CliAP. XXX.

RAILROADS.

1573

arising from the variations of temperature rendering it difficult to pass the pins through themand the sides of the chairs, as had been done with those of shorter lengths. The joints areliable to become loose from the constant action of the carriages, and the most effectual wayof tightening them is to drive wedges of iron along the sides of the rail.

London and Birmingham Railway has a joint or double chair, and a single or interme-diate, made of strong grey cast-iron, of the No. 1. quality. The double chair has 2 wrought

Fig. 2944. SINGLE CHAIR,

Fig. 2945. plan

iron pins, 2 wrought-iron wedge bolts, and 2 wrought-iron keys: the single or intermediatechairs have 2 wrought-iron pins, and 1 wrought-iron key, which are of the best malleableiron.

By a reference to the plan it will be seen that the seat of the rail is convex on the one, anddouble convex in the other; the side of the chair next to the flanges of the wheels is incontact with the rail at only two points: on the other side, the rail is secured by a cast-iron

Fig. 2947.

Fig. 2946. DOUBLE CHAIR.

rmmm.

Fig. 2949.

chock of a spheroidal form where it touches the rail; this chock has a step or foot by whichit rests on the bottom of the chair, and is wedged into its place by means of a wrought-iron *key, which passes perpendicu-larly into a mortise, one-half ofwhich is cut through the chock,and the other half onthe chair.

The chairs were pinneddown to the blocks with ironspikes 7 inches long, and ^inch in diameter, their headsbeing 1^ inch in diameter.

Some of the fish-bellied railswere laid down upon this rail-

., , . e f. , • u Fig. 2948. STEPHENSON’S PATENT.

way with chairs, for which °

Mr. Robert Stephenson took out a patent; the weight of the rail was 50 pounds per yardin length, and it fitted exactly into the chair, with no space for lateral movement. A keyacts directly against the side of the rail through amortise-hole passing into the sides of the chair; throughthese holes is driven a tapering key, which, acting uponthe pin, forces it against the sides of the rail. The pinhas a sharp point, and therefore, when tightly driven, in-dents itself into the rail.

On the London and Croydon Railway chairs are dis-pensed with altogether, and the rail is screwed down tolongitudinal sleepers, laid on transverse timbers through-out The base of the rail is in width 4\ inches, producinggreat steadiness : in every yard in length are two sleepers,and over them four rows of longitudinal sleepers; 16,672cubic feet of timber were used for every mile, pie crossor transverse sleepers are 8 feet in length, and 9 by 4^inches: the longitudinal timbers 9 by 4£ also.

The iron rails were in weight per lineal yard 48pounds, and that per mile was 337,930 pounds; thereare 7040 trenails, as many bolts, and 16 screws to every yard, making 28,160 screws,

5 h 3

Fig. 2950.