the results of which were there given, had been chiefly directed to the determining the amount of rough gluten which they contained.  My reasons for adopting this plan, and the arguments in favor of its general accuracy, as compared with other modes of analysis, and especially that by which the ultimate composition is ascertained, were also detailed.  A more full examination of this subject has served only to strengthen the opinion already expressed, that for the great purpose to be answered by these researches, the process which I have adopted is, to say the least, as free from objection as any other, and if carefully and uniformly carried out, will truly represent the relative values of the several samples of wheat flour.  As this is a matter of much consequence in a practical point of view, I trust I shall be excused for introducing some additional facts in regard to it.

The term gluten was originally applied to the gray, viscid, tenacious, and elastic matter, which is obtained by subjecting wheat flour to the continuous action of a current of water.  But it appears that this is a mixture of fibrine and caseine, with what is now called glutine, and a peculiar oily or fatty matter.  Now these substances may be separated from each other, but the processes employed for this purpose are tedious, and to insure accuracy the various solvents must be entirely pure—­a point which, especially in the case of alcohol and ether, is not ordinarily easy to be attained.  This will be rendered still more evident by a reference to a French process, which will hereafter be noticed.

But were it much less difficult in every case accurately to separate the constituents of gluten, it would not, in my opinion, be of the least practical utility.  It is to the peculiar mechanical property of this gluten that wheat flour owes its superior power of detaining the carbonic acid engendered by fermentation, and thus communicating to it the vesicular spongy structure so characteristic of good bread.[37] It may also be added, that the results of more than one hundred trials have satisfied me that a diminution or loss of elasticity in the gluten is the surest index of the amount of injury which the sample of flour has sustained.  Whether, therefore, the sample contains a certain proportion of nitrogen, or whether it contains albumen, fibrine, and caseine in sufficient quantity, it may still want the very condition which is essential to the manufacture of good bread.  My objection, therefore, to the mere determination, however accurate, of the proportion of nitrogen contained in wheat flour, or of the various principles which form the gluten, is, that it does not represent the value of the various samples for the only use to which they are applied, viz., the making of bread.  The remarks of Mulder, the celebrated Dutch chemist, upon the subject of manures, are so applicable to this point that I cannot refrain