THE ATMOSPHEEE. 91 



agitation, motion, mixing, and circulation, the airj- covering of 

 the globe is kept in that state which the well-being of the 

 organic world requires. Every breath we draw, every fire we 

 kindle, every blade of grass that grows or decays, eveiy blaze 

 that shines and burns adds something that is noxious, or takes 

 something that is healthful away from the surrounding air. 

 Diligent, therefore, in their offices must the agents be which 

 have been appointed to maintain the chemical status of the 

 atmosphere, to preserve its proportions, to adjust its ingredients, 

 and to keep them in that state of admixture best calculated to fit 

 it for its purposes. 



237. Experiments by the French Academy. — Several years ago 

 the French Academy sent out bottles and caused specimens of air 

 from various parts of the world to be collected and brought home 

 to be analyzed. The nicest tests which the most skilful chemists 

 could apply were incapable of detecting any, the slightest, differ- 

 ence as to ingredients in the specimens from either side of the 

 equator ; so thorough in the performance of their office are these 

 agents. Nevertheless, there are a great many more demands on 

 the atmosphere by the organic world for jpahulum in one hemi- 

 sphere than in the other ; and consequently a great many more 

 inequalities for these agents to restore in one than in the other. 

 Of the two, the land of our hemisphere most teems with life, and 

 here the atmosphere is most taxed. Here the hearthstone of the 

 human family has been laid. Here, with our fires in winter and 

 our crops in summer, with our work-shops, steam-engines, and 

 fiery furnaces going night and day — with the ceaseless and almost 

 limitless demands which the animal and vegetable kingdoms are 

 making upon the air overhead, we cannot detect the slightest 

 difference between atmospherical ingredients in different hemi- 

 spheres ; and yet, notwithstanding the compensations and adjust- 

 ments between the two kingdoms of the organic world, there are 

 almost in every neighbourhood causes at work which would pro- 

 duce a difference were it not for these ascendinsr and descendino* 



o o 



columns of air ; — were it not for the obedient winds, — for this 

 benign system of circulation, — these little cogs and ratchets 

 which have been provided for its perfect working. The study of 

 its mechanism is good and wholesome in its influences, and the 

 contemplation of it well calculated to excite in the bosom of 

 right-minded philosophers the deepest and best of emotions. 



238. How supplies of fresh air are brought down from the upper 



