FAST AND HEAVY RAILWAY SERVICE.
253
dicated horse power. The coal used on the locomotives
amounted to 6.2 lbs. per horse power hour while in use.
With these facts as to power required the electrical
conditions are easy tofind. The motors should together be
able to work readily up to 200 h.p. with a good efficiency
at half this output. The average power required is not
far from that already computed for. the case of suburban
service at higher speed and with rather lighter trains.
The load, however, is on the whole more uniform on
the elevated line, although varying more as regards indi-
vidual units. The cost of power should therefore be
somewhat less.
The first notable electric elevated road in service in
this country was the Metropolitan line in Chicago. This
road, which went into operation in the springof 1895, was
designed to furnish rapid transit on the west side of Chi-
cago. Its general location is well shown on the map
(Fig. 128).
The portion now in operation consists of 1372 miles of
double track with thirty-two stations. ‘The structure is a
substantial one of deep plate girders, admirable mechanic-
ally, but very unsightly. ‘The track is of ninety pound rail
with massive guard timbers.
The electrical equipment, with which only we are here
concerned, involved tlivers excellent and novel features. In
the first place the track rails are not bonded together in
the usual way, buteach rail is bonded in the middle to the
supporting structure, thus giving an enormous iron con-
ductor for the return circuit. If thoroughly carried out
this arrangement is exceedingly effective, although it
would be well to bond the track itself as a precaution
against bad bonds in occasional rails.
The working current is taken from a contact rail lo-
cated a few inches outside of and above the track rail.
T'his contact rail is supported about every six feet by blocks
of paraffine-soaked wood to which it is secured by clips held
in place by wood screws. This rail weighs forty-five
pounds per yard and the insulated blocks are six inches
