i54 
Becords of the Geological Survey of India. 
[vOL. XIII. 
Basin and oilier parts of America, and of the methods used to reclaim them, I 
hog to submit a feiv notes on my observations. I am indebted to Captain Ottley, 
of the Irrigation Department, and Mr. Miller, Secretary to the Financial Com¬ 
missioner, for access to the literature on the subject in the form of reports to 
Government. I propose considering more especially the chemistry of the pro¬ 
duction of those salts and the conditions of their accumulation in soils and in the 
underground water,—points intimately connected with each other, and equally 
important in the agricultural and sanitary aspects. The efflorescences consist 
chiefly of sodium chloride and sulphate in varying proportions. In addition 
there is sometimes carbonate of soda, and I have usually found some magnesian 
sulphate. In certain localities the last-named salt is in very considerable propor¬ 
tion. In other cases nitrate of lime or alkali is present. 
2. Various theories have been started regarding the origin of these efflores¬ 
cences, the oldest being probably the marine theory. 
Marine theoiy. According to this the Indo-Gangetic depression was con- 
sidei-ed to be an old sea bed, the soil of which became impregnated with salts 
from the existence of shallow “ rans ” and lagoons in a former geological age. 
In favour of this it might be mentioned that there is certain geological evidence 
that an Eocene sea covered the Punjab plain, its shore coinciding with some 
part of the outer slope of the Himalaya, with a gulf or gulfs penetrating the 
mountains as far as the valley of the Upper Indus. On the other hand, to the 
east of Knmaun and to the north of the Gangetic valley, the situation of this 
shore line is obscured till the Assam region is reached, The theory of recent 
marine impregnation is now entirely to bo abandoned. It is proved beyond 
doubt that the whole of the materials of the Indo-Gangetic basin are fresh water 
alluvia to an unknown depth, and consist in fact of the debris of the Himalayas 
carried down by its drainage and deposited in this immense depression. There 
are no deep natural sections in which to observe the structure, but in the Umballa 
boring of 701 feet, the Calcutta boring of 481 feet, and that near Eajanpur of 464 
feet, nothing but fresh-water alluvia were met. We do not speak here of the Salt 
Eange region, in which are accumulations of salt as old as the Silurian period. 
3. The true origin of reh or alkali efflorescence is the decomposition of the 
^ elements of rocks and soils which is continually going on 
rue origin . Tender the action of air and water. The accumulation of 
the resulting salts in superficial soils or in subsoil waters depends on various con¬ 
ditions of chemical constitutions and permeability of soils, and on the nature of 
the surfaee and subsoil drainage, which will be considered in detail. 
4. If the rain water that runs off the surface of the hills be examined, it is 
Decomposition in liill found to have washed out appreciable amounts of soluble 
regions. salts, chiefly carbonate of lime and alkaline chloride and 
sulphate. If such water runs off crystalline or schistose rocks, the amount of 
salts washed out may be extremely small,—even 2 grains per gallon, as at 
Dalhousie. If it runs off a loose decomposing rock the quantity may be consider¬ 
able,—for example, 8 grains near Murree. The rainfall that percolates the debris 
of the decomposed rock which covers the surface of the hill-sides and fills up the 
channels of ravines issues in springs at lower levels, and is found to contain 
