The grapnel just described we had in use on the Minia since April last. We have tried it severely, and have never known it to fail. No swivel has been used with the rope, in the heart of which is the insulated wire, as it would allow the grapnel to turn over on the bottom, and would be apt to twist and break the wire short off. As a matter of fact, the grapnel will turn, and does turn, with the rope; a swivel is therefore of no value. We are perfectly awake, however, to the fact that a grappling-rope should be made in a manner that will not allow it to kink; and engineers should avail themselves of such rope, especially in deep water. Patents have lately been granted to Messrs. Trott & Hamilton for the invention of a form of rope or cable answering all the requirements of this work.
A small type of grapnel fitted in the manner I have described may be very advantageously used for searching purposes, to ascertain the position either of telegraph or torpedo lines; by towing at a quick rate much time may be saved. The position being ascertained, if it be not desired to lift the cable, the grapnel can be released and hove on board by a tripping line, which can always be attached when such work is contemplated. The great importance of being able to localize an enemy's torpedo lines without raising an alarm will be readily seen by engineers engaged in torpedo work.
REFERENCES TO THE DIAGRAMS.
a, stem of the grapnel containing core; b, flukes; c, recess for insulated contact-plate connected to core; d, covering plate screwed on bottom of grapnel; e, button of plug; f, rubber washer and button; g, metal-plate; h, stem of plug, on which in the under counter-sink, U is a small metal disk which prevents the fittings from fallings out; i, needle; j, spring; k, counter-sink for head of plug; l, counter-sink for spring.
HUGHES' NEW MAGNETIC BALANCE.
A new magnetic balance has been described before the Royal Society by Prof. D. E. Hughes, F.R.S., which he has devised in the course of carrying out his researches on the differences between different kinds of iron and steel. The instrument is thus described in the Proceedings of the Royal Society:
"It consists of a delicate silk-fiber-suspended magnetic needle, 5 cm. in length, its pointer resting near an index having a single fine black line or mark for its zero, the movement of the needle on the other side of zero being limited to 5 mm. by means of two ivory stops or projections.
