62 THE LINE OF PERPETUAL SNOWS. 



shown that it decreases in a considerably greater ratio 

 as the altitude increases, and it may be taken as an 

 ascertained fact that in the intertropical regions the 

 limit of the line of perpetual snow lies at about 16,000 

 feet above the level of the sea. "In the Bolivian 

 Andes," for instance, "the snow line is fixed at this 

 point," * and observations taken in Mexico and other 

 places, have given results almost identical. 



Descending from this extreme elevation we have 

 every gradation of climate, down to the normal tem- 

 perature of the Equatorial zone, amounting to about 

 86 Fahr. as the mean shade temperature of the day, 

 at sea-level, throughout the year the most characteristic 

 feature of this region being the wonderful uniformity 

 of its temperature "As a general rule the greatest 

 heat of the day does not exceed 90 or 91 Fahr., 

 while it seldom falls during the night below 74 Fahr." f 

 but " the usual daily range of the thermometer is only 

 a little more than 11 Fahr." 



The hottest places in the world, that is to say, those 

 places where the mean temperature of the year stands 

 highest, are mostly situated in these regions upon, or 

 adjacent to, the margin of the sea. In saying so, we 

 wish to guard against misconception : we refer therefore 

 at present, let it be distinctly understood, to the mean 

 temperature only because those places where the most 

 intense heats are prevalent, at certain seasons, are 

 usually subject to extreme ranges of temperature, being 

 intensely hot at one time, and bitterly cold at others. 



* Stanford's Compendium of Geography and Travel for Central 

 and South America, 1878, edited by H. W. Bates, p. 207. 

 f Tropical Nature, by Alfred R. Wallace, 1878, p. 3. 

 Ibid. p. 4. 



