ON AMERICAN PERMANENT WAT. 605 



in details, or in the application of the principle. This form of switch 

 consists simply of a movable pair of split or tapering rails, which are 

 fastened to the two inside rails of the four that come together, the outer 

 rails being fixed, and connected and made continuous with the siDgle 

 track from which the divergence takes place. These split rails at the 

 opposite end are free to be shifted sideways and move with each other 

 being tied together to a certain fixed distance apart by rods, this dis- 

 tance being made so that only one of them can be in contact with a fixed 

 rail at the same time, the other being separated from the fixed rail by a 

 space, called the ' throwing ' of the switch, sufficient to pass the flanges 

 ef wheels of trains. The free end of the pointed rails is called the ' toe,' 

 and the fixed or pivot end the 'heel' of the switch. At the heel, the 

 fixed distance from the adjoining rail must be enough to pass wheels 

 easily. It is essential that the point when pressed up against the fixed 

 or ' stock ' rail, as it is called, should leave no projection that a wheel 

 approaching the switch could run against. For some years it was 

 customary to make the points quite blunt, and to cut a recess into the 

 side of the stock rail for the point to fit into ; but as now made tho 

 point rails are tapered down to a thin wedge, and shaped so as to fit 

 very closely to the stock rails resting on thsm, and having the thin point 

 also tapered for a short distance from the end, so that there will be no 

 risk of the wheels touching the point rails until they reach a thicker 

 part. Nothing has to be done to the stock rails, and no chancres of 

 temperature or creeping of rails will affect the point rails. The throw of 

 the switch is usually made about 3-£ or 4 inches, to avoid any danger 

 of the open end of the point beiDg struck by the back of a wheel, although 

 less throw would answer. Sometimes short guard rails are used in 

 front of the points to protect them. The two point rails require to be 

 connected together by rods or bars, which should be as low to the sur- 

 face of the cross-ties as possible, and rigid vertically, while flexible to 

 some extent sideways to allow of self-adjustment. 



Split switches are made by a number of firms, each of which usually 

 has some special patent or detail of its own in the style which it builds. 

 Fig. 1, Plate VIII., shows the split switch as made by the Pennsylvania 

 Steel Company, which will very well illustrate the type. The form of 

 connecting bar is also shown. The two arms of the bar are rigidly 

 attached to the webs of the rails, and are secured together in the centre 

 by means of two flat plates, which lay on each side of them, and arc 

 riveted together through a separating block. The arms, having only one 

 rivet in tacti, can adjust themselves between the plates about tins rivet as 

 a pivot. The point rails of this Company are made 15 feet long, bein"- 

 one-half of a 30-feet rail. They are planed and tapered down without 

 being heated, and are shaped so as to completely fit the stock rails and 

 to rest on the flanges of the same throughout the whole length of the 

 tapered portion, in such a manner that the point rails receive substantial 

 support if required, although the wheels do not come in contact with them 

 until they have passed the extreme end. The slide plates under the point 

 rails are of wrought iron, quite plain except near the point, where they 

 extend also under the stock rails, and have the ends turned up to hold rait 

 braces. 



When a train approaches a split switch by the heel, it is called a 

 'trailing switch;' but if the toe or point is approached first, then it is 

 called a ' facing switch.' Single point switches are sometimes made, with 



