22 TECHNOLOGY. 
flanges to pass when the train continues on the main track. Two rails of 
the main track are connected by the iron bars ce, and are attached as usual 
to chairs at the ends furthest distant from the turnout; each rests on a cast- 
iron plate provided with shoulders, ¢e, and is movable by means of a lever 
attached to the end of the bar d, its elasticity allowing it to be bent so as 
to be on a line with 6, the shoulder e limiting the extent of the motion. 
When it is desired to turn out on either side of the main track, the switch 
is arranged as in jig. 51, where the rails ef turn out to the left and gk to 
the right. : 
Another kind of switch is shown in jig. 50; the movable rails and the 
tongue s turn on pivots, and are placed in the desired position by means 
of a lever attached tom. The construction of such a lever is seen in pil. 3, 
jig. 29; it is contained in a box, ghkl, which is partly imbedded in the 
earth. The lever d turns on the pivot ¢ and moves the switch by means of 
the bar b, attached at a; it is also connected by the band e with a spring, 
which is compressed when the lever is brought from the position p into the 
position g, when the switch is aligned with the side-track. When the pres- 
sure on the lever is relinquished, the action of the spring will replace the 
switch in its position in the main track. The switch just described is 
used on the London and Greenwich Railroad. When the guide-rails do 
not move on pivots, but are only bent, they will of their own accord return 
to their former position as soon as the pressure on the bar is relinquished. 
Another switch for a turnout is shown in pl. 2, jig. 49, which is an excel- 
lent plan. 
An arrangement similar to a siding, termed a crossing, is made on roads 
with double tracks to enable trains to pass from one track to the other. 
Fig. 52 represents a crossing connecting the two tracks cx and pF in every 
direction; ab, cd, ef, gh, are the rails of the tracks; 2h, lm, no, pq, rs, tu, 
ow, xy, those of the crossing. «8 and yé are two rails 6 ft. in length, form- 
ing part of the main tracks and held together by ties as the figure shows ; 
they can be moved about a pivot in the centre so as to form the connexion 
between any set of corresponding rails, as may be desired. Cast-iron plates, 
called crossing-plates or frogs (fig. 54), are laid where the rails cross each 
other: d, ¢,.f, g, are the ends of the rails ; the piece abe of wrought-iron is 
riveted or screwed on the plate, and the cheeks m and prevent the wheels 
from sliding off. It may be preferable to weld the rails together in the 
requisite form, as in jig. 53, and to lay the pieces p and g at the sides to 
keep the flanges in the proper direction. For unimportant crossings short 
tongues of wrought-iron, fastened on wood and brought into the required 
position with the foot, are generally sufficient. 
Pl. 3, fig. 9, represents a switch with a counterpoise, wu, which causes the 
switch to assume its position in the main-track whenever left to itself. The 
switch in use on the Magdeburg and Leipsic road is represented in jigs. 10, 
11, and 12. It is moved by a crank, A, A (jig. 12), or an eccentric in the 
box, ¢, and the position of the target, n (jig. 11), to the right or left always 
indicates the position of the switch, the two sides of the target being, more- 
over, painted of different colors. 
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