1840.] The Galvanic Battery. 1165 



Section V. — Of the Application of the Galvanic Battery in 

 Blasting Rocks. 



The arrangements necessary for the employment of the Battery in 

 blasting operations, are exceedingly simple. The blast hole having 

 been prepared, and the charge introduced, the igniting wires must be 

 inlaid in a conical piece of wood, and fixed in the grooves prepared for 

 them by a thin wedge of wood, as shewn in Diagram No. 8. The 

 [Fig VIII. a.] igniting wires projecting about an inch beyond the base, 

 or larger end of the cone, must be connected by a fine platinum or 

 iron wire, and round this a cartridge of finer priming powder must be 

 placed. The cone is then to be inserted in the blast hole, and by 

 gently pressing it down and turning it round, the larger end should be 

 made to rest on the charge. A tamping of small fragments of rock 

 must then be poured in over the cone, and the whole arrangements are 

 complete. The main conductors should then be attached to the 

 priming wires, and on the circuit being completed at the Battery 

 explosion will ensue. In the event of the common methods of tamping 

 being employed, it would perhaps be the best plan to continue the use 

 of the priming needle, and have an open communication from the 

 surface through the tamping to the charge. The priming wires, inlaid 

 in opposite sides of a bamboo, could then be introduced, and the 

 igniting wire placed in direct contact with the powder of the charge. 

 Had there been satisfactory grounds for believing sand a good 

 tamping material, the use of the battery would have been much 

 facilitated, as it would only have been necessary to pour the sand into 

 the blast hole after the wires had been properly arranged ; but I have 

 in another place detailed some experiments, which, as far as they 

 extend, militate against the employment of this material in blasting, 

 and confirm Colonel Pasley's previously expressed unfavourable 

 opinion of it.* 



For blasting rocks under water, a very slight modification of the 

 existing plan will admit of the use of the Battery. The tin case in 

 [Fig. IX. a.] which the charge is to be lodged, must be made with a 

 collar about three inches high, and IJ inch in diameter. A wooden 

 plug &, must be turned to fit closely into this collar, and grooves ^ 



* Professional Papers of the Madras Engineers, Vol. I. 



7 K 



