52 flature'0 



mountain has had no difficulty in determin- 

 ing two things. One is that the air is very 

 much colder than at sea-level, and the other 

 that it is very much lighter in weight. We 

 find it difficult, when we first reach the sum- 

 mit, to take enough of oxygen into our lungs 

 to carry on the natural operations of the 

 bodily functions. To overcome this difficulty, 

 if we remain at this altitude for a considerable 

 time, we shall find that our lungs have ex- 

 panded, so as to make up in quantity what is 

 lacking in quality. 



If a man lives for a long time at an altitude 

 of 10,000 feet he will find that his lungs are 

 so expanded that he experiences some difficulty 

 when he comes down to sea-level. And the 

 reverse is true with one whose lungs are 

 adapted to the conditions we find at sea-level, 

 when he ascends to a higher altitude. There 

 is a constant endeavor on the part of nature to 

 adapt both animal and vegetable life to the 

 surroundings. While no exact formula has 

 been established as to the rate of decrement of 

 temperature as we ascend, we may say that it 

 decreases about one degree in every 300 or 400 

 feet of ascent. There is no exact way of ar- 

 riving at this, as in ascending a mountain the 

 temperature will be more or less affected by 

 local conditions. If we go up in a balloon we 

 have to depend upon the barometer as a means 

 of measuring altitude, which, owing to the 



