May 17, 1883] 



NATURE 



67 



experimental investigation by the lecturer. Different samples of 

 comparatively thin wires, made from commercial platinum, 

 showed very great variations in electrical conductivity. Very 

 considerable differences in the amount of forging to which the 

 metal, in 'he form of sponge, had been subjected, did not im- 

 portantly affect either its specific gravity or its conductivity, and 

 the fused metal had only a very slightly higher degree of con- 

 ductivity than the same metal forged from the sponge. The 

 conductivity of very fine wires could therefore be but slightly 

 affected by physical peculiarities of the metal, and the consider- 

 able differences in conductivity observed in different samples of 

 platinum were therefore chiefly ascribable to variations in the 

 degree of its purity. It appeared likely that definite alloys 

 might furnish more uniform results than commercial platinum ; 

 experiments were therefore made with fine wires of German 

 silver and of the alloy of sixty-six of silver with thirty-three of 

 platinum employed by Matthiessen for the reproduction of B.A. 

 standards of electrical re istance. Both were greatly superior 

 to ordinary platinum in regard to the resistance opposed to the 

 passage of a current ; Genr.an silver was in its turn superior to 

 the platinum-silver alloy ; although the difference was only 

 trifling in the s-nall lengths of fine wire used in a fuze (o'25 

 inch), while the comparatively ready fusibility of platinum- 

 silver contributed, with other physical peculiarities of the 

 two alloys, to reduce German silver to about a level with 

 it. Moreover, the latter did not resist the tendency to corrosive 

 action exhibited by gunpowder and other more readily explosive 

 agents which had to be placed in close contact with the wire 

 bridge in the construction of a fuze, while the platinum-silver 

 alloy was found to remain unaltered under corresponding con- 

 ditions. Experiments having also been n.ade with alloys of 

 platinum with definite proportions of iridium, the metal with 

 which it is chiefly associated, very fine wires of an alloy con- 

 taining 10 per cent, of iridium were eventually selected as 

 eminently the best materials for the production of wire fuzes of 

 comparatively high resistance and uniformity, this alloy being 

 found decidedly superior in the latter respect as well as in point 

 of strength (and therefore of manageableness in the state of very 

 fine wire oooi inch in diameter) to the platinum-silver wire. 

 The fuze; now used in military and submarine services were 

 made with bridges of iridio-platinum wire containing 10 per 

 cent, of the first-named metal. 



The electrical gun-tubes in the navy were fired by means of a 

 specially arranged Leclanche battery, and branch circuits worked 

 to the different guns ; in broadside firing it was important that 

 the wire bridge of any one of the gun-tubes which was first fired 

 should be instantaneously fused on the pas-age of the current, 

 so as to cut this branch out of circuit ; in this respect the 

 comparatively fusible platinum-silver alloy appeared to present 

 an advantage, hence the naval electrical fuzes were made with 

 bridges of that alloy. Uniformity of electrical resistance had 

 become a matter of such high importance in the delicate 

 arrangements connected with the system of submarine mines, 

 as now perfected, that the very greatest care was bestowed upon 

 the manufacture of service electric fuzes and detonators, which 

 were in fact made in all their details with almost the precision 

 bestowed upon delicate scientific instruments, and the successful 

 production of which involved an attention to minutire which 

 would surprise a superficial observer. 



One of the earliest applications of electricity to the explosion 

 of gunpowder was the firing of guns upon proof at Woolwich by 

 means of a Grove battery and a gun-tube, which was fired by a 

 platinum wire bridge, a shunt arrangement being used for 

 directing the current successively into the di-tinct circuits con- 

 nected with the guns to be proved. When the hi^h-tension 

 fuze had been devised, gun-tubes were made to which it was 

 applied, and an exploder was arranged by Wheatstone, having a 

 large number of shunts, so that as many as twenty-four guns 

 might be brought into connection with the instrument, and 

 fired in rapid succession by the depression of separate keys 

 connected with each. 



The firing of cannon as time-signals was an ancient practice 

 in garrison towns, but the regulation of the time of firing the 

 gun by electrical agency from a distance appears first to have 

 been accomplished in Edinburgh, where, since 1S61, the time- 

 gun had been fired by a mechanical arrangement actuated by a 

 clock, the time of which is controlled electrically by the mean- 

 time clock at the Royal Observatory on Calton Hill. 



