290 
PROCEEDINGS OF SECTION B. 
The determination especially of the quantities of nitrates, of 
ammonium compounds, and of “ organic” nitrogen provides us with 
no information to the purpose, for these, of all soil constituents, are 
most rapid in their changes. 
Further difficulties present themselves in the large quantities of 
soil which it is necessary to employ in the determination of the sub- 
stances soluble in water and weak acids, and the consequent length of 
time required for each determination, and also in the initial difficulty 
which presents itself in all soil analysis of ensuring the proper 
selection of a sample which shall represent anything but itself. 
This difficulty, which is felt in all attempts to judge of the 
character of a soil from a given sample, applies more particularly to a 
chemical analysis, and increases in proportion as the quantities of the 
estimated substances diminish. 
A chemical analysis alone, therefore, is of little value in guiding 
the farmer as to the requirements of his soil, and it is not in the 
refinement of chemical methods that we may look for help in this 
direction, We shall, I believe, obtain much more valuable information 
if we can ascertain the conditions under which the fertility of the soil 
is maintained. 
The fertility of a soil depends in the first place upon the presence 
of a sufficiency of plant food, and secondly upon certain properties, 
possessed more or less by all soils, which effect the splitting up of the 
mineral ingredients in such a manner as to render them available to 
plants, as well as regulating the supply of water, air, warmth, &c. 
We shall discuss the most important of these properties, and shall 
find, I think, that they are capable of identification in the laboratory. 
A large number of those properties conducive to fertility are 
dependent upon the porosity of the soil ; in other words, its fineness 
of texture. 
Bv the porosity of a soil is meant the fineness and number of 
its pores. We must distinguish between this and permeability to 
water ; a coarse sand, for example, being permeable to water, but 
possessing properties exactly opposed to those of a porous soil. Humus 
soils are especially porous. On the fineness of texture depend the 
following characteristics : — 
The capillary power , by which is understood the power of imbibing 
water. This property maintains a continual circulation of water 
within tho soil, and consequent aeration. It is, moreover, largely 
through the agency of this circulating water, which is charged with 
carbonic acid and different salts, that the mineral, and in a less degree 
the organic matter, of the soil is rendered available for plant food and 
presented in solution to the plant. 
The capillary power of a soil depends very largely upon the fineness 
of its texture. The nearer the texture approaches that of a sponge the 
greater will be its capillarity. 
Humus has a very high capillary power, which is not possessed to 
a*ny extent by either coarse sand or clay. 
This property is determined by filling a tube of known length 
with the finelv powdered air-dried soil ; the tube is open at both ends, 
the lower end being closed by a piece of fine muslin, and stands in 
