out that peopled the coast countries of the Gulf of Mexico, of
+parts of the valley of the Mississippi, the basin of the Amazon, the
+western coasts of South America, parts of Europe, the shore lands of
+the Mediterranean Sea, the coasts of Europe, including the Caspian and
+the Black Seas, and even of parts of Africa.
+
+It has also been asserted that this mighty nation of Atlantis carried
+the worship of the sun to Egypt, which was one of its first colonies,
+and, therefore, the civilization of Egypt was but an offshoot of
+prehistoric Atlantis.
+
+But it will be reasonably objected that, if such a mass of land ever
+existed in the North Atlantic, some evidences should still be found
+on the bed of the ocean. Even though great periods of time have
+elapsed since the disappearance of Atlantis, some traces of its former
+existence should still remain on the floor of the ocean. Are there
+any evidences of an old land mass on this part of the floor of the
+Atlantic? The answer is unmistakable.
+
+Deep-sea soundings show beyond question that there still exists in
+the North Atlantic in the region where Atlantis is said to have been
+located a submarine island, the summits of which appear above the
+waters in the Azores and the Canary Islands. This submarine island
+has been traced southwest over the bed of the ocean for a distance of
+several thousand miles with a breadth of fully 1,000 miles. Toward the
+south there is connected with it another submarine island, the summits
+of which reach above the surface in the islands of Ascension, St.
+Helena, and Tristan d'Acunha.
+
+But the testimony of the submarine islands extends further than this.
+According to a number of careful soundings it appears that the bed
+of these parts of the ocean, instead of being characterized by a
+comparatively level surface due to the gradual accumulation of silt,
+possesses, to a great extent, the peculiarly sculptured surfaces which
+are only produced by exposure for a long time to the atmosphere.
+
+Other facts might be adduced to show that some time during the first
+appearance of man on the earth there was a large land mass connecting
+the Eastern and Western Continents. These facts include the wonderful
+resemblances existing between the plants and animals of the Eastern
+and Western Continents, the close resemblances of the myths and
+legends of the races of the Eastern and Western Continents, as well
+as the identity of their religious ideas, and the close similarity of
+their language so far as relates to certain fundamental ideas. These
+facts all point unquestionably to the existence of some large land
+mass between the two continents, and to this extent to throw light on
+the probable existence of prehistoric Atlantis.
+
+
+
+
+CHAPTER XXXVIII
+
+PLATO'S ACCOUNT OF ATLANTIS
+
+
+The following is a translation of Plato's record in full:
+
+      Critias. Then listen, Socrates, to a strange tale, which
+      is, however, certainly true, as Solon, who was the wisest
+      of the seven sages, declared. He was a relative and great
+      friend of my great-grandfather, Dropidas, as he himself
+      says in several of his poems, and Dropidas told Critias, my
+      grandfather, who remembered, and told us, that there were
+      of old great and marvellous actions of the Athenians, which
+      have passed into oblivion through time and the destruction
+      of the human race--and one in particular, which was the
+      greatest of them all, the recital of which will be a
+      suitable testimony of our gratitude to you....
+
+      Socrates. Very good; and what is this ancient famous
+      action of which Critias spoke, not as a mere legend, but
+      as a veritable action of the Athenian State, which Solon
+      recounted?
+
+      Critias. I will tell an old-world story which I heard from
+      an aged man; for Critias was, as he said, at that time
+      nearly ninety-years of age, and I was about ten years of
+      age. Now the day was that day of the Apaturia which is
+      called the registration of youth; at which, according to
+      custom, our parents gave prizes for recitations, and the
+      poems of several poets were recited by us boys, and many
+      of us sung the poems of Solon, which were new at the time.
+      One of our tribe, either because this was his real opinion,
+      or because he thought that he would please Critias, said
+      that, in his judgment, Solon was not only the wisest of men
+      but the noblest of poets. The old man, I well remember,
+      brightened up at this, and said smiling: "Yes, Amynander,
+      if Solon had only, like other poets, made poetry the
+      business of his life, and had completed the tale which he
+      brought with him from Egypt, and had not been compelled, by
+      reason of the factions and troubles which he found stirring
+      in this country when he came home, to attend to other
+      matters, in my opinion, he would have been as famous as
+      Homer, or Hesiod, or any poet."
+
+      "And what was that poem about, Critias?" said the person
+      who addressed him.
+
+      "About the greatest action which the Athenians ever did,
+      and which ought to have been most famous, but which,
+      through the lapse of time and the destruction of the
+      actors, has not come down to us."
+
+      "Tell us," said the other, "the whole story, and how and
+      from whom Solon heard this veritable tradition."
+
+      He replied: "At the head of the Egyptian Delta, where the
+      river Nile divides, there is a certain district which is
+      called the district of Sais, and the great city of the
+      district is also called Sais, and is the city from which
+      Amasis the king was sprung. And the citizens have a deity
+      who is their foundress: she is called in the Egyptian
+      tongue Neith, which is asserted by them to be the same
+      whom the Hellenes called Athene. Now, the citizens of
+      this city are great lovers of the Athenians, and say that
+      they are in some way related to them. Thither came Solon,
+      who was received by them with great honor; and he asked
+      the priests, who were most skilful in such matters, about
+      antiquity, and made the discovery that neither he nor any
+      other Hellene knew anything worth mentioning about the
+      times of old.
