DR. DAUBENY ON THE ROTATION OF CROPS, ETC. 



239 



The results in the two first instances would seem to lead to opposite conclusions 

 from those suggested by the three latter, inasmuch as, whilst in the barley and the 

 potatoes, the difference between the amount of inorganic constituents in the two cases 

 was much less than that between the permanent and shifting crop collectively taken ; 

 in the hemp, flax and beans the contrary remark applies. 



If we take the phosphoric acid, we find also that in the barley, and turnips, it stands 

 in a higher ratio to the other constituents in the permanent, than in the shifting crop, 

 whilst in the hemp, flax and beans, it stands in a much lower one. 



A similar remark applies to the alkalies, so that no general conclusion, as it might 

 seem, is deducible from these premises. 



It appears to me, however, that the existence of a larger relative amount of phos- 

 phoric acid in the permanent than in the shifting crops of barley and of turnips, affords a 

 stronger presumption in favour of a certain dependence of the produce on the organic 

 matter, than the opposite result arrived at in the three other cases does of the reverse. 



If the falling-off of the crop in these instances had arisen from a deficiency of cer- 

 tain of its inorganic principles, such for instance as the phosphates or the alkalies, at 

 least a corresponding reduction in these latter might have been expected to have been 

 found in the ashes of the one which proved deficient in quantity ; whilst on the other 

 hand, if the deficiency of organic matter be supposed to have checked the develop- 

 ment of particular parts, as, for example, of the seeds, it might thereby affect the 

 character of the ashes obtained, and thus a smaller amount be abstracted, without any 

 actual failure, in the supply afforded by the soil to the plants that grew in it, taking 

 place with regard to them. 



I am led to this opinion, by the result of an examination, which I requested Mr. 

 Way to institute, into the nature of the inorganic constituents present in ordinary 

 gluten, and in starch. 



The first, obtained from wheat, yielded about three parts of inorganic matter in the 

 1000 parts, which latter contained as much as 33 per cent, of phosphoric acid com- 

 bined with lime, and a trace of magnesia, but no carbonate of lime*. 



* I found also that the bran contained a larger proportion of silica than the albumen of the grain itself, and we 

 know that the proportion of these several parts, one to the other, varies considerably in different samples of flour. 



