566 



POPULAR SCIENCE MONTHLY. 



times cover the tracks and fill the conduits, hence the securing of 

 perfect insulation presents great difficulties. The manner in which 

 inventors have sought to surmount the obstacles can be made clear 

 bj the aid of a few illustrations of typical designs. 



riG. 25. — UNnEUGRoirND Conddit with Protecting Shield for the Conpttctor. 



Fig. 25 shows one of the forms of a class of underground con- 

 duits belonging to the inclosed conductor type. The track rails 

 are supported upon the outer ends of large castings, F F, com- 

 monly called yokes. These are made of such size that the portion 

 below the opening which incloses the conduit may be of sufficient 

 depth to afford the requisite strength to properly support the track. 

 The conductor that carries the current is located at / and is insu- 

 lated from the casing ;, which forms the lower half of the conduit, 

 by the stands g. From the car a bar, P, which is called a plow, 

 projects downward through the slot between the rails, 1c h, and on 

 its end is spread out into a fork, d, which carries a pulley, e. Wlien 

 this pulley is in contact with the conductor f the current passes 

 through the plow P to the motors upon the car, and thence to 

 the track rails and back to the power house. 



As the yokes F F and the conduit casing j are made of iron 

 and are in metallic connection with the track rails, it is evident 

 that if the conduits should fill with water to the depth of the wire 

 / the current would pass directly to the rails, and thus would avoid 

 the longer path through the motors. To prevent this occurrence, 

 the sides of the conduit are inclosed with the sheet-iron covers c c, 

 which nominally are in the position shown by the dotted lines i i. 



