through these deposits towards the surface, becomes saturated with
their alkaline salts; and, as it reaches the surface and becomes
evaporated in the pure state, it leaves them behind at or near the
surface. On its way to the surface, or at the surface, the chloride
of sodium becomes decomposed by contact with _carbonates of ammonia
and potassa--sulphuric and nitric acids_. In a soil well supplied
with decaying animal or vegetable matter, these carbonates or
sulphates of soda, as they rise to the surface, might be formed into
nutriment for plants, and taken up by their roots; or in one well
flooded occasionally with fresh water, any superabundance of the
salts or their bases might be taken up in solution and carried off.
The people say, that the soil in which these carbonates of soda
(reha) abound, are more unmanageable than those in which nitrates
abound: they tell me that, with flooding, irrigating, manuring, and
well ploughing, they can manage to get crops from all but the soils
in which this _reha_ abounds.

The process above described, by which the bracelet makers extract the
carbonates of soda and potash from the earth of the small, shallow
tanks, is precisely the same as that by which they are brought from
the deep bed of earth below and deposited on or near the surface. In
both processes, the water which brings them near the surface goes off
into the atmosphere in a pure state, and leaves the salts behind. To
make soap from the reha, they must first remove the silex which it
contains.

There are no rocks in Oude, and the only form in which lime is found
for building purposes and road-pavements is that of kunkur, which is
a carbonate of lime containing silica, and oxide of iron. In
proportion as it contains the last, the kunkur is more or less red.