356 Apparatus for Rock Blasting. 
powerful. Metallic arsenic, and chlorate of potash finely powder- 
ed and mingled, made an excellent explosive powder for this pur- 
pose; being more ready to explode from heat, and less so from oth- 
er causes, than fulminating silver or mercury. Sulphur may be used 
in lieu of arsenic. Yet the use of these is not necessary, as the gun- 
powder will take fire directly from the wire, at least as effectually as 
in the usual mode. 
Description of a Galvanic Machine, for producing ingnition in Roek 
Blasting. 
GG 
= aEaae 
Diagram illustrating the arrangement of the plates. 
1 A 2 
ELE = : - s : 
Ae : _—— 
Bis = E 
EF ee ee 
EEE == = 
This machine consists of sixteen plates of zinc, and twenty plates 
of copper, each twelve inches by seven, arranged in four galvanic 
pairs. The plates are supported within a box with a central parti- 
tion of wood, A B, dividing it into two compartments. Each of 
