'Transactions of the Bombay Geographical Society, from September 1850 to June 1852. Edited by the Secretary. Volume X.' [‎108] (129/458)

PROCEEDINGS OF THE SOCIETY, June 17.
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The Ordinary Monthly Meeting of the Bombay Geographical Society was held in their Rooms
Town Hall, on Thursday the 17th June, 1852. Commodore Sir Henry J. Leeke, Kt'
President in the Chair.
The Minutes of last Meeting were read and confirmed.
Submarine-Current Measurer. —An instrument contrived by Dr. Buist for determining
the direction and velocity of currents under the surface of the sea, was laid on the table and
explained to the meeting. This instrument, as first constructed, had been before the Society
nearly two years since: an account of it would be found in the ninth volume of the Transactions
The principle of the first was very nearly the same as that of the second instrument, but the
whole details were altered,— Captain Campbell having ascertained by experiment that it was next
to impossible to exclude the water at great depths from the compass-box, and it appearing that
the traversing of the needle was but little affected by water, and that steel might be protected
either by electrotype gilding or by varnishing,—so the attempt to exclude the water was given
up, and it was freely admitted. Under these considerations, and with an alteration in the con-
trivance for measuring the velocity, the whole became capable of infinite simplification. The
instrument as it now stands might be constructed for from Rs. 30 to Rs. 50, according to the
style in which it was made up. It consisted of a heavy lead or sinker, A B,two inches in
diameter and 14 in length, and about 15 lbs. in weight. A hollow cylindrical compass-box of
brass was slipped over the upper end of this, and made fast with screws. In this was a small
pocket compass,—the brass card and needle protected by varnish ; a lever arm for clamping the
needle terminated in a small brass eye at G. The whole could be removed and taken to pieces
to be dried or cleaned, without trouble : this was the direction posture of the implement. On
the lower end of the sinker or lead was a copper vane, D, 14 inches long and 5 across, with a
counterpoise at C : the whole looked like an inverted weather-cock, and when lowered down to
any depth would of course turn in the direction of the current. A square hole was cut in the
vane about one-third out from the cylinder—as near to it as to be beyond the reach of the eddy
or dead water the cylinder itself might create. A fly like that of a window ventilator, or the
vane of a patent log, was fitted up on an horizontal axle, turning on points to avoid friction:
on this was a single thread or helix of a screw, which moved a vertical wheel of sixty teeth,
also turning on points to avoid friction—-the fly was three inches, the wheel it turned two in
diameter. Over this was a simple latch like that of a door—it was loaded at the extremity E,
and might be lifted from close by the fulcrum near the other extremity next to the cylinder.
A brasswire was attached to the latch, and this passed through the eye of the compass clamp at
G.—A stop or bead was here fixe ! upon it, by means of which it lifted the clamp and made fast
the needle, leaving it so while it dropped the latch, which fell down and clamped the fly. The
whole apparatus was suspended by a set of copper wires bound together every six feet by a fine
brass wire, so as to be kept close as one, but within any twisting such as might occasion a
tendency to turn round the vane. The copper wire rope as it may be termed was made up in
lengths of fifty feet, united together by simple couplings, and might be employed to any extent
that was required. The brass wire H F, which formed the lanyard, passed through a series of
small loops along the line of the copper wires so as to slide through them without difficulty : when
the whole was to be used the needle was unclamped and the fly left clamped by the latch E.
It was lowered over the ship’s side, care being taken that the brass wire remained perfectly slack,
when the proper depth was attained, say fifty or five hundred feet, it was allowed a few minutes
to swing freely, and so settle steadily in the direction of the current. The brass wire was now
gently pulled up to a mark indicating that it had performed its task—a minute glass being at the
same time turned—when the sand was run out, the wire was let go, and the whole hauled up.
By the pull on the brass wire the needle was at once fixed, and remained so while the fly was