Phosphatic Materials used for Agricultural Purposes. 5 



men, gluten, legumine, arid indeed all albuminous compounds. 

 How large then is the demand for those constituents which even 

 the best soils supply but in scanty proportions ! We can thus 

 understand why their direct supply in an available condition is 

 of more vital importance to our cultivated crops than that of 

 any other fertilizing substance. 



Generally speaking, phosphatic manures produce a more 

 marked effect upon root-crops than upon cereals. At one time 

 it was supposed that root-crops removed more phosphoric acid 

 from the soil than white crops, and on that account required to 

 be more abundantly supplied with phosphates. But this expla- 

 nation is as little correct as all others in which no account is 

 taken of the respective periods of vegetation of green and white 

 crops, and the different mode in which these crops take up the 

 food at their command in the soil. The roots of swedes and 

 turnips, unlike the deep penetrating roots of the wheat-plant, 

 with their numerous fibriles, feed, comparatively speaking, upon 

 a small portion of the cultivated soil, and their whole period of 

 vegetation is very much shorter than that of our cereals, espe- 

 cially that of wheat. Whilst the wheat-plant is thus enabled 

 to search for proper food in a considerable depth of soil, and 

 by degrees accumulates in its organism the requisite amount of 

 phosphoric acid which is distributed in small quantities in a 

 large mass of soil, turnips, swedes, and mangolds, in consequence 

 of the peculiarities of their growth, do not find at their disposal 

 available phosphoric acid in sufficient quantity to supply that 

 weight of bulbs which we now look for in average seasons. 

 Hence it is that manures, rich in soluble phosphates, produce 

 such a striking effect on root-crops, no matter what the character 

 of the soil may be on which they are grown. 



Although superphosphate and bone-dust do not generally 

 benefit wheat to the same extent as turnips, these and other 

 phosphatic manures are very efficacious when cereals are grown 

 on light sandy soils or land naturally very poor in phosphoric 

 acid. I do not purpose to institute at present a minute inquiry 

 into the relative utility of the various organic and mineral con- 

 stituents which constitute the food of plants, nor to extend the 

 preceding observations. They are merely offered as suggestions 

 which to some extent, at least, explain the fact that the sale of 

 phosphatic manures has been steadily increasing from year to 

 year, and has now assumed gigantic dimensions. 



The supply of bones is totally inadequate to meet the present 

 large demand for superphosphate and similar fertilizers. It is 

 fortunate, therefore, that England possesses an abundant - source 

 of phosphates in the extensive Suffolk and Cambridgeshire 

 coprolite deposits, and that the enterprising character of English- 



