ESSENTIAL  FEATURES  OF  ELEVATED  AND  SUBURBAN  RAILWAY

                                        EQUIPMENT
 

     Coming to New York conditions  1  may say  that,

based upon the Chicago pcrformance, antl allowing for

difference of coal cost, the Manhattan roa<l, now operating

at twclve and one-half miles aetual schedule during tinie of

maximum  load, and making about 43,000,000 miles an-

uually, can bc opcratcd at over a sixtccn-mile  schcdule at

uot cxcccdiug nine cents, iustcad of 11.9, and on the exist-

ing mileage (his would mean a saving, exeluding interesl

011 investment of about $1,250,000 per annum,  or allowing

interest on  investmcnt of about $750,000, to say nothing of

any other gains,  A seveuteen-mile  schetlulc can  actuallv

bc made witli tWO motor equipments.

     In closing, perhaps I  may venture an opinion as lo

thc general íeatures which should charactcrize  a suburban

passenger railway  equipment. I  think it  may be  safely

statcd that  thc first is the usc oE the  continuous cttrrent Ín

thc motor  equipmcnt in spite of  the claims  which  have

been made  anri the results accomplished  with  alternat-

ing current motors, at least  so £ar as we can judge by any

present developmcnts.

    The problem then is whence shall be derived this con-

tinuous currcnts, and that dcpends  upon distances.  For

moderate  distances,  continuous  current generators sup-

plying  current  directly to the line,  with or without the

adclition of  storage batteries, is preferable.  When the cx-

tent  of the line becomes at all  serious,  then  it  must be

consiriered  as  made up ol a  number of shorter sections

joined togethcr, each of which derives its principal source

of supply from a local station, wlrich statton can be driven

directly by water or steam powcr, or by an alternating cur-

rent  from  a distant station, using a motor-dynamo  com-

bined in a singlc type of machine, the rotary converter, or

joined in the form of a directly coupled  set, the dynamo
 

cnd  bcing  for  continuous current and the  driver  a

synchronous or induetion type of motor.

     Gcnerally the sub-station should be supplemented by

a storage battery, to take eare of fluctuatíons in the load,

to even up the duty on the sub-station  and as far as pos-

sible at thc  eentral station,  and to take  care of some por-

tion  of the pcak load causcd bv abnormal variations in the

aggregate service at different times of the day.

     Of course, with the storage battcry comes the neces-

sity oí a means of some kind of  automatic regulation; there

are various  methods, but I  will not  enter inĩo them here.

     Looking  forward, however, to a  períectly  assured

futurc of a  hcavy service over considerable dístances,  I

may state that  the gencral equîpment of such a road shotild

generally involve the following  essentials:

     High potential altcrnating currenf  transