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DEVOTED TO AGRICULTURE AND ITS KINDRED ARTS AND SCIENCES. 



NO.IO. 



VOL. IX. 



BOSTON, OCTOBER, 1857. 



JOEL NOURSE, Proprietor. 

 Office.. .13 Commercial St. 



SIMON BROWN, EDITOR. 



FRED'K nOLBKOOK, ) Associatb 

 UENEY F. FRENCH, J Editors. 



OCTOBER—THE ATMOSPHERE. 



TJE present remarks 

 on the atmosphere 

 are not intended as 

 a scientific essay 

 on its nature and 

 constitution, but 

 father as an inqui- 

 ry how far, or to 

 what extent, it may 

 possibly be affected 

 by the limited ex- 

 ertions of man up- 

 on the face of the 

 globe. We shall make a 

 few preliminary remarks, 

 however, on its character 

 il and the elements of which it is 

 composed. The atmosphere is 

 a thin, transparent, invisible 

 and elastic fluid, which surrounds the 

 earth, and reaches to a considerable 

 height above its surface, usually estimat- 

 ed at about forty miles. Its essential component 

 parts are oxygen and nitrogen ; but near the earth's 

 surface where it receives the vapors and exhalations, 

 it usually contains a large quantity of water in an 

 aeriform state, and a small portion of carbonic acid 

 gas. AVithout this power of holding water in an in- 

 visible state, the water from which the clouds are 

 formed could not be mingled with the air without 

 rendering it more or less opaque. Hence, as it al- 

 ways contains a considerable quantity of water, the 

 sun's rays would be continually obscured. Not a di- 

 rect ray of the sun's light, or in other words, of sun- 

 shine, would reach the earth's surface, on account of 

 the constant vaprous obscurity of the atmosphere. 

 By a wise provision of Providence, the atmosphere 

 is so constituted as to have the power of holding 

 in solution a determinate quantity of water in an 

 invisible form ; and not until it is completely satu- 

 rated with water does the formation of visible va- 



pors take place, which then gather together by a 

 law of electric attraction, and descend again to the 

 earth in the form of rain or snotv. By this law of 

 its constitution, therefore, the atmosphere, though 

 full of water, if not overcharged, is always clear and 

 transparent. 



Carbonic acid gas is one of the contents, but not 

 one of the essential ingredients of the atmosphere. 

 This gas is combined with it in very small propor- 

 tions, and is injurious to all animals ; but serves the 

 necessary purpose of sustaining vegetation, by fur- 

 nishing the substance which is absorbed by the leaves 

 of plants. This gas is breathed out or rejected 

 from the lungs of animals, and it is breathed in or 

 absorbed by the leaves of plants, which are their 

 lungs. Hence plants are necessary for the purifi- 

 cation of the atmosphere from this deleterious gas, 

 thereby rendering it fit for the use of animals. 



But this is not all the purpose they serve, as it is 

 well known that they are constantly giving out 

 or producing oxygen, as animals are constantly 

 producing carbonic acid g"as. "The leaves absorb 

 carbon from the carbonic acid present in the atmo- 

 sphere, and evolve oxygen. This evolution of oxy- 

 gen takes place while the plants are exposed to the 

 solar rays, and appears one of the most efficient 

 causes hitherto suggested, of the purification and 

 renovation of the air." It is probable, therefore, 

 that without vegetation there would be no atmo- 

 sphere ; for when oxygen is taken up or absorbed 

 by animals, or by the chemical affinity of certain 

 substances for this gas, it is not in either case giv- 

 en out again, but it becomes consolidated. It is 

 only, therefore, by the combustion or chemical de- 

 composition of animal and mineral substances that 

 their oxygen can be restored to the atmosphere. 



This decomposition takes place in the soil to a 

 certain extent ; the elements arising from this de- 

 composition are taken up by the roots of plants, 

 and the oxygen is finally exhaled into the atmo- 

 sphere and thus restored to it by the leaves of 

 plants. The leaves of plants likewise absorb the 



