490 
Atjricultural Chemiatnj. 
siagaiUt ascribes to manures coutaiuiug nitrogen, for, according to Lis view,' 
the commercial value of a manure depends on its amount of nitrogen. But aU 
these conclusions arc thoronglily tironeous ; for, if they were 7wt so, it must fol- 
low that potass, lime, and silica 2'lants, unless they belonged to the leguminosce, 
woidd not produce any nitrogen, unless they %vere supplied with manure con- 
taining that element.'''' — Edition, p. 207, 208. 
Baron Liebig goes on to maintain, that, owing to the method 
of experimenting adopted by M. Boussingault, he had obviously 
under-estimated the amount of nitrogen which he had supplied in 
the manure at the commencement of his rotations ; and that, in 
point of fact, he had added much more of that constituent to the 
soil, than he had taken off in his course of crops. And, on this 
point, he says : — 
" Hence his erroneous conclusion, that the leguminos:\3 alone possess the 
power of condensing nitrogen from the air ; and that it is necessary to furnish 
nitrogen to the gramineas, and to plants such as turnips and potatoes." — 
Uh Edition, p. 208, 209. 
Baron Liebig supports his general argument by reference to 
the produce of Hungary, Sicily, the vicinity of Naples, the 
valley of the Nile, the meadows of Holland, and of other locali- 
ties ; and he maintains, that the nitrogen in these cases must have 
been derived from the atmosphere, and not from manure. And, 
he asks : — 
" Arc the fields of Virginia, the fields of Hungary, our own cultivated 
plants, not ahlc to receive it from the same sources as the wild-growing vege- 
tation ? Is the supply of nit rogen in animal excrements a matter (f absolute 
indifference ; ou do we obtain in our fields a quantity of the constitu- 
ents OF THE BLOOD, ACTUALLY COURESrONDING TO THE SUPPLY OF AMMONIA ? 
" These questions are completely solved by the investigations of M. Boussin- 
gault; luliich are so much the more valuable, as they were instituted tuiih a 
tot'dly distinct object in vieiu." — ith Edition, p. 205. 
We could point out other sources of error in the reasoning of 
Baron Liebig, but we will here simply call attention to the fact, 
that in the amount of nitrogen (22 lbs. per acre), which he says 
the fields of Virginia annually yield without manure, we have 
the most satisfactory proof of the inapplica\)ility of any deduction 
from such an instance, regarding tlie requirements of our own 
cultivated jilnitts. Thus, an average crop of wheat in this country, 
under good cultivation, will contain twice as much nitrogen as is 
here supposed. 
It is in reference to the facts and arguments above alluded to, 
that Baron Liebig concludes as follows, in the sentence which, 
with reference to special points, we have quoted already more 
than once : — 
" Hence it is quite certain, that in our fields, the amount of nitrogen in the 
croi)S is not at all in proj/orl ion to tlie quantity supplied in the manure, and that 
the soil cannot he exhausted by the exportation of jjroducts containing nitrogen, 
(unless these products contain at the same time a large amount of mineral 
