In various parts of the earth, there are mountains that send out from their highest peaks, smoke, ashes, and fire. Mountains of this class are called volcanoes, and they present a striking contrast to other mountains, on account of their conical form and the character of the rocks of which they are composed. All volcanoes have at their summits what are called craters. These are large, hollow, circular openings, from which the smoke and fire escape.

Nearly all volcanoes emit smoke constantly. This smoke proceeds from fires that are burning far down in the depths of the earth. Sometimes these fires burst forth from the crater of the volcano with tremendous force. The smoke becomes thick and black, and lurid flames shoot up to a height of hundreds of feet, making a scene of amazing grandeur. With the flames there are thrown out stones, ashes, and streams of melted rock called lava. This lava flows down the sides of the mountain, and, being red hot, destroys everything with which it comes in contact. At such times, a volcano is said to be in eruption. Such is the force of some of these eruptions, that large rocks have been hurled to great distances from the crater, and towns and cities have been buried under a vast covering of ashes and lava.

The quantity of lava and ashes which sometimes escapes from volcanoes during an eruption, is almost beyond comprehension. In 1772, a volcano in the island of Java, threw out ashes and cinders that covered the ground fifty feet deep, for a distance of seven miles all around the mountain. This eruption destroyed nearly forty towns and villages. In 1783, a volcano in Iceland sent out two streams of lava; one forty miles long and seven miles wide, and the other fifty miles long and fifteen miles wide. These streams were from one hundred to six hundred feet deep.

Near the city of Naples, in Italy, is situated the volcano Mt. Vesuvius. This fiery monster has probably caused more destruction than any other volcano known. In the year 79, A.D., it suddenly burst forth in a violent eruption, that resulted in one of the most appalling disasters that ever happened. Such immense quantities of ashes, stones, and lava were poured forth from its crater, that within twenty hours, two large cities were completely destroyed. These cities were Herculaneum and Pompeii.

At this eruption of Vesuvius, the stream of lava flowed directly through and over the city of Herculaneum into the sea. The quantity was so great that, as it cooled and became hardened, it gradually filled up all the streets and ran over the tops of the houses. While the lava was thus turning the city into a mass of solid stone, the inhabitants were fleeing from it along the shore toward Naples, and in boats on the sea. At the same time, too, the wind carried the ashes and cinders in such a direction as to deluge the city of Pompeii. Slowly and steadily the immense volume of ashes and small stones, blocked up the streets and settled on the roofs of the houses. The light of the flames that burst out from the awful crater, aided the people in their escape; but many who for some reason could not get away, perished.

Pompeii was so completely covered that nothing could be seen of it. Thus it remained, buried under the ground, until the year 1748, when it was discovered by accident. Since that time much of the city has been uncovered, and now one can walk along the streets, look into the houses, and form some idea how the people lived there eighteen hundred years ago.