SOIL. 
denote the specific gravity of the soil compared to 
water as 1,000. Suppose, for example, that silice- 
ous sand, which is 2°7 times denser than water, is 
poured into the vacant space, it will require 2,700 
grains to fill the space occupied by the 1,000 grains 
of water; and thus we have the specific gravity 
without any calculation. If instead of 1,000 grains, 
we use only 500, or 250, the result will be the same, 
if we multiply the grains in the other scale by 2 or 
4. We will give a few examples of soils of which 
the specific gravity has been carefully determined. 
A rich garden soil, which contained per cent., 
Clay 52-4 
Siliceous Sand 365 
Caleareous Sand ‘ 0 . 18 
Carbonate of Lime 6 : 5 aD? 0 
Humus 6 3 
had a specific gravity of 2°332. 
A good loam, consisting of 
Clay Oe EER io) ster gO kee 
Siliceous Sand 5 . 427 
Calcareous Sand : \ ‘i Or-4 
Carbonate of Lime 3 : 5 OFS! 
Humus 34 
had a specific gravity of 2°401. 
A poorer soil, of which the component parts were 
Siliceous Sand 64:0 
ay 5 5 32:3 
Caleareous Sand . 1:2 
Carbonate of Lime . Ne? 
Humus 13 
suffice to show that the specific gravity of a soil 
is some tolerable indication of its fertility. It can- 
not, however, be entirely relied upon in the absence 
of other proofs; for there may be many different 
mixtures of earths which will have the same specific 
gravity, although they may differ greatly in their 
fertility; but it will facilitate the analysis, and often 
detect mistakes in the process, if the result does not 
accord with the specific gravity found. 
‘* We proceed now to the analysis. The portion 
of soil which has been deprived of all its water, as 
described above, must be sifted through metallic 
sieves of different fineness. The first 1s made of a 
perforated tin plate, the holies of which are about 
one-twentieth of an inch in diameter. Whatever 
does not go through this is put by. The remainder 
is successively passed through two or three more 
sieves, increasing in fineness to the last, which is of 
the finest wire-cloth, having from 150 to 170 threads 
in an inch: whatever passes through this is impalpa- 
ble powder. Thus we have al- 
ready a division of the soil ac- 
cording to the size of its parti- 
cles:—Ist, the coarse grit left 
in the first sieve; 2d, the finer 
grit in No. 2; 3d, fine sand in 
No. 3; and 4th, impalpable pow- 
der, which has passed through 
the last sieve. To facilitate 
this part of the operation the 
sieves may be made so as to fit 
into one another, like the fil- 
terers in a coffee-biggin, the 
last fitting into a tin pot which 
will hold about a pint of water: 
a cover being made to fit on the 
top sieve, the instrument is com. 
plete. (See Fig.) Thus all the 
sifting may be done at once, 
without any loss. Any lumps 
which are not thoroughly pulverised must be broken. 
The coarser sand left in the sieve No. 1 must now 
be washed with pure water to detach any fine dust 
adhering to it; what runs through may be used to 
wash No. 2, in the same manner, and then may pass 
through No. 3 to the impalpable matter which 
passed through all the sieves. A sufficient quantity 
of water must be used to render the whole of this 
last nearly fluid. There will then be three different 
portions of the washed soil left in the sieves, and a 
portion of impalpable matter diffused through the 
water in the lower division of the instrument. This 
last is the principal object of analysis, and that 
to which Sir Humphrey Davy usually confined his 
attention, merely noticing the proportion of coarser 
sand in the soil. It contains, no doubt, the great 
principle of fertility and nutrition; and the effect of 
the coarser parts may be considered as chiefly me- 
chanical. But they may much affect the fertility of 
the finer parts, and are of the greatest importance to 
the soil in which they are blended: they conse- 
quently deserve a more minute examination, to which 
we will return. In the mean time our attention shall 
be directed to the composition of the finer earth in 
No. 4, which is mixed with water in a semi-fluid 
state. This is well shaken, and suddenly poured 
into a deep glass vessel, and allowed to settle fora 
few minutes, when the heavier earth, which is sand, 
will be deposited, and the lighter may be poured off 
suspended in the water. It requires some little 
practice to effect this at once, but a few trials will 
soon enable any one to doit. This operation may 
be repeated until all the sand, of which the particles 
are visible to the naked eye, is separated. The 
earth and water decanted out of this last vessel are 
now poured into a glass tube, 18 inches long (No. 
1), the bore of which is less than an inch: one end 
is stopped with a cork fitted into it, and the other 
has a small lip for the convenience of pouring out 
the contents. In a short time there will be a further 
deposition of earth, which will be principally alu- 
mina. What remains suspended in the water over 
it is gently poured off into another similar tube (No. 
2): this will contain nearly the whole of the humus, 
which will take some hours to be deposited in the 
form of a fine brown mud. The contents of the 
tube No. 1 may now have a little more water 
added to them; after being well shaken, the tube 
may be set upright, and left for half an hour to 
settle: what remains suspended in the water after 
this must be added to the humus in the tube No. 2. 
After some time this will also be deposited; and the 
clear water may be decanted off. The mud which 
remains is put on filtering-paper ina glass funnel, 
and, when all the water has drained from it, it is 
dried over the fire, and weighed. This is the most 
important portion of the soil. The fine earths de- 
posited in the tube No. | will consist of very fine 
particles of sand, clay, and perhaps carbonate of 
lime. The sand will appear deposited in the bottom 
of the tube. The clay may be easily diffused in the 
water above it by stirring it carefully with a small 
rod without reaching the sand. It may then be de- 
canted off with the water into another tube (No. 3), 
and allowed to settle: this part of the operation may ~ 
be carried to a great degree of perfection by great 
care, and by examining the results occasionally with 
a small microscope; but for al] common practical 
purposes, it is sufficient to separate the vegetable 
earth from the mineral, and the visible particles of 
sand from the finer. The contents of No. 1 having 
been collected, as well as those of No. 3, are dried 
over the fire and accurately weighed. ‘lhe same is 
done with the earths which remain on the sieves. 
All the water in which the earths have been diffused 
and washed is collected and passed through filtering. 
paper, and then set over the fire in a common sauce- 
pan. It is boiled away gently until it is reduced to 
a small portion, which begins to look turbid. The 
complete evaporation is finished in an evaporating 
dish, as slowly as possible, and the residue is the 
soluble matter contained in the soil. It will be 
sufficient to dry and weigh this, as its further analysis 
would require more skill and chemical knowledge 
