EXPERIMENTS OK BOUSSINGAULT. 197 



wild plants by the hand of man. Then it is impossible to doubt 

 the source whence the nitrogen is obtained. The source of the 

 nitrogen can only be the atmosphere. It matters not in what 

 form it is contained therein, or in what form it is taken from it ; 

 the conclusion is the same, that the nitrogen of wild-growing 

 plants must be derived from the atmosphere. 



Are the fields of Virginia, the fields of Hungary, our own cul- 

 tivated plants, not able to receive it from the same sources as the 

 wild-growing vegetation ? Is the supply of nitrogen in animal 

 excrements a matter of absolute indifference : or do we obtain 



IN OUR FIELDS A QUANTITY OF THE CONSTITUENTS OF THE BLOOD, 

 ACTUALLY CORRESPONDING TO THE SUPPLY OF AMMONIA 1 



These questions are completely solved by the investigations of 

 Boussingault ; which are so much the more valuable, as they 

 were instituted with a totally distinct object in view. 



From the known quantity of manure (common stable manure) 

 which Boussingault put every five years upon his field (amount- 

 ing to four Hessian acres), he estimated, by the analysis of the 

 manure, the total quantity of nitrogen furnished for the rotation 

 of five, years. For this purpose, the moist stable manure was 

 first dried by exposure to the air and to the sun, and afterwards 

 was further dried in vacuo, by exposing it to a temperature of 

 230° F. ; the manure thus treated was subjected to an ultimate 

 analysis. The average crops of the field, treated with manure, 

 were then determined ; and the products, corn and straw, turnips, 

 potatoes, peas, clover, &c, were analysed for the purpose of 

 ascertaining their composition with reference Xo nitrogen, carbon, 

 hydrogen, and ashes.* 



In this manner the quantities of nitrogen conveyed to the field 

 in the form of manure, and reaped from it in the crops, were 

 ascertained, and could be compared together. If the plants 

 depended for their nitrogen upon the manure, and did not receive 

 any of that element from the air ; the nitrogen of the crops could 



* The greatest number of these analyses — viz. the composition of pota- 

 toes (Boeckmann) ; of beet and turnips (Will) ; of wheat straw (Will) ; 

 of the carbon and nitrogen of peas (Noll and Zytowieki) ; and of their 

 carbon (Playfair), were repeated in this laboratory, and ascertained t« 

 be perfectly correct. 



