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blasting, a battery on this construction, not much larger than 

 a quarto volume, would answer well enough : but the one 

 now shown to you is of a very large size, and sufficient for 

 the most extensive operations. Its construction renders it of 

 easy management to the workman, as he has only to place it 

 on the ground twenty or thirty feet from the rock, and pull the 

 string, when the explosion is wanted. The master miner or 

 quarryman will occasionally replenish the battery with acid ; 

 but as it is in action for so short a time at every discharge, 

 this need hardly be done above once in the month, and a 

 shilling's worth of acid would last ten or twelve months, even 

 were the apparatus in daily or hourly use. 



It would trespass too much upon your time were I to enter 

 into more minute details of the construction of the battery, 

 but if persons desire it more fully explained to them, I shall 

 be happy to do so at any time ; and indeed it would give me 

 much pleasure to instruct any party wishing to use the pro- 

 cess, in all the details of its management. I would suggest 

 that a competent person be made master of the whole matter, 

 for the purpose of afterwards lecturing in the mining and 

 quarrying districts, and of teaching workmen to make and 

 use the apparatus ; to learn this requires no great stretch of 

 intellect. I have found parties of sappers and miners made 

 perfect masters of the subject by practising with the battery 

 a few hours under my guidance. I must repeat, that its use 

 will not only give security to the workman, but also save much 

 money to the master ; but to return to our apparatus. 



For the purpose of conveying the electricity from the 

 battery to the rock, a copper wire is used, which must be 

 covered with cotton thread or twine, for the purpose of in- 

 sulation, — that is to prevent the electricity passing in any 

 other direction than through that part of the wire immersed 

 in the powder, which, being heated by the passage of elec- 

 tricity, fires the charge. In order to economise the electric 



