"64 
Records of (he Geological Harvey of India, 
[vOL. XIII. 
Bhort distances. Possibly many of the sheets of clay may have more or less of a 
basin form. The important points for us to remark in considering the surface 
and sub-soil drainage are that this immense plain has an average breadth of 
about 200 miles, that practically the Gangetic and Punjab plains are one, the 
water-shod between the two being only perceptible bj' accurate scientific measure¬ 
ments, and that its length is about 1,200 miles. There are also no deep natural 
sections exposing outcrojjs of the deep strata so as to allow of escape of under¬ 
ground w'ater to the sea. In consequence of the very small surface slope, and 
on account of the horizontal disposition of the strata over such an enormous 
area, the conditions as regards drainage approach to those of a basin. The sur¬ 
face drainage is weak, but ultimately finds its way by the rivers to the sea, but 
the underground drainage is usually imperceptible. 
22. As regards the production of elHorescences, we have further to consider 
that in the Punjab there are three belts of plain. That adjoining the hills, the 
sub-montane tract, has a plentiful rainfall and moister air; south of this is a 
sub-desert tract with small rainfall, and still further south is the desert country 
with deficient rainfall. In the sub-montane belt the rainfall is sufficient to scour 
the surfa,ce, and as it is more permeable from the presence of gravel and sand, 
and has greater slope, the surface and subsoil drainage are more efficient. In 
the other two tracts the working of these agencies is defective. In the hills 
themselves the annual rainfall of a series of years is as follows: Murreo, 66-8 
inches; Dharmsala, 123-2 inches; Simla, 68-6 inches. This does not include 
snowfall however. In the sub-montane belt we would have—RawaljDindi, 
32 inches ; Sialkot, 39-3 inches ; Gurdaspur, 33-1 inch ; Hoshiarpur, 36-5. Of 
the less-watered region there is Lahore, with 19-3 inches; Shahpur, 14-5 inches ; 
Sirsa, 14-5 inches ; while about Mooltan the rainfall is 6-9 and at Dera Ismail 
Khan 8 2. 
23. The simplest case to consider is that which occurs in the more desert 
country, in which the rainfall is only enough to moisten the surface and promote 
decomposition. If the soil is sandy the dissolved salt is carried down to the un¬ 
derground water and the accumulation takes place there. If the ground is not 
porous, as where clay predominates, only the upper portion is soaked, and on 
drying the soluble salts arc brought to the surface. Instances of both these cases 
are found everywhere along the southern portion of the Punjab plain. In the 
middle portion of the plain, where the rainfall may go up to 20 inches, similar 
actions take place. The first drops of rainfall dissolve any efflorescence and 
sink into the gi-ound, carrying it out of the reach of surface scour, which on 
account of the flatness of the plains and small rainfall is slight. In the more 
porous portions the salt is earned down to the undergi’ound water; in the 
more impermeable it is brought to the surface by evapoi-ation. It thus hajipcns 
that in certain places there is a scum of efflorescence on the sui-face, while 
generally the ground water is saline. These remarks apply to the Doab or 
Lhangar land, the more elevated part of the plain lying betwen adjacent rivers. 
In this the water lies at a considerable depth, from 30 to 100 or more feet, and is 
more or less saline ; in many places on digging deeper to another stratum fresher 
water is found. In the other great plains of the earth where the climate is dry 
