^40 On Gypsum, 



and immediately unite with it, and form a sulphat. 

 This renders it a very valuable chemical test. That 

 this is a most powerful manure, (though, that it may 

 be the more readily decomposed, it must be reduced 

 to a sulphur et,) is clearly proved, by our intelligent 

 correspondent, Dr. Isaac Chapman ; page 120, of this 

 volume. 



Strange, then, (to one of the Laugens,) that this 

 commonproperty of possessing the sulphuric acid, 

 should go for nothing ; and other causes of operating 

 on vegetation should be sedulously sought for ! If my 

 conjecture, (whether original or borrowed, I cannot 

 myself now tell) should really be, as some respectable 

 chemists deem it, unfounded ; I see not that those they 

 have substituted, (opposite and variant) have more 

 fact, or probability, to support them. It is of no other 

 consequence to farmers, — than that it will furnish a 

 guide to discover what substances are likely to be 

 operative on vegetation ; until a more certain index 

 be established. Mean time, a conjecture which has 

 been, and may be, practised upon, seems to be, — to 

 say no more of it, — quite as good as any other. 



It is practically well known to multitudes of farmers 

 here ; to me particularly, who have been the longest 

 acquainted with this substance ; — that, in proper soils, 

 and in places free from constant moisture, and not im- 

 pregnated with, or affected by, common salt, either in 

 the earth or atmosphere ; the plaster operates, or not, 

 accordingly as decayed vegetable, or putrescent animal 

 matter, is, or is not, found in the soil. If none such 

 originally exists, or becomes exhausted, one or the 

 other must be supplied, by green-manures, dung, (in 



