In many parts of South
America, wherever the climate is moderately dry, these
incrustations occur; but I have nowhere seen them so abundant as
near Bahia Blanca. The salt here, and in other parts of Patagonia,
consists chiefly of sulphate of soda with some common salt. As long
as the ground remains moist in the salitrales (as the Spaniards
improperly call them, mistaking this substance for saltpetre),
nothing is to be seen but an extensive plain composed of a black,
muddy soil, supporting scattered tufts of succulent plants. On
returning through one of these tracts, after a week's hot weather,
one is surprised to see square miles of the plain white, as if from
a slight fall of snow, here and there heaped up by the wind into
little drifts. This latter appearance is chiefly caused by the
salts being drawn up, during the slow evaporation of the moisture,
round blades of dead grass, stumps of wood, and pieces of broken
earth, instead of being crystallised at the bottoms of the puddles
of water.
The salitrales occur either on level tracts elevated only a few
feet above the level of the sea, or on alluvial land bordering
rivers. M. Parchappe found that the saline incrustation on the
plain, at the distance of some miles from the sea, consisted
chiefly of sulphate of soda, with only seven per cent of common
salt; whilst nearer to the coast, the common salt increased to 37
parts in a hundred.
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