from quoting them.  “It has,” he says, “become almost a regular custom to determine the value of manures by the quantity of nitrogen they yield by ultimate analysis.  This method is entirely erroneous; for it is based upon the false principle, that by putrefaction all nitrogeneous substances are immediately converted into ammonia, carbonic acid, and water!  But these changes sometimes require a number of years.  Morphine, for example, is prepared by allowing opium to putrefy; and the process for preparing leucin, a substance which contains 10.72 of nitrogen, is to bring cheese into putrefaction.  Cheese, therefore, does not perhaps in a number of years resolve itself into carbonic acid, ammonia, and water, but produces a crystalline substance, which contains no ammonia.  Hence the proportion of nitrogen yielded by manures is not a proper measure of their value, and therefore this mode of estimating that value ought to be discontinued."[38] We infer, therefore, that the proportion of nitrogen furnished by food of various kinds is not the true measure of their nutritious value, and cannot for practical purposes take the place of that process by which the amount of rough gluten is determined.

No better illustration can be given of the uncertainty which attends the inferences drawn from the ultimate composition, than the fact heretofore stated in regard to hay, the nutritive value of which is placed in the tables containing the results of these analyses, at a figure nearly the same as that of ordinary wheat flour.[39] In the paper on the “Composition of Wheat,” by M. Peligot—­(” Comptes Rendus,” February 5th, 1849)—­to which I have already referred, the author gives the results of the various analyses which he has made, and details the process he adopted.

Aware of the complex and difficult nature of the examination as conducted by him, he seems to doubt in regard to some of the results given in his tables In the fourteen samples which he analysed, the proportion of water ranges from 13.2 to 15.2, which is a rather higher average than is yielded by our American samples, especially those which have not been shipped across the Atlantic.  Of the nitrogenous matter, soluble and insoluble, the proportions range from 9.90 per cent, to 21.50 per cent.; the former being from a sample of very soft and white French wheat; the latter from a very hard wheat with long grains, from Northern Africa, cultivated at Verrieres.  Another sample from Egypt yielded 20.60 per cent, of these nitrogenous matters, both of which are very remarkable proportions.

In describing the process for ascertaining the amount of insoluble nitrogenous matters, this author adverts to their estimation either by the quantity of nitrogen gas furnished, or of ammonia formed, the last being preferred for substances, which, like wheat, contain only a few hundredths of nitrogen.  The results which he obtained by this method were