164 Transactions.—Miscellaneous. 
inside of hollow snags. The result of these experiments will probably be 
sent to you at some future time. 
ArT. XIIT.—Notes on the firing of Torpedoes by Electricity. By J. A. Pour. 
[Read before the Auckland Institute, 19th November, 187 7-] 
Tue short note by R. R. 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 plaee 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 powerful electric or 
galvanic battery. The wire having been cut, and a few inches of platinum 
wire 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 points of economy the firing by electricity will 
be advantageous, as only a small portion of the insulated 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 wires, providing that the charges are 
not too numerous and too far apart, 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 
