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MA SEEV Li PRODE-CT 8, 
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plied. Particular experiments have 
proved its value, if laid on from fifty 
to sixty bushels to the acre. It gives 
great improvement to cold grass 
Jands, and is consistent with all 
kinds of sodt. 
Rave cake has been in common 
use in Norfolk for more than half a 
‘century, and the quantity was 
, usually half a ton to the acre 3 an 
advance of price has, however, now 
compelled the -agriculturalist. to 
~lesscn the quantity, and Mr. Coke 
_ makes a ton do for five or six acres 
by drilling it with turnip seed. 
When ploughed in with wheat, it 
has been found more forcing to the 
crop than either dung or fold; but 
the turnips after the wheat have not 
been so good as after those manures. 
Malt dust and soot were found 
equal for wheat, but rape dust 
better than either. The operation 
of this manure is assignable toa very 
obvious theory; for all oleaginous 
bodies abound greatly with hydro- 
gen and carbon, and their utility 
_ consequently must be great. 
These manures are all vegetable 
_ substances, and their nature and 
properties do not differ from the ve- 
getable substances in the first class ; 
the most beneficial quantity has been 
_ mentioned under each. 
Among fossil manures coal ashes 
_ might have been classed, but for 
obvious reasons they are mentioned 
_ with other ashes ; lime kas also been 
treated of in the first part of the 
essay ; there only then remain to be 
noticed, salt and gypsum. 
Satr, by various experiments, 
and by observations made appa- 
_ rently with care, has been decided 
to act as a manure in some cases, to 
_ adegree which proves its excellence, 
when properly applied, but other 
Ak ia: 2 
973 
persons have reported unfavourably 
of it. ‘The knowledge of this ma- 
nure is yet in its infancy, but ex- 
periments have generally shewn it 
to be beneficial, but more especially 
when added to any dung or dung- . 
hills; and it probably acts as an 
assistant to putrefaction. 
Gypsum is scarcely known at all 
as amavure: the reports of those 
who have made experiments with it, 
are very contradistory. In this 
state of our Knowledge both of this 
and the preceding article, it is wise 
to accept the favourable reports, 
and attribute the failures to soil, 
season, or some unrelated circum- 
stance. ‘The quantity of gypsum 
usually applied has been about six 
bushels to the acre. 
Experiments on mixtures, or 
_composts, are extremely difficult, 
and must be ever unsatisfactory. If 
composts be resorted to to promote 
putrefaction, that is inconsistent 
with the idea that putrefaction 
should be retarded till the manure 
be applied to the land; they may 
be useful to get rid of an evil, as to 
mix pot-ash, or lime, or chalk, with 
pond mud to destroy its sterility ; 
but here seems to end the benefit 
of composts. 
THe FOOD OF PLANTS deserves 
much consideration in the applica- 
tion of manures. From experi- 
ments extremely numerous, and 
observations made by eminent che- 
mists, it appears that the two sub- 
stances which play the greatest part 
in vegetation, are hydrogen and 
carbon (the presence of light and 
heat is always to be supposed): 
those manures then, which supply 
the greatest proportion of these, 
must be most beneficial in pro- 
moting vegetation, Theory has 
furnished 
