0.08 0.02
Peroxide of iron 4.45 6.68
Alumina 2.40 3.00
Lime 1.23 1.33
Magnesia 0.45 0.25
Potash 0.20 0.22
Soda 0.07 0.09
Sulphuric acid 0.05 0.08
Phosphoric acid 0.38 0.07
Carbonic acid 0.09 0.34
Chlorine trace trace
Humic acid 0.42 0.43
Humine ... 0.10
Insoluble organic matters 3.70 3.61
Water 2.54 2.52
---- ----
99.96 100.08
Nitrogen 0.15 1.15

In this instance such difference as exists is rather in favour of the
soil on which clover fails, but it is exceedingly trifling; and it is
necessary to seek an explanation in the special properties of its
mechanical constituents.

These properties are partly mechanical and partly chemical, and in both
ways exercise an important influence on the fertility of the soil.

Sand and clay, the most important of the mechanical constituents, confer
on the soil diametrically opposite properties; the former, when present
in large quantity, producing what are designated as light, the latter
stiff or heavy soils. The hard indestructible siliceous grains, of which
sand is composed, form a soil of an open texture, through which water
readily permeates; while clay, from its fine state of division, and
peculiar adhesiveness or plasticity, gives it a close-textured and
retentive character, and their proper intermixture produces a light
fertile loam, each tempering the peculiar properties of the other.
Indeed, their mixture is manifestly essential, for sand alone contains
little or none of the essential ingredients of plants; and if present in
large quantity, the openness of the soil is excessive, water flows
through it with rapidity, manures are rapidly wasted, and on the
accession of drought, the plants growing upon it soon languish and die.
Clay, on the other hand, is by itself equally objectionable; the
closeness of its texture prevents the spreading of the roots of plants,
and the access of carbonic acid,