° = 
as the greatest effect of the plaister is discoverable upon 
eloyer.* 
Your most obedient, 
Humble servant, 
Epwarp DurFrFiELpB. 
Benfield, August 16th, 1796. 
~The Hon. Ricnarp Perers, Esq. 
. 
* T was gratified by Mr. D’s agreeing in an opinion I had 
long held, and frequently mentioned to many others. I had 
conversations with Mr. D. since this answer. He, with me, 
tried many experiments with the view to this theory; and 
both were confirmed in it: though he, as well as mysel!, were 
not reckoned orthodox, by chemical savans. They insisted 
that the gyps was an insoluble compound, and that the acid 
must be first disengaged (which no doubt it is) before it can 
act. R. P. 
September 1810. 
On Plaister of Paris. = 877 
+ 
=) 
