4 
On Plaister of Paris. 1 
will produce good effects; but in all cases where the 
acid prevails, it will certainly do harm, ap 
“This account of the nature of gypsum we are en- 
abled to give, from having carefully examined different if 
sorts of it. In some of these the calcareous earth pre- 
vailed ; and in others the substance was a neutral com: 
pound. We pronounce, therefore, that in all cases where 
the calcareous earth prevails in gypsum, z will be use- 
Sul, if the ground has not been previously timed. 
In cases where the acid and earth are equally balane- 
ed, it will have other effects. 
And in cases where the acid prevails, it will uniformly 
do harm ; unless, perhaps upon chalk or limestone lands. 
It is therefore a manure that can seldom be used 
with advantage in this country upon arable lands, as 
there are few situations indeed in which the soil does 
not either contain calcareous matter in itself or has re- 
ceived it as a manure.” | 
OBSERVATIONS. 
‘THE writer of this article is misinformed when he 
says that ‘‘ in America scarcely a particle of calcareous 
earth is to be found.” We have enough of it, mixed 
with a great variety of substances. Our attention has 
not been sufficiently paid to subterraneous explorations, 
to enable us accurately to class or designate the seve- 
ral species, either of those unmixed, or in combination. 
We know most about the argillaceous (clayey) earths, 
because we have had them more in use, and they are 
more common. This account of eypsum, as to its agri- 
-< 
2.» 
