162 



simple subtraction of logarithms. M. de la 

 Condamine had no instruments with him, when 

 he visited the crater of Rucu-Pichincha. If this 

 celebrated astronomer then attained an eleva- 

 tion equal to that of a rock, of which I shall 

 speak in another place, and on which I had 

 nearly perished with the Indian Philip Aldas, on 

 the 16th of May, 1802, he found himself, with- 

 out knowing it, at a greater height * than when he 

 was on the top of Corazon. The absolute height 

 of this rock, according to the formula of Mr. 

 Laplace, is 4858 metres (2490 toises) : and con- 

 sequently exceeds near forty metres the elevation 

 of the point, measured in 1738 by the French 

 academicians. Besides, the calculation of these 

 philosophers are all affected by the uncertainty 

 that prevails respecting the height of the signal 

 on Caraburn, to which Bouguer assigns 2366 

 metres (1214 toises), and Ulloa 2470 metres 

 (1268 toises.) 



* See my Collection of Astronomical Observations, vol. 1, 

 p. 338. 



