178 



FIRST YEAR SCIENCE 



In temperate latitudes, where there is need of providing 

 for the winter when plants do not grow and when food 

 is hard to find, where the blood is stirred by the invigo- 

 rating cold, and where 

 nature in her ever chang- 

 ing mood gives zest to 

 living, is the place where 

 man has attained his 

 highest achievements. 

 Here the fight for exist- 

 ence does not require 

 all man's energy, and the 

 bounty of nature does not 

 free him from strenuous 

 effort. Thus it is seen 

 that even upon man the 

 influence of climate is 

 great. How great, it is 

 impossible fully to realize, 

 so complex are his rela- 

 tions. 



Summary. The atmosphere is just as important to life 

 upon the earth as are energy, light, heat, water and land. 

 Air contains oxygen from which we get heat and energy, 

 carbon dioxide, from which plants build up their tissues, 

 and nitrogen which dilutes these two. 



The weight of air is not usually realized because it 

 presses uniformly in all directions. Air expands when 

 heated ; so a cubic foot of warm air weighs less than a 

 cubic foot of cold air. Warm air will also hold more 

 moisture than cold air. 



The pressure of air, due to its weight, may be measured 

 by a barometer. The heights of mountains may also be 

 measured by this instrument, as there is less air above a 



A LAPLANDER. 



