148 
Manures ♦ 
which will not melt when it comes to be used ; so that it will not 
answer for blue*makers, nor for the purpose of the laundry. 
When sufficiently dried on the bricks it is put into the store* 
(which is nearly the same as a sugar-baker’s,) where it remains 
some time ; the duration must depend on the judgment of the ma- 
rker, and the degree of heat in the stove. It is then taken out and 
set on a table or dresser, when all the sides are carefully scraped 
or pared with a thin knife ; after which, it is tied up in paper the 
same as we see it in the shops ; when it is again returned into the 
stove, and continued with a regular heat night and day till com- 
pletely dry $ it requires some days, but the length of time can only 
Ibe ascertained by an experienced maker. 
It may be necessary to observe, that from the first laying in 
the meal to steep, till the last operation of taking from the stove 
to be weighed, the manufacture is constantly under the survey of 
one or more officers of excise. 
19 Philosophical Magazine, fi> 1 6$, 
MANURES. 
A PLANT contains water; that is hydrogen and oxygens 
Carbon , that is charcoal : Hydrogen , usually combined with the 
charcoal, and giving out light and flame when the vegetable is 
burnt, as carburetted hydrogen : Vegetable acid , that is carbon, 
hydrogen, and oxygen ; Potass , whence derived or how formed 
1 know not ; carzhs and salts in small and accidental quantities, 
deposited as I apprehend from the fluids taken up by the roots : 
these are not found uniformly, either in kind or quantity, and they 
•Vary in both respects with the nature of the soil and of the ma- 
nure. Thus, the calcareous earth found in potatoes, and the sill-, 
ceous earth found in the scouring flag, in the straw of grain, in 
the joints of reeds and canes, &c. can hardly be considered as es^ 
sential parts of vegetable substance, any more than the nitre in 
borage, in tobacco, &c. which, if the vegetable organization cannot 
decompose, must exist deposited in its proper form. 
Hydrogen, oxygen, and carbon then, are the principal compo- 
nent parts of vegetables : even potash seems not essential to all 
vegetables, inasmuch as the resinous plants contain it in very small 
