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rate of 100 fathoms in 50 seconds, and seldom, at less rate than a minute.
For instance, at the beginning of the mast, the weights on the pendant generally aggregate 90 lbs.—the indication shown by the dynamometer being 37 lbs., and when the wire is going out with the greatest speed admissable the pendant weight is 25 lbs. and the indication shown by the dynamometer 15 lbs.
On the left side of the drum is attached a counter which registers the number of revolutions, and an officer stands with watch and book in hand to note the time of each 100 fathoms running out. The wire has previously been carefully measured as it was wound on the drum, the number of fathoms in each splice being registered in the book; thus when bottom is reached, the depth is known with great accuracy, especially as there is no appreciable stretch to the wire, as there is to rope or cord.
Now when it is supposed the sinker is nearing the bottom, the speed of egress is diminished by replacing the weight up to 90 lbs. or 100 lbs., the dynamometer showing from 35 lbs. to 40 lbs.
The moment the sinker strikes bottom it becomes detached, and the strain which has retarded the descent of the sinker, is now only resisted by the weight of the wire, and pulls back with a force equal to the weight of the shot now resting on the bottom. This causes the index hand of the dynamometer to fly up, and the drum to stop revolving. So perfect and unmistakable are the indications at whatever depth, that a person standing in any part of the ship and looking at the machine, can tell the moment bottom is reached. In reeling in, the dynamometer wheel is unshipped, and the pulley line is shifted for a larger one. The inventor’s plan was to reel in by men hauling in on the pulley line, hand over hand, but after a while a heavy balance wheel was fitted for reeling in on board the Tuscarora, enabling four men to do the work with more ease, facility and quickness, than six men could do it under the old method.
As compared with rope, the time of the running out of
