2 72 



SCIENCE. 



[Vol. XIII. No. 323 



THE SMITH ELECTRIC CONDUIT SYSTEM. 



The Smith conduit is an hermetically sealed tube or box, prefer- 

 ably of wood, properly treated by any process calculated to resist 

 moisture and rot, which is laid midway between the rails of any 

 car-track. This conduit or tube contains the electric conductor or 

 supply-wire on its inside bottom surface, insulated from loss by 

 leakage, corrosion, or wear; and its upper or exposed surface is 

 covered with a series of non-magnetizable metallic plates, each 

 about four feet in length, which are screwed down on to strips or 

 sheets of insulating material, and each insulated from its neighbor, 

 so that the surface of the conduit becomes a strip of metal, broken 

 up into sections of not more than four feet each, from which the 

 car, in passing along over its surface, may take off and use a cur- 

 rent of electricity, provided they are, for the time being, directly 

 connected with the source of supply at the bottom of the conduit. 



This connection is made in the following manner (see cut) : At 

 distances of one or two feet apart, movable connecting pieces are 

 attached to the electric conductor, and rest thereon by gravity until 

 such time as they are attracted from above. The car is provided 



cars. By the use of large conductors and a current of low tension, 

 the loss by leakage is reduced, and should almost cease to be a 

 factor in our calculations. The inventor claims that from actual 

 experiment's he is assured that this loss, even at such points as 

 may be covered by cars, and under unfavorable circumstances, 

 such as heavy rain and flooded streets, cannot exceed two or three 

 per cent. 



The conduit, being not over nine inches deep by five in width, 

 can be laid directly on the cross-ties of the ordinary street-railway 

 track without any cutting of timber or alteration whatever, while it 

 may also be carried around sewer man-holes and ordinary street 

 obstructions. In the case of a single-track road, the benefits of 

 this system are obvious, as the conductor may be branched through 

 all switches and turnouts, and no car can be without power, or 

 light at night, at any point on the road. 



The company claims, that, under the patents granted March 5, a 

 conduit can be laid down ready for use at not more than one-half 

 the cost of any other underground system. 



It is a part of the plan, as covered by patents, that a blower, or 

 exhaust-fan, or combination of both, should be used to keep a con. 



'^lffigbppijiSD^%^^g:^:r:^.4 



A, longitudinal section of conduit; B, insulated top plates; C, connectors; X>, electric brushes; £, electro-magnets unde 

 of conduit and track ; jFf^ scale-beam connector ; /, steel spring or band iron connector. 



y^, sweeping brooms ; (?, vertical 



with a row of magnets on its under surface, which pass along close 

 to the metallic top of the conduit, and, in passing, attract by mag- 

 netic influence the connecting pieces before referred to, each of 

 which is provided at one end with a small soft-iron armature. It 

 will thus be seen that as these "connectors" each rises up in its 

 turn through small holes in the top board of the conduit, on touch- 

 ing the lower part of the surface plate, they form a direct electric 

 connection between the cable and such top plates as the car and 

 its magnets cover ; so that such parts of the top plates, and only 

 such parts, are always in electrical connection, and form the me- 

 dium from which the car in its passage is supplied with its cur- 

 rent, and power for its electro-motor. It will be noticed that there 

 is no dependence placed on any one connector, but that the mag- 

 nets are at all times holding up a number of them, or all which 

 may at any one time be beneath the car ; and as these connections 

 are constantly being made ahead of the car in its passage, while at 

 the same time broken behind it, the direct attachment of the motor 

 with its source of supply is never broken, and there is no " spark- 

 ing " between the contact-pieces and the conductor, and no danger 

 of burning out dynamos or connections. 



In this system an underground electric supply is given for use 

 where overhead wires are not desired. As the conduit is hermet- 

 ically sealed, and without any slot or opening whatever, it cannot 

 catch rain, snow and dirt, etc. Immunity from danger is claimed, 

 as the surface of the conduit is dead, and contains no current of 

 electricity, excepting such portions as are covered by the car or 



stant current of air passing through the conduit tube at all times, 

 in order to keep its interior free from moisture of condensation, and 

 all its parts thoroughly insulated. This air-current will also serve 

 to detect leaks caused by damage to the conduit from any cause, 

 and insure its immediate repair. 



A "non-magnetic shield," not shown in the cut, covers the mag- 

 nets, and prevents the picking-up of iron fragments from the sur- 

 face of the track, and insures the full efficiency of magnet-power 

 for the purposes for which it is intended. 



Each car is provided with brooms at either end, to sweep off 

 surface dirt on its passage, and insure good connections to the 

 rubbing or frictional contact of the electrical brushes or shoes 

 which follow, and carry the current to the motor, from which, after 

 having done its work, it passes off to either rail or the ground. 

 The illustration shows the simplest forms of scale-beam levers, 

 used as " connectors," and not necessarily the form preferred in 

 use. 



A full investigation as to the merits of the system is invited by 

 Harry W. Smith, the inventor, and the Smith Electric Conduit 

 Company, 120 Broadway, New York. 



A COJMPOSITE photograph, nearly life-size, of eleven members 

 of the faculty of Washington and Lee University, has been taken 

 upon one sensitive-plate with a total exposure of forty-four seconds, 

 each person receiving an exposure of four seconds. The photog- 

 rapher was Mr. Miley of Lexington, Va. 



