72 THE ATMOSPHERE. 



and satisfaction. How interesting, for instance, is the 

 knowledge of the composition of light, for by an exami^ 

 nation of its constituents, we are enabled to account for 

 the color of the sky. How curious is the fact that 

 ohemistry exhibits in the composition of the atmosphere, 

 whereby certain proportions of oxygen and nitrogen r&- 

 sult in a compound of qualities so useful. In other 

 proportions they form the nitrous oxide or exhilarating 

 gas, and again, in others, nitric acid, or aqua fortis. 



The science of chemistry is filled with this variety of 

 combinations of the same materials resulting in different 

 compounds, and by the aid of analysis, the chemist is 

 able to separate the constituents, and explain the cause 

 of the result. He shows us that the difference between 

 the air we breathe, exhilarating gas, and aqua fortis, 

 merely depends on the quantity of oxygen employed; 

 and that the only philosophical difference of ice, water, 

 and vapor, consists in their relative proportions of heal. 

 By experiment, also, Philosophy has ascertained the 

 weight of the atmosphere, and informs us of its precise 

 pressure on the whole surface of the earth. It tells us 

 that the motion of a fly on the perpendicular plane of 

 glass, the process of drinking, and the power of the old 

 Steam engine, are effected by the pressure of the air. 



By the aid of a very few instruments, all these facts 

 have been discovered, which prove to us that nature 

 develops more curious circumstances than fancy can 

 conceive, and at the same time assures us that her most 

 sublime operations may be explained on the simple prin- 

 ciples of philosophy. 



