176 THE VOYAGE OF H.M.S. CHALLENGER 



XV.— EOCKS OF THE ISLAND OF JUAN FEENANDEZ. 



The coasts of Chili, like all those of Western South America, have relatively very 

 few large and profound indentations, and there are few islands in the adjoining ocean. 

 With the exception of the Galapagos Islands, well known from Darwin's description, and 

 those of Juan Fernandez, the only islets to be found along this coast are those of the 

 Fjords, situated southward of the continent, and which belong to the older formations 

 of Patagonia. The group of Juan Fernandez ' is composed of several islands, the most 

 important of which, bearing the name of Juan Fernandez or Mas-a-tierra, is famous 

 from the sojourn of Alexander Selkirk, hero of Defoe's "Eobinson Crusoe." With 

 regard to natural history, Juan Fernandez has most interesting characteristics, which 

 have long ago attracted the notice of zoologists and botanists. This islet, only a few 

 miles in extent, is inhabited by birds and terrestrial molluscs, and covered by trees and 

 ferns, which are not to be found on any other part of the globe, except perhaps at Mas- 

 a-fuera, a little neighbouring islet. As just remarked, the fauna and flora of this group 

 of islands have been already closely studied, but such is not the case with its geology, 

 which is as yet but vaguely known. 



The group is composed of Juan Fernandez, Mas-a-fuera, Santa Clara, and the little 

 Goat Island ; they are surrounded by numerous rocks, which rise to the surface at a 

 short distance from the shore. Juan Fernandez, where the rocks that we shall presently 

 describe were collected, is situated in lat. 33° 37' 45" S., long. 78° 53' W. (Fort Juan 

 Baptista) ; it measures 13 English miles by 4, with an area of 28 square miles. From 

 the monument erected to Selkirk's memory by Commodore Powell and the officers of 

 the " Topaze," the whole island may be seen ; it is crescent-shaped, curved from E. to 

 W. ; a channel, 1 mile in width and 19 fathoms deep, divides Juan Fernandez from the 

 islet of Santa Clara. The island rises into a peak, and is surrounded by high black 

 cliffs intersected by deep gullies, where the most splendid vegetation is to be found. 

 A mountain, called the Anvil (El Yunque) from its remarkable shape, surmounts 

 the cbfis. 



The rocks collected show (as already indicated by the shape of the island) that Juan 

 Fernandez is composed of volcanic materials, but no crater nor recent flow of lava is 

 to be seen. The shape of the island, the nature of its rocks, must cause Juan Fernandez 

 to be classed, with regard to physiography, amongst the oceanic islands formed by the 

 remains of ancient volcanoes, which do not any longer show the complete volcanic 



1 For the physical and political geography of these islands, see Wappaus, Panama, New Grenada, Venezuela, 

 Guyana, Ecuador, Bolivia, Chili, geographisch und statistisch dargestellt, p. 850, Leipzig. The natural history of 

 Juan Fernandez, and the questions relating to the fauna and flora, are summed up in Narr. Chall. Exp., vol. i. pp. 818 

 et seq. A bibliography, almost complete, of the works on this group of islands is to be found there. See also Hahn, 

 Jnsel Studien, p. 108. 



