Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

structed for the purpose. It is in the highest degree dangerous to attempt to soften or thaw explosives by placing them on or near a fire, or in a can heated by a candle or lamp, and many lives have been lost through this criminally reckless practice. PREPARING THE BOREHOLE. Borehole.—After the Borehole is carefully drilled—and for economical reasons it should be as nearly circular as possible—it is cleaned out so that no débris remains. CHARGING. Cartridges (i.e., Dynamite or other Explosive in watertight cases).—The Cartridge or Cartridges should be of such a size as to pass in easily—that is, the diameter of the borehole should be ^in. to Jin. larger than the diameter of the cartridges, and they should be in- serted singly in the borehole. Cartridges ordered of, say, lin. diameter are made somewhat smaller so as to suit boreholes of that diameter. Fixing Fuse.—When the last Cartridge (or Primer Cartridge) comes to be inserted, a hole should be made in it by means of a small pointed wooden stick, and the Detonator (attached to the fuse wires) should be pressed lightly therein until it is completely buried in the cartridge, the operator then tying the cartridge tightly over the wires with a piece of twine, to prevent the withdrawal of the Detonator from the explosive. The Primer Cartridge is then gently pressed into the borehole by the wooden tamping rod, and brought into contact with the main charge. It has been claimed that in many instances there is a distinct advantage in inserting the Primer Cartridge (/.<?., the cartridge into which the Detonator is inserted) in the borehole with the Detonator downwards. This will also prevent the Detonator being withdrawn by any chance during the operation of tamping. But when such procedure is adopted, special care should be taken not to injure the wires during the process of tamping. Tamping.—A lump of clay should be pressed in after the last cartridge, next a cushion of paper to withstand the tamping, and then the usual tamping material should be rammed in without using rough force ; care should be taken that a wooden Tamping Rod (not worn to a point, but cylindrical throughout) alone is used. The topmost 3Ù1. or 4m. of the hole need not be tamped, but should be filled with tempered clay lightly squeezed in. Ordinary clay is apt to become soft and is liable to disintegrate under water when being applied as a tamping. It has been found that a mixture of dried clay and oil of the consistency of putty forms an excellent medium for the purpose. In submarine blasting, where so much depends upon the efficiency of each shot, the extra trouble of preparing such a tamping is amply repaid. Connecting the Cable.—The ends of the Fuse wires and Cable wires should be stripped for a length of about 2in., and made perfectly bright and clean. They should then be carefully joined together by twisting the bare end of the Fuse wire tightly round the bare end of the Cable wire (this precaution will tend to prolong the life of the Cable). To ensure perfect insulation of the wire connections of importance, especially in simultaneous or circuit shot-firing, the use of Chatterton’s Compound and of Prepared Rubber Taping is recom- mended. TWIST EXPLODER. High and Tow Tension.—This Exploder has been specially designed as a Machine capable of firing both High and Low-Tension Fuses. It is provided with a cover, which pro- tects the firing handle and the connecting screws, and also with a strong shoulder strap for convenience in carrying. Note.—Care must be taken that the hands do not touch the terminals during shot- firing. Disconnecting the Cable.—Immediately after a shot has been fired, the shot-firer should disconnect the Cable from the Exploder. This instruction should be followed even when, by defective manipulation, a miss-fire has occurred. 104