ABSTRACT
September 15th, 1835. The Beagle arrived at the southernmost o f the Galapagos islands. This archipelago consists o f ten principal islands, o f which five much exceed the others in size. They are situated under the equatorial line, and between five and six hundred miles to the westward o f the coast o f America. The constitution of the whole is volcanic. With the exception o f some ejected fragments o f granite, which have been most curiously glazed and altered by the heat, every part consists o f lava, or o f sandstone resulting from the attrition of such materials. The higher islands, (which attain an elevation o f three, and even four thousand feet) generally have one or more principal craters towards their centre, and on their flanks smaller orifices. I have no exact data from which to calculate, but I do not hesitate to affirm, that there must be, in all the islands of the archipelago, at least two thousand craters. These are o f two kinds; one, as in ordinary cases, consisting o f scoriae and lava, the other o f finely-stratified volcanic sandstone. The latter in most instances have a form beautifully symmetrical: their origin is due to the ejection o f mud, that is, fine volcanic ashes and water, without any lava.
