--+-------+-------+--------+
| Organic matter | 0.25 | 0.24 | 0.16 | 0.06 | 0.63 | 0.56 |
| Carbonate of lime | 0.84 | 0.84 | 1.27 | 0.79 | 0.71 | 0.84 |
| Sulphate of lime | 2.08 | 2.10 | 1.14 | 0.17 | 0.77 | 0.72 |
| Nitrate of lime | 0.02 | 0.02 | 0.01 | 0.02 | 0.02 | 0.02 |
| Carbonate of magnesia | 0.70 | 0.69 | 0.47 | 0.27 | 0.27 | 0.16 |
| Carbonate of iron | 0.04 | 0.04 | 0.04 | 0.02 | 0.02 | 0.01 |
| Potash | 0.02 | 0.02 | 0.02 | 0.02 | 0.04 | 0.06 |
| Soda | 0.11 | 0.15 | 0.13 | 0.10 | 0.05 | 0.04 |
| Chloride of sodium | 0.08 | 0.08 | 0.07 | 0.03 | 0.01 | 0.01 |
| Silica | 0.07 | 0.07 | 0.06 | 0.05 | 0.06 | 0.05 |
+-----------------------+-------+-------+-------+-------+-------+--------+

In order to obtain from these experiments an estimate of the quantity of
the substances actually dissolved, we shall select the results obtained
by Way. The average rainfall in Kent, where the waters he examined were
obtained, is 25 inches. Now, it appears that about two-fifths of all the
rain which falls escapes through the drains, and the rest is got rid of
by evaporation. An inch of rain falling on an imperial acre weighs
rather more than a hundred tons; hence, in the course of a year, there
must pass off by the drains about 1000 tons of drainage water, carrying
with it, out of the reach of the plants, such substances as it has
dissolved, and 1500 tons must remain to give to the plant all that it
holds in solution. These 1500 tons of water must, if they have the same
composition as that which escapes, contain only two and a half pounds of
potash, and less than a pound of ammonia. It may be alleged that the
water which remains, lying longer in contact with the soil, may contain
a larger quantity of matters in solution; but even admitting this to be
the case, it cannot for a moment be supposed that they can ever amount
to more than a very small fraction of what is required for a single
crop. It may therefore be stated with certainty that solubility in water
is not essential to the absorption of substances by the plant, which
must possess the power of itself directly attacking, acting chemically
on, and dissolving them. The mode in which it does this is entirely
unknown, but it in all probability depends on very feeble chemical
actions, and hence the importance of having the soil con