I have but slight confidence in the results heretofore given.  The difficulties which attend the obtaining the ash in a proper condition, and the fact that the products of all the organs and parts of the plants have been analysed together, must necessarily impair the accuracy of the experiments, and render the inferences drawn from them of uncertain value.  Much, indeed I may say almost everything, still remains to be done in this department of agricultural chemistry.

    Weight of wheat as an index to its value.—­Much has been said in
    regard to the relative weights of the bushel of wheat of different
    varieties or under different modes of culture.

As ordinarily determined, this weight ranges from fifty-six to sixty-five or sixty-six pounds, being in a few cases set down somewhat higher.  It is said also that the bushel of wheat weighs less in some years than it does in others, and that the difference often amounts to two, or three, or even four pounds.  Though this may seem of comparatively little consequence for a few bushels, yet, for the aggegate of the wheat crop of the United States, or for a State, or even a county, it makes a great difference.  Thus, were we to estimate the product of one year in the United States at one hundred and ten million bushels, weighing fifty-six pounds to the bushel, and another year at one hundred and eight million bushels, weighing sixty-two pounds, the difference in favor of the latter, though the least in quantity, would amount to five hundred and thirty-six million pounds in weight, or more than one million and a quarter of barrels of flour.—­(Report of the American Commissioner of Patents for 1847, p. 117.)

It may be remarked, however, that it is not after all so easy to determine with accuracy the weight of a bushel of wheat, nor to decide upon the circumstances which have an influence in increasing the density of a grain of wheat.  If the microscopical representations of wheat are to be relied on, it is probable that the increase in the density of wheat depends upon the increase in the proportion of gluten.  I have found in several cases that, the proportion of water being the same, those samples of wheat which contain the largest proportion of gluten exhibit the highest specific gravity, or, in other words, will yield the greatest number of pounds to the bushel.  But the weight of wheat will be influenced by the proportion of water which it contains; the drier the grain, the greater is its density; a fact which may account for the difference which has been observed in the weight of wheat in different seasons.  If this is the cause, the calculation above given in reference to the United States is fallacious—­but if the amount of gluten is actually, instead of relatively, increased by peculiarities in seasons, it is no doubt correct.

    I have devised a series of experiments to test the accuracy of the
    statements made upon this point, but have not yet had leisure to
    complete them.