'The Transactions of the Bombay Geographical Society. From January 1865 to December 1867. (Edited by the Honorary Secretary.) Volume XVIII.' [‎98] (234/268)

98
GEOLOGICAL ACTION ON THE SOUTH COAST OE
uThe Gulf of Cambay Is at the head of the great tidal ware
which hows into the Indian Ocean, and is here heaped up in an
extraordinary manner, having a rise of 28 feet during spring
tides, which occur at 5 hours 20 minutes. Full and change at
Cambay. The corresponding node ot this great tidal wave is
at the Maidive Islands.
From an examination of the co-tidal lines drawn from ascer
tained data, It is evident that the tidal wave sets into the Gulf
from a South-Westerly direction, and is in fact a considerable
way up it before reaching the mouth of the Taptee River on the
East shores. There are five large rivers which empty themselves
Into the Gulf of Cambay, and it is from the detritus brought
down by these rivers that the banks are formed at the entrance
into the Gulf. Shallow soundings Measurements of the depth of a body of water. of 20 fathoms only, extend
for a distance of 100 miles beyond the entrance of the GulL
The line of 20 fathoms soundings Measurements of the depth of a body of water. runs from immediately
opposite Bombay in a North-Westerly direction up to the en
trance to the Gulf of Kutch. The waters over this expanse
of sea are thick and muddy, containing matter in suspension, a
portion of which is gradually deposited at the bottom of the
sea, thus increasing the banks. It would be interesting to
ascertain by a comparison of soundings Measurements of the depth of a body of water. at distant periods at
what rate this deposit takes place, but owing to the great tidal
rise and the scouring process going on at the bottom of the
ocean, especially the latter, it is believed that the deposit is
exceedingly slow, and that much of the detritus is carried down
by the ebb-tide along the coast to the node of the tide near the
Maidive and Lacadive Islands.
5C The peculiar scouring and grinding process is very clearly shown
to a depth of 50 fathoms by the soundings Measurements of the depth of a body of water. (see Model Chart)?
though it has usually been assumed that the action of the sea
does not affect the bottom at a greater depth than ten fathoms-—
the effect of the prevailing strong winds can however be traced
to a very much greater depth. By an inspection of the Chart
it is evident from the soundings Measurements of the depth of a body of water. that the greatest effect produced
by this scouring process is on the Eastern side of the Gulf.
Dr. Oldham in his memorandum assumes that the detritus brought
down by the Taptee and other Rivers in the Gulf of Cambay is depo