TORPEDOES. 



.723 



cables are stored in salt-water tanks, so that the 

 (inter coat is saturated and a defect may be dis- 

 covered before it is laid. The dynamite and the 

 fulminate in the primer are tested In-fore loading 

 the torpedo shells. With the laying of each 

 separate mine the electrical connection is tested. 

 When a grand group is laid every feature of it 

 is daily examined, tho multiple cable tested for 

 insulation and conductivity, as well as each core 

 and liraneh of a core. The fault can be located 

 within a few feet. The junction boxes are sub- 

 jected to a daily inquisition. A difficulty in 

 the circuit-closer or its wire connections, a leak 

 in tho torpedo case, a wetting of the dynamite 

 charge or the fulminate of the primer are at once 

 made known and the fault properly placed. 

 This is done by delicate electrical apparatus in 

 which the galvanometer plays the most impor- 

 tant part. The method may be illustrated in 

 some of its applications in the use of the sea-cell 

 test. First take, for example, the testing of the 

 dryness of the dynamite charge. The principle of 

 the sea-cell depends on the fact that two plates 

 of suitable metal form a voltaic battery when 

 placed in salt water and properly connected by 

 a metal conductor. This battery will produce 

 considerable deflection in the needle of a galva- 

 nometer, which varies in direction and violence 

 with the metals used. There is a plate of zinc 

 inside the dynamite charge at the point which 

 connects it with the conductor of the cable be- 

 tween the fuse and the shore. There is also a 

 plate of carbon connected with the wire beyond 

 the fuse to form the earth connection, while a 

 copper earth plate is used at the home end. In 

 case the charge is dry, we should have a sea-cell 

 composed of a copper and a carbon pair, which 

 would produce a certain deflection on the needle 

 of a galvanometer in circuit, say from right to 

 left. If the charge is wet, the zinc plate would 

 corne in contact with salt water, and the sea-cell 

 composed of a copper and a zinc pair would give 

 a deflection of the galvanometer in the opposite 

 direction. Again, suppose the insulation of the 

 electric cable has become damaged to such ex- 

 tent as to expose the copper conductor. Under 

 these conditions the sea-cell would be formed of 

 two copper plates one the permanent earth plate, 

 the other the exposed conductor and a certain 

 kind and degree of deflection would be noticed. 

 This deflection would differ in character from 

 that produced by the copper carbon sea-cell, 

 which would exist if the insulation were good, 

 indicating a change in the electrical conditions 

 and the probability that there had been an injury 

 to the insulation of the cable. Now if the earth 

 plate at the home end of the cable should be 

 changed from copper to zinc or carbon, fresh 

 combinations would give new indications on the 

 galvanometer, and these would provide the means 

 of determining with accuracy the reason for the 

 change in the electrical conditions of the combi- 

 nation which they indicated. In this way the 

 fact of a leak in insulation could be discovered. 

 Its extent and position would be determined by 

 further tests. Should the conductor of an elec- 

 tric cable be fractured within the insulation with- 

 out injury to the latter, the sea-cell test would 

 denote the fact, that lack of continuity in the 

 conductor would result in lack of deflection in 

 the galvanometer needle. Want of conductivity 



or inefficient connections in the fuse would be 

 similarly shown. When submarine mines are 

 laid in expectation of the arrival of a h>-nlc 

 fleet, the-e te>ts are supposed to be daily applied 

 to every port ion of the mining apparatus. While 

 the main current is dynamic electricity, the vol- 

 taic battery is generally used for the firing box 

 and the testing table, as being more easily and 

 economically administered for these uses. After 

 the tprpedos are laid and fully adjusted, the 

 question arises as to their methods of use in the 

 exigencies of battle. Discharge by contact 

 through the circuit-closer is already provided for 

 in the torpedo apparatus. But in firing at will, 

 means of exactly determining the vessel's posi- 

 tion on the mining plot are necessary. This po- 

 sition is determined by intersection. The sim- 

 plest and, on the whole, the surest plan is that 

 which accomplishes this by theodolite observa- 

 tions from different stations, one of which may 

 or may not be at the mining casemate, prefer- 

 ably the latter, as the firing station would in any 

 case have electrical communication with both. 

 Before the officer in the mining casemate, who 

 has at his elbow the different firing boxes, lies 

 a chart of the whole field of mines. It is divided 

 into small squares, which show the precise loca- 

 tion of all the mine groups, the definitibns being 

 made by the markings or the degrees of a great 

 circle laterally and lengthwise. Remote points 

 at some elevation, not likely to be discovered by 

 the enemy, and at the end of a fixed base line 

 are selected, which overlook the field of operations. 

 These points are electrically connected with each 

 other and with the mining casemate. At each 

 of the observation stations an officer and his as- 

 sistants take the readings, as indicated on the 

 graduated scale of a theodolite telescope, of the 

 moving vessel which is being tracked. The 

 scales of the two instruments correspond, and of 

 course the alignments intersect at tne ship's lo- 

 cation. The markings in degrees at the subsid- 

 iary station, constituting the record of one align- 

 ment, are telegraphed at once to the main sta- 

 tion, and the officer there in command traces 

 these in connection with the readings of his own 

 alignment on the chart, or both alignments may 

 be telegraphed to the mining casemate, and there 

 traced on the chart. The movement of the 

 point of intersection over the squares indicates 

 the course of the ship and its precise relation to 

 any torpedo group. If the theodolite scales are 

 properly set and the officers and their assistants 

 careful in their readings, this method is almost 

 infallible except in case of heavy fog or battle 

 smoke, when dependence would need be left to 

 explosion by contact or the signaling from an 

 unexploded mine. At night it would be neces- 

 sary to make use of powerful search lights. ;m 

 assistance also indispensable in guarding against 

 attack- on the torpedo field at night by picket 

 boats or other means of aggression on the part 

 of the enemy. 



The art of countermining has advanced pro- 

 portionably with that of torpedo defense. This 

 is accomplished mainly by heavy charges of 

 dynamite or gelatin exploded over a suspected 

 field of mines, or by boat parties with means of 

 taking up buoyant mines, or the circuit-closers, 

 of ground mines if detached, or of cutting the 

 electrical connections. It is probable that any 