+
+      "On one occasion, when he was drawing them on to speak of
+      antiquity, he began to tell about the most ancient things
+      in our part of the world--about Phoroneus, who is called
+      'the first,' and about Niobe; and, after the Deluge, to
+      tell of the lives of Deucalian and Pyrrha; and he traced
+      the genealogy of their descendants, and attempted to
+      reckon how many years old were the events of which he was
+      speaking, and to give the dates. Thereupon, one of the
+      priests, who was of very great age, said: 'O Solon, Solon,
+      you Hellenes are but children, and there is never an old
+      man who is an Hellene.' Solon, hearing this, said, 'What do
+      you mean?' 'I mean to say,' he replied, 'that in mind you
+      are all young; there is no old opinion handed down among
+      you by ancient traditions, nor any science which is hoary
+      with age. And I will tell you the reason of this: there
+      have been, and there will be again, many destructions of
+      mankind arising out of many causes.
+
+      "'There is a story which even you have preserved, that
+      once upon a time Phaëthon, the son of Helios, having yoked
+      the steeds in his father's chariot, because he was not
+      able to drive them in the path of his father, burnt up all
+      that was upon the earth, and was himself destroyed by a
+      thunder-bolt. Now, this has the form of a myth, but really
+      signifies a declination of the bodies moving around the
+      earth, and in the heavens, and a great conflagration of
+      things upon the earth recurring at long intervals of time:
+      when this happens, those who live upon the mountains and in
+      dry and lofty places are more liable to destruction than
+      those who dwell by rivers or on the sea-shore; and from
+      this calamity the Nile, who is our never-failing savior,
+      saves and delivers us.
+
+      "'When, on the other hand, the gods purge the earth with a
+      deluge of water, among you herdsmen and shepherds on the
+      mountains are the survivors, whereas those of you who live
+      in cities are carried by the rivers into the sea; but in
+      this country neither at that time nor at any other does
+      the water come up from below, for which reason the things
+      preserved here are said to be the oldest. The fact is,
+      that wherever the extremity of winter frost or of summer
+      sun does not prevent, the human race is always increasing
+      at times, and at other times diminishing in numbers. And
+      whatever happened either in your country or in ours, or in
+      any other regions of which we are informed--if any action
+      which is noble or great, or in any other way remarkable has
+      taken place, all that has been written down of old, and is
+      preserved in our temples; whereas you and other nations are
+      just being provided with letters and the other things which
+      States require; and then, at the usual period, the stream
+      from heaven descends like a pestilence, and leaves only
+      those of you who are destitute of letters and education;
+      and thus you have to begin all over again as children, and
+      know nothing of what happened in ancient times, either
+      among us or among yourselves.
+
+      "'As for those genealogies of yours which you have
+      recounted to us, Solon, they are no better than the tales
+      of children; for, in the first place, you remember one
+      deluge only, whereas there were many of them, and, in the
+      next place, you do not know that there dwelt in your land
+      the fairest and noblest race of men which ever lived, of
+      whom you and your whole city are but a seed or remnant. And
+      this was unknown to you, because for many generations the
+      survivors of that destruction died and made no sign. For
+      there was a time, Solon, before that great deluge of all,
+      when the city which now is Athens, was first in war, and
+      was preëminent for the excellence of her laws, and is said
+      to have performed the noblest deeds, and to have had the
+      fairest constitution of any of which tradition tells, under
+      the face of heaven.'
+
+      "Solon marvelled at this and earnestly requested the priest
+      to inform him exactly and in order about these former
+      citizens. 'You are welcome to hear about them, Solon,' said
+      the priest, 'both for your own sake and for that of the
+      city; and, above all, for the sake of the goddess who is
+      the common patron and protector and educator of both our
+      cities. She founded your city a thousand years before ours,
+      receiving from the Earth and Hephæstus the seed of your
+      race, and then she founded ours, the constitution of which
+      is set down in our sacred registers as 8,000 years old. As
+      touching the citizens of 9,000 years ago, I will briefly
+      inform you of their laws and of the noblest of their
+      actions; and the exact particulars of the whole we will
+      hereafter go through at our leisure in the sacred registers
+      themselves. If you compare these very laws with your own,
+      you will find that many of ours are the counterpart of
+      yours, as they were in the olden time.
+
+      "'In the first place, there is the caste of priests,
+      which is separated from all the others; next there are
+      the artificers, who exercise their several crafts by
+      themselves, and without admixture of any other, and also
+      there is the class of shepherds and that of hunters, as
+      well as that of husbandmen; and you will observe, too, that
+      the warriors in Egypt are separated from all the other
+      classes, and are commanded by the law only to engage in
+      war. Moreover, the weapons with which they are equipped
+      are shields and spears, and this the goddess taught first
+      among you, and then in Asiatic countries, and we among the
+      Asiatics first adopted.
+
+      "'Then, as to wisdom, do you observe, what care the law
+      took from the very first, searching out and comprehending
+      the whole order of things down to prophecy and medicine
+      (the latter with a view to health); and out of these divine
+      elements drawing what was needful for human life, and
+      adding every sort of knowledge which was connected with
+      them. All this order and arrangement the goddess first
+      imparted to you when establishing your city; and she chose
+      the spot of earth in which you were born, because she saw
+      that the happy temperament of the seasons in that land
+      would produce the wisest of men.
+
+      "'Wherefore the goddess, who was a lover both of war and
+      of wisdom, selected, and first of all settled that spot
+      which was the most likely to produce men likest herself.
+      And there you dwelt, having such laws as these and still
+      better ones, and excelled all mankind in all virtue,
+      as became the children and disciples of the gods. Many
+      great and wonderful deeds are recorded of your State in
+      our histories; but one of them exceeds all the rest in
+      greatness and valor; for these histories tell of a mighty
+      power which was agressing wantonly against the whole of
+      Europe and Asia, and to which your city put an end.
