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

ROCK REMOVAL WITHOUT EXPLOSIVES. Submarine Rock-cutting Plant. (Illustrated on page 111.) Description of the Cutter. Working Principle. Another method of rock removal which has been very successfully employed, and in which the use of explosives is not required is the Lobnitz system, which is worked from a barge or other vessel. The expense of plant of this description would, however, only be justified in cases where large quantities of rock had to be dealt with. Briefly, the plant consists of a forged steel circular bar called the "cutter,” which is fitted with a removable point similar in form to that of a large projectile and made of armour-piercing steel. In certain cases, however, a chisel-shaped point has been found more suitable for driving into very tough rock ; in other in- stances a point with a series of tooth edges has been used, as in the Irrawaddy River operations where the current made it difficult to ensure that the blows would be struck on the same spot every time. In every case these points are separate so that they can be replaced without necessitating the renewal of the whole bar. The bars themselves are tapered according to the stresses due to the drop, their weight per metre of length being one ton. The composition of the steel for the points varies according to the material to be pulverised ; for instance, what would answer for granite would not give such satisfactory results in limestone. The plant is built in sizes having rock-cutters weighing from six tons upwards. The principle of working this rock-cutter ts that it is hoisted by a powerful steam winch and then released, and the cutter allowed to fall freely by its own weight on to the rock, the whole force of the blow being concentrated on a very small surface as many times as may be necessary to effect the required disintegra- tion. Special devices are employed to ensure that successive blows are struck on the right spot, and for quick hoisting and release. The barges from which the cutters are worked can be built self-propelling if required. The cutters are worked from the middle of the barge, or they can be supplied to work from one end to suit the exigencies of the work. When asking for estimates for this plant, the following particulars should be sent, viz. :— (i) Approximate quantity of rock to be excavated. (2) Nature of the rock (a small sample piece will assist in determining the most suitable cutter). no