CHEMICAL MANURES. 25 



most beneficial which draw most from fhe air, and the more fertile 

 the soil the greater the amount they draw from the air. 



This theory of high culture may be explained in a clearer and 

 more scientific manner. Suppose, for example, a plant is cultivated 

 in burnt sand, receiving nourishment only from air and water, and 

 produces 20 leaves in 15 days after germination. If the leaves give 

 nutriment to the plant sufficient to form a new leaf every fifteen days, 

 at the end of three months and a half the plant will have produced 

 2460 leaves. 



On the other hand, suppose another plant cultivated in manured 

 soil, and we admit that the manure determines the formation of only 

 live leaves every fifteen days, besides those that the air and water had 

 supplied in the preceding experiment. After the lapse of the same 

 time the plant will have produced 3475 leaves ; -that is, nearly twice 

 as many as in the first case, although the manure alone has deter- 

 mined the formation of but 35 leaves. This result you justly think 

 very singular ; -it is, however, easily explained, when we reflect that 

 the first leaves formed by the manure aid not only in numbers, but 

 by the formation of other leaves, drawing their food from the atmo- 

 sphere. 



I have told you that the quantity of azote must be proportioned to 

 the nature of the plant cultivated. 



To show you how necessary it is that nothing be left to chance, I 

 will cite the report of an eminent agriculturist, Monsieur Cavallier, 

 from the farm of Mesnil-Saint-Nicaise. 



It is on the beet, cultivated in four different ways by mineral fer- 

 tilizers without azote, and the same fertilizers with increasing quanti- 

 ties of sulphate of ammonia : 



With mineral fertilizers without azote the return was 32,741 

 pounds the acre. 



With the same fertilizer, phos. 71.11 pounds azote, the return was 

 42,066 pounds. 



With the same fertilizer, phos. 88.88 pounds azote, the return was 

 45,333 pounds. 



With the same fertilizer, phos. 106.66 pounds azote, the return was 

 53,021 pounds. 



If we take as a basis 32,741 pounds obtained from fertilizers with- 

 out azote, we find (the sulphate of ammonia being deducted) the fol- 

 lowing increase : 



With 71 pounds of azote $5.73 



With 88.88 pounds of azote _ 9.13. 



With 106.66 pounds of azote 19.30 



From this you see that azotic fertilizers play a prominent part in 

 the economy of vegetation. In practice we find the greatest advan- 

 tage in using the salts of ammonia ; the certainty of their action, their 

 ease of assimilation, give them a marked superiority over all other 

 azotic compositions. 



I am accustomed to employ from 53 to 80 pounds of azote the 



