290 
any common dung, and tends to render the ex- 
tractive matter insoluble. 
I made an experiment on this subject : I mixed 
a quantity of the brown soluble extract, which was 
procured from sheep’s dung, with five times its 
weight of quicklime. I then moistened them with 
water ; the mixture heated very much ; it was suf- 
fered to remain for 14 hours, and was then acted 
on by six or seven times its bulk of pure water : 
the water, after being passed through a filter, was 
evaporated to dryness ; the solid matter obtained 
was scarcely coloured, and was lime mixed with a 
little saline matter. 
In those cases in which fermentation is useful to 
produce nutriment from vegetable substances, lime 
is always efficacious. I mixed some moist tanner’s 
spent bark with one-fifth of its weight of quicklime, 
and suffered them to remain together in a close 
vessel for three months ; the lime had become 
coloured and was effervescent: when water was 
boiled upon the mixture, it gained a tint of fawn 
colour, and by evaporation furnished a fawn-co- 
loured powder, which must have consisted of lime 
united to vegetable matter, for it burnt when 
strongly heated, and left a residuum of mild lime. 
The limestones containing alumina and silica 
are less fitted for the purposes of manure than 
pure limestones ; but the lime formed from them 
has no noxious quality. Such stones are less effi- 
cacious, merely because they furnish a smaller 
quantity of quicklime. 
I mentioned bituminous limestones. There is 
very seldom any considerable portion of coally 
1 ? 
