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Answers to Queries on Plaister of Paris, by Mr. John 
Curwen, of Upper Merion, Montgomery County. 
W. Hill, August 10th, 1796. 
Dear Sir, 
Inclosed are my answers to your queries, agreeably 
to your request. 
If the plaister is compounded of a mineral acid and 
ealcareous earth, it may be suspected that both have a 
share in its effects ; for it can hardly be supposed that 
such can be produced from it less than a bushel of cal- 
-eareous earth to an acre; and may it not be presumed 
that some active substances, which in large quantities 
are poison to vegetation, may, in very small ones be 
friendly to it; or may not the compound have quali- 
ties, not found in any of its parts ? 
If in England it has no effect on grounds which have 
been long under cultivation, and especially those which 
have been limed, America may boast of superior ad- 
vantages. My answer to the 10th Query shews the re- 
sult of my experience on that point. 
Query 1. How long have you used the plaister ? 
Answer. ‘Ten or eleven years ; at first in small quan- 
tities, but finding it beneficial, have used a good deal 
for several years past. 
Query 2. What state was the land in when you be- 
gan to use it ? 
Answer. Generally on limed and. dunged land which 
had been much exhausted previous to this by bad tillage 
without manure. 
Query 3. What quantity per acre have you generally 
used ? ; F 
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