62 



NATURE 



[May 1 8. 1882 



A full account of this particular worm, with anatomical 

 illustrations, is given in the Journal of the Royal Micro- 

 scopical Society for October, 1881, by Dr. Charles 

 Stewart, secretary of the Society. The bore-holes, after 

 passing through the oakum of the inner sheathing, either 

 pursue a tortuous course along the surface of the gutta- 

 percha core, or go right into the copper wire, thereby 

 causing a " dead earth " fault. Dr. Stewart classes the 

 worm as one of the Eunicidas, but proposes for it the 

 generic name of Lithognatha worslei, because of its pos- 

 sessing a pair of calcareous mandibles or cutting jaws, 

 and after Capt. VVorsley, the Commander of the repairing 

 ship which picked up the worm-eaten cable. The pair of 

 calcareous jaws, in addition to three pairs of chitinous 

 ones, is the most remarkable feature about the animal, 

 and the white plates which form them make the creature 

 look as if it were in the act of swallowing a tiny bivalve 

 shell. 



The best protection hitherto formed against it is to 

 cover the core with a ribbon of sheet-brass, laid on with- 

 out a lap. First the gutta-percha is covered with cloth, 

 then the brass is overlaid. Canvas is then put over the 

 brass, and the hemp and iron wires over all. A close layer 

 of iron wires is not a sufficient protection, for the worm 

 can sometimes wriggle in between the wires where they 

 are not close enough ; and, moreover, the rapid decay of 

 iron wires in tropical seas is certain to leave the core a 

 prey to these pests in a few years. 



The Eastern Extension Telegraph Company also ex- 

 hibit some interesting samples of stones picked up from 

 the sea-bottom; for example, limestone blocks and shells 

 bored by the bivalve, Saxicava ragosa, the worm 

 Sabella, and the sponge Hymeniacidon celata ; wood 

 honeycombed by the teredo, a red stone pitted by the 

 bivalve shell (pholas), and a ferruginous flaky stone 

 brought up from the bottom between Penang and Singa- 

 pore. Most interesting, however, of these inanimate 

 waifs is a flat piece of black flinty rock hollowed into cup- 

 like pits by the sucking feet of the sea-hedgehog. The 

 pits are excavated as lairs for the animal and some of 

 them are nearly three inches in diameter by one inch 

 deep. To make the rocky bed softer to the feel, the 

 hedgehog has lined it with a calcareous enamel, probably 

 secreted by its body, much in the same way as the pearl 

 oyster coats its shell. 



In the earlier days of submarine telegraphy, Sir 

 William Tho.nson declared the life of a cable to 

 be practically inviolable ; and Robert Stephenson, on the 

 other hand, was of opinion that no cable would last out 

 ten years. The latter view has proved the more cor- 

 rect, for the average life of a cable hitherto has been 

 about eleven years. Thanks to the improved means of 

 repairing them, however, the outbreak of faults does not 

 mean the loss of a cable, for these flaws can be cut out in 

 water, however deep, and the cable put to rights again. 

 Indeed every cable company expects a recurrence of 

 faults, and provides a fully-equipped repairing ship always 

 on the spot. A fine model of such a ship is exhibited by 

 the Po t Office, after the designs of Mr. R. S. Culley. 

