The change is already spreading to model plant, and not without good reason, as the miniature electric railway possesses decided advantages of its own.  Instead of having to chase the locomotive to stop or reverse it, one merely has to press a button or move a switch.  The fascinations of a model steam locomotive, with its furnace, hissing of steam, business-like puffings, and a visible working of piston and connecting rods, are not to be denied, any more than that a full-sized steam locomotive is a more imposing object at rest or in motion than its electric rival.  On the other hand, the ease of control already noticed, and the absence of burning fuel, water leakage, smoke and fumes, are strong points in favour of the electric track, which does no more harm to a carpet than to a front lawn, being essentially clean to handle.  Under the head of cost the electric locomotive comes out well, as motors can be purchased cheaply; and connecting them up with driving wheels is a much less troublesome business than the construction of an equally efficient steamer.  One may add that the electric motor is ready to start at a moment’s notice:  there is no delay corresponding to that caused by the raising of steam.

The Track

We will consider this first, as its design must govern, within certain limits, the design of the locomotive.  There are three systems of electrical transmission available.

1.  The trolley system, with overhead cable attached to insulators on posts, to carry the current one way, the rails being used as the “return.”  This system has the disadvantages associated with a wire over which the human foot may easily trip with disastrous effect.

2.  That in which one of the wheel rails is used for taking the current to the motor, and the other as the return.  The objection to the system is that the wheels must be insulated, to prevent short circuiting; and this, besides causing trouble in construction, makes it impossible to use the ordinary model rolling stock.  To its credit one may place the fact that only two rails are needed.

3.  The third and, we think, best system, which has an insulated third rail as one half of the circuit, and both wheel rails as the return, the motor being kept in connection with the third rail by means of a collector projecting from the frame and pressing against the top of the third rail.  The last, for reasons of convenience, is placed between the wheel rails.  We will assume that this system is to be employed.

[Illustration:  Fig. 42.—­Details of rails for electric track.]

Gauge.—­For indoor and short tracks generally it is advisable to keep the gauge narrow, so that sharp curves may be employed without causing undue friction between rails and wheels.  In the present instance we specify a 2-inch gauge, for which, as also for 1-1/2 and 1-1/4 inch, standard rolling stock is supplied by the manufacturers.