464 THE GARDENER’S ASSISTANT. 
and beaten up with as much stable-drainings 
as may be necessary to reduce the whole to the 
consistence of mortar. It may then be spread 
on the floor of an open shed, and when some- 
what firm it may be cut into cakes of 6 inches 
square, placed on edge in a dry, airy place, and 
frequently turned and protected from rain. 
When half dry, make a hole in each with a 
dibber, so as to admit of about 1 inch square 
of good old spawn being inserted so deeply as 
to be a little below the surface; close it with 
some moist composition similar to that of which 
the bricks were formed. When the bricks are 
nearly dry make, on a dry bottom, a layer 9 
inches thick of horse-dung, prepared as for a 
of horse, cow, and sheep’s dung. — Analyses of 
these are of course subject to variation; but ~ 
those made by Boussingault, and other eminent 
authorities, may be considered a fair estimate 
of the percentage of nitrogen which the sub- 
stances in question usually contain, and this is 
exhibited in the following table :— 
SOLID EXCREMENTS. | URINE. 
Fresh. Dry. 
Horses 4 eee 0:54 22 1:55 
COW 2. 5.2 0°32 he: 0°44 
Sheep Grits see eee 0:72 1k 27 Sil 
From the above it appears that in the solid 
excrements of the horse there is rather more 
hot-bed, and on this pile the bricks rather openly. | than one-half per cent of nitrogen, in that of 
Cover with litter, so that the steam and heat 
of the layer of dung may circulate among the 
Fig. 1221.—Mushroom Brick Spawn. 
bricks. The temperature should not rise above | 
60°. The spawn will soon begin to run, and | 
when, on breaking a brick, the spawn appears | 
throughout pretty abundantly hke a_ white | 
mould, the process has gone far enough. The 
bricks should therefore be removed, allowed to 
dry, and then be kept in a dark dry place. 
As there is so much difference of opinion as 
regards the substances employed in making 
spawn-bricks, and as different combinations of 
them are successfully employed, it will be worth 
while to endeavour to ascertain whether there 
is not one common principle in all of them, 
which is more especially essential for the growth 
of the Mushroom. The quantity of nitrogen 
which it contains being much greater than in 
other plants subjected to cultivation, it follows 
that this element must be abundantly supplied ; 
and accordingly all the substances usually em- 
ployed for the spawn to feed upon contain 
the cow scarcely one-third per cent, while in 
that of the sheep there is nearly three-fourths 
per cent. The amount of nitrogen 
in dried horse and cow dung is 
nearly equal, and about one-fourth 
more than in dried sheep’s-dung. 
The urine of the horse, it will also 
be seen, yields a large amount of 
nitrogen. 
Although horse-dung contains a 
greater amount of ammonia, and 
ferments more readily than cow- 
dung, yet the heat of the latter con- 
tinues longer, and on this account a 
mixture of the two may be employed 
for the growth of Mushrooms. 
Some recommend these substances 
to be used in a fresh state, others 
after they have undergone a con- 
siderable degree of fermentation. In the latter 
state, much of their nitrogen must have been 
driven off in the form of ammonia, so that 
there is no question as to the superiority of the 
'fresh materials, if the heat generated by such 
can be controlled; but this is the difficulty. 
They can be disposed in thin layers, but then 
they do not afford such good produce as when 
in a greater mass. It may here be observed, 
that firmly beating the materials tends to lessen 
the fermentation, and by boring holes the heat 
is permitted to escape, but likewise the ammonia, 
which it would be desirable to retain for the 
benefit of the crop. Therefore, whilst the fer- 
mentation is going on, the beds should be 
covered with loam, by which much of the am- 
monia will be absorbed. For the same purpose 
a little leaf-mould might be spread over the 
surface of the dung, and then about 2 inches 
thick of loam, or of a compost of loam and cow- 
nitrogen in considerable quantity, as in the case | dung which has. been frequently turned, and 
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