+
+      "'This power came forth out of the Atlantic Ocean, for in
+      those days the Atlantic was navigable; and there was an
+      island situated in front of the straits which you call the
+      Columns of Heracles: the island was larger than Libya and
+      Asia put together, and was the way to other islands, and
+      from the island you might pass through the whole of the
+      opposite continent which surrounded the true ocean; for
+      this sea which is within the Straits of Heracles is only
+      a harbor, having a narrow entrance, but that other is a
+      real sea, and the surrounding land may be most truly called
+      a continent. Now, in the island of Atlantis there was a
+      great and wonderful empire, which had rule over the whole
+      island and several others, as well as over parts of the
+      continent; and, besides these, they subjected the parts of
+      Libya within the Columns of Heracles as far as Egypt, and
+      of Europe as far as Tyrrhenia.
+
+      "'That vast power, thus gathered into one, endeavored to
+      subdue at one blow our country and yours, and the whole of
+      the land which was within the straits; and then, Solon,
+      your country shone forth, in the excellence of her virtue
+      and strength, among all mankind, for she was the first
+      in courage and military skill, and was the leader of the
+      Hellenes. And when the rest fell off from her, being
+      compelled to stand alone, after having undergone the very
+      extremity of danger, she defeated and triumphed over the
+      invaders, and preserved from slavery those who were not
+      yet subjected, and freely liberated all the others who
+      dwelt within the limits of Heracles. But afterward there
+      occurred violent earthquakes and floods, and in a single
+      day and night of rain all your warlike men in a body sunk
+      into the earth, and the island of Atlantis in like manner
+      disappeared, and was sunk beneath the sea. And that is
+      the reason why the sea in those parts is impassable and
+      impenetrable, because there is such a quantity of shallow
+      mud in the way; and this was caused by the subsidence of
+      the island.' ('Plato's Dialogues,' ii, 517, Timæus.)...
+
+      "But in addition to the gods whom you have mentioned, I
+      would specially invoke Mnemosyne; for all the important
+      part of what I have to tell is dependent on her favor, and
+      if I can recollect and recite enough of what was said by
+      the priests, and brought hither by Solon, I doubt not that
+      I shall satisfy the requirements of this theatre. To that
+      task, then, I will at once address myself.
+
+      "Let me begin by observing first of all that nine thousand
+      was the sum of years which had elapsed since the war which
+      was said to have taken place between all those who dwelt
+      outside the Pillars of Heracles and those who dwelt within
+      them. This war I am now to describe. Of the combatants on
+      the one side the city of Athens was reported to have been
+      the ruler, and to have directed the contest; the combatants
+      on the other side were led by the kings of the islands
+      of Atlantis, which, as I was saying, once had an extent
+      greater than that of Libya and Asia; and, when afterwards
+      sunk by an earthquake, became an impassable barrier of mud
+      to voyagers sailing from hence to the ocean. The progress
+      of the history will unfold the various tribes of barbarians
+      and Hellenes which then existed, as they successively
+      appear on the scene; but I must begin by describing, first
+      of all, the Athenians as they were in that day, and their
+      enemies who fought with them; and I shall have to tell of
+      the power and form of government of both of them. Let us
+      give the precedence to Athens....
+
+      "Many great deluges have taken place during the nine
+      thousand years, for that is the number of years which have
+      elapsed since the time of which I am speaking; and in all
+      the ages and changes of things there has never been any
+      settlement of the earth flowing down from the mountains, as
+      in other places, which is worth speaking of; it has always
+      been carried round in a circle, and disappeared in the
+      depths below. The consequence is that, in comparison with
+      what then was, there are remaining in small islets only the
+      bones of the wasted body, as they may be called, all the
+      richer and softer parts of the soil having fallen away, and
+      the mere skeleton of the country being left....
+
+      "And next, if I have not forgotten what I heard when I was
+      a child, I will impart to you the character and origin
+      of their adversaries; for friends should not keep their
+      stories to themselves, but have them in common. Yet, before
+      proceeding further in the narrative, I ought to warn you
+      that you must not be surprised, if you should hear Hellenic
+      names given to foreigners. I will tell you the reason
+      of this: Solon, who was intending to use the tale for
+      his poem, made an investigation into the meaning of the
+      names, and found that the early Egyptians, in writing them
+      down, had translated them into their own language, and he
+      recovered the meaning of the several names and retranslated
+      them, and copied them out again in our language. My
+      great-grandfather, Dropidas, had the original writing,
+      which is still in my possession, and was carefully studied
+      by me when I was a child. Therefore, if you hear names such
+      as are used in this country, you must not be surprised, for
+      I have told you the reason of them.
+
+      "The tale, which was of great length, began as follows:
+      I have before remarked, in speaking of the allotments
+      of the gods, that they distributed the whole earth into
+      portions differing in extent, and made themselves temples
+      and sacrifices. And Poseidon, receiving for his lot the
+      island of Atlantis, begat children by a mortal woman, and
+      settled them in a part of the island which I will proceed
+      to describe. On the side toward the sea, and in the centre
+      of the whole island, there was a plain which is said to
+      have been the fairest of all plains, and very fertile.
+      Near the plain, and also in the centre of the island, at a
+      distance of about fifty stadia, there was a mountain, not
+      very high on any side. In this mountain there dwelt one of
+      the earth-born primeval men of that country, whose name was
+      Evenor, and he had a wife named Leucippe, and they had an
+      only daughter, who was named Cleito.
