LIMIT OF PERPETUAL SNOW. 827 



cular months in the plains of Prance and Italy. While the 

 heat which prevails daily on the forest-covered banks of the 

 Orinoco is 4.0 Cent. (7.2 Fah.) greater than that of the 

 month of August at Palermo, we find on ascending the 

 chain of the Andes, at Popayan, (at an elevation of 

 5826 English feet), the mean temperature of the three 

 summer months at Marseilles ; at Quito, (at a height of 

 9541 English feet), that of the end of the month of May 

 at Paris; and, on the paramos, (at an altitude of 11510 

 English feet), where only dwarf Alpine bushes grow 

 though flowers are still numerous, that of the beginning of 

 April at Paris. 



The ingenious Peter Martyr de Anghiera, one of the 

 friends of Christopher Columbus, seems to have been the 

 first to recognise (in the expedition undertaken in October 

 1510 by Rodrigo Enrique Colmenares) that the snow line 

 becomes always higher as the equator is approached. We 

 read in the fine work, entitled De rebus Ocean im ( 4()0 ) : 

 " The river Gaira comes from a mountain (in the Sierra Ne- 

 vada of Santa Martha), which, according to the report of 

 Colmenares's travelling companions, is higher than any 

 mountain hitherto discovered ; doubtless it must be so, if in 

 a zone distant not more than 10 from the equinoctial line, 

 it yet retains snow permanently." The lower limit of per- 

 petual snow in a given latitude is the boundary line of the 

 snow which resists the effect of the summer ; it is the highest 

 elevation to which the snow line recedes in the course of 

 the whole year. We must distinguish between the limit 

 thus defined, and three other phenomena ; viz, the annual 

 fluctuation of the snow line ; the phsenomenon of sporadic 

 falls of snow ; and the existence of glaciers, which appear to be 



