EXPERIMENTS WITH DIFFERENT LIMES. 241 



To some persons these quantities may both appear too small 

 to produce any very sensible effect upon the land or the crops. 

 In answer to this, I have already shown that a ton of lime 

 containing 2 per cent of phosphate carries on to the land 45 Ib. 

 of this compound, and, therefore, that a large dose of lime must 

 mix with the soil a quantity of phosphate, which cannot be 

 without an important influence. 



But it may also be said that, in the experiments with 

 mineral phosphates in a comparatively pure state, the results of 

 which have been given in the preceding section, their effects 

 were small when applied in the state of powder, and that they be- 

 came distinctly marked only when the phosphates were dissolved 

 in sulphuric acid. It is an advantage, however, which we gain 

 by the burning and slaking of lime that it is thereby reduced to 

 the state of an exceedingly fine powder, and that any substance 

 which is mixed with the lime is at the same time brought into 

 an exceedingly minute state of division. In regard to the 

 phosphate of lime which burned limes contain, we may therefore 

 consider that the slaking does for it in a great measure what 

 the action of the acid does for the compact mineral apatite and 

 phosphatic nodules, and that in our common limes it is in a suffi- 

 ciently divided state to act at once upon the land, and to pro- 

 duce an effect in proportion to the quantity of it which has 

 been applied. I would therefore suggest that experiments 

 should be made, 



a With the different limes which are accessible in a district, 

 in which by analysis a sensible difference in the proportion of 

 phosphates has been found, 



b On different soils, and on such as have been previously 

 subjected to different kinds of manuring. 



It is especially desirable to ascertain how far the previous 

 use of bones affects the comparative action of each variety of 

 lime ; how far the previous application of each variety modifies 

 the effect of bones subsequently applied to the land ; if they 

 appear to exhaust the land in different degrees, or in different 

 periods of time ; if one variety, for example, can be safely 

 applied for a much longer period than another ; if they diffe- 

 rently affect the growth of corn crops, and especially the filling 



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