Apparatus for Rock Blasting. 355 
The apparatus being thus prepared, by a galvanic discharge, pro- 
duced by the movement of a lever through the quarter part of a cir- 
cle, the finer wire is ignited, in the place where it intervenes solely 
in the circuit, so as to set fire to the surrounding gunpowder. 
As the enclosure of the gunpowder in the tube, must render it im- 
possible that it should be affected by a spark elicited by ramming, as 
no means of ignition can have access to the charge besides the galva- 
nic discharge ; and as this can only occur by design, without an in- 
tention to commit murder or suicide, or by unpardonable neglect, it 
. is inconceivable that an explosion can take place in this method of 
blasting, when any person is so situated as to suffer by it. 
It must be obvious that in all cases of blasting under water, the 
plan of a tin tube, and ignition by a galvanic circuit, must be very 
eligible. 
At A is represented a cylinder or tube of 
tinned iron, charged with gunpowder. At C, 
the twisted wires are represented as they pro- 
trude from the cylinder through a cork, by 
which the latter is closed at the upper end. 
The other ends of the wires are soldered to 
the metallic disk which forms the bottom of 
the cylinder. D represents the twisted wires 
as they appear when all the larger ones are 
cut, the smaller wire still uniting them. F | 
represents the piece of dogwood, duly prepar- 
ed; and E the wires as when supported by 
the wood. The reader has only to imagine 
the hole in the wood, to be supplied with the 
fulminating composition, and covered by a fil- 
let of paper or cloth, glued or pasted around 
the wood, in order to complete his conception 
of the wires as finally accoutred and situated 
within the cylinder A. 
Besides affording support to the larger wires, and thus protecting 
from fracture, the smaller wire, which unites them to the piece of dog- 
wood that has been described, by means of the small hole represent- 
ed in it, serves to hold, and to preserve in contact with the little wire, 
some fulminating powder. ‘This not only facilitates the incipient ig- 
nition of the contents of the cylinder, but must make it extend more 
rapidly throughout the mass, and must, of course, cause it to be more 
Vou. XXVI.—No. 2. 46 
