Minutes of Proceedings of the Institution of Civil Engineers Volume 80, PT. 2

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1885 Excerpt: ...the easy passage of the insulated wires; the latter were drawn tightly, passing along outside the tube, which was carefully lowered to the bottom of the hole. A wooden rod was gently pushed by hand through the tube, to keep the cartridge down, and the tube withdrawn. A quantity of explosive, varying from 2 lbs. to 5 lbs., in proportion to the depth of rock, was then poured through a funnelshaped copper tube into the hole, and afterwards a few gallons of hot water to remove any particles of explosive adhering to the sides of the tube, the wires were finally connected with the battery and the charge exploded. The practice generally followed was to charge and explode each hole so soon as the drill was removed, and before commencing to drill another hole, as any disturbance of the wires after loading tended to injure the circuit. The explosive, before being used, was congealed by packing in ice and sawdust; the temperature was raised before loading to 60D Fahrenheit by immersing the can in hot water. The loading of each hole occupied only a few minutes, but had to be conducted with the greatest care, the following rules being strictly observed: --1. That the hole was drilled to a sufficient depth below the required bottom. 2. That the cartridge was placed at the bottom of the hole. 3. That in withdrawing or inserting the tubes and completing the loading no obstruction was allowed to enter the hole. The necessity for such precautions is obvious, from the fact that pure nitro-glycerine can only be exploded by concussion, hence the necessity for placing the cartridge containing the exploder in such a position as would ensure its contact with the liquid explosive that completed the charge, and which, owing to its specific gravity, would speedily fill every space aro..