a eee 
264 
is necessarily followed by a relative addition to 
them all. If, for example, a plant possesses one 
part containing 2 grains of azote, combined 
with 18 grains of other elements, and another 
portion containing 2 grains of azote, combined 
with 48 grains of other elements; if we, by any 
means, prevent the development of the more 
highly azotised portion, viz. the 2 to 18, we 
shall produce a proportional increase in the 
other ; so that, by preventing the formation of 
20 grains of the highly azotised portion, we ob- 
tain 50 grains of that which contains propor- 
tionally less azote. 
The Analysis of Soils—The meanings of the 
word analysis, a brief general view of the im- 
portance of the analysis of soils, and a detailed 
account of the principles of all chemical analysis, 
are given in the article AnaLysiIs; and a number 
of statements and discussions which have a strong 
bearing on questions as to the methods and uses 
of analysis of soils occur in the articles Manurg, 
Farm-Yarp Manure, Guano, Foop or Puants, and 
many others, The analysing of soils affords more 
certain and more valuable information respect- 
ing them than any other mode of investigation, 
and is essential for opening a balance-account 
between the withdrawal of substances by crops 
and the adding of them in manures, and forms a 
chief means of reducing the general doctrines 
and discoveries of agricultural chemistry to bene- 
ficial practice, and in general serves as a mighty 
appliance for carrying forward in the world, and 
fixing down on individual farms, the great and 
growing agricultural intelligence of the age. 
Two kinds of it may be practised, the mechanical 
and the chemical; and excellent methods of 
these—the mechanical by the Rev. W. L. Rham, 
and the chemical by Dr. Ure—have been pub- 
lished in the Journals of the Royal Agricultural 
Society, and shall here be transcribed. 
‘«The soil to be examined must be taken a few 
inches under the surface, and in different parts of a 
field. If there appears much uniformity, the por- 
tions may be mixed, in order to have the average 
quality of the soil: should there be a visible differ- 
ence between one portion and another, which is 
often the case, each may be analysed separately. A 
portion of the earth to be analysed is dried in the 
sun or near a fire, until it feels quite dry in the hand. 
It is then reduced to powder by the fingers, or 
by rolling it on a deal board with a wooden roller, 
so as to separate the particles, but not to grind them: 
any small stones above the size of a pea must be 
taken out. If these form a considerable part of the 
soil, their proportion must be ascertained by weight; 
their nature and quality may be afterwards examined. 
This, being a very simple operation, and obvious to 
the sight, need not be described. Where the stones 
and pebbles are evidently accidental, they may be 
overlooked, as having little influence on the fertility. 
The dry earth, cleared from stones, should be ac- 
curately weighed; and it is convenient to take some 
determined quantity of grains, as 1,000, 500, or 250, 
according to the accuracy of the instruments at hand. 
This portion should be put into a shallow earthen 
or metal vessel, and heated over the fire, or a lamp, 
for about ten minutes, stirring it with a chip of dry 
SOIL. 
wood: the heat should not be so great as to dis- 
colour the wood. It may then be allowed to cool, 
and be weighed again; the loss of weight indicates 
the water which remained uncombined after the soil 
appeared quite dry. This is the first thing to 
be noted. The power of retaining water, without 
any external appearance of moisture, is greatest in 
humus, next in clay, both of which readily absorb it 
from the atmosphere; carbonate of lime does so in a 
less degree, and siliceous sand least of all. ‘This 
moisture occupies the pores of the soil, and is very 
different from the water which is combined with 
clay as a part of its substance, and to which it owes 
its ductility; for when this last is expelled by a 
great heat, the clay loses its quality, and approaches 
to the nature of sand. Pounded brick will not bind 
with water; and porcelain reduced to a fine powder 
has all the properties of siliceous sand in the soil. 
The finer the division of the particles of the soil, 
the greater will be its power of absorbing and re- 
taining water; but in a soil where clay greatly pre- 
dominates, the lumps sometimes become so hard and 
baked by the sun that the moisture cannot penetrate, 
and in this case the power of absorption is much 
diminished. Hence loams in which there is a good 
proportion of humus have a greater power of absorp- 
tion than the pure earths. ‘Taking all circumstances 
into consideration, it will be found that the soils 
which most readily absorb moisture are also the 
most fertile, and therefore it is important to ascer- 
tain their power of absorption. This can be found 
by comparison. Equal portions of different soils, 
dried as before, are placed in the opposite scales of a 
good balance, and left exposed for some time to a 
moist. atmosphere. ‘That which preponderates has 
the greatest power of absorption; the degree is 
measured by the difference of the acquired weights. 
““ Another important circumstance is the specific 
gravity of a soil. ‘The different earths have very 
different specific gravities; and humus being lighter 
than any mineral earth, the lightness of the soil is a 
sure indication of its richness, excepting where this 
lightness is occasioned by an excess of undecomposed 
vegetable matter, or peat. Humus, when nearly 
pure, has a specific gravity varying from ]°2 to 1°5; 
fine porcelain.clay, 2; chalk, about 2:3; siliceous 
sand from 2.5 to 2°7. Mixed soils have specific gravi- 
ties varying according to the proportions of their 
component parts. Those in which clay, chalk, and 
humus abound, and which are generally the most 
fertile, are the lightest. The sandy soils are heavier, 
and the more so if they contain oxides of iron or of 
other metals; and it is well known that the ferru- 
ginous sands are the most barren. The common 
expression of light, when applied to a sandy soil, has 
no reference to its specific gravity, but merely to 
the force required to plough it. No carrier would 
say that a loose sandy road was a light one. The 
easiest and readiest method of determining the spe- 
cific gravity of earth, or any substance which is of 
a loose texture, is that described by Dr. Ure in his 
Philosophy of Manufactures (page 97), as employed 
by him to ascertain the specific gravities of cotton, 
wool, silk, and flax. It is as follows:—Take a nar- 
row-necked phial capable of holding four or five 
ounces of water; mark a line round the middle of 
the neck with the point of a diamond or a file; fill 
the phial up to the mark with river or rain water, 
and poise it with sand or any other substance ina 
scale; then put 1,000 grains’ weight in the same 
scale with the phial, and pour out water till the 
equilibrium is restored. In the vacant space, which 
is evidently equal to the bulk of 1,000 grains of 
water, introduce the soil till the water rises to the 
mark in the neck. Then put into the opposite scale 
grain weights sufficient to restore the equilibrium. 
The number of grains required for this purpose will 
