Apparatus for Rock Blasting. 353 
be procured, than by the old plan. I have, however, to lament my 
inability to succeed in this method of blasting, during a great part of 
the year, when, in consequence of the unfavorable state of the wea- 
ther, the ignition cannot be effected by electricity in any mode which 
I have devised, or which has been suggested by others, although I 
have consulted all the best informed professors to whom I have had 
access.” 
It occurred to me, as soon as this statement was made by Mr. 
Shaw, that the ignition of gunpowder, for the purposes he had in 
view, might be effected by a galvanic discharge from a deflagrator, 
or calorimotor, in a mode which I have Jong used in’ my eudiomet- 
rical experiments to ignite explosive gaseous mixtures. ‘This pro- 
cess is free from the uncertainty, which is always more or less atten- 
dant upon the employment of mechanical electricity, for similar pur- 
poses. 
The expectation thus arising, has since been fully verified. Ihave 
ignited as many as twelve charges of gunpowder at the distance of 
one hundred and thirty feet, from the galvanic machine employed. 
This distance is much greater than is necessary to the safety of the 
operator, as the deflagrator may be shielded so as not to be injured 
by the explosion, and by means of levers and pulleys, it may be made 
to act at any distance which may be preferred. There is no limit 
to the number of charges which may be thus ignited, excepting those 
assigned, by economy, to the size of the apparatus employed. 
These remarks have reference to the principal and highly impor- 
tant object of Mr. Shaw’s project, which is to ignite at once a great 
number of charges, in as many perforations so drilled in a rock, as to 
co-operate simultaneously in the same plane. By these means it is 
conceived that the stone may be separated into large prismatic, or 
tabular masses, instead of being reduced to irregular fragments of an 
inferior size. The object to which I propose now to call attention 
more particularly, isa modification of the common process of blasting 
by one charge, which renders that process perfectly safe. 
This part of the subject I shall introduce by premising, that almost 
all the accidents which have taken place in blasting rocks, have oc- 
curred in one of the three following modes :— 
1st. The explosion has taken place prematurely, before the opera- 
tor has had time to retire. 
2nd. A premature explosion has ensued from a spark produced 
by the collision arising from ramming into the perforation, containing 
