416 [Assembly 



that the more minutely the substances containing these [thos- 

 phates are divided, the more powerful will be the effect. Thus 

 bones reduced to powder are more potent than tliose denomina- 

 ted ' half-inch' from the size of the sieve through which they 

 have to pass after crushing. The coprolite is almost impervious 

 to either air, frost or water, and will resist all efforts at decom- 

 position for a very long period, and hence has to be powdered 

 before it produces any very striking effect ; and the limestone 

 has to be burnt, and its panicles disintegrated, before it will 

 yield up its constituents to the plants which need it. The effect 

 of the^e operations is purely mechanical. It increases the points 

 of attack; it enables the {dant, and the water, and the oxygen 

 "to have free play at a much greater surface, and hence places the 

 locked-up acid much more within the range of their power. 

 According to our present views of vegetation, physiology and 

 chemistry, tlie more soluble the component parts of a manure 

 may be, the more potent will they be found in their agency. 

 Now, phosphoric acid, as it exists in bones, is either insoluble in 

 water, or so slightly so as to be almost inappreciable to chemical 

 tests. It is locked up by the lime which holds it with a very 

 powerful affinity ; but if an acid, such as sulphuric, muriatic, nitric, 

 &.C., is added, it displaces a portion of the phosphoric acid, and 

 takes its place; the displaced acid unites with a smaller portion 

 of lime, and becomes a bi-phosphate ; and in this combination it 

 is soluble in water. 



Now this operation may either be performed by the farmer 

 himself, or it may be done by the manufacturer, on a large scale, 

 and purchased ready made. The reason against the farmer doing 

 it at home is mainly the danger of persons unacquainted with 

 the nature of chemicals, exposing themselves to the intluence of 

 so powerful an acid, and the chances of such persons, by some 

 bungling in the process, endangering the success of the operation. 

 And not only the danger of mixing, kc, but the difficulty of 

 drying and rendering fit for the drill are nice operations, to 

 which all farm tenants are not easily made adepts. Hence many 

 persons buy superphosphate of lime ready made, pulverized, 

 dried, and ready for work. And the question arises, is this 

 economical] Now, Dr. Anderson, the chemist of the Highland 



