. Revised and enlarged ed. of the science of railways . thought or are, however, certain objections to thissystem which in some cases may be sufficient toexclude its use. Live rails are inadmissible incity streets, therefore, this system cannot beused for street railways. They may also becomeobjectional)le in yards where many tracks inter-sect in a complicated manner, as they thusbecome dangerous to yardmen and third rail must be omitted at all gradestreet crossings. This cuts off the source of power and the lightsfrom the train whenevera crossing is passed un-less
. Revised and enlarged ed. of the science of railways . thought or are, however, certain objections to thissystem which in some cases may be sufficient toexclude its use. Live rails are inadmissible incity streets, therefore, this system cannot beused for street railways. They may also becomeobjectional)le in yards where many tracks inter-sect in a complicated manner, as they thusbecome dangerous to yardmen and third rail must be omitted at all gradestreet crossings. This cuts off the source of power and the lightsfrom the train whenevera crossing is passed un-less the rear car is alsoprovided with shoes andconnected with the motorcar by a sectional cablerunning through thewhole length of the third rail may beplaced between the trackrails or on either side ofthe track, as may be desired. It must always beraised several inches above the track rails so theshoe will clear at switches and crossings. Theshoe is usually of cast iron, simple in form andof low cost. It is suspended from tlm truck in 30 Vol. 1. Shoe for Thinl Rail BetweenMain Rails. Cast iron, five bytwelve inches; weight, twentypounds. Nantasket Beach Rail,way. inc RAIL WAV EQUIPMENT. siicli iiKiiiner as to i-ecliice shocks iiiul ])o easilyadjusted or renewed. Underground Sijstems for collecting currentare of two general types, the open conduit andthe closed conduit. The open conduit systememploys some form of trolley wire or rail laidin a conduit having a slot or groove in theupper portion through which a suitable bar isdrawn by each car, making contact with thewire or rail and conducting the current to thecar. Foreign substances, such as ^vater, snow%ice, dirt, etc., getting into these conduits impair the insulation of theconductors and clog theconduit, making itsoperation under someconditions unreliableand unsatisfactory. Inthe closed conduit sys-tem the conductors arecompletely inclosed inwater-tight is made tosectional rails or con-tact blocks
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