 Messrs. Johnson and Phillips also exhibit a variety of 

 buoys and grapnels for cable operations. The ordinary 

 grapnel is liable to have its prongs broken off in dragging 

 over a rocky bottom, as may be seen from one exhibited 

 which had every prong bent back among the coral reefs 

 of the Brazilian coast. Centipede grapnels are therefore 

 fitted with removable prongs ; and Mr. A. Jamieson has 

 invented a grapnel with spring teeth which bend back 

 when they meet a rock, so as to slip over it, but catch 

 and hold th? cable. A sample of this grapnel is shown 

 in the Western Gallery, and a sample of Messrs. Johnson 

 and Phillips' grapnel for cutting the cable and holding 

 one end is shown in front of the Roman court, together 

 with a very large buoy for buoying the cable in deep 

 water. A very convenient and novel "mark" buoy for 



marking positions in cable woik is exhibited by the same 

 firm in the Western Gallery. The buoy is suspended by 

 a line from the ship's quarter or stern, and when the line 

 is cut, the buoy drops into the water. The copper float 

 ball (see Fig. 4) is then raised, and lifts a detent which 

 allows the drum of steel wire to revolve. The centipede 

 anchor then sinks to the bottom, and moors the buoy. A 

 winch handle is provided, so that the moorings can be 

 recovered if need be, but the cost of the sinker, drum, 

 and wire is so slight that it may readily be abandoned. 

 While upon the subject of deep-sea operations, we may 

 also mention the "nipper lead" of Mr. Lucas, by which 

 specimens of the sea-bottom are caught in two spoons or 

 tongs hinged to the bottom of the lead, and kept apart by 

 a trigger arrangement, which is sprung by the lead 

 striking the bottom. 



Coming now to the working of submarine cables, there 

 are several very neat mirror galvanometers exhibited by 

 Messrs. Latimer Clark, Muirhead, and Co. The Eastern 

 Telegraph Company exhibit the siphon recorder of Sir 

 William Thomson, working through one of Dr. Muir- 

 head's artificial cables on the duplex system, the counter 

 instrument being placed at the stall of the School of 

 Telegraphy. The bold electromagnets of this fine instru- 

 ment have been excited hitherto by Sir W. Thomson's 

 large tray-form of Daniell cell ; but quite recently Mr. 

 Clement Chevallier, electrician to the Eastern Telegraph 

 Company at Aden, has substituted permanent magnets, 

 with a great gain in economy. These magnets were spe- 

 cially made by Mr. Le Neve Foster, at Silvertown, and 

 their magnetic power is much heightened by a small 

 percentage of tungsten in the steel. An interesting ex- 

 periment, showing the retardation of signals through a 

 long submarine cable, is made by the School of Tele- 

 graphy. Ten mirror galvanometers, throwing ten light- 

 spots in a vertical row on a white screen, are connected 

 in turn at different points of a long cable, and the travel 

 of the charge when the circuit is closed by a key is shown 

 by the successive movements of the light-spots across the 

 screen. 



Mr. C. F. Varley, F.R.S., who by his application of 

 condensers to the submarine circuit did so much to im- 

 prove cable signalling, has a very interesting exhibit of 

 his past inventions. These include his gravity battery 

 patented in 1854 (No. 2555), and repatented in 1861 by 

 Menotti, whose name it bears. In the same patent the 

 sulphate of mercury battery, subsequently known as the 

 Marie-Davy, was also described. This patent, like most 

 of Mr. yarley's, was very rich in devices, and contains 

 his application of the condenser not only to telegraphy, 

 but to electric lighting, a plan subsequently patented by 

 Jablochkoff. Mr. Varley's exhibit also includes the first 

 polarised relay used in this country, and the rotary elec- 

 trical machine made and patented in i860, and held by him 

 to be the parent of the Holtz and other induction machines, 

 such as the mousemill of the siphon recorder and the 

 replenisher of the quadrant electrometer. But it is pro- 

 bable that Mr. Varley's claim must give way in favour ot 

 M. Belli, who invented a similar induction machine many 

 years ago, which the writer saw in the Retrospective 

 Museum of the recent Paris Electrical Exhibition. 



THE EARLIEST USE OF THE LXCANDESCENT 



ELECTRIC LIGHT 

 A CORRESPONDENT writes:— 

 -'*■ The following extract from a memoir by Sir William 

 Grove, published more than thirty-six years ago, will be 

 of interest to future historians of the progress of lighting 

 by electricity. The memoir is entitled " On the Applica- 

 tion of Voltaic Ignition to Lighting Mines," by W. N. 

 Grove, F.R.S., and is published in the Philosophical 

 Magazine, May, 1845. It begins by stating that M. De 

 la Rive had proposed the use of the voltaic arc for illumi- 



