The various modes of piercing beds of quicksand are;--By hanging tubbing to that already fixed, and adding fresh rings as the sand is removed. This is only practicable when the quantity of sand is inconsiderable. By heavily weighting a cylinder of iron of the same size as the shaft, and thus forcing it down through the sand. By keeping back the sand by the use of piles--a resource that can only be recommended when the bed of sand is not of great thickness. When the water is excessive, by using pneumatic agency. As these operations are apart from our immediate subject we need not further discuss them. M. Chaudron's system, which is a modification of Kind's, is divisible into the following distinct processes, which consist of;-- The erection of the necessary machinery on the surface, and the opening of the mine. The boring of the pits to the lowest part of the water-bearing strata. The placing of the tubbing. The introduction of cement behind the tubbing to complete its solidity. The extraction of the water from the pits, and the placing of the wedging cribs, or "faux cuvelage," below the moss box. [Illustration: Surface Plant Elevation. Fig. 119.] [Illustration: Surface Plant Elevation. Fig. 120.] [Illustration: Surface Plant Plan. Fig. 121.] Figs. 119 to 121 show in elevations and in plan the plant usually employed on the surface. O is a small capstan engine, having a cylinder 20 inches in diameter and a stroke of 32 inches, working on the third motion. Attached to this engine, and working in the small pit C, is a counterbalance weight. This engine is used for raising and lowering boring tools, and for lifting the _débris_ resulting from the boring. As far as the platform, which is about 10 feet from the surface, the pit has a diameter of 19 feet, or 4 feet more than the diameter of the pit below. A at level of about 38 feet above this platform there is a tramway on which small trucks run, carrying the _débris_ cylinder on one side, and the boring tools on the other. At a level of 48 feet above the platform are placed supports for the wooden spears to which the boring tools are attached. The machinery for boring is worked by a cylinder, which has a diameter of 39-1/3 inches, and a full stroke of 39-1/3 inches, the usual stroke varying from 2 feet to 3 feet. A massive beam of wood transmits motion from this cylinder to the boring apparatus, the connection between the beam and the piston-rod and the beam and the boring tools being made by a chain. The engine-man sits close to the engine, and applies the steam above the piston only. The down stroke of the boring tools is caused by the sudden opening of the exhaust, and a frame then prevents the shock of the boring rods from being too severe. The engines work at speeds varying from 12 to 18 strokes a minute, according to the character of the strata passed through. [Illustration: The Small Trepan. Fig. 122.] [Illustration: The Small Trepan. Fig. 123.]