386 REACTION OF THE INTERIOR OF THE EARTH 



having been found in them, so that we have not here 

 the trachyte formation of Toluca, Orizaba, and of some 

 of the volcanoes of Java, from which Dr. Junghuhn 

 sent me selected solid pieces of lava to be examined 

 by Gustav Eose. In Albemarle island, which is the 

 largest and westernmost of the Galapagos, the conical 

 mounts are arranged linearly, and we may infer there- 

 fore over fissures. Their greatest height, however, does 

 not exceed 4636 feet. The western bay, in which rises 

 the island peak of Narborough which in 1825 was in 

 vehement eruption, is described by Leopold von Buch ( 528 ) 

 as a crater of elevation, and is compared to Santorin. 

 Many of the margins of craters in the Galapagos are 

 formed of beds of tufa which fall away on all sides. It is 

 remarkable, and indicative of the simultaneous action 

 of a great catastrophe, that all the crater-margins are 

 either broken down or entirely destroyed on their 

 southern side. Part of what in older descriptions is 

 termed tufa consists of beds of palagonite, quite similar 

 to that of Iceland and Italy, as has been established 

 by Bunsen's exact analysis of the tufas of Chatham 

 island. ( 529 ) This, which is the easternmost island of 

 the entire group, and of which the exact position has 

 been astronomically determined by Beechey, is still 536 

 geographical miles distant from Punta de S. Francisco 

 on the American continent, according to my determina- 

 tion of the longitude of the town of Quito, 81 4' 38" W. 

 from Paris, and Acosta's Mapa de la Nueva Granada of 

 1849. 





