[ 46) 
Answers to Queries on Plaister of Paris, by John Sellers, 
Esq. of Derby Township, Delaware County. 
August 15th, 1796. 
Dear Friend, 
It would afford me much pleasure to have it in my 
power to communicate any observations generally use- 
ful on the subject of thine of the 19th of last month, to 
which the obliging thee would be an addition. ‘The 
analysis thee mentions in an English work I consider as 
auseless inquiry, until we were able to know with the 
same certainty all the properties of plants, and the por- 
tions of the variety of elementary foods nescessary for 
the greatest promotion of vegetation. I therefore should 
suppose acids friendly or unfriendly, according to the 
quantity of the other kinds and portions of manure ap- 
plied therewith, as we know a due quantity of lime is 
friendly, and that too much is entirely destructive to 
vegetation, and that a greater quantity may with safety 
be applied with dung than without it. The knowledge 
most to be depended on, is to apply such manures as 
from experience we find best to promote vegetation. 
I have thought a repetition of the same sort of manure 
on the same ground would not have so good an effect as 
a change, which perhaps may be as necessary as that 
of different kinds of grain, flax, potatoes, &c. 
My first use of plaister was in the year 1786, on 
land limed about fifteen years before, and afterwards 
manured with dung ina moderate degree. It was at” 
that time sown with clover on the wheat in the spring, 
