Geysers have been recently discovered in California; but the jets do not rise higher than twenty or thirty feet. They are, however, very numerous, there being upwards of a hundred openings within a space of half a mile square. The vapour from the whole group rises to upwards of a hundred and fifty feet into the air. The boiling water issues from conical mounds, with great noise. The whole ground around them is a mere crust, and when it is penetrated the boiling water is seen underneath. The Californian geysers, however, are impregnated, not with silica, like those of Iceland, but with sulphur, of which they form large deposits. The sulphurous vapours from the water corrode the rocks near the fountains; nevertheless trees grow, without injury to their health, at a distance from them of not more than fifty feet. Besides obsidian, already mentioned as a product of its volcanoes, Iceland is famed for another mineral of great scientific value. It is that fine variety of carbonate of lime named Iceland-spar. Transparent and colourless, like glass, this mineral possesses the property of double refraction--any small object viewed through it in a particular direction appearing double. It is much used for optical purposes--especially for obtaining polarized light. There is another volcano lying far to the northward of Iceland. It is in the island of Jan Mayen, off the coast of Greenland, and has on its summit a vast crater, 2000 feet in diameter, and 500 in depth. CHAPTER III. Mount Vesuvius--Origin of Name--Former Condition--Eruption of A D 79--Death of Pliny--Destruction of Pompeii and Herculaneum--Appearance of the Mountain before and after Eruption--Formation of Monte Nuovo--Eruption of Boiling Water--Coloured Vapours--Cascade of Lava--Discovery of Remains of Herculaneum and Pompeii--The Buildings of Pompeii--Street of Tombs--Skeletons--Sundry Shops--Ascents of Vesuvius--Crater--Temple of Serapis. Mount Vesuvius is the only active volcano on the continent of Europe, and it is highly interesting both from its historical associations and the frequency of its eruptions. It is situated on the coast of the Bay of Naples, about six miles to the eastward of the city and at a short distance from the shore. It forms a conspicuous feature in the beautiful landscape presented by that bay, when viewed from the sea, with the city in the foreground. Mount Vesuvius was in ancient times held sacred to the deified hero Hercules, and the town of Herculaneum, built at its base, was named after him. So also, it is said, was the mountain itself, though in a more round-about way. Hercules, as you will doubtless learn, was feigned to have been the son of the heathen god Zeus and Alcmena, a Theban lady. Now one of the appellations of Zeus was Υης, which was applied to him as being the god of rains and dews--the wet divinity. Thus Hercules was Υησουυιος, the son of Ves. How this name should have become corrupted into "Vesuvius," you can be at no loss to perceive.