339 
Observations on Manures , Esfc. 
position and substance of the vegetable, can only be considered as 
a manure, by stimulating the healthy fibre of the plant, by destroy- 
ing the dead and decaying fibres, and by assisting the decompo- 
sition of undecomposed animal and vegetable substances disper- 
sed through the soil. It is thus that gypsum or plaister of 
Paris acts, being the most efficacious septic among the neutral 
saline substances. Of these manures of stimulus, none are as yet 
in common use, but lime, gypsum, and common salt. 
Lime, is limestone deprived of its water and carbonic acid a- 
mounting to 44 per cent, by fire. In this state, its stimulating 
j powers are obviously much greater, than in it's natural and neutral 
state of limestone. But even pounded limestone is a promoter 
I . 
of vegetation mechanically, on clayey and sandy lands ; and this 
earth appears to be a specific stimulus to white clover, and perhaps 
to the potatoe. Hereto may be referred the rubbish of old build- 
ings, and marl, which is clay about one half of limestone. 
Common Salt. This, until the duty of two thousand per cent, 
in England, was a very common manure in Cheshire ; the facts re-> 
fating to it, in this point of view, are collected in Watson’s che- 
mical essays. In this country, Gypsum is much cheaper. 
Gypsum , plaister of Paris, vitriolated limey or sulphat of lime. 
This has not been certainly found in any plant, but by M. Model, 
accidentally, in rhubarb, ( Journ . de fihys. vol. 6. p. 14,) even this 
I suspect to be a fallacy ; for the characters of gypsum were not 
then well ascertained. About two bushels per acre to clover 
or corn seem to be a full quantity. It attracts the moisture 
from the air, and dissolves gradually when strewed on the ground. 
It is brought here from France and the bay of Fundy, and has 
also been lately found in N e w-H ampshir e , and on lake Erie. 
There is also some in Maryland on the Chesapeake, about one 
hundred miles below Baltimore, and throughout the Genesee 
country, and on the waters of the Chippawa. As it is not a com- 
ponent part of any plant, cither in whole, or in its own component 
parts, it cannot act upon healthy vegetables but as a' stimulus, and 
upon diseased and dead ones, by its septic power. Experiments 
remain to be tried as to other manures of this description. 
Gypsum particularly deserves attention, considering that it has 
effected almost a complete revolution in the agriculture of Penn- 
sylvania. Many thousand acres of land hitherto barren, have been 
converted into excellent pasture ground, by its surprising influence- 
Even the products of land, tolerably good, have been in some in- 
