34 INSTANCE OF FALSE PRACTICE. 



the idea jeing that the improvement at first is re- 

 markable, but that in the end the land is ruined. Is 

 the blame in such cases to be laid upon either the lime 

 or the plaster? Let us reason a moment upon the facts 

 of the case. 



Here was a soil well supplied with all of the sub- 

 stances mentioned in Table L, excepting, by way of 

 example, sulphuric acid and lime (plaster of paris). 

 The farmer adds plaster, which at once supplies the 

 deficiency, and the land produces heavy crops; he adds 

 it the second year with perhaps even increased effect, 

 and so on year after year, until there is as much as is 

 necessary in the soil. Now what is the reason that 

 after a time the crops begin to decrease? There is an 

 abundance of plaster, but may there not be a deficiency 

 of something else? He has been constantly taking off 

 large crops, and carrying them away from the land, 

 with a variety of inorganic substances contained in 

 them. As the crops have been larger than ever before, 

 so the quantities of phosphoric acid, chlorine, mag- 

 nesia, potash, soda, etc. taken off, have been cor- 

 respondingly great. How has this constant drain upon 

 the stock of these substances in the soil been met ? 

 Why by a constant supply of plaster, that is, of sul 

 phuric acid and lime. At last one or more of them 

 are exhausted; and how is the loss made up? Still 

 by an increased supply of plaster; and because this 

 plaster no longer does any good, it is said that the 

 land has been ruined by its injurious influence. 



From the foregoing explanation, we may easily 

 perceive that it is no longer plaster which the land 

 requires, but perhaps phosphoric acid, potash, mag- 

 nesia, or some of the other constituents of a fertile 

 soil. They have been taken away, and nothing 

 brought back but plaster; and now that they are ex- 

 hausted, hundreds of tons of plaster would not make 

 good their loss. It is then the false practice of the 