+
+      "The maiden was growing up to womanhood when her father
+      and mother died; Poseidon fell in love with her, and had
+      intercourse with her; and, breaking the ground, enclosed
+      the hill in which she lived all around, making alternate
+      zones of sea and land, larger and smaller, encircling
+      one another; there were two of land and three of water,
+      which he turned as with a lathe out of the centre of the
+      island, equidistant every way, so that no man could get
+      to the island, for ships and voyagers were not yet heard
+      of. He himself, as he was a god, found no difficulty in
+      making special arrangements for the centre island, bringing
+      two streams of water under the earth, which he caused to
+      ascend as springs, one of warm water and the other of cold,
+      and making every variety of food to spring up abundantly
+      in the earth. He also begat and brought up five pairs of
+      male children, dividing the island of Atlantis into ten
+      portions; he gave to the first-born of the eldest pair his
+      mother's dwelling and the surrounding allotment, which was
+      the largest and best, and made him king over the rest; the
+      others he made princes, and gave them rule over many men
+      and a large territory.
+
+      "He named them all: the eldest, who was king, he named
+      Atlas, and from him the whole island and the ocean received
+      the name of Atlantic. To his twin brother, who was born
+      after him, and obtained as his lot the extremity of the
+      island toward the Pillars of Heracles, as far as the
+      country which is still called the region of Gades in that
+      part of the world, he gave the name which in the Hellenic
+      language is Eumelus, in the language of the country which
+      is named after him, Gadeirus. Of the second pair of twins,
+      he called one Ampheres and the other Evæmon. To the third
+      pair of twins he gave the name Mneseus to the elder, and
+      Autochthon to the one who followed him. Of the fourth pair
+      of twins he called the elder Elasippus and the younger
+      Mestor. And of the fifth pair he gave to the elder the name
+      of Azaes, and to the younger Diaprepes.
+
+      "All these and their descendants were the inhabitants
+      and rulers of divers islands in the open sea; and also,
+      as has been already said, they held sway in the other
+      direction over the country within the Pillars as far as
+      Egypt and Tyrrhenia. Now Atlas had a numerous and honorable
+      family, and his eldest branch always retained the kingdom,
+      which the eldest son handed on to his eldest for many
+      generations; and they had such an amount of wealth as
+      was never before possessed by kings and potentates, and
+      is not likely ever to be again, and they were furnished
+      with everything which they could desire both in city and
+      country. For, because of the greatness of their empire,
+      many things were brought to them from foreign countries,
+      and the island itself provided much of what was required by
+      them for the uses of life.
+
+      "In the first place, they dug out of the earth whatever
+      was to be found there, mineral as well as metal, and that
+      which is now only a name, and was then something more
+      than a name--orichalcum--was dug out of the earth in many
+      parts of the island, and, with the exception of gold, was
+      esteemed the most precious of metals among the men of those
+      days. There was an abundance of wood for carpenters' work,
+      and sufficient maintenance for tame and wild animals.
+      Moreover, there were a great number of elephants in the
+      island, and there was provision for animals of every kind,
+      both for those who live in lakes and marshes and rivers,
+      and also for those which live in mountains, and on plains,
+      and therefore for the animal which is the largest and most
+      voracious of them.
+
+      "Also whatever fragrant things there are in the earth,
+      whether roots, or herbage, or woods, or distilling drops
+      of flowers, or fruits, grew and thrived in that land; and
+      again, the cultivated fruit of the earth, both the dry
+      edible fruit and other species of food, which we call by
+      the general name of legumes, and the fruits having a hard
+      rind, affording drinks, and meats, and ointments, and good
+      store of chestnuts and the like, which may be used to play
+      with, and are fruits which spoil with keeping--and the
+      pleasant kinds of dessert which console us after dinner,
+      when we are full and tired of eating--all these that
+      sacred island lying beneath the sun brought forth fair and
+      wondrous in infinite abundance.
+
+      "All these things they received from the earth, and they
+      employed themselves in constructing their temples, and
+      palaces, and harbors and docks; and they arranged the
+      whole country in the following manner: first of all they
+      bridged over the zones of sea which surrounded the ancient
+      metropolis, and made a passage into and out of the royal
+      palace; and then they began to build the palace in the
+      habitation of the god and of their ancestors. This they
+      continued to ornament in successive generations, every king
+      surpassing the one who came before him to the utmost of his
+      power, until they made the building a marvel to behold for
+      size and for beauty.
+
+      "And, beginning from the sea, they dug a canal three
+      hundred feet in width and one hundred feet in depth, and
+      fifty stadia in length, which they carried through to the
+      outermost zone, making a passage from the sea up to this,
+      which became a harbor, and leaving an opening sufficient
+      to enable the largest vessels to find ingress. Moreover,
+      they divided the zones of land which parted the zones
+      of sea, constructing bridges of such a width as would
+      leave a passage for a single trireme to pass out of one
+      into another, and roofed them over; and there was a way
+      underneath for the ships, for the banks of the zones were
+      raised considerably above the water.
+
+      "Now the largest of the zones into which a passage was cut
+      from the sea was three stadia in breadth, and the zone of
+      land which came next of equal breadth; but the next two,
+      as well a zone of water as of land, were two stadia, and
+      the one which surrounded the central island was a stadium
+      only in width. The island in which the palace was situated
+      had a diameter of five stadia. This, and the zones and the
+      bridge, which was the sixth part of a stadium in width,
+      they surrounded by a stone wall, on either side placing
+      towers, and gates on the bridges where the sea passed
+      in. The stone which was used in the work they quarried
+      from underneath the centre island and from underneath the
+      zones, on the outer as well as the inner side. One kind of
+      stone was white, another black, and a third red; as they
+      quarried, they at the same time hollowed out decks, double
+      within, having roofs formed out of the native rock.
+
+      "Some of their buildings were simple, but in others they
+      put together different stones, which they intermingled for
+      the sake of ornament, to be a natural source of delight.
