On Plaster. 299 



the spot on which the small heap was spread, was uni- 

 versally whitened by it. 



Having, frequently and successfully, rotted down 

 leaves, tussocks and wood-soil, plastered lightly; I was 

 surprised at the disappointment in this instance. I can- 

 not account for the circumstance, otherwise than by 

 presuming, that an overcharge of plaster is a quiescent 

 force ; that is, — it preserves compounds in a state of 

 rest. A moderate quantity may be divellent ; — that is, 

 — it assists in destroying a state of combination. Plas- 

 ter must, no doubt, be decomposed itself, before it 

 acts on other substances. So must be marine salt ; 

 which is also a chymical compound. But whether there 

 be, or not, any analogy in their modes of operating ; 

 I do not presume to decide. 



The instance I relate, reminded me of the fact, and 

 my conclusion from it, mentioned in our first volume, 

 page 174. — No more of the plaster will act, than the 

 materials, necessary to cooperate with it, require. The 

 balance remains in its original state of composition ; — 

 inert and useless. And yet had even the quantity ap- 

 plied in the small heap, had access to all the materials ; 

 one would imagine, there were more than sufficient of 

 them, for the pabulum of a larger proportion of the 

 plaster ; when it is considered that the number of loads 

 of the raw materials, before rotting down, was far great- 

 er than after the putrefaction. 



Whether my conjectures be or not sound or rele- 

 vant, in a chymical point of view, I think farmers may 

 from this and numberless other fiicts, conclude ; that 

 plaster does not operate, like dung, according to the 

 abundance bestowed on the ground. At all times, it is 



