364 TRANSACTIONS OF SECTION C. 
The discovery of small undamaged foraminifera in the desert sands of 
Barmer and Bikaner by Mr. T. H. D. La Touche * gave the first clue to the origin 
of this salt, for such foraminifera must have reached the heart of the desert 
by wind transportation over a distance of some five hundred miles from the 
coast of Cutch. Consideration of the meteorological conditions of the area 
increased the plausibility of this suggestion; for during the hot dry season, 
from April to June, strong winds blow from the south-west, sometimes with the 
force of gales, especially during the day-time, when, under a scorching sun, 
the salt is absolutely dry and easily powdered. The Rann of Cutch during the 
hot dry season partly dries up and becomes covered with a thin incrustation 
of salt, so that every traveller—man or beast—crushes the hopper-shaped 
skeleton crystals of sodium chloride, forming puffs of fine saline dust, which | 
are wafted away by the strong winds to the north-east and towards the desert 
region of Rajputana. During the hot dry season these winds maintain a con- 
stant direction; they are strong during the day, moderating to a comparative 
calm at nights, but there is never a set-back, and they are followed every year 
by the rainy season, which commences about the middle of June. 
These winds are specially strong near the coast, but they diminish in force 
in the central part of the desert region, and there their load of saline dust 
becomes deposited over the surface of the sand, being washed in solution into 
convenient hollows during the rainy season, thus forming small lakes, which 
become rapidly reduced to bodies of concentrated brine during the next follow- 
ing dry cold weather. 
During the cold weather which follows the rainy season the atmosphere is 
dry, and winds blow generally from the north and north-east. These winds 
are, however, comparatively feeble, and in any case are unable to carry an 
appreciable quantity of salt back to the south-west, as the salt is by then 
accumulated in the lakes, which are seldom completely dry before the com- 
mencement of the next following hot weather, when the recurring south-west 
winds bring in another load of salt-dust. 
By the elimination of all other possible sources of the salt in the lakes of 
the Rajputana highlands, and by consideration of the meteorological conditions, 
a satisfactory theory thus became established to account qualitatively for the 
origin of the salt. It then became necessary to check the theory by a quanti- 
tative test, and this onerous task was undertaken by Dr. W. A. K. Christie, 
with the assistance of M. Vinayak Rao, of the Geological Survey of India, 
during the hot weather of 1908. After some months of preliminary experiments 
with artificial winds to ascertain the best method of collecting samples and of 
determining the limits of experimental error, a laboratory was built in the 
desert, where anemometer records, temperatures, and barometic pressures were 
taken at regular and frequent intervals, while samples of the wind were 
collected at different elevations and analysed. As a result of this work, it was 
found that during four months of the hot dry season of 1908 the amount of 
wind-borne salt passing a front 300 kilométres broad and 100 métres high must 
have been something of the order of 130,000 tons. As the meteorological 
records showed that the hot weather of 1908 was a season of unusually weak 
winds, the figure obtained is probably well below the annual average influx of 
salt-dust. 
Although the results can thus be stated in figures, they refer to one year 
only, and are, in a sense, still only of qualitative value. There is no doubt, 
however, that they establish beyond reasonable doubt the theory which had 
been formulated on wider considerations, both negative and positive, as to the 
origin of the enormous quantities of salt now accumulated in the Rajputana 
desert. 
It is necessary, naturally, to exercise caution in extending this theory to 
other desert regions, some of which are, nevertheless, areas of wind inflow 
during hot dry seasons. It is also significant that rock-salt deposits are 
frequently associated with formations that can best be accounted for as due to 
desert conditions, although such phenomena would be characteristic also of 
' Mem. Geol. Surv. Ind., vol. xxxv., p. 42, 1902. 