+      The entire circuit of the wall which went around the
+      outermost one they covered with a coating of brass, and
+      the circuit of the next wall they coated with tin, and the
+      third, which encompassed the citadel, flashed with the red
+      light of orichalcum. The palace in the interior of the
+      citadel was constructed in this wise: in the centre was
+      a holy temple, dedicated to Cleito and Poseidon, which
+      remained inaccessible, and was surrounded by an enclosure
+      of gold; this was the spot in which was originally begotten
+      the race of ten princes, and thither they annually brought
+      the fruits of the earth in their season from all the ten
+      portions, and performed sacrifices to each of them.
+
+      "Here, too, was Poseidon's own temple, of a stadium in
+      length and half a stadium in width, and of a proportionate
+      height, having a sort of barbaric splendor. All the outside
+      of the temple, with the exception of the pinnacles, they
+      covered with silver, and the pinnacles with gold. In the
+      interior of the temple the roof was of ivory, adorned
+      everywhere with gold and silver and orichalcum; all the
+      other parts of the walls and pillars and floor they lined
+      with orichalcum. In the temple they placed statues of
+      gold: there was the god himself standing in a chariot--the
+      charioteer of six winged horses--and of such a size that
+      he touched the roof of the building with his head; around
+      him were a hundred Nereids riding on dolphins, for such was
+      thought to be the number of them in that day.
+
+      "There were also in the interior of the temple other images
+      which had been dedicated by private individuals. And around
+      the temple, on the outside, were placed statues of gold
+      of all the ten kings and of their wives; and there were
+      many other great offerings, both of kings and of private
+      individuals, coming both from the city itself and the
+      foreign cities over which they held sway. There was an
+      altar, too, which in size and workmanship corresponded to
+      the rest of the work, and there were palaces in like manner
+      which answered to the greatness of the kingdom and the
+      glory of the temple.
+
+      "In the next place, they used fountains both of gold and
+      hot springs. These were very abundant, and both kinds
+      wonderfully adapted to use by reason of the sweetness and
+      excellence of their waters. They constructed buildings
+      about them, and planted suitable trees; also cisterns,
+      some open to the heaven, others which they roofed over,
+      to be used in winter as warm baths: there were the king's
+      baths, and the baths of private persons, which were kept
+      apart; also separate baths for women, and others again for
+      horses and cattle, and to them they gave as much adornment
+      as was suitable for them. The water which ran off they
+      carried, some to the grove of Poseidon, where were growing
+      all manner of trees of wonderful height and beauty, owing
+      to the excellence of the soil; the remainder was conveyed
+      by aqueducts which passed over the bridges to the outer
+      circles: and there were many temples built and dedicated
+      to many gods; also gardens and places of exercise, some
+      for men, and some set apart for horses, in both of the
+      two islands formed by the zones; and in the centre of the
+      larger of the two, there was a racecourse of a stadium
+      in width, and in length allowed to extend all round the
+      island, for horses to race in.
+
+      "Also there were guard-houses at intervals for the
+      body-guard, the more trusted of whom had their duties
+      appointed to them in the lesser zone, which was nearer the
+      Acropolis; while the most trusted of all had houses given
+      them within the citadel, and about the persons of the
+      kings. The docks were full of triremes and naval stores,
+      and all things were quite ready for use. Enough of the plan
+      of the royal palace. Crossing the outer harbors, which were
+      three in number, you would come to a wall which began at
+      the sea and went all round; this was everywhere distant
+      fifty stadia from the largest zone and harbor, and enclosed
+      the whole, meeting at the mouth of the channel toward the
+      sea.
+
+      "The entire area was densely crowded with habitations;
+      and the canal and the largest of the harbors were full
+      of vessels, and merchants coming from all parts, who,
+      from their numbers, kept up a multitudinous sound of
+      human voices and din of all sorts, night and day. I have
+      repeated his descriptions of the city and the parts about
+      the ancient palace nearly as he gave them, and now I must
+      endeavor to describe the nature and arrangement of the
+      rest of the country. The whole country was described as
+      being very lofty and precipitous on the side of the sea,
+      but the country immediately about and surrounding the city
+      was a level plain, itself surrounded by mountains which
+      descended toward the sea; it was smooth and even, but of
+      an oblong shape, extending in one direction three thousand
+      stadia, and going up the country from the sea through the
+      centre of the island two thousand stadia; the whole region
+      of the island lies toward the south, and is sheltered from
+      the north.
+
+      "The surrounding mountains were celebrated for their number
+      and size and beauty, in which they exceeded all that are
+      now to be seen anywhere; having in them also many wealthy
+      inhabited villages, and rivers and lakes, and meadows
+      supplying food enough for every animal, wild or tame, and
+      wood of various sorts, abundant for every kind of work.
+      I will now describe the plain, which had been cultivated
+      during many ages by many generations of kings. It was
+      rectangular, and for the most part straight and oblong; and
+      what it wanted of the straight line followed the line of
+      the circular ditch. The depth and width and length of this
+      ditch were incredible, and gave the impression that such a
+      work, in addition to so many other works, could hardly have
+      been wrought by the hand of man. But I must say what I have
+      heard.
+
+      "It was excavated to the depth of a hundred feet, and its
+      breadth was a stadium everywhere; it was carried round the
+      whole of the plain, and was ten thousand stadia in length.
+      It received the streams which came down the mountains,
+      and winding round the plain, and touching the city at
+      various points, was there let off into the sea. From above,
+      likewise, straight canals of a hundred feet in width were
+      cut in the plain, and again let off into the ditch, toward
+      the sea. These canals were at intervals of a hundred
+      stadia, and by them they brought down the wood from the
+      mountains to the city, and conveyed the fruits of the earth
+      in ships, cutting transverse passages from one canal into
+      another, and to the city. Twice in the year they gathered
+      the fruits of the earth--in winter having the benefit of
+      the rains, and in summer introducing the water of the
+      canals. As to the population, each of the lots in the plain
+      had an appointed chief of men who were fit for military
+      service, and the size of the lot was to be a square of ten
+      stadia each way, and the total number of all the lots was
+      sixty thousand.
