II 



PHYSICAL ASPECTS. 



The Air. 

 By GEORGE O. SQUIER. 



Everyone knows of course that if there were no atmosphere 

 there could be no Hfe, but probably very few fully realize its immense 

 importance in almost every thing we do. In one condition it is 

 invigorating and gives us a zest for hard work whether mental or 

 physical, in another it leaves us depressed and incapacitated for effi- 

 cient labor of any kind. Numerous manufacturing processes are 

 radically affected by the amount of moisture in the air, and many 

 others by its temperature. Power is transmitted by it ; we com- 

 municate our thoughts one to another by vibrations of the air; and 

 by its aid we have recently acquired our swiftest mode of travel. 

 Obviously then a knowledge of the composition and physical proper- 

 ties of the air is of such vital importance as to justify most pains- 

 taking study and investigation. 



In the past few years, for instance, several elements, helium, 

 argon, neon, krypton, xenon, have been found in the atmosphere 

 that previously were unknown and even unsuspected, for they were 

 not recjuired by the Mendeleeff table of the elements as then under- 

 stood. One of these, argon, amounts to nearly one part in a hun- 

 dred of the whole atmosphere, and yet through decade after decade 

 of chemical investigations involving countless thousands of air 

 analyses, it, and all its family of gases, remained undiscovered! 



Recently, too, means have been found for drawing directly on 

 the atmosphere for an inexhaustible supply of nitrogen compounds 

 used in the production of powerful explosives, fertilizers and many 

 other things of great value. 



Not long ago even the most profound scientists believed that with 



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