l\^ov. 15, 1877] 



NATURE 



51 



powder was insufficient to effect any material injury. All 

 this has been remedied. Electricity is nowadays em- 

 ployed as the igniting agent, and those terribly violent 

 explosives, gun-cotton and dynamite, replace the com- 

 paratively innocuous gunpowder. 



Electric torpedoes may be broadly divided into two 

 classes : offensive and defensive torpedoes. The latter 

 are employed for the protection of harbours, channels, and 

 roadsteads ; the former, in the shape of drifting or spar- 

 torpedoes, are carried to the attack in small swift-sailing 

 steam-launches. In this country we are favourably dis- 

 posed to the employment of compressed gun-cotton in our 

 machines, while on the Continent they seem to entertain a 

 predilection for nitroglycerine, or rather dynamite. "Both 

 compounds are what chemists term nitro-compounds, in 

 contradistinction to gunpowder, which comes under the 

 class of nitrate-compounds, and appear to exercise an ex- 

 plosive force'of almost similar violence, measuring the sub- 

 stances weight for weight. Compressed gun-cotton, we 

 need hardly say, is cotton yarn acted upon by nitric and 

 sulphuric acids and then pulped and washed, so that the 

 result is a finely-divided mass which may be made to 

 assume any shape or form. As a rule the material is 

 pressed into cakes of disc-like form, which weigh from a 

 few ounces to a pound, and while still wet the slabs are 

 stored away in the magazines. In this moist condition 



Fig. I. — Fish Torpedo exploding against a ship. 



the compressed pulp is not only non-explosive, but actu- 

 ally non-inflammable, except one possesses the key to its 

 detonation. This is nothing more than a dry cake of the 

 same material, or as the latter is termed in military par- 

 lance, a "primer," which on being detonated by a few 

 grains of fulminate, brings about the explosion of any 

 wet gun-cotton in its immediate neighbourhood. Thus 

 if simply a net is filled with gun-cotton slabs and 

 thrown into the sea, the whole charge may be ignited 

 by a primer contained in a waterproof bag having 

 an electric fuze and wire attached. The possibility 

 of communicating explosion in this way by vibration 

 instead of by spark or flame is, too, as we shall presently 

 see, the germ of a system of counter-mining, or torpedo 

 annihilation, which bids fair to develop into a particularly 

 effective means of defence against these terrible machines. 

 Dynamite is similarly exploded to gun-cotton. The 

 active principle in this case is nitro-glycerine, or, if 

 you will, liquid gun-cotton, prepared by simply allowing 

 glycerine to fall drop by drop into nitric acid. As a solid 

 is usually more convenient to handle than a liquid, the 

 use of pure nitro-glycerine has given way to dynamite, 

 which may be described as siliceous earth impregnated 

 with the explosive fluid. 



Dynamite and gun-cotton explode with something like 

 four or five times the force of gunpowder, and for this 

 reason a very destructive charge may be confined 



within a comparatively small space. Moreover they are 

 peculiarly adapted to submarine mines, since nitro- 

 glycerine is no more affected by water than gun-cotton ; 

 and the old adage '' to keep your powder dry " does not 

 apply to either of them. In the case of moored torpedoes 

 which are connected with batteries to the shore or cany 

 their own means of generating electricity, as in the Herz 

 topedo of our German cousins, there is no limit to size, 

 and machines containing as much as 500 lbs. of gun-cotton 

 have, in fact, been constructed; but for a spar- torpedo, 

 or in other words one which is thrust under an enemy's 

 keel by means of a thirty-foot pole projecting from 

 the prow of a launch, the charge must be con- 

 siderably smaller, and for two reasons. A great weight 

 at the end of such a lever could not be properly ma- 

 nipulated, while the explosion, if the charge were a very 

 large one, would destroy both the attacking and attacked. 

 A big moored torpedo of 500 lbs. has been found, when 

 sunk in thirty or forty feet of water, to be fatal to a strong 

 ironclad if the latter happens to be within this distance of 

 the source of explosion ; or, in other words, a cushion of 

 water forty feet in thickness is not sufficient to secure the 

 immunity of such a vessel. What would happen if this 

 terrible volcano were to erupt — if we may use the word — 

 in contact with the sides of an armoured ship, must be 

 left to the imagination ; but despite Mr. Ward Hunt's 

 opinion to the contrary, we do not think it would require 



Fig. 2. 



-A moored Torpedo exploding. 

 220 feet. 



Height of column 60 feet, base 



three such torpedoes successfully exploded, to bring our 

 boasted Inflexible to grief. And in this opinion our 

 readers, we suspect, will fully agree, when we inform them 

 that a heavy torpedo like tltiis throws up a cone of water 

 sixty feet in height, with a diameter at its base of no less 

 than 220 feet. Such an heaving of waters, if it did not 

 break the back of an ironclad, as there is every reason 

 to suppose it would, must inevitably capsize her with- 

 out more ado. But it is, of course, only on very rare 

 occasions that such a monster torpedo could be brought 

 to bear, and in all cases of attack the charge must needs 

 be considerably less. The smaller Whitehead torpedoes, 

 which, as our readers know very well, are narrow cigar- 

 shaped weapons, that move through the water by the 

 agency of compressed air, do not in all probability carry 

 more than a 40 lb. or 50 lb. charge in the head, while a 

 spar or drift torpedo of 100 lbs. is already as large as 

 would be convenient to handle. At the same time either 

 of these would quite suffice to fracture an iron plate 

 several inches in thickness, and therefore be fatal, pro- 

 bably, to any ironclad afloat, supposing there was no 

 water-cushion between the craft and the torpedo. We 

 have no definite information respecting the size or weight 

 of the torpedoes which sank the Turkish monitor in the 

 Matchin Canal, but as the expedition was hastily arranged 

 and organised, the charges were, no doubt, not very large. 

 The fish torpedo is a rare example of a comphcated 

 apparatus coming into practical use, and its elaborate 