+
+      "And of the inhabitants, of the mountains and of the rest
+      of the country there was also a vast multitude having
+      leaders, to whom they were assigned according to their
+      dwellings and villages. The leader was required to furnish
+      for the wars the sixth portion of a war-chariot, so as
+      to make up a total of ten thousand chariots; also two
+      horses and riders upon them, and a light chariot without
+      a seat, accompanied by a fighting man on foot carrying a
+      small shield, and having a charioteer mounted to guide the
+      horses; also, he was bound to furnish two heavy-armed men,
+      two archers, two slingers, three stone-shooters, and three
+      javelin men, who were skirmishers, and four sailors, to
+      make up a complement of twelve hundred ships. Such was the
+      order of war in the royal city.
+
+      "That of the other nine governments was different in each
+      of them, and would be wearisome to narrate. As to offices
+      and honors the following was the arrangement from the
+      first: each of the ten kings, in his own division and in
+      his own city, had the absolute control of the citizens,
+      and in many cases, of the laws, punishing and slaying
+      whomsoever he would.
+
+      "Now the relations of their governments to one another
+      were regulated by the injunctions of Poseidon as the law
+      had handed them down. These were inscribed by the first
+      men on a column of orichalcum, which was situated in the
+      middle of the island, at the temple of Poseidon, whither
+      the people were gathered together every fifth and sixth
+      years alternately, thus giving equal honor to the odd and
+      to the even number. And when they were gathered together
+      they consulted about public affairs, and inquired if any
+      one had transgressed in anything, and passed judgment on
+      him accordingly--and before they passed judgment they gave
+      their pledges to one another in this wise:
+
+      "There were bulls who had the range of the temple of
+      Poseidon; and the ten who were left alone in the temple,
+      after they had offered prayers to the gods that they might
+      take the sacrifices which were acceptable to them, hunted
+      the bulls without weapons, but with staves and nooses; and
+      the bull which they caught they led up to the column. The
+      victim was then struck on the head by them, and slain over
+      the sacred inscription. Now on the column, besides the law,
+      there was inscribed an oath invoking mighty curses on the
+      disobedient. When, therefore, after offering sacrifices
+      according to their customs, they had burnt the limbs of the
+      bull, they mingled a cup and cast in a clot of blood for
+      each of them. The rest of the victim they took to the fire,
+      after having made a purification of the column all round.
+
+      "They then drew from the cup in golden vessels, and,
+      pouring a libation on the fire, they swore that they would
+      judge according to the laws on the column, and would punish
+      any one who had previously transgressed, and that for the
+      future they would not, if they could help, transgress any
+      of the inscriptions, and would not command, or obey any
+      ruler who commanded them, to act otherwise than according
+      to the laws of their father Poseidon.
+
+      "This was the prayer which each of them offered up for
+      himself and for his family, at the same time drinking, and
+      dedicating the vessel in the temple of the god; and, after
+      spending some necessary time at supper, when darkness came
+      on and the fire about the sacrifice was cool, all of them
+      put on most beautiful azure robes, and, sitting on the
+      ground at night near the embers of the sacrifices on which
+      they had sworn, and extinguishing all the fires about the
+      temple, they received and gave judgment, if any of them had
+      any accusation to bring against any one; and, when they had
+      given judgment, at daybreak they wrote down their sentences
+      on a golden tablet, and deposited them as memorials with
+      their robes.
+
+      "There were many special laws which the several kings had
+      inscribed about the temple, but the most important was the
+      following: that they were not to take up arms against one
+      another, and they were all to come to the rescue, if any
+      one in any city attempted to overthrow the royal house.
+      Like their ancestors, they were to deliberate in common
+      about war and other matters, giving the supremacy to the
+      family of Atlas; and the king was not to have the power of
+      life or death over any of his kinsmen, unless he had the
+      assent of the majority of the ten kings.
+
+      "Such was the vast power which the god settled in the lost
+      island of Atlantis; and this he afterward directed against
+      our land on the following pretext, as traditions tell. For
+      many generations, as long as the divine nature lasted in
+      them, they were obedient to the laws, and well-affectioned
+      toward the gods, who were their kinsmen, for they possessed
+      true and in every way great spirits, practicing gentleness
+      and wisdom in the various chances of life, and in their
+      intercourse with one another.
+
+      "They despised everything but virtue, not caring for
+      their present state of life, and thinking lightly on the
+      possession of gold, and other property, which seemed only a
+      burden to them; neither were they intoxicated by luxury,
+      nor did wealth deprive them of their self-control; but
+      they were sober, and saw clearly that all these goods are
+      increased by virtuous friendship with one another, and that
+      by excessive zeal for them and honor of them, the good of
+      them is lost, and friendship perishes with them.
+
+      "By such reflections, and by the continuance in them of a
+      divine nature, all that which we have described waxed and
+      increased in them; but when this divine portion began to
+      fade away in them, and became diluted too often, and with
+      too much of the mortal admixture, and the human nature
+      got the upper hand, then, they being unable to bear their
+      fortune, became unseemly, and to him who had an eye to see,
+      they began to appear base, and had lost the fairest of
+      their precious gifts; but to those who had no eye to see
+      the true happiness they still appeared glorious and blessed
+      at the very time when they were filled with unrighteous
+      avarice and power. Zeus, the god of gods, who rules with
+      law, and is able to see into such things, perceiving that
+      an honorable race was in a most wretched state, and wanting
+      to inflict punishment on them, that they might be chastened
+      and improved, collected all the gods into his most holy
+      habitation, which, being placed in the centre of the world,
+      sees all things that partake of generations. And when he
+      had called them together, he spake as follows:"
+
+The story abruptly ends here, for Plato left no further record.
