36 PHYSIOGNOMY OP PLANTS. 



in two estimable English journals. (Compare my Asie 

 Centrale, T. iii. p. 262, with Hooker, Journal of Botany, 

 vol. i. 1834, p. 327, and Edinburgh New Philosophical 

 Journal, vol. xvii. 1834, p. 380.) The Saxifrage discovered 

 by Boussingault is certainly, up to the present time, the 

 highest known phsenogamous plant on the surface of the earth. 

 The perpendicular height of the Chimborazo is, according 

 to my trigonometrical measurement, 3350 toises (21422 E. 

 feet.) (Kecueil d'Observ. Astron., vol. i., Introd. p. Ixxii.) 

 This result is intermediate between those given by French 

 and Spanish academicians. The differences depend not on 

 different assumptions for refraction, but on differences 

 in the reduction of the measured base lines to the level of 

 the sea. In the Andes this reduction could only be made 

 by the barometer, and thus every measurement called a 

 trigonometric measurement is also a barometric one, of 

 which the result differs according to the first term in the 

 formula employed. If in chains of mountains of great 

 mass, such as the Andes, we insist on determining the 

 greater part of the whole altitude trigonometrically, mea- 

 suring from a low and distant point in the plain or nearly 

 at the level of the sea, we can only obtain very small angles 

 of altitude. On the other hand, not only is it difficult to 

 find a convenient base among mountains, but also every 

 step increases the portion of the height which must be 

 determined barometrically. These difficulties have to be 

 encountered by every traveller who selects, among the ele- 

 vated plains which surround the Andes, the station at which 

 he may execute his geodesical measurements. My measure- 



