Figs. 26, 27.
All tamping should be selected for its freedom from particles likely to strike fire, but it must not be overlooked that the cause of such a casualty may lie in the sides of the hole itself. Under these circumstances is seen the advisability of using bronze or copper tamping tools, and of not hammering violently on the tamping until a little of it has been first gently pressed down to cover over the charge, because the earlier blows on the tamping are the most dangerous in the event of a spark occurring. A little wadding, tow, paper, or a wooden plug is sometimes put to lie against the charge before any tamping is placed in the hole.
Fig. 28.
To lessen the danger of the tamping being blown out, plugs or cones of metal of different shapes are sometimes inserted in the hole. The best forms of plug are shown in Figs. 28 and 29; [Fig. 28] is a metal cone wedged in on the tamping with arrows, and [Fig. 29] is a barrel-shaped plug.
When all is ready, the sinkers, with the exception of one man whose duty it is to fire the charge, are either drawn out of the shaft, or are removed to some place of safety. This man then, having ascertained by calling and receiving a reply that all are under shelter, applies a light to the fuse, shouts “Bend away,” or some equivalent expression, and is rapidly drawn up the shaft.
To avoid shattering the walls of a shaft, no shot should be placed nearer the side than 12 inches. The portion of stone next the wall sides of the shaft left after blasting is removed by steel-tipped iron wedges 7 or 8 inches in length. These wedges are applied by making a small hole with the point of the pick and driving them in with a mall. The sides may be then dressed as required with the pick.