+
+
+
+
+CHAPTER XXXIX
+
+NATURE'S WARNING OF COMING EARTHQUAKES
+
+
+That there are signs of coming earthquakes which might be read by
+man, had he sufficient knowledge, there would seem to be but little
+doubt. These phenomena follow natural laws so that the approach of an
+earthquake must necessarily be in a definite order both as regards
+the phenomena which precede as well as those which follow it. There
+should, therefore, be signs that would enable one to predict its
+coming, although it must be acknowledged that these signs, so far as
+we actually know, are indistinct.
+
+It may seem to the unthinking and unobservant that the awful
+catastrophe of an earthquake comes entirely unheralded; that,
+apparently, it is not until the earth's surface begins to rock to
+and fro under the mighty forces that are causing destruction that
+its presence can be known. There are, however, many reasons for
+believing that in, perhaps, the greatest number of cases, it might
+have been foreseen, if greater attention had been given to the
+slight indications of its probable approach a short time before its
+occurrence.
+
+It is evident that the conditions of great pressure or stress in the
+earth's crust which finally result in a disastrous earthquake have
+been slowly accumulating for a long time, and that when the pressure
+at last reaches a point where the crust has to yield or slip, the
+ground is suddenly crushed and tossed to and fro while vast fissures
+and chasms are produced in the subterranean regions. At those points
+of the earth immediately above or in the neighborhood of such regions
+it is possible that there are many signs of the coming quake;
+and, although indistinguishable by our duller senses, are readily
+appreciated by the more highly developed senses of the lower animals.
+Indeed, had we accustomed ourselves to reading the various indications
+of nature as the lower animals have, we, too, might be able to read
+these warnings of the coming earthquake.
+
+At great distances from the place where the earthquake starts there
+would necessarily be a better opportunity for predicting its approach.
+As already stated, what is called an earthquake does not consist
+of a single shaking of the ground, but of a highly complex series
+of shakings. According to Mallet, the following waves start at the
+same time from the place of origin of an earthquake, when located
+on the bed of an ocean; i. e., an earth sound wave and a earth wave
+constituting the earth's shake; a sound wave through the ocean,
+another through the air; a sea wave called by him a forced sea wave,
+and finally the great sea wave.
+
+These waves reach a distant point in the following order: the sound
+wave through the earth and the great earthquake or shake which
+produces the damage. Then a smaller sea wave called the forced sea
+wave. This is followed almost immediately by the sound wave through
+the sea. Next come the air sound wave and finally the great sea wave;
+which, rushing in on the shore, sweeps nearly everything before it.
+
+In other words, the disturbances produced by the great earthquake
+follow in this order of sequence. If, therefore, the great earthquake
+wave proper transmitted through the earth should for any reason be
+delayed in reaching a distant place, the great sound waves should be
+able to give warning of the coming disturbances.
+
+Again, as we have already seen, the earthquake wave is preceded by a
+number of preliminary tremors, and is followed by a number of after
+tremors or _earthquake echoes_. Since, therefore, the preliminary
+waves reach a place first, it would seem that the approach of an
+earthquake must be heralded by the preliminary tremors. These,
+perhaps, at least in part, enable the lower animals to detect its
+coming.
+
+Again, in almost all instances there are a number of preliminary
+shocks that precede the great earthquake shock. Some of these
+preliminary shocks continue at intervals for several days or even
+longer. Sometimes, indeed, these subterranean sounds fail to be
+followed by earthquakes. Milne thinks that these sounds are caused
+by the preliminary tremors which precede the principal shock of the
+earthquake and that they reach the place first. Here again then it
+is evident that, were we able to interpret properly these sounds, we
+would probably be able to foretell the coming quake with a fair degree
+of certainty.
+
+There would appear to be no reasonable doubt that in some manner
+which we have not yet been able to discover, but probably along some
+of the lines indicated above, animals are capable of recognizing a
+coming earthquake. Long before the coming of the catastrophe they are
+said to exhibit extreme terror, and in many cases appear to seek the
+companionship of man, as if for protection.
+
+That the senses of smell and hearing are far more acute in the lower
+animals than in man no one can reasonably doubt. The manner in which
+a trained dog can follow a scent, for a long time after the animal
+or thing producing it has passed, far exceeds the power of scent
+possessed by man, and it is more than likely that this same power is
+possessed by all animals who live upon or prey upon other animals. It
+is probable that faintly odorous vapors or gases escape from the crust
+shortly before the great shock occurs, and that these faint odors are
+warnings to the animals of the approaching calamity. The sense of
+hearing also is much more acute in the lower animals.
+
+Daubeny is evidently of this belief, as will be seen from the
+following:
+
+      "These gases and vapors (alluding to emanations given off
+      from the ground during earthquakes) exert an influence
+      on the barometer, which does appear to be indirectly
+      affected by the earthquake. Then, similar properties
+      also may occasion that uneasiness which animals are said
+      to evince before any such event. Thus, according to the
+      accounts of some writers, rats and mice leave their holes,
+      alligators seek the dry land, quadrupeds snuff the ground,
+      and manifest such signs of the impending calamity that in
+      countries where earthquakes are common, the inhabitants
+      take the alarm in consequence, and escape from their
+      houses. It is right, however, to add, that more recent
+      authorities dispute altogether the correctness of these
+      statements."
