The following brief statement concerning “Reh” is chiefly derived from the Report of the Committee on Reh, November 1878:—

Large tracts of country in the north-west of India have from time immemorial been covered with a white alkaline efflorescence, which renders them incapable of supporting any form of vegetable life. These tracts are called “usar” plains, and the white efflorescence “reh.”† The appearance of this reh on the surface is owing to the subsoil water, which is impregnated with sodium salts, being sucked up to the surface by capillary attraction and there evaporated by the fierce heat of the Indian summer sun. The reh is often very irregularly distributed,—bald patches occurring in the midst of cultivation, or cultivated patches surrounded by reh,—and this capricious distribution has rendered a right comprehension of its mode of production difficult.