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sinker to be detached by Brooke’s apparatus was adopted on board the Tuscarora. Sir William has now abandoned the hauling back of the sinker, I believe.
The cups or cylinders, of three different designs, used on board the Tuscarora with the Brooke apparatus, were devised on board, and work so well that mud enough to fill a five ounce vial is sometimes brought up.
The soundings are taken from the gangway, as being nearer the centre of motion than any other convenient part of the ship, and therefore less subjected to the pitching and yawing motion of the vessel.
When it is required to sound, supposing the ship to be under sail, the fires, which have been banked, are spread, and when steam is ready, say in half an hour, the usual time, all sails are furled, and kept in that position by the backing of the engines. In calm or light weather, the use of the engines is only required at intervals, at other times, when the wind is fresh and the sea heavy, they are kept backing all the time, and sometimes at full speed.
Meanwhile the machine has been got ready, and when the ship has lost headway and become steady, so that the wire can run straight down, the sinker is carefully lowered into the water by hand. Then the self-registering thermometer for ascertaing the bottom temperature is attached to the cod-line, and the line is allowed to run out gently until the wire is reached, when the latter is clamped to prevent further egress until a leaden weight of some four pounds can he attached to the ring. This precaution is necessary to prevent the wire flying upwards when the sinker strikes bottom, and relieves the wire of its tension, otherwise, it would be apt to take in kinks and break, as in the other case mentioned.
Now a man has been attending at the pendant with the weights during this time, and, being all ready, the officer in charge has the wire unclamped and lets it run slowly at first; then, when well started, directs some of the weights to be taken off to allow the wire to run more freely, but it is never allowed to run out faster than at the
