207 



long ascent, slopes of three or four degrees alter- 

 nate with others which are inclined from 25 to 

 30 degrees ; and the latter only strike our imagi- 

 nation, because we think all the slopes of moun- 

 tains more steep than they really are. I may 

 cite in support of this consideration the example 

 of the ascent from the port of Vera Cruz to the 

 elevated plain of Mexico. It is on the eastern 

 slope of the Cordilleras that a road has been 

 traced, which for ages has not been frequented 

 except on foot, or on the back of mules. From 

 Encero to the small Indian village of Las Vigas, 

 there are 7500 toises of horizontal distance ; and 

 Encero being, according to my barometric mea- 

 surement, 746 toises lower than Las Vigas, the 

 result, for the mean slope, is only an angle of 



I have drawn on the same plate, the profiled 

 of the Peak of TenerifFe, Cotopaxi, and Vesuvius. 

 I could have wished to have substituted Etna 

 for this last mountain, because it's form is more 

 analogous to that of the two volcanoes of Ame- 

 rica and Africa ; but I chose to trace only the 

 outlines of mountains that I had visited and 

 measured myself ; and with respect to Etna I 

 should have wanted data for the intermediary 

 heights. I ought also to observe, that, in the 

 three profiles, the scales of distances and of 

 heights have the same proportions. The dis- 

 tances have been determined after the charts of 



