42 PHYSIOGNOMY OF PLANTS. 



the sea-shore, thus passing rapidly through all gradations of 

 climate. The membranous air-bags of the Condor, if filled 

 in the lower regions of the atmosphere, must undergo extra- 

 ordinary distension at altitudes of more than 23000 English 

 feet. Ulloa, more than a century ago, expressed his astonish- 

 ment that the vulture of the Andes could soar in regions 

 where the atmospheric pressure is less than 14 French inches, 

 (Voyage de TAmerique meridionale, T. ii. p. 2, 1752 ; 

 Observations astronomiques et physiques, p. 110). It was 

 then believed, in analogy with experiments under the air- 

 pump, that no animal could live in so low a pressure. I 

 have myself, as I have already noticed, seen the barometer 

 sink on the Chimborazo to 13 French inches 11 '2 lines 

 (34.850 English inches). Man, indeed, at such elevations, 

 if wearied by muscular exertion, finds himself in a state of 

 very painful exhaustion ; but the Condor seems to perform 

 the functions of respiration with equal facility under pres- 

 sures of 30 and 13 English inches. It is apparently of 

 all living creatures on our planet the one which can remove 

 at pleasure to the greatest distance from the surface of the 

 earth ; I say at pleasure, for minute insects and siliceous- 

 shelled infusoria are carried by the ascending current to 

 possibly still greater elevations. The Condor probably flies 

 higher than the altitude found as above by computation. I 

 remember en the Cotopaxi, in the pumice plain of Suniguaicu, 

 13578 (14470 English) feet above the sea, to have seen the 

 bird soaring at a height at which he appeared only as a small 

 black speck. What is the smallest angle under which feebly 

 illuminated objects can be discerned ? Their form, (linear 



