Fig. 22.
Fig. 23.
Sometimes in wet ground it becomes necessary to shut back the water from the bore-hole before introducing the charge of gunpowder. This happens very frequently in shaft sinking. The method employed in such cases is to force clay into the interstices through which the water enters. The instrument used for this purpose is the “claying-iron” or “bull,” represented in [Fig. 22]. It consists of a round bar of iron, called the stock or shaft, a little smaller in diameter than the bore-hole, and a thicker portion, called the head or poll, terminating in a striking face. The lower end of the shaft is pointed, to enable it to penetrate the clay, and the head is pierced by a hole about an inch in diameter to receive a lever. Clay in a plastic state having been put into the bore-hole, the bull is inserted and driven down by blows with the sledge. As the shaft forces its way down, the clay is driven into the joints and crevices of the rock on all sides. To withdraw the bull, a bar of iron is placed in the eye and used as a lever to turn it round to loosen it; the rod is then taken by both hands and the bull lifted out. To allow the bull to be withdrawn more readily, the shaft should be made with a slight taper and kept perfectly smooth. As the bull is subjected to a good deal of heavy hammering on the head, the latter part should be made stout. This tool, which should be considered as an extra instrument rather than as an essential part of a blasting set, is a very serviceable one, and should always be at hand in wet ground when loose gunpowder is employed.
Another instrument of this auxiliary character is the beche, [Fig. 23], used for extracting a broken drill. It consists of an iron rod of nearly the diameter of the bore-hole, and hollow at the lower end. The form of the aperture is slightly conical, so that the lower end may easily pass over the broken stock of the drill, and, on being pressed down with some force, may grasp the stock in the higher portion of the aperture with sufficient firmness to allow of the two being raised together. When only a portion of the bit remains in the hole, it may often be extracted by means of the drag-twist end of the scraper, or the swab-stick may be driven down upon the broken portion, and latter withdrawn with the swab.
Sets of Blasting Gear.
—On [Plates I.], [II.], and [III.], will be found three sets of blasting gear; a set of coal-blasting gear; a set of single-hand stone-blasting gear; and a set of double-hand stone-blasting gear. In the first set, the drill, shown in [Fig. 1], is 22 inches in length; the cutting edge is straight and 11⁄2 inch wide, and the weight is 21⁄2 lb. The other drill, [Fig. 2], is 42 inches in length; it has a straight cutting edge 17⁄16 inch wide, and weighs 4 lb. 10 oz. The hammer used in this set and shown in [Fig. 3] weighs 2 lb. 14 oz.; the length of the head is 41⁄2 inches, and that of the handle 73⁄4 inches. In the second or single-hand stone set, the shorter drill, [Fig. 6, Plate II.], is 22 inches in length; the cutting edge is strongly curved, and is 11⁄2 inch in width, and the weight is 3 lb. 10 oz. The longer drill, [Fig. 7], is 36 inches in length; the width of the cutting edge, which is curved as in the shorter drill, is 17⁄16 inch, and the weight is 6 lb. 5 oz. The hammer used with this set, and represented in [Fig. 8], weighs 3 lb. 6 oz.; the length of the head is 5 inches, and that of the handle 10 inches. In the third or double-hand stone set, [Plate III.], the first or shortest drill, [Fig. 12], is 18 inches in length, 13⁄4 inch wide on the cutting edge, and weighs 41⁄4 lb. The second drill, [Fig. 13], is 27 inches in length, 111⁄16 wide on the cutting edge, and weighs 6 lb. The third or longest drill, [Fig. 14], is 40 inches in length, 15⁄8 inch wide on the cutting edge, and weighs 91⁄4 lb. The cutting edges of all these drills are strongly curved as in the preceding set. The sledge used with this set, and represented in [Fig. 15], weighs about 5 lb.