238 



of results useful to the progress of science ; the 

 traveller finds himself on ground covered with 

 snow, in a stratum of air, the chemical mixture 

 of which is the same as that of the lower re- 

 gions, and in a situation in which delicate expe- 

 riments cannot be made with all the exactness 

 requisite. 



If we compare the fifth, tenth, and sixteenth 

 plates of this work with those of the geographi- 

 cal and physical Atlas, which acccompanies my 

 Essay on the Kingdom of New Spain, we dis- 

 tinguish three kinds of principal forms belonging 

 to the high tops of the Andes. The volcanoes 

 which are yet burning, those which have but a 

 single crater of extraordinary size, are conic 

 mountains, with summits truncated in a greater 

 or less degree : such is the figure of Cotopaxi, of 

 Popocatepec, and the Peak of Orizaba. Volca- 

 noes, the summits of which have sunk after a long 

 series of eruptions, exhibit ridges bristled with 

 points, needles leaning in different directions, 

 and broken rocks falling into ruins. Such is the 

 form of the Altar, or Capac-Urcu, a mountain 

 once more lofty than Chimborazo, and the de- 

 struction of which is considered as a memorable 

 period in the natural history of the New Conti- 

 nent ; such; is the form also of Carguairazo, a 

 great part of which fell in on the night of the 

 19th of July, 1698. Torrents of water and mud 

 then issued from the opened sides of the moun- 



