52 
Records of the Geological Survey of India. 
[vol. vm. 
not more than 15 or 20 feet in depth; those at the village, which is, I think, on rather 
lower ground, are double that depth. It appears evident that the water in the bun¬ 
galow wells is derived from the sand resting upon the comparatively impervious black soil, 
and that the water in the sand is sweet, because any salt originally contained in the porous 
sand has long since been washed out of it, as water can percolate it freely in descending to a 
lower level. 
I am informed by Mr. Clarke, the Executive Engineer, that the case at Yaux’s tomb, 
especially mentioned in Mr. Hope’s letter, is precisely similar to Dumas, whilst at Bhugwa 
Dundee, where no good water could be found, there are no sand hills. If my explanation be 
correct, the sinking of deeper wells at the Dumas bungalows or at Yaux’s tomb will probably 
result in brackish water being found in the beds underlying those which now supply the wells. 
The other difficulty to which I have referred is the existence of numerous wells in vari¬ 
ous parts of the country, the water of which is said to have become gradually salter. This is 
rather opposed to the view above expressed, because it is probable that percolation removes 
the salt in any given stratum, and consequently wells should become sweeter by use if they 
undergo any change; that is, provided that the water always finds its way from the surface 
into the wells by the same route, and traverses the same beds in its course. But the removal 
of water from a well may occasionally produce an inflow from other strata than those from 
which the supply was originally derived, and thus salter water may be introduced. The 
question is a difficult one, and 1 think some further information on the subject of wells 
becoming salter is desirable. In the first place, I think the evidence of increasing saltness 
in wells should be rather carefully examined ; of course no analyses of the water have been 
made, and, so far as I can learn, complaints about water becoming salt have been frequently 
made in order to obtain remissions of rent, as irrigated land is more highly taxed than land 
which is not irrigated. I should like to suggest the possibility that, in some cases at least, 
the change has not been in the water, but in the soil of the fields. As all the well water 
contains salts in solution, and as the water poured upon the land is evaporated, leaving the 
salts behind, a gradual concentration of the salt must take place in irrigated lands until 
it may, unless remedial measures be taken, become so saturated as to be unfit for cultivation, 
as in the case of the‘reh’ lands of Upper India. In this case the blame would infallibly 
and justly be laid on the water used for irrigation, although no increase has really taken 
place in the saline impurities contained in the water. 
I cannot say how far the wells in and around Surat represent those of the district 
generally, but if they do, I may add that the impurities of the water are not confined to 
common salt (sodium chloride). Some rough tests which I have applied with such means 
as were available showed the presence of lime, alumina, and of an alkaline earth, which I 
believe to be magnesia, in considerable quantities. 
If the views above expressed are correct, it is evidently improbable that better water 
will be obtained by deep boring, unless the strata at a depth below the surface are much 
more permeable than the superficial deposits ; on the contrary, the deeper beds will have had 
less chance of being purified from salt by percolation than those near the surface. Where 
the beds at a greater depth are very porous, they may contain sweet water, but this is by 
no means certain, and I can see no reason for anticipating that the lower strata will prove 
very different in character from those exposed at the surface of the ground. Should rock 
be found, it is impossible to form an opinion without actual trial as to what the character of 
the associated water may be. The rock may very possibly belong to the lower tertiary 
strata, and similar beds in Kachh and Sind often yield brackish water. 
Before concluding I may briefly advert to the water-supply of the town of Surat, to 
which my attention has been particularly drawn. I went over the town with Mr. Pandurang 
