XC1V NOTES. 



f 359 ) p. 292. Asie centrale, T. i. pp. 284286. The Adriatic also follow* 

 a south-east and north-west direction. 



( 36 ) p. 293. De la hauteur moyenne des continents n Asie centrale, T. . 

 pp. 82 90, and 165 189. The results which I have ohtained are to be 

 regarded as the extreme values or " nombres-limites." Laplace's estimation 

 of 3078 French feet as the mean height of continents, is at least three times 

 too great. The illustrious geometer was conducted to this erroneous result by 

 hypotheses as to the mean depth of the sea (Mecanique Celeste, T. v. p. 14). 

 I have shown, in my Asie centrale, T. i. p. 93, that the mathematicians of 

 the Alexandrian school supposed the depth of the sea to be determined by the 

 height of the mountains (Plut. in JEmilio Paulo, cap. 15). The height of 

 the centre of gravity of the volume of the continental masses probably under- 

 goes small alterations in the course of many centuries. 



(3 61 ) p. 294. Zweiter geologischer Brief von Elie de Beaumont and Alex- 

 ander von Humboldt, in PoggendorfPs Annalen, Bd. xxv. S. 1 58. 



t 362 ) p. 295. Humboldt, Relation hist. T. iii. chap. xxix. pp. 514530. 

 f 363 ) p. 296. See the series of observations made by me in the Pacific, 

 from 5' to 13 16' N. lat. (Asie centr. T. iiii. p. 354). 



C 364 ) p. 296. "On pourra (par la temperature de 1'Ocean sous les tropiques) 

 attaquer avec succes une question capitale restee jusqu'ici indecise, la question 

 de la Constance des temperatures terrestres, sans avoir a s'inquieter des influ- 

 ences locales naturellement fort circonscrites, provenant du deboisement des 

 plaines et des montagnes, du dessechement des lacs et des marais. Chaque 

 sieele, en leguant aux siecles futurs quelques chiffres bien faciles a obtenir, leur 

 donnera le moyen peut-t-tre le plus simple, le plus exact et le plus direct, de 

 decider si le soleil, aujourd'hui source premiere, a peu pres exclusive, de la 

 chaleur de notre globe, change de constitution physique et d'eclat, comme la 

 plupart des etoiles, ou si au contraire cet astre est arrive a un etat permanent'* 

 (Arago, in the Comptes rendus des seances de 1'Acad. des Sciences, T. xi. 

 P. 2, p. 309). 



t 365 ) p. 297. Humboldt, Asie centr. T. ii. pp. 321 and 327. 

 C 366 ) p. 297. See the numerical results in pp. 328333 of the volume 

 just named. The geodesical levelling which, at my request, my friend 

 General Bolivar caused to be executed in 1829 and 1822, by Lloyd and 

 Falmarc, has shewn that the Pacific is, at the utmost, 3 '4 French feet 

 higher than the Caribbean Sea, and even that, at different hours of the day, 

 each of the two seas is in turn the highest, according to their respective hours 

 of ebb and flood. As the levelling extended over a distance of 64 miles, and 



