simple subtraction of logarithms. M. de la 
Condamine had no instruments with him, when 
he visited the crater of Riicu-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 
fnetres (1214 toises), and Ulloa 2470 metres 
(1268 toises.) 
* See Hiy Collection of Astronomical Observations, vol. 1, 
p. 338. 
