xcvm NOTES. 



velocity of nearly three miles an hour, its original direction being but little 

 altered, and the fresh water but partially mixed with that of the ocean. In 

 both the cases referred to, the river current crosses nearly at a right angle a 

 stream current of the ocean, viz. the two branches into which the equa- 

 torial current divides at Cape St. Roque. From the less specific gravity of 

 its water, the river current flows over as well as across the ocean current, 

 which reappears on either side of it. On the side where the ocean current 

 impinges on the river stream, the line of separation of the waters in the case 

 of the Amazon was very distinctly marked by difference of colour, and the 

 river water was nearly a degree of temperature warmer than that of the ocean. 

 On the opposite side of the river stream the distinction between its water and 

 that of the sea was gradually and insensibly lost, but was clearly determinable 

 for a breadth of above 100 miles (Sabine, Pendulum and other Experiments, 

 London, 1825, pp. 445 to 448.) EDITOR.] 



C 374 ) p. 304. The unknown voice said to him, " Maravillosamente Bios 

 \I\ZQ sonar tu nombre en la tierra ; de los atamientos de la mar Oceana, que 

 estaban cerrados con cadenas tan fuertes, te dio las llaves." The dream of 

 Columbus is related in the letter to the Catholic moiiarchs of July 7, 1503 

 (Humboldt, Examen critique, T. iii. p. 234). 



C 376 ) p. 305. Boussingault, Recherches sur la composition de 1' Atmosphere, 

 Annales de Chimie et de Physique, T. Ivii. 1834, pp. 171173 ; ib. T. Ixxi. 

 1839, p. 116. According to Boussingault and Lewy, the proportion of 

 carbonic acid in the atmosphere at Andilly, at a distance, therefore, from the 

 exhalations of cities, varied only between 0*00028 and 0'00031 in volume. 



C 376 ) p. 305. Liebig, in his important work, entitled Die organische 

 Chemie in ihrer anwendung auf Agricultur und Physiologic, 1840, S. 64 72.of 

 On the influence of atmospheric electricity in the production of nitrate 

 ammonia, which is changed into carbonic acid by contact with lime, see 

 Boussingault's Economic rurale considered dans ses rapports avec la Chimie 

 ct la Meteorologie, 1844, T. ii. pp. 247 and 697. Compare also T. i. p. 84. 



C 577 ) p. 306. Lewy, in the Comptes rendus de 1'Acad. des Sciences, 

 T. xvii. P. 2, pp. 235248. 



I 378 ) p. 306. J. Dumas, in the Annales de Chimie, 3 Se'rie, T. iii. 1841, 

 p. 257. 



(S 79 ) p. 306. I have not included in this enumeration the exhalation of 

 carbonic acid gas by plants during the night, when they inhale oxygen, be- 

 cause this source of addition to the quantity of carbonic acid in the atmosphere 

 is fully compensated by the respiration of plants during the day. Compare 



