=44. Sinking a Shaft with Cases.=--(Pl. XII, Figs. 26 and 27.)--A case of the required size is put together and accurately placed upon the site of the shaft, whose dimensions are marked upon the ground outside it. The case is then removed and the earth excavated to the depth of the case, which is placed in the excavation with its top flush with the surface of the ground. Its position is carefully verified, and it is secured in position by packing earth around it. The excavation is then continued for the depth of another case, which is put in place as follows, viz.: One end piece is placed in position, the tenons of the two side pieces are inserted in the mortises at its ends, and the side pieces are pushed back into position; a pocket-shaped excavation is made with a push-pick beyond the end of one of the side pieces and running back three or four inches into the side wall; the remaining end piece is inserted in this far enough to allow the mortise at its other end to slip over its corresponding tenon; it is then drawn back, and the tenons at both ends fitted into their mortises. The notches cut in the sides of the pieces allow them to be easily handled. The next case is placed in the same way, care being taken not to excavate two consecutive pockets at the same angle. When practicable, it is well to fill up these pockets by stuffing in sods from below before placing the next case. Some miners prefer to place one tenoned piece first, then the two mortised pieces, leaving a wedge-shaped opening behind one of them, and insert the other tenoned piece last, drawing the mortised piece forward upon its tenon. When the sides of the cases are tenoned at one end only and secured by wedges at the other, they are easily placed in position without cutting out behind them. =45.= Upon reaching the level of the top of the gallery, the pieces on the gallery side of the shaft are omitted if the ground is firm, but if it needs support these pieces are put in place and secured by cleats or braces, but the tenons are not inserted in the mortises. =46. Driving a Gallery with Cases= (Pl. XII, Fig. 27).--This is practicable only when the soil is somewhat firm. In breaking out from the side of the shaft, a frame is first placed inside the shaft to support the ends of the shaft cases resting against the pieces which are to be removed. The latter pieces are then taken out and grooves are cut in the earth for the ground-sill, stanchions, and cap-sill of the gallery, and these are put in place in a manner entirely analogous to that described for sinking a shaft. This case is set flush with the inside of the shaft and supports the side pieces, whose tenons rest upon its stanchions. The projecting earth is then cut away and grooves are cut for the next case, which is placed in position and the excavation continued as before.