TRANSACTIONS OF THE SECTIONS. 173 



(so far as they are chemical), are not measurable by the amount of the additional 

 mineral food of plants liberated thereby, these being under ordinary cultivation in 

 excess of the assimilable nitrogen existing in, or condensed within the soil in the 

 same period of time ; the amount of which latter therefore — the available nitrogen — 

 is the measure of the increased produce of grain which will be obtained. 



4. That the beneficial effects of rotation, in increasing the production of saleable 

 produce (so far as they are chemical), are not explained by the fact of one plant 

 taking from the soil more of the different mineral constituents than another, but 

 depend on the property of the so-called green or fallow crops bringing on, or con- 

 serving upon the farm, more of substance rich in nitrogen than is yielded to them in 

 manure, whilst the crops to which they are subservient are both largely exported 

 from the farm, and yield in their increase considerably less of nitrogen than is given 

 to them in manure. 



5. In a word, that in the existing condition of ^H^xsh agriculture, a full pro- 

 duction of the saleable cereal grains, with at the saiie time other exportable produce, 

 is only attained — whether by manures, fallow, or rotation — by an accumulation of 

 available nitrogen (normally an atmospheric constituent), within the soil itself. 



On the Composition of Wheat-Grain, and its Products. 

 By J. B. Lawes, F.R.8., F.C.S., and J. H. Gilbert, Ph.D., F.C.S. 



The authors had for a series of years conducted experiments on the successive 

 growth of wheat, on the same land, by different chemical manures. The general 

 result of these experiments had been to show, that, although the amount of the pro- 

 duce had been much increased by the use of nitrogenous manures, the per-centage of 

 nitrogen in the grain had been, comparatively speaking, but little affected thereby. 

 Variation in season had had more influence on the composition of the crop in this 

 respect. It had further appeared, that, within the limits of their own locality and 

 climate, there was, on the average of the seasons, a lower per-centage both of nitrogen 

 and of mineral matter in the grain, the more favourably the produce was developed 

 and matured. The varying composition of the entire grain as affected by season and 

 manuring, the authors hoped to treat of more fully elsewhere * ; their object, in the 

 present paper, being chiefly to call attention to some points in the character and com- 

 position of the different products obtained from wheat-grain by means of mechanical 

 separation. 



With a view to the prosecution of this part of the inquii"y, in selected cases, quan- 

 tities of the experimentally grown grains, namely, seven lots from the produce of 1846, 

 nineteen from that of 1847, and two from that of 1848, had been carefully watched 

 through the milling process. In some of the cases nine, and in others seven different 

 products of the dressing apparatus, were separately taken. The proportion of each of 

 the several products in the respective grains was ascertained and recoi'ded, and the 

 per-centages of dry substance and mineral matter were also in every case determined. 

 The three first wires of the dressing machine gave on the average rather more than 

 70 per cent, of the grain asjine flour; but in practice about 10 per cent, more would 

 be obtained from the next two products, yielding in all 80 per cent, or move of pretty 

 good bread flour. The average amount of dri/ substance in the various mill products 

 was about 85 per cent. ; the external or more branny portions containing rather mere, 

 and the finer flours rather less. The per-centage oi mineral matter varied very much 

 in the different products, it being scarcely |ths of 1 per cent, in the fine flours, and 

 ten times as much, or more than 7 per cent., in the coarsest bran. From the much 

 larger proportion of flour than bran, however, it resulted that rather more than -^^rd 

 of the total mineral matter of the grain would be accumulated in its currently edible 

 portions. 



In one series of these mill-products, from the finest flour at the head of the ma- 

 chine down to the coarsest bran, the nitrogen was determined, and also some of 

 the constituents of the respective ashes. It appeared that the per-centage of nitrogen 

 was about once and a half as great in the bran as in the finer flours. And even in- 

 cluding all the currently edible portions, still the excluded branny parts contained 



* See Guarterly Journal of the Chemical Society, April, 1857 ; where also is given, with 

 additions, the tabular matter, &c. to which this abstract relates. 



