ASHPITS.

53

The coping of the side walls is made of large stones, timber stringers, or iron plates.Where coping-stones extend over the full width of the wall, it is not necessary to anchor themto the side walls below them ; but where the stones are small they should be anchored to thewall and tied together with iron clamps. Timber coping should be fastened to the wall underit about every 5 or 6 ft. with iron anchor-bolts. Where wrought- or cast-iron coping-platesare used, special coping-stones are not required. The coping should always be properlysecured in place, so as to prevent the rails spreading. In some designs transverse walls areprovided at intervals to tie the side walls together, or iron tie-rods and braces are used inplace of transverse walls.

The rail-fastenings vary according to the kind of coping used on the side walls. On tim-ber coping the rails are either fastened in the usual manner with track-spikes with reversedheads (bridge-spikes), or with screw-spikes, or the rail is riveted to a wrought-iron plate, whichplate is fastened to the timber coping about every 5 ft. with bolts or dowels, as shown in Figs.144 and 145. Where a cast- or wrought-iron plate is used as coping, covering the top wallentirely, the rail is fastened to it by means of screw-bolts and small clips. Where stonecoping is used the rails can be fastened by ordinary track-spikes driven into wooden dowels,about 2 in. in diameter, bedded in holes drilled in the stone. Another form of connection tostone coping is by rag-bolts or split-bolts with keys, set with cement, lead, or sulphur in holesdrilled in the coping, the rail flange being caught by an appropriate clip, as shown in Fig. 141.Another method, shown in Fig. 142, is to use regular bed-plates or clip-plates under the rail,spaced at intervals of 3 to 4 ft., and properly fastened to the stone coping with rag-bolts or split-bolts, as above described. Where iron rail-chairsare used as rail supports and fasteners, they areeither small cast-iron chairs, about 8 in. high,bedded in the side walls and spaced about 4 ft.apart, as shown in Figs. 153 and 154, or largecast-iron chairs spaced about 3 to 4 ft. apart, theside walls being either walled up between thechairs, as shown in Figs. 148 and 149, or left open, as shown in Figs. 150 to 152.

The paving usually consists of brick or stone, although concrete is sometimes employed.The material under the paving should be carefully tamped and consolidated, and a sublayerof concrete under the brick or stone paving is to be recommended. Firebrick pavement resiststhe heat better than common hard brick, but it is soon worn out by the shovelling and frommen working on it. Some roads, therefore, prefer to use common hard brick, which is easilyand cheaply replaced when necessary. Stone flagging, unless well bedded, is easily broken,and, therefore, not desirable. Ordinary rough stone paving, such as is generally used underbox culverts on railroads, is too rough for shovelling, if the bottom of pit is to be kept clean.City paving-blocks are generally too expensive, and do not present a much better surface toshovel on than ordinary paving-stones. A concrete bottom will soon disintegrate on thesurface, and, once started, will grow rapidly worse. A pavement of common hard brick, seton edge, and laid on a good foundation or in a bed of concrete, will prove most desirable inthe long-run.

To secure proper drainage of the pit, the paving is dished transversely and pitched longi-

Fig. 141.—Cross-section Fig. 142.—Perspective

of Rail-fastening. of Rail-fastening.