Application of Galvanic Ignition in Rock Blasting. 139 



Art. XVII. — On the Application of Galvanic Ignition in Rock 

 Blasting; by Robert Hare, M. D., Prof, of Chemistry in the 

 University of Pennsylvania, &c. he. he. 



I HAVE ascertained that the process for blasting rocks may be ren- 

 dered safer than the firing of a fowling piece, by a new application 

 of galvanism. I was led to make this improvement in consequence 

 of an application by a patentee (Mr. Moses Shaw,) for assistance in 

 perfecting his patented mode of blasting rocks by an electrical dis- 

 charge from a Leyden Jar. 



In a letter dated June 1st, 1831, he says, "I have been engaged 

 in blasting rocks by means of a fulminating powder introduced into 

 several cavities, and ignited in all of them simultaneously, by a spark 

 from an electrical machine, by which means masses of a much lar- 

 ger size, and of a much more suitable shape, for any object in view, 

 may 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 

 weather, the ignition cannot be effected by electricity in any mode 

 which I have devised, or which has been suggested by others, al- 

 though I have consulted all the best informed professors to whom I 

 have had access." 



It occured 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 long used in my eudiometrical experiments 

 to ignite explosive gaseous mixtures. This process is free from the 

 uncertainty which is always more or less attendant upon the employ- 

 ment of mechanical electricity for similar purposes. 



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 preferable. There are no limits 

 to the number of charges which may be thus ignited, excepting those 

 assigned by economy, to the size of the apparatus employed. 



