4 CHYMISTRY APPLIED TO AGRICULTURE. 



nomena of composition and decomposition, which take 

 place upon the surface of the globe, present only changes 

 of combinations, which are formed according to fixed, 

 eternal, and unchangeable laws. Thus nature is regene- 

 rated, without being impoverished ; and matter expe- 

 riences only those changes which are reproduced uniformly 

 and periodically, especially in organic bodies. 



3. Carbonic acid is found constantly, but in various 

 proportions, in the atmosphere. Though much heavier 

 than azote or oxygen, its weight being to that of the 

 latter, as 1,520 to 1,000, it is found disseminated through- 

 out the whole atmospheric region. The elder M. de 

 Saussure has, by means of lime-water, drawn it from the 

 air upon the summit of Mont Blanc. From the results of 

 all the experiments that have been made, there can be no 

 doubt, that the proportions of azote and oxygen in the 

 composition of the atmosphere are uniform and nearly in- 

 variable ; and it appears to be likewise proved, that car- 

 bonic acid is also found there, and at all heights, but in 

 various proportions. 



M. Th. de Saussure has compared the different portions 

 of carbonic acid in the atmosphere which he has analyzed, 

 and found the difference between them, in summer and in 

 winter, to be as follows. 



IN WINTER. 



31st of January, 1809, 10,000 parts of air 



contained carbonic acid 4,570 



2d of February, 1811 " " 4,660 



7thof January, 1812 " , " 5,140 



The mean- term in winter from 10,000 parts of air was, 



In volume . . . 4,790 



In weight . . • . 7,280 



IN SUMMER. 



20th of August, 1810, 10,000 parts of air 



contained carbonic acid 7,790 



27th of July, 1811 '' " 6,470 



15th of July, 1815 " " 7,130 



The mean term in summer from 10,000 parts of air was, 



In volume . . . 7,130 



In weight . . . 10,830 

 Without doubt, when the air is tranquil, or when the 

 carbonic acid, which is produced so abundantly by fer- 

 mentation, respiration, combustion, &.C., is retained in 

 confined places, the quantity of this acid will exceed the 



