164 Transactions. — Miscellaneous. 



inside of hollow snags. The result of these experiments will lorobahly be 

 sent to you at some future time. 



Art. XIII. — Notes on the firing of Torpedoes by Electricity. By J. A. Pond. 



[Read before the Auckland Institute, 19th November, 1877.] 

 The short note by E. E. Hunt read at the last meeting, relative to 

 destroying snags by dynamitic charges, has led me to bring this subject 

 again before the members, as I believe an alteration in the manner of 

 firing the charges, which was carried out by the fuse, may lead to more 

 comprehensive working in this matter, with more certainty, safety, and 

 economy. 



In the first place I would premise that the charges placed for the 

 demolition of the snags are of gunpowder, and so arranged as to be fired 

 by the ordinary fuse : this being so, it simply remains to exchange the 

 latter for an insulated copper wire from a moderately XDOwerful electric or 

 galvanic battery. The wu-e having been cut, and a few inches of platinum 

 wn-e inserted, it only remains to enclose this in the powder, place the 

 charge and withdraw ; the- connection with the battery then being com- 

 pleted, the platinum wire through its inferior conductivity becomes incan- 

 descent, and the charge is exploded. When, however, the cartridge is of 

 dynamite, lithofracteur, or nitro-glycerine, it requires the addition of fulmi- 

 nate of mercury to explode it, and this being placed in a small copper tube 

 may be ignited either with platinum wire as before or by the spark ; the 

 former, however, is the safer, as any disarrangement of the striking dis- 

 tance might prove fatal to the explosion of the charge. 



I need hardly remark that the distance which may be gained from the 

 scene of danger, the security attained, the precision and certainty of the igni- 

 tion, place this means of firing far before that of the fuse for sub-aqueous 

 explosions. And even on iDoints of economy the firing by electricity wiU 

 be advantageous, as only a small portion of the msulated wire is injured 

 sufficiently to be valueless for future operations. Another advantage is 

 gained when a number of charges are to be fired simultaneously, as this 

 can be done at one connection of the wii'es, j)roviding that the charges are 

 not too numerous and too far a^Dart, as in that case, after a few have been 

 exploded the electric current chooses the shorter circuit through the water, 

 caused by the rupture of the wire. When blasting is carried on upon the 

 land or in mines, the value of this manner of firing would be shown chiefly 

 in the reduction of the number of serious accidents caused by the hanging 



