sorbent power, but that artificial compounds can be formed which act
upon solutions of ammonia and potash in a manner very similar to the
soil; but there is not the slightest evidence that these compounds exist
in the soil, and in the year 1853[I] I pointed out the probability that
clay is not the only agent at work, but that the organic matters take
part in the process. So powerful indeed is the affinity of these
substances for ammonia, that chemists are at one as to the difficulty of
obtaining humic and other similar acids pure, owing to the obstinacy
with which they retain it; and there cannot be a doubt that in many
soils these substances are in this point of view of much importance.
This is particularly the case in peat soils, which, though naturally
barren, may be made to produce good crops by the application of sand or
gravel; and as neither of these can cause any absorption of the valuable
matters, we must attribute this effect to the organic matter. Referring
to an earlier series of experiments made in 1850, I showed that, if a
quantity of dry peat be taken and ammonia poured on it, its smell
disappears; and this may be continued until upwards of 1.5 per cent of
dry ammonia has been absorbed, and this quantity is _retained_ by the
peat.

In this case pure ammonia was used, but Way's experiments having shown
that this alkali is not absorbed from its salts by organic matters, I
expressed the opinion that humate of lime (which certainly exists in
most soils) ought on chemical grounds to decompose the salts of ammonia
and cause the retention of their base. The recent researches of
Brustlein have shown that lime does cause the organic matters to absorb
ammonia from its salts. He confirms the fact that pure ammonia is
absorbed by peat, and shows that decayed wood has the same effect,
although both are without action on solutions of its salts. A stiff
clay, on the other hand, containing organic matters and much carbonate
of lime, readily absorbed ammonia, both when pure and combined; but
after extracting the lime by means of a dilute acid, it lost the power
of taking it from its salts, although it retained the free alkali as
completely as before. On the addition of a small quantity of lime, it
again acquired the power of withdrawing ammonia from its compounds.
These experiments may be explained, either on the supposition of the
presence of humate of lime, or by supposing that the carbonate of lime
first decomposed the