| } 6.63 | 5.05 | 0.08 | 1.17 |
| Alumina | } | 8.18 | 0.39 | 0.41 |
| Phosphate of Iron | 0.58 | 1.04 | trace | 0.28 |
| Silica | ... | 9.05 | 0.14 | 2.77 |
| Sand and Stones | 29.15 | 55.87 | 95.91 | 84.97 |
| |---------|--------|---------|--------|
| | 100.00 | 100.00 | 100.00 | 100.00 |
+---------------------------------+---------+--------+---------+--------+

It is easy to understand the importance of the effects produced by
adding to any soil large quantities of a mud containing upwards of one
per cent of phosphate of iron; and in point of fact, Herapath has
calculated that in one particular instance the quantity of phosphoric
acid brought by warping upon an acre of land, exceeded seven tons per
acre. As, moreover, the matters are all in a high state of division,
they must exist in a condition peculiarly favourable to the plant. The
overflow of the Nile is only an instance of warping on the large scale,
with this difference, that it is repeated once only in every year,
whereas, in this country, the operation is repeated at every tide until
a deposit sometimes of several feet in thickness is obtained, after
which it is stopped, and the soil brought under ordinary cultivation.

An operation which is, in some respects, the converse of warping, has
been carried out on Blair-Drummond Moss, where the peat has been
dislodged and carried off by the action of water, leaving the subjacent
soil in a state fitted for cropping. Of course both this and warping are
restricted to special localities, but they are most important means of
ameliorating the soil when circumstances admit of their being carried
out.

_Mixing of Soils._--When soils possess conspicuous defects in their
physical, and even in their chemical properties, great advantages may,
in some instances, be derived from their proper admixture. A light sandy
soil, for instance, is greatly improved by the addition of clay, and
_vice versa_; so that, when two soils of opposite properties occur near
to one another, both may be improved by mixture. It has been applied to
the improvement of heavy clay soil and of peat, the former being mixed
with sand or marl so as to diminish its tenacity; the latter with clay
or gravel to add to its inorganic matters, and in both insta