NOTES. C1X 



with a mean temperature of 20'4 C. (68'7 Tali.) ; whilst at Bogota, in lat. 

 4'36', at an elevation of 1358 toises (8684 E. feet), and with a mean tem- 

 perature of 14'5 C. (58 Fah.), the annual fall of rain is only 37 inches and 

 1 line. [In English measure the ahove quantities are at Marmato, 64'1 

 inches, and at Bogota, 39'4 inches of rain,] 



C 407 ) p. 332. For the details of this observation, see my Asie centrale, 

 T. iii. p. 85 89 and 567 ; and on the hygrometric state of the atmosphere 

 over the lowlands of tropical South America, see my Relation hist. T. i. 

 p. 242248, and T. ii. p. 45164. 



C 408 ) p. 332. Kamtz, Vorlesungen iiher Meteorologie, S. 117 



C 409 ) p. 333. On electricity from evaporation at a high temperature, see 

 Peltier, in the Annales de Chimie, T. Ixxv. p. 330. 



( 41 ) p. 333. PouiUet, in the Annales de Chimie, T. xxxv. p. 405. 



( 4U ) p. 333. De la Rive, in his admirable Essai historique sur 1'Electri- 

 cite, p. 140. 



( 412 ) p. 333. Peltier, in the Comptes rendus de 1'Acad. des Sciences, 

 T. xii. p. 307 ; Becquerel, Traite de 1'Electricite et du Magnetisme, T. iv. 

 p. 107. 



( 413 ) p. 334. Duprez, sur I'Electricite de Fair (Bruxelles, 1844), p. 

 5661. 



( 414 ) p. 334. Humboldt, Relation historique, T. iii. p. 318. I would 

 refer, however, exclusively to those experiments which were made with 

 Saussure's electrometer, with a metallic conductor of a metre in length, and 

 in which the electrometer was not moved either upwards or downwards, nor 

 the conductor armed, according to Volta's proposal, with a sponge dipped in 

 burning alcohol. Those of my readers who are acquainted with the points at 

 present in discussion with reference to the subject of atmospheric electricity, 

 will understand the reason of this limitation. On the formation of thunder- 

 storms in the tropics, see my Rel. hist. T. ii. p. 45, and 202209 



( 415 ) PP- 334. Gay-Lussac, Annales de Chimie et de Physique, T. viii. 

 p. 167. The discordant views of Lame, Becquerel, and Peltier, render it 

 difficult to arrive at present at any conclusion respecting the cause of the 

 specific distribution of electricity in clouds, some of which have a positive, and 

 others a negative tension. The negative electricity, which, near lofty cascades, 

 is developed in the air by the finely-divided particles of water, is a very 

 striking phsenomeuon : it was first observed by Tralles, and since then by 

 myself in many latitudes. "With a sensitive electrometer the effect can be 

 distinctly recognised at a distance of three or four hundred feet. 



