SECT. III. ALTITUDE. 433 



SECTION III. 

 Altitude. 



ALTHOUGH the above rule with regard to cli- 

 mates is of pretty general application, yet it is at 

 the same time liable to a good many exceptions, 

 owing chiefly to the difference of altitude that may 

 and often does occur in countries of the same lati- 

 tude ; as well as to a variety of other causes af- 

 fecting the vegetable. This must be obvious from 

 the consideration that the temperature of any place 

 is affected as much from its altitude as from its lati- 

 tude. The summit of the mountains of the Andes, AS effect* 

 even where situated almost directly under the pe^ui" 

 equator, are yet covered with eternal snow. 



Hence it follows that all variety of climates may And con- 

 exist even in the same latitude merely by means of vegetable 

 the altitude of the place, and consequently all va- ha ltat ' 

 rieties of vegetable habitat. And this was found 

 by Tournefort to be literally the case during his 

 travels in Asia. At the foot of mount Ararat he 

 met with plants peculiar to Armenia ; above these 

 he met with plants which are found also in France ; 

 at a still greater height he found himself surrounded 

 with such as grow in Sweden, and at the summit 

 with such as vegetate in the polar regions. 



This accounts for the great variety of plants And natu- 

 which are often found in a Flora of no great ex- ra 



VOL. ii. 2 F 



