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Proceedings of the Royal Society 
mode of production difficult. It seems certain, however, that its 
appearance depends chiefly on the distance of the water-table from 
the surface of the ground and upon the nature of the intervening soil. 
When reh exists in the soil it is more largely developed on a 
surface where the water level is nearer the surface ; while, on the 
other hand, a soil of a close texture, — a clay soil, for instance, — 
may prevent the formation of reh by hindering the upward passage 
of the water, even where the water-table is comparatively near the 
surface. Of course anything which affects the rapidity of evapora- 
tion must affect the rapidity with which the reh accumulates, so 
that the cutting down of trees, and thus exposing the surface of the 
soil to the unmitigated action of the sun’s rays, has an injurious 
effect and tends to promote the formation of the efflorescence. Until 
lately an equilibrium of reh distribution was established, at all 
events approximately. The great usar plains which have existed 
from unknown times did not increase in extent or change their 
position ; but it would seem that by the introduction of the canal- 
irrigation system this equilibrium has been disturbed. The Western 
Jumna Canal — which runs from the Jumna, where it leaves the 
hills, down as far as Delhi — has developed large tracts of reh, land 
which was formerly cultivated and fruitful being covered with it, 
and the same process has begun and is going on with alarming 
rapidity on the Ganges and Eastern Jumna canals in the country 
between the Jumna and the Ganges. The evil is of great magni- 
tude, and large tracts of fertile land are fast becoming waste and 
unproductive, and the condition of the people and their cattle is 
deteriorating in consequence. Two years ago a committee was 
appointed by Government to discover the cause or causes of the 
evil, and suggest, if possible, some remedy. As the result of their 
deliberation, it is established beyond doubt that this new production 
of reh is chiefly, if not solely, caused by the system of canal irriga- 
tion as at present carried out. In the first instance, the level of 
the salt-impregnated subsoil water has been much raised, so as to be 
more readily drawn up to the surface by capillary action and there 
evaporated, leaving the salts it held in solution as a crust on the 
surface. There seems to be some difference of opinion amongst the 
members of the committee, as to whether this is chiefly due to 
percolation from the bottom and sides of the canals, which are at a 
