M. Von Buch an Vokanos and Craters q/' Elevation. 203 



settlement. When Cabral, provided with every thing that was 

 necessary, again arrived at St Miguel, he was greatly astonished 

 to find that the part of the island previously visited by him had 

 during the summer been completely overturned and destroyed. 

 Instead ol* the plain he saw a high mountain ; the whole district 

 was devastated and covered by slags and large blocks, and the 

 cultivation of the land was now quite impracticable. The moun- 

 tain is 2000 feet in height. It surrounds an enormous crater, 

 which at the upper edge has a circumference of fifteen English 

 miles. Two lakes are situated in its interior, iMgoa Grande 

 and Lagoa Azul, and the whole internal flat surface is termed 

 the Vale de las sete citades. The circumference of the interior 

 of the crater amounts to nine English miles, and the declivities 

 are composed of beds of pumice. This, then, is a mass which 

 of itself would have formed a considerable island ; an island 

 which would have equalled in size and in height most of the 

 Sandwich islands, or those which surround Otaheite. It lies, as 

 is well worthy of observation, in the same direction, viz. from 

 N. W. to S. E., as both the other similar craters of elevation 

 which occur in St Miguel, and in the general direction of the 

 Azores. It is the direction of a great rent on which the vol- 

 canic phenomena have manifested themselves. St Marie, the 

 most remote island of this group, and a little out of the direc- 

 tion, forms the edge of the fissure. It is entirely composed of 

 clay-slate and limestone, presenting ho example of volcanic 

 rocks, and is the only one of these islands which has this geo- 

 logical constitution (Captain Boid on the Azores, p. 10). Since 

 then craters of elevation can be formed both on the solid land 

 and on islands which have already been raised up, it cannot sur- 

 prise us that in such a position the beds composing their walls 

 or occurring in their vicinity should contain land productions. 

 No other conclusion can thence be drawn, but that such land 

 productions have been carried thither by the sea, or that the 

 elevated surface was not covered by the water of the sea. 



That the greater number of elevation craters, and almost all 

 volcanos, are surrounded by trachyte, or rocks resulting from 

 it, or are composed of such substances, was some years ago 

 considered by me as a very certain inference. But the discove- 

 ries of Gustavus Hose regarding felspar, have thrown a new 



