Page:Popular Science Monthly Volume 2.djvu/533

Rh or night. On the night of the 29th, flames issued from the ground near the baths of Nero, the earth rose and burst at the top with tremendous roar, and discharged steam, gas, pumice, mud, and ashes. A mountain 1,000 feet high was formed, known as Monte Nuovo, which, at the present time, is 8,000 feet in circumference, and 440 feet above



the bay. The present aspect of Monte Nuovo is represented in Fig. 1, and the region around is shown in the frontispiece, from the last edition of Lyell's "Principles of Geology."

The Phlegræan Fields, of which Monte Nuovo now forms a part, have, in the opinion of Sir Charles Lyell, a "mutual relation with Vesuvius—a violent disturbance in one district serving as a safety-valve to the other—both never being in full activity at once."

In the Sandwich Islands, in 1868, Mauna Loa and the craters of Kilhauea on its flank were in active eruption. The valleys of the mountains were filled with rivers of fire, and a cloud of smoke and vapor arose, it is said, over the mountain, to a height of eight miles. During these fearful phenomena, which continued more than a month, 1,500 earthquake-shocks occurred, 300 of which were counted in five days. But whether shocks occur in the immediate vicinity of volcanoes during eruptions, or whether activity of the one diminishes the violence of the other, it is certain that they have a mutual relation, and probably a common origin.

The opening and closing of fissures and chasms in the ground during earthquakes is a common phenomenon. Men, animals, and dwellings, are sometimes swallowed in them, and forever disappear. In 1848 an earthquake shook a large portion of New Zealand, and a fissure of great depth opened along a chain of mountains from 1,000