ON AMERICAN PERMANENT WAY. 607 



to carry a train off on to a siding without any break in the con- 

 tinuity of the rails. This is accomplished in the following manner : — ■ 

 The switch rails and a movable guard rail are connected together, the 

 inner switch rail being shaped like the letter U, and having one side, 

 next the rail, terminating in a point, which, when tbe switch is set for 

 the side track, laps under the main rail and guides the wheel away from 

 it. The guard rail acts also to draw this wheel away from tbe main 

 line, so as to insure the point being cleared by the flanges. The result 

 brings the tread of the wheel upon the outer switch rail, which at the end 

 is flush with the main rail, but. gradually rising, lifts the wheel in a 

 distance of about 4^ feet, until it can pass over the top of the main 

 rail. Each end of the longitudinal shaft of the operating machinery has a 

 crank, one connected with the guard rail and the other with the switch 

 rails, and the angles of these are so arranged with reference to each other 

 that while the crank holding the switch is on the dead centre or a little 

 below it, that at the other end is at such a position as to be easily acted 

 on by the movable guard rail. Any lateral pressure, therefore, against 

 the switch when it is in use, tends to hold it in position. If the switch 

 should accidentally be left closed, the first wheels of a train on main line, 

 acting on the guard rail, operate the switch, placing it all right for main 

 track. These switches are rather expensive, but have given great satis- 

 faction where used. Their employment depends upon the question 

 as to whether their increased expense, complication, multiplication of 

 parts, &c, are more than compensated for by their increased efficiency 

 over the simpler safety split switch. 



The Wharton Switch Company also manufacture a safety split switch, 

 with the guard rail attachment for throwing it right for main line, by the 

 action of the wheels of a train, when left wrong. 



When one rail is crossed by another rail, unless under some such ar- 

 rangement as the Wharton switch, the rail crossed must have an opening or 

 slit in it to allow the flanges of the wheels to pass through. The arrange- 

 ment that provides for this is called a ' frog.' The earliest forms of frogs 

 were of cast iron ; then they were steel-plated, afterwards cast-steel frogs 

 were used, and several forms of construction have been made of steel 

 plates alternating with layers of wood and rubber to seenre elasticity. 

 Frogs were also made of iron rails, such as are used in the tracks, fitted 

 together in various ways ; but iron rails wore out so rapidly under service 

 that they were not found satisfactory. When, however, steel rails came 

 into the market, it became entirely practicable to make use of them for 

 frogs, and the result has been that frogs of this kind have superseded 

 everything else. Steel rail frogs possess many advantages over the other 

 varieties. Using the same standard rail as in the track, they become an 

 integral part of it, can be secured with the same splice joints, use the 

 same ties, spikes, &c, and for a perfect realisation of the problem there 

 should be no necessity for cutting away any parts of the ties, or adjust- 

 ment of them, different from what is required in standard track, and the 

 rails which make the frog should be kept to their full section and have 

 their full resistance to service that they possess in their ordinary location. 

 What is wanted, then, is a simple construction that will bind the rails 

 together in the form required in a solid, permanent manner. The nearer 

 these conditions can be fulfilled the better. 



There are two principal kinds of frogs in use, the ' Spring Rail ' and 

 the ' Stiff Frog.' Spring rail frogs are sometimes made by riveting the 



