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.

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.

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:

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":

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.

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.

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."

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: