134 LESSONS IN CHEMISTRY. 



with advantage been applied, and maintains, that it depended 

 npon the soil being ah*eady supplied with compounds of 

 phosphorus. Professor Johnston, who is among the most 

 earnest advocates for the fertiUzing vhtues of the organic 

 matter of bones, does not accept Spren gel's explanations of 

 the failure of bones in Northern Germany, but argues, that it 

 arises from the undrained state of the land to which they 

 were applied. There can be no doubt that the organic mat- 

 ter of bones, as theory would lead us to suppose, possesses 

 valuable qualities as a manure. The liquid which is ex- 

 tracted by boiling bones, in the dyeing manufactories of 

 Manchester, even after it has been deprived of so much of its 

 size as to be considered unfit for stiffening, is found to pro- 

 mote vegetation, and is eagerly purchased by the farmers of 

 Lancashire and Cheshire. Burnt and boiled bones have been 

 found to commence their action sooner than those unburned ; 

 but this cannot be regarded as a proof that the organic por- 

 tion is of no value, but merely shows, that the fat and 

 gelatine may retard the progress of decay, and the action of 

 the gases, by which the insoluble phosphates are rendered fit 

 for being taken up by plants. Again, the observations fre- 

 quently made by experienced practical farmers, in England 

 that twenty stones of horse-hair, which are considered to 

 contain organic matter equivalent to that of sixteen bushels 

 of bones, will not produce an equal effect upon the soil, may 

 also be regarded as a proof, that, to the phosphates, bones 

 owe a large share of their useful quahties. We may fairly 

 assume, that the effects which burnt or unburnt bones pro- 

 duce upon a soil will, like the effects of all special manures, 

 be materially affected by chemical composition. When a 

 field contains a sufficient supply of organic matter, and is 

 deficient in phosphates, burnt bones may produce the most 

 immediate and decided effects; while, upon a soil which has 

 become poor in decomposing vegetable matter, the crushed 

 bones will be found the best application. Though there are 

 few soils in Ireland that would not be greatly benefited by 

 the use of burnt bones alone, yet I would not advise our 

 farmers to prepare them in that form, or to destroy matters 

 which we know contain ingredients of great value. From 

 what has been stated of the fertilizing qualities of the size 

 liquid, and also of the ash or bone earth, we may, I think, 

 conclude, that both of these substances, as tlieir composition 