Shortly after the establishment of the Edinburgh tirnegun, 

 others were introduced at Newcastle, Sunderland, Shields, Glas- 



gow, and Greenock. The firing of the gun was arranged for in 

 various ways ; in some instances it was effected either direct from 

 the Observatory at Edinburgh, or from shorter distances, by 

 means of Wheatstone's magnetoelectric exploders. At present 

 there were time-guns at West Hartlepool, Swansea, Tynemouth, 

 Kendal, and Aldershot, which were fired electrically, either by 

 currents direct from London, or by local batteries, which were 

 thrown into circuit at the right moment by means of relays, con- 

 trolled from St. Martin's-le-Grand. 



About thirteen years ago the electrical firing of guns, especia'ly 

 for broadsides, was first introduce 1 into the navy, with the em- 

 ployment of the Abel high-tension gun-tube and voltaic piles. 

 The gun tubes then used were manufactured originally for the 

 proof of cannon and for experimental artillery operations, and 

 were of very simple and cheap construction. Experience proved 

 them to be unfitted to withstand exposure to the very various 

 climatic influences which they had to enounter in Her Majesty's 

 ships, and in store in different parts of the world. The low- 

 tension gun tubes, having a bridge of very fine platinum-silver 

 wire, surrounded by readily ignitible priming composition, was 

 therefore adopted as much more suita'ole for our naval require- 

 ments. 



The arrangements for broadsides or independent firing, and 

 also for the firing of guns in turret-ships, had been very carefully 

 and successfully elaborated in every detail, including the pro- 

 vi-ion of a so-called drill- or dummy electrical gun-tube, which 

 was u-ed for practice and refitted by well i structed sailors. 

 The firing-keys, and all other arrangements connected with 

 electrical gun-firing, were specially designed to insure safety and 

 efficiency at the right moment. 



The electric detonators for firing outrigger-torpedoes, or for 

 other operations to be performed from open boats, c irresponded, 

 so far as the bridge was concerned, with the nival electric gun- 

 tubes, and were fired with a sp:cially fitted Leclanche battery. 

 These electric appliances were now distributed throughout the 

 navy, and the men were kept, by instruction and periodical 

 practice, well versed in their use. 



The application of electricity to the explosion of submarine 

 mines, for purposes of defence and attack, received some atten- 

 tion from the Russians during the Crimean War, under the 

 direction of Jacobi ; thus a torpedo, arranged to he exploded 

 electrically when coming into collision with a vessel, wa; disco- 

 vered at Yeni-Kale during the Kertsch expedition in 1855. 

 Some arrangements were made by the British at the conclu-ion 

 of the war to apply electricity to the explosion of lir,e powder- 

 charges for the removal of sunken ships, &c, in Sebastopol and 

 Cronstadt Harbours. In 1859, a system of submarine mines, 

 to be fired through the agency of electricity by operators on 

 shore, was arranged by von Ebner for the defence of Venice, 

 which, however, never came into practical operation. Early in 

 i860 Henley's large magnetoelectric machine, with a supply 

 of Abel fuzes, and stout iudiarubber bags, with fittings to resist 

 water- pressure, was despatched to China for use in the Peiho 

 River, but no application appeared to have been made of them. 

 The subject of the utilisation of electricity for purposes of 

 defence, however, did not receive systematic investigation in 

 England or other countries until some years afterwards, when 

 the great import vnce of submarine mines, as engines of war, was 

 demonstrated by the number of ships destroyed and injured 

 during the war in America. 



The application of electricity to the explosion of submarine 

 mines was very limited during that war, but arrangements for its 

 extensive employment were far advanced in the hands of both 

 the Federals and Confederates at the close of the war, men of 

 very high qualifications, such as Capt. Maury, Mr. N. J. Holmes, 

 and Capt. McEvoy having worked arduou ly and successfully at 

 the subject. 



The explosion of submerged powder-charges, by mechanical 

 contrivances, either of self-acting nature or to be set into action 

 at desired periods, was accomplished as far back as 15S3, during 

 the siege of Antwerp, by the Duke of Parma, and from that 

 period to 1854 mechanical devices of more or less ingenious 

 and practicable character had been from time to time applied 

 to some small extent, indifferent countries, to the explosion of 

 torpedoes. The Russians were the first to apply self acting me- 

 chanical torpedoes with any prospect of succe-s, and had the 

 machines used for the defence of the Baltic been of larger size 

 (they only contained 8 or 9 lb. of gunpowder), their presence 

 would probably have proved very disastrous to some of the 

 English ships which came into collision with and exploded them. 



