238 VIEWS, &C. PHYSIOGNOMY OP PLANTS. 



the sea-shore, and thus in the course of a few hours traverse, 

 as it were, all climates. At heights of 23,000 feet and upwards 

 the membranous air-sacs of the Condor must undergo a re- 

 markable degree of inflation after being filled in lower regions 

 of the atmosphere. 



Ulloa, more than a hundred years ago, expressed his asto- 

 nishment that the Vulture of the Andes could soar at heights 

 where the pressure of the atmosphere was less than fifteen 

 inches.* An opinion was at that time entertained, from the 

 analogy of experiments made with the air-pump, that no 

 animal could exist under this slight amount of atmospheric 

 pressure. I have myself, as has already been mentioned, seen 

 the barometer fall to 14*85 inches on the Chimborazo; and 

 my friend, M. Gay-Lussac, breathed for a quarter of an hour 

 an atmosphere in which the pressure was only 12 '9 inches. 

 It must be admitted that man, when wearied by muscular 

 exertion, finds himself in a state of painful exhaustion 

 at such elevations; but in the Condor, the respiratory 

 process seems to be performed with equal facility under 

 a pressure of 30 or of 13 inches. This bird probably raises 

 itself voluntarily to a greater height from the surface of our 

 earth than any other living creature. I use the expression 

 *' voluntarily," since small insects and siliceous-shelled infusoria 

 are frequently borne to greater elevations by a rising current 

 of air. It is probable that the Condor flies even higher than 

 the above calculations would appear to show. I remember 

 observing near the Cotopaxi, in the pumice plain of Suni- 

 guaicu, at an elevation of 14,471 feet above the level of the 

 sea, this bird soaring at such a height above my head that it 

 appeared like a black speck. But what is the smallest angle 

 under which faintly illumined objects can be distinguished ? 

 Their form (linear extension) exercises a great influence on 

 the minimum of this angle. The transparency of the mountain 

 air is so great under the equator, that in the province of Quito, 

 as I have elsewhere stated, the white cloak (poncho^ of a horse- 

 man may be distinguished with the naked eye at a horizontal 

 distance of 89,664 feet, and therefore under an angle of thirteen 

 seconds. It was my friend Bonpland whom we observed, 

 from the pleasant country-seat of the Marques de Selvalegre, 



* Voyage de I'Amerique meridionale, t. ii. p. 2. 1752; Observation* 

 astronomiques et physiques f p. 110. 



