582 " THE DIFFICULT AIR." 



is found at 7650 feet, which is nearly that of the table. On the 

 southern slope of the Himalayas the traveller ascends to an elevation 

 of upwards of 15,000 feet before he enters the realms of snow and 

 ice, and on the northern slope to 12,750 feet. Finally, in the Andes 

 of Bolivia, according to Pentland, the curve of congelation lies between 

 14,400 and 14,800 feet. 



Thus, then, in the mid Torrid Zone, we must accomplish a weary 

 ascent of 13,000 to 15,000 feet before we can find ourselves trans- 

 ported from the calcined plains whose sands scorch and blister our 

 feet, or the dense forests whose innermost depths teem with the most 

 exuberant and beautiful floral life, to the heart of icy deserts and the 

 sublime silence of the mountains. And in passing from one to the 

 other of these extremes, we traverse in a few hours all the climates 

 which succeed one another from the Equator to the Pole. Neverthe- 

 less, I must point out an important difference between the Polar 

 deserts and the snowy regions of the mountains, which is wholly to 

 the advantage of the former. 



I have already shown that, under the highest latitudes, men find, 

 in the exceptional activity of their functions of nutrition, and, above 

 all, of respiration, a powerful re-agent against the intensity of the 

 external cold. This resource fails him on the mountain summit. In 

 vain will he attempt, as a succedaneum against the cold, to modify 

 his ordinary regimen, to drink warm blood, to eat fat and raw flesh ; 

 his stomach will reject such aliment, or digest it only with difficulty, 

 and he will not surfer less from the extreme rigour of the tempera- 

 ture. At the Pole air pours freely into our lungs, and its pressure 

 stoutly maintains the equilibrium of the fluids of our body. Such is 

 not the case when we soar, Icarus like, into the higher regions of the 

 atmosphere ; in proportion as we ascend, the air rarefies, and its pres- 

 sure diminishes. Consequently, respiration becomes difficult and 

 painful ; the quantity of oxygen designed to cherish animal heat by 

 the combustion of the carbon and hydrogen of the blood becomes in- 

 sufficient ; at the same time, the tissues and the liquids which they 

 enclose expand ; perspiration, instead of diminishing, experiences a 



