As an accessory, a picker, shown by the three views, [Figs. 41 to 43], [Fig. 42] indicating its correct position when in operation, is employed where the strata is too irregular or compact to be effectually cleared away by the cutter of the mizer. The picker is fixed upon the same rods above the mizer, and is used simultaneously, being raised and lowered with that tool.
Figs. 46-48.
Sectional Plans.
The cutting end of the picker is frequently replaced by a scratcher, [Figs. 44, 45]. This useful tool rakes or scratches up the débris thrown by the mizer beyond its own working range, and causes it to accumulate in the centre of the sinking, where it is again subjected to the action of the mizer.
Brick steining is executed either in bricks laid dry or in cement, in ordinary clay 9-inch work being used for large wells, and half-brick, or 41⁄2-inch work, for small wells.
[Figs. 46 and 47] show the method of laying for 9-inch work, and [Fig. 48] for 41⁄2 inches. The bricks are laid flat, breaking joint; and to keep out moderate land-springs clay, puddle, or concrete is often introduced at the back of the steining; for most purposes concrete is the best, as, in addition to its impervious character, it adds greatly to the strength of the steining. A ring or two of brickwork in cement is often introduced at intervals, varying from 5 feet to 12 feet apart, to strengthen the shaft, and facilitate the construction of the well.
Too much care cannot be bestowed upon the steining; if properly executed it will effectually exclude all objectionable infiltration, but badly made, it may prove a permanent source of trouble and annoyance. Half the wells condemned on account of sewage contamination really fail because of bad steining.