DR. DAUBENY ON THE ROTATION OP CROPS, ETC. 217 



we could positively assure ourselves that no admixture of the soil had got in, namely, 

 in the grain of barley from Ensham, nothing was thrown down by the last application 

 of ammonia, and in one sample of ash from flax (viz. the standard crop), only a mexe 

 trace was discoverable. 



Considering indeed that the soluble salts of alumina are poisonous to plants, and 

 that the earth itself is confessedly present in very variable, sometimes very minute^ 

 quantities, I am inclined to doubt whether it be in reality a constituent of their ashes 

 at all. 



With respect to manganese, two methods were adopted for ascertaining its presence. 



The first, that of boiling the muriatic solution with carbonate of lime, and then, 

 after filtering it, adding hydrosulphuret of ammonia. 



The second, the blow-pipe test, fusing a little of the muriatic salt with borax, when 

 a very minute quantity of manganese would produce its characteristic colour in the 

 bead of glass produced. 



By neither of these methods were any indications of manganese obtained. 



I next proceed to state the results of the analyses made in my laboratory by Mr. 

 Way, of six kinds of crops grown in the experimental garden, together with those 

 obtained from certain standard crops of the same species, grown in another part of the 

 garden, or in other places in the vicinity of Oxford, under more natural circumstances. 



My original object being merely that of ascertaining the quality and quantity of 

 the inorganic matters abstracted from the soil in these instances, the crop of barley, 

 flax, hemp and beans, was burnt altogether without any separation of their respectivie 

 parts having been previously made, and it was only in the case of the potatoes and 

 the turnips that a distinct portion of the plant was selected for analysis, namely, the 

 tubers in the former, and the bulbs in the latter. 



Barley. 



Permanent crop, ^fter ten years' repetition. 



100 grains of the dried crop, including both the straw and grain, left of ash 8*7 grains. 



100 grains of this ash contained as follows: — 



Sand and charcoal, extraneous 22*36 



Peroxide of iron, chiefly extraneous . . . 212 



24-48 



Silica of the plant 24*60 



Phosphoric acid - 7*3i 



Sulphuric acid 2*12 



Carbonic acid 1'94 



Chloride of sodium 4*73 



Potass 17*33 



Magnesia 4*68 



Lime . , 13-91 



Total . . 101-14 