+
+Dutton doubts the ability of animals to foretell coming earthquake
+shocks.
+
+But that the lower animals do exhibit signs of fear at the approach of
+an earthquake has been repeatedly asserted by good observers.
+
+Hamilton, who made a careful examination of the neighboring country
+during the great earthquake at Calabria, asserts that horses and oxen
+during the shocks extended their legs widely in order to avoid being
+thrown down, "and that hogs, oxen, horses, and mules, and also geese,
+appeared to be painfully aware of the approach of the earthquake of
+Calabria; and the neighing of a horse, the braying of an ass, or the
+cackling of a goose, even when he (Hamilton) was making his survey
+(after the occurrence of the great earthquake shock), drove the people
+out of their temporary sheds in expectation of a shock."
+
+It is asserted that birds appear to be especially sensible to a coming
+earthquake shock. That geese will quit the water in which they were
+swimming before the earthquake and will not return to it. It is quite
+possible that these birds with their heads immersed in the water can
+hear the distant murmurings long before they become audible in the air.
+
+Von Hoff makes the following statement:
+
+      "It has been remarked that at such times (immediately
+      before the coming of an earthquake shock), domestic animals
+      showed a decided uneasiness, dogs howled mournfully, horses
+      neighed in an unusual manner, and poultry flew restlessly
+      about. These latter phenomena might easily be produced by
+      mephitic vapours, which often ascend to the surface of the
+      earth before the breaking out of an earthquake."
+
+Mallet states that there is abundant evidence that earthquake shocks,
+even when not of very great intensity, produce nausea in both men and
+women. This would seem natural, since, as everyone knows, until one
+is accustomed to sea-voyages, merely to be tossed to and fro by the
+motion of the waves results in the production of sea-sickness.
+
+It has been also noticed that during earthquakes fish which under
+ordinary circumstances live in the mud at the bottom of bodies of
+water come near to the surface and at such times can be caught in
+great numbers.
+
+Mallet cites the following effects produced by earthquakes:
+
+      "Amongst the effects supposed to be produced by the
+      earthquake on the atmosphere were reckoned tempestuous
+      winds, thunder-storms, meteors, coldness of the air,
+      severe winters, heavy rains, miasmata, producing diseases
+      and affecting vegetation. A very remarkable instance of
+      the latter is quoted, namely, that in Peru, after the
+      earthquake of 1687, wheat and barley would not thrive at
+      all, though formerly the country was remarkably favourable
+      for them."
+
+Sir Charles Lyell notes the following phenomena attending earthquakes:
+
+      "Irregularities in the seasons preceding or following the
+      shocks; sudden gusts of wind, interrupted by dead calms;
+      violent rains at unusual seasons, or in countries where,
+      as a rule, they are almost unknown; a reddening of the
+      sun's disk, and haziness in the air, often continued for
+      months; an evolution of electric matter, or of inflammable
+      gas from the soil, with sulphurous and mephitic vapours;
+      noises underground, like the running of carriages, or
+      the discharge of artillery, or distant thunder; animals
+      uttering cries of distress, and evincing extraordinary
+      alarm, being more sensitive than men to the slightest
+      movement; a sensation like sea-sickness, and a dizziness in
+      the head, experienced by men. These, and other phenomena,
+      less connected with our present subject as geologists, have
+      recurred again and again at distant ages, and in all parts
+      of the globe."
+
+
+THE END
+
+
+
+
+FOOTNOTES:
+
+[Footnote 1: A point on the other side of the earth directly opposite
+a given point.]
+
+[Footnote 2: A fracture of a stratum, or a general rock mass, with a
+relative displacement of the opposite sides of the break.
+
+The plane or fracture of a fault, known as the fault-plane, is seldom
+vertical. The higher side is called the heaved or upthrow side; the
+opposite side the thrown or downthrow side.]
+
+[Footnote 3: _Tectonic Earthquake_. An earthquake due to the sudden
+slip of faulted strata.]
+
+[Footnote 4: _I. e._, burnt out mountain, extinct volcano.]
+
+[Footnote 5: _Epicentre._ A point on the surface of the earth
+vertically above the point of origin of an earthquake, or the place
+where it starts.]
+
+
+
+
+Transcriber's Notes
+
+
+Obvious printer errors have been silently corrected.
+
+Some illustrations have been moved to paragraph breaks.
+
+Page 43: Kamehamoha could be a typo for Kamehameha.
+
+Page 68: Changed "salter" to "saltier."
+  (Orig: another with water salter than the sea,)
+
+Page 76: Changed "Ena" to "Etna."
+  (Orig: during his time Mt. Ena had lost so much of its height)
+
+Page 115: "eruption during the winter of 1841-43," could be a typo for
+1841-42 or 1842-43.
+
+Page 122: "Mont Pelée" could be a typo for "Mount Pelée."
+
+Page 136: 43° C." (109° 4' F.). could be a typo for (109.4° F.).
+
+Page 341: Changed one-eight to one-eighth.
+  (Orig: It was equal to one-eight of a Roman mile)
+
+Retained the following spelling variations:
+
+  Page 49: The largest volcano in Iceland, the Dyngjufköll,
+  Page 57: The largest volcano in Iceland is Dyngjufjoll.
+
+  Pages 52, 193, 311: Geikie
+  Page 181: Geicke
+
+  Pages 17, 156, 257: Hindostan
+  Page 165: Hindustan
+
+  Page 63: Lucullis
+  Page 76: Lucullus
+
+
+
+
+
+
+
+End of the Project Gutenberg EBook of The Wonder Book of Volcanoes and
+Earthquakes, by Edwin J. Houston
+
+*** END OF THE PROJECT GUTENBERG EBOOK 43320 ***