twenty hours without water, and only part of the time under
a hot sun, yet the thirst rendered me very weak. How people
survive two or three days under such circumstances, I cannot
imagine: at the same time, I must confess that my guide did
not suffer at all, and was astonished that one day's
deprivation should be so troublesome to me.

I have several times alluded to the surface of the ground
being incrusted with salt. This phenomenon is quite
different from that of the salinas, and more extraordinary.
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 saltpeter), 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 crystallized
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 [7] found that the saline incrustation on the plain,