114 ACTION OF SALTS. 



being witnessed ; yet so slowly, that its use has been often 

 condemned. The principle which is here discussed, may 

 account for this apparent discrepancy. Suppose a barren, 

 worn-out, exhausted soil, containing yet, a portion of insolu- 

 ble geine and decayed vegetable matter, between the state 

 of wood and insoluble geine, or even a portion of undecayed 

 dead wood. It seems too unpromising to give it manure ; 

 little of that is to be spared, and that is bestowed upon 

 better land. If this is in a country where lime is cheap, that 

 is purchased, and freely applied, as it is in England, at the 

 rate of about a cask to the rod. Even in this case no 

 change is produced, the soil is as unproductive as ever. The 

 experiment has failed, and is charged to book farming. 



160. The properties of lime, and geine, are here to be 

 remembered. Lime in excess, renders geine insoluble, 

 granting it to have been in a soluble state. Lime changes 

 vegetable fibre into soluble geine, but being applied in 

 excess, it forms an insoluble salt. Now, by the supposition, 

 there was no great excess of vegetable matter, and the lime 

 rendering only a small portion of that soluble, is itself, then, 

 always in excess, and though it converts, it at the same time 

 locks up that geine which it had converted. The reasoning 

 will hold good, whether a cask to the acre, or a cask to the 

 rod, has been applied. 



161. The lime has been, perhaps, in a caustic state, fresh 

 from the kiln, and as soon as it falls into powder it is spread 

 and covered in. It is greedy of carbonic acid ; so long as it 

 remains caustic, it absorbs this gas, and slowly becomes car- 

 bonate of lime. It is now like shell marl, clam, oyster and 

 muscle shells. The mode of reasoning applies to all these 

 forms. Slowly, but surely, it may not be for some years, a 

 gradual improvement in the limed soil of the exhausted field 

 is perceived. The carbonate of lime begins to act on the 



