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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 tome, 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 long 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. I have 

 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, is a 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 



