well-borers. However, like the disengagement of the tool intended to comminute the rock, it depends for its success upon the bore-hole being filled with water. The presence of a column of water is, however, not always to be commended, especially when the borings have to be executed in the carboniferous strata.

E. Fauck's Boring System with Free-fall Drill.

The principal constituents of this system are as follows: The drilling chisels, Figs. 33 and 34, which are made of best cast

steel in numbers of from 2.4 to 24.4 inches cutting width. The side edges are curved towards the centre of the bore-hole. The double keying, b, serves for connecting the drill with the upper

The connection is rapidly

portion of the disengaging rod. broken by means of special wedges, which are driven in the holes, a, Fig. 35. The collar, a, Figs. 33 and 34, serves for conveniently taking hold of the drill in case of breakage. The boring rod, Fig. 35, serves to increase the weight of the droptool, thus giving greater effect to the stroke.

The reamer, Figs. 36, 37 and 38, is inserted between the boring rod and the drill when the tubing is to be carried below the drill-hole by enlarging the latter. The body is of wrought iron, and is provided above with a spindle, a, and below with a

socket, b, for a double key joint. In the centre are two cutting jaws, c, of best crucible steel, which can be readily replaced by others of different dimensions. When introducing the tool in the bore-hole, the cutting jaws are tied together with wire (Fig. 37), which is carried over the edge of the drill. The latter on striking the bottom of the bore-hole cuts the wire, and the cutting jaws separate below the tubes. The contrivance for holding the cutting jaws lies protected in the interior of the apparatus, and will be understood from Fig. 38.

The free-fall tool consists of two parts, viz., the drop-tool and the socket. The so-called catch-wedge, c, Fig. 39, slides up and down in the two longitudinal slits of the socket. It connects the wrought-iron drop-tool, a, with the socket, b. The catch-wedge, c, Fig. 40, is held below by another wedge, c2, which, in its turn, is secured by a conical pin, c. On the lower end the drop-tool is provided with a collar, e, and spindle, f, for joining it to the boring rod by means of a double key joint. The collar, g, serves for taking hold of the tool in case of breakage.

Below the slits

The wrought-iron socket is connected with the boring rod by means of a ferrule on the screw-bolt h and collar i. The slits d are enlarged to wedge-points k, the cushions of which are formed of inserted steel segments /, Fig. 41. widen to the so-called safety-lock m, Fig. 39. When letting down the boring tools in the bore-hole, the catch-wedge rests in this safety lock, and in case the drill, on its way down, sticks fast, strikes the upper grooving, whereby the drop-tool is prevented from being caught on the wedge-cushion above, and from causing damage by suddenly dropping down.

F. Fauck's Self-acting Free-fall Drill.

The self-acting free-fall drill, Fig. 42, is arranged for diameters of from 11.81 to 19.37 inches, and for depths of over 1,000 feet. The apparatus consists of the chisel a, free-fall tool e, and frame d. Instead of one, the free-fall tool has two catch-wedges. The lower one, f, of these catch-wedges is immovable and intended for guidance and suspension in the safety-lock, while the upper one, g, the actual catch-wedge, turns in steel bands. The catching of the drop-tool is effected in the ordinary manner, and the self-acting detachment by the pressure of the lower oblique plane of the rail h against the catch-wedge. The upper continuation of the socket of the free-fall tool forms a longer rod i of square cross section. It is guided in the upper portion d' of the frame and takes the latter along when the boring rod is turned round. On top it is

provided with the screw k, which serves for connecting it with the boring rods. The frame, which consists of four round iron rods and the connecting pieces d and d', is slightly raised during the descent of the instrument, the turning of the boring rod being also effected during this time.

The boring rods, Fig. 43, of square wrought iron, are each 16 feet 4 inches long, and are screwed together by conical male screws a and female screws b. The upper collar c below the male screw a serves for the lift-pulley, while the key catches under the lower collar d. A diameter of 3/4 inch gives the rods sufficient solidity for attaining a considerable depth and spring, as well as for the transmission of the turning of the boring rod to the free-fall tool. For exceptionally great depths it is better to give the rods a diameter of about 1 inch.

The boring transmission, Figs. 44 and 45, is arranged in accordance with the following points:

1. Good spring of the beam as principal condition.

2. As high a stroke as possible, from 3 to 41⁄2 feet.

3. High position of the stirrup of the beam for emptying the bore-shaft.

4. A beam stirrup which can be laid back without moving back the entire beam.