SOILS, MANURES, &c. 255 
■■ ; . ■ ,■■ ■■ ■ 
abfolute poifons to fuch plants ; hence 
the neceffity of expofing manures and 
compofts for a fufficient time, and in a 
proper manner, to the atmofphere, that 
their crude acrid properties may be dis¬ 
charged, their falts neutralized, and that 
they may pafs through their various 
ftages of putrefatlion ; in the courfe of 
which, and likewife after application, 
the nutritive matter they contain fhould 
neither be loft by too copious exhala¬ 
tions, nor buffered to ftagnate and corrupt 
for want of the due adion of the air, 
agreeable to the foregoing obfervations. 
Many vegetable fubftances afford but a 
very frnall proportion of fixed alkaline falts 
upon incineration; among which are the 
aftringent plants of moraffes, &c. and the 
faccharine tribe, of which the potatoe 
is a fpecies: their falts are too volatile 
to bear the operation of burning without 
being 
