IMPROVEMENTS IN APPARATUS FOR TAKING SOUNDINGS ON BOARD SHIPS
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Josiah Latimer Clark and Edward
Jacob Hill at the Office of the Commissioners of Patents on the 30th January
1878.
JOSIAH LATIMER CLARK and EDWARD JACOB HILL, both of 6, Westminster
Chambers, Victoria Street, London, in the County of Middlesex. "IMPROVEMENTS
IN APPARATUS FOR TAKING SOUNDINGS ON BOARD SHIPS."
The object of our improvement is to enable soundings to be taken from vessels
while they are under way. The instrument we employ for this purpose we term a
"dolphin," and consists of a plate of metal or other material formed like a kite and
provided with two lines, one of which is the towing. line, and is carried to the fore-
part of the vessel; the other line is the sounding line, marked with fathom or other
marks, which is suspended over the side of the vessel farther aft, and is attached to
the tail of the dolphin. The towing line is of wire or other strong material, and is
attached to the centre of the dolphin by a bridle arrangement, or preferably to a
projecting piece standing some distance forward from the face of the dolphin.
The sounding line is also of wire or other material, and is attached to the dolphin
at its tail, and has the same steadying effect as the tail of an aerial kite; it serves
at the same time to indicate and also to regulate the depth at which the dolphin is
submerged.
The dolphin may be made of various forms, and when in use it is passed over
the side of the ship, and the towing line led forward, the dolphin is then allowed
to drop by means of the sounding line, and as soon as it reaches the water it
endeavours to dive downwards, and is allowed to descend by paying out the
sounding line to any depth desired; as often as it touches the bottom the effect is
indicated by the momentary slackening of the strain and the marks on the sounding
line indicate the depth.
.
As this line descends at an angle varying with the length of the towing line, and
also has a slight curvature dependent on the speed of the vessel, the actual depth
is less than that indicated on the sounding line, and this difference is allowed for
either by altering the distance of the fathom marks on the line, or
culation based on actual experiments.
by a simple cal-

page_text: The towing line has also marks upon it corresponding in number with those on
the sounding line, and proportionally adjusted as to length, so that when it is
required to ascertain accurately any given depth, say 10 fathoms, the towing line
must be adjusted to the corresponding 10 fathom mark, and so on. These lines may
be wound on rollers or reels, and the length of wire or rope out indicated on the
roller.
Sometimes we attach a trigger or triggers to the head part of the dolphin, which
are so arranged that as soon as they touch the bottom the towing line is released
and the dolphin rises to the surface towed by the sounding line, the object being
that the ship approaching land may be warned when she has arrived at any given
depth of soundings. As the angle of the sounding line is greatly varied by the
dolphin coming to the surface we utilise this movement by a simple mechanical
arrangement, and cause it to ring a bell, or give similar warning. To effect this we
lead the sounding line through a pully fixed at the extremity of an arm which
projects from the ship; the strain ordinarily comes from forward, but after touching
the ground the dolphin towes aft, and this change of direction causes the arm to
move or to partially rotate on its axis and to start the alarum. The alteration of
strain on the towing line may be utilised in a similar manner,
Sometimes we enclose an electrical conductor in one or both of the lines with a
contact maker attached to the dolphin, so that as often as it touches the bottom
the circuit is completed or broken, and an electric warning given in any part of
the vessel.