TOIU'KDOKS. 



721 



be accurately tested in all their details of device, 



kept in perfect working order, ami made i 

 cuii- the Commands givta them with the precision 

 of an infantry soldier at drill. This form of tor- 

 pedo is mif df I he splendid triumphs of military 

 -cienee. Its terrors an- docile and can lit- disarmed 

 at a touch, and its obedience to orders is us swift 

 rethought. It telegraphs ashore its own <-on- 

 ditiun and that of all the electrical apparatus 

 connected with it; it can instantly destroy on 

 contact or signal to the " mining casemate " that 

 a ship is in position for submarine attack and 

 wait for the orders at the will of its master. It 

 is almost like an intelligent creature. Mines 

 working on the shore circuit can be laid so as to 

 be at once transformable from " judgment" tor- 

 pedoes (discharged at will) to those of automatic 

 action ; or they may be so arranged as to be 

 capable of ignition only by judgment from the 

 shore. These distinctions depend on the arrange- 

 ment of the circuit-closer. 



Torpedoes in their outer form are divided into 

 buoyant and ground mines. The shape of the 

 torpedo case adopted in the United States and 

 to some extent in foreign countries is spherical, 

 constructed of two hemispheres with heavy 

 liana's welded together. This form of the 

 sphere is found to be the strongest, the most 

 capacious weight for weight, and to possess the 

 greatest power of flotation. The metal is pressed 

 out as thin as possible from low-carbon steel of 

 the greatest tensile strength. In deep water, say 

 more than seven fathoms, the buoyant form is 

 used, while in shallower channels the ground 

 mine becomes desirable, as it can take a much 

 heavier charge of explosive. The question of 

 weight in relation to buoyancy here ceases to be 

 a factor. The ground mine is hemispherical, ad- 

 hering to the bottom by its own weight, and the 

 buoy, consisting of an unloaded torpedo sphere, 

 floats above it at from 10 feet to 20 feet oelow 

 the level of ebb tide. 



The buoyant mine is anchored to the bottom. 

 The circuit-closing apparatus is in the very heart 

 of the torpedo itself, and so constructed that 

 when the electric current is turned on, a very 

 slight shock to the torpedo case discharges it. 

 On the other hand, in the case of a ground mine 

 the circuit-closer is in the buoy above the tor- 

 pedo. The size of a torpedo varies according to 

 the load it is intended to carry, the law of rela- 

 tive flotation, the strength of tide and current, 

 the limits of tidal change, and the depth of chan- 

 nel. These must all be carefully calculated. It 

 may be said that an average standard for a buoy- 

 ant mine is 36 inches diameter. The explosive 

 mostly in vogue for loading torpedoes is one of 

 the higher powers of dynamite or other nitro- 

 eompound. In the American system it is the 

 grade known as No. 1. The base of this is the 

 infusorial earth known as kiettelgahr, found in 

 Hanover, Germany, which absorbs nitro-glycerin 

 in the ratio of 3 to 1. No inert base known has 

 so high a power of absorption. Another, si ill 

 higher form of explosive which has been adopted 

 in England and Germany, and will probably 

 come into use here, is "bLuting gelatin." first 

 made by Nobel, who was the discoverer of dy- 

 namite, and afterward improved by Prof. Abel, 

 the chemist of the English War Department. The 

 base of this is gun-cotton, which is also a nitro- 

 VOL. xxxin. A 46 



compound and a most powerful explosive. AH 

 "lublc in nitro-glycerin. the c<,ni|niiind i* 

 a pure explosive with nothing inert. For a time, 

 this explosive, the most energetic known, was 

 dreaded as unsafe for handling. Hut the diffi- 

 culty has been removed, and it can now be used 

 with no greater precautions than dummite, than 

 which it has nearly 50 per cent, higher energy. 

 An essential portion of the torpedo apparatus is 

 the circuit-closer, which is ordinarily designed 

 to be used with the fuse, either in or out of the 

 permanent circuit. In the former case it can be 

 fired either by a blow from an outside object or 

 by judgment from shore ; in the latter case only 

 by a blow. The circuit-closer can either be in- 

 closed in a separate case and connected with the 

 mine by a mooring line and electric cable, or it 

 can be included with the charge in the mine. A 

 description of Prof. Abel's apparatus, which is 

 the favorite form of the British War Department, 

 will sufficiently indicate the general principles 

 involved in the construction of all. The form 

 illustrated is that in which the apparatus oc- 

 cupies a separate shell. It consists of a strong 

 case made buoyant by means of an air-tight 

 chamber. 



Within is set a brass tube (d), into the lower 

 extremity of which a pair of insulated wires (e 

 and /) are introduced through a water-tight 

 stuffing-box. Within the brass tube is another 

 tube of brass or iron (h) extending vertically 

 through the whole apparatus and working on a 

 universal joint (i) at its lower extremity. The 

 upper portion of this tube is rigidly connected 



SECTION OF ELECTRIC TORPEDO. 



with a metal bar (k\ which is attached to a top 

 (/) supported on the ca-c t) and separated from 

 it by a vulcanized rubber ring (m). One of the 

 insulated conducting wires (e), passing through 



