Caves sometimes exhale poisonous vapors. Of these, the most remarkable is near Naples, named the Grotto del Cane. In Iceland, there are many formed by the lava from its volcanoes. In the volcanic country near Rome, are many natural cavities of great extent and coolness, which form pleasant places of resort in the hot weather. The grottoes in the Cevennes Mountains, in France, are both numerous and extensive, and abound in objects of curiosity. In South America is the cavern of Guacharo, which is said to extend for leagues. CHAPTER IX.――ISLANDS. MOST of the coast of Maine is thickly strewn with islands. The largest is _Mount Desert_, on the west side of Frenchman’s Bay; it is fifteen miles long, and twelve broad. Many fine islands lie in Penobscot Bay, as _Long Island_, on which is the town of Islesborough; the _Fox Islands_, containing the town of Vinalhaven; and _Deer Isle_, on the east side of the bay, about eight miles from Castine. The _Isles of Shoals_ belong partly to New Hampshire, and partly to Maine. They lie about eight miles out at sea, between Portsmouth and Newburyport, and are hardly more than a cluster of rocks rising above the waters; but they are, on many accounts, worthy of notice. They have but a thin and barren appearance, yet for more than a century previous to the revolution they were quite populous, containing at one time six hundred inhabitants, who found there an advantageous situation for carrying on fisheries. To this day the best cod in the world are those which are known in the market as _Isle of Shoals dun fish_. These islands were discovered by the celebrated Captain Smith in 1614, and called at first Smith’s Isles. The New Hampshire portion now constitutes the town of Gosport. In all of them are chasms in the rocks apparently caused by earthquakes. There is a remarkable chasm on Star Island, where one of the female inhabitants secreted herself when the islands were invaded, and the people carried into captivity by the Indians. The largest is named Hog Island, and contains three hundred and fifty acres; Star Island has one hundred and fifty, Hayley’s one hundred; they are in all seven. The inhabitants are about one hundred; they live solely by fishing, and in connection with those of the shore in their immediate neighborhood, who follow the same mode of life, are the most rude and uncivilized beings in New England, except the Indians. They supply the markets of Newburyport with fish, and have long been known there by the name of _Algerines_. Efforts have recently been made to improve their social condition.