Apparatus for Rock Blasting. 357 
these may be considered as separated into two subdivisions by four 
plates of copper between the letters C C. Of course the box may be 
considered as comprising four distinct spaces, No. 1, No. 2. No. 3, 
and No.4. The circuit is established in the following manner. Be- 
tween the zine plates of compartment No. 1 and the copper plates of 
compartment No. 2, a metallic communication is produced, by sol- 
dering their neighboring corners to a common mass of solder with 
which a groove in the wooden partition between them is filled. With 
similar masses of solder, two grooves severally made in the upper 
edges of each end of the box are supplied. To one of them, the cor- 
ners of all the copper plates of space No. 1, and the zinc of space 
No. 4, are soldered. To the other the zinc plates of space No. 2, 
and the copper plates of space No. 3, are soldered in like manner. 
Lastly the zinc plates of No. 3 are connected by solder in a groove, 
and the copper plates of No. 4 are ia like manner connected by sol- 
der in another groove. Upon the ends, S S, of the solder just men- 
tioned, the gallows screws are severally soldered, and to these the rods, 
PP, called poles, are fastened. 
Rationale. 
The zine and copper surfaces of No. 1 and No. 2, communicating, 
have their naturally opposite electric powers exalted, and induce in 
the plates with which they are alternated, a like exaltation, still high- 
er. By the communication of the latter with the surfaces in No. 3, 
and No. 4, a similar effect is induced, and again by induction the 
electric powers of the plate alternating with those last mentioned are 
augmented. Hencea discharge between the latter will have a quad- 
ruple intensity, and hence the poles, or rods, communicating with the 
gallows screw, soldered as above described to the zinc and copper 
plates last mentioned, will make a discharge through any conductor 
whenever the apparatus is put into operation by raising the acid, so 
as to enable it to surround and act upon the galvanic surfaces. 
When, agreeably to the project of Mr. Shaw, several masses of 
gunpowder are to be simultaneously ignited, in as many different 
holes in the same rock, I purpose to introduce into each hole, a cy- 
linder prepared as here represented and to secure them by ramming in- 
to the hole, sand, brickdust, or other suitable matter, through which 
the wires are allowed to pass so as to project on the outside. All 
the wires corresponding with that represented at B in the engraving, 
are then to be soldered to arod proceeding from one pole to a calori- 
