'Transactions of the Bombay Geographical Society, from September 1850 to June 1852. Edited by the Secretary. Volume X.' [‎204] (337/458)

204
GKOLOGY OP BOMBAY.
water flowing, a flow proceeds from them which forms a considerable
rivulet from fifty or a hundred feet of outcrop. Of this I shall have
occasion to speak more fully when I come to treat on the subject of
water. These beds I believe extend over the whole length of the
island, and probably into Salsette : they are generally hid under
alluvial matter, and the wells in this quarter are few in number, and
mostly old.
THE CHERT DYKE OF SEWREE AND MATOONGA HILL.
51.—Unless very closely examined, the black rock which constitutes
the promontory on which Sewree Fort is built may be mistaken for
basalt, similar to that of Malabar Hill : a narrow inspection discloses
the unexpected fact that it is black jasper or Lydian stone—-it has the
same specific gravity as jasper, strikes fire with steel, is luminous when
rubbed in the dark and gives out a strong sulphurous smell—it scratches
glass, and breaks with an uneven eonehoidal fracture. It still shows
considerable tiaces of stratification, especially towards the northern
end of the mass ; the dip is at an angle of about 25°, or double that
of the locks adjoining, and it is split across into semi-prismatical masses.
The Sewree mass is about 200 feet across, 1000 in length, and 40 or
50 m elevation. It suddenly disappears on the verge of the salt pans,
but a thin vein of it can be traced for nearly two miles to the north-
westwaid, where it leappears in mass, forming a considerable hill to
the southward of Matoonga burying-ground, on the margin of the
creek betwixt the rice fields and the salt pans—beyond this I have,
not been able to tiace it towards Sion. The rock decomposes very
slowly, and affbids a poor arenaceous debris: its surface yields
scarcely any sustenance to vegetables-the palmyra is the only
tiee that giows on it, and the short grass which covers it during
the rainy season vanishes on the return of the dry weather. It
is too haid foi a building stone, and too sharp and splintery and
difficult to bed for road metal. The heat to which it has been sub
jected has nearly obliterated all traces of stratification, and of course
extinguished every appearance of organic matter. It seems as if it were
the remains of beds lower than any we have described—subjected to
semi-fusion, and forced up from beneath. Betwixt this and the island
of Trombay is a sludgy creek, here nearly three miles across, and
^ tan ;
ji*!®' 1 * °
jJasaH.—^
,i is in all like!
uiscdementary :
jitle island and
taiption of Bon
| tali; and gre
hraess in this :
i I have inci
ilbise to arise,
lumbers, with 1
LBasalfc,—Tb
swall from Ma
fcst perfectly 1
Malabar Hill ov<