'Transactions of the Bombay Geographical Society, from September 1850 to June 1852. Edited by the Secretary. Volume X.' [‎209] (342/458)

s > marked 1
^ detaclied|i
laterite. Aftert;
rocks in contiti
jable, that fc;i
autiful specitui!
in its viscous I
is been sliglitljls
jxture obliteratfil
i is the correct I
jcasionally top
n coated witlil
th other roct ' 4
urnish a caW'
properly ®i»*|
ion ofttoS**
j, and
from ''l |atll,il '
to be met” 11 ';;
1 atsofc’ f °l
SUPPLIES OF WATER. 0
- uy
ties present themselves of having these carefully examined. I have
already instanced the case at Sewree, where so beautiful an example
presents itself between two beds of stratified rock, fusing the upper
part of the lower, and the lower surface of the upper beds, into a
hard flinty matter. Generally speaking, however, the sedimenta’ry rock
has been but slightly altered. At the line of junction, at the Baboola
Tank, all the most beautiful of the minerals are to be found, and here
cavities and veins of spar are occasionally to be detached in the semi-
fused stratified rock. The trap just under this is full of cavities with
veins of from a few lines to half an inch in diameter, runnino-
downwards sometimes for several feet, when they disappear ; and
this holds also along the face of the rock at Nowrojee Hill, and in
the wells in the Jail compound,—and probably at every point through
out the island where the stratified rock and trap meet together without
disturbance. The lower strata of Baboola Tank and Nowrojee Hill
are very little affected by the volcanic matter, the carbonaceous
matter still remaining in them in abundance. Along the line of
Railway the two varieties of rock are so confused and intermingled
that it is difficult to see where the line of junction occurs, a mass of
tuffa intervening which seems sometimes trappsean, sometimes sedimen
tary. It may be laid down as a general rule, that where trap has been
forced upwards, and has affected the sedimentary rock, it has itself
always been much altered, and rendered cavernous and irregular.
This is readily observed at the sluices and at Breach Candy, where
the denudation has left its surface exposed.
SUPPLIES OF WATER.
When it is considered that the annual evaporation over the island
amounts to about 70 inches, or close upon the average of the annual fall
of rain, and that for eight months during the year scarcely a shower
ever reaches us, the capacity of the Island of Bombay for preserving
water (adequate to the supply of nearly half a million of people located
elose together upon little more than ten square miles of ground) must
be very remarkable. Our Marine and fresh water formations seem to
constitute reservoirs ; the volcanic rocks preventing easy exit, and to some
extent cutting them off from the sea. The basalt is nearly destitute
water, although wells are now formed in it in abundance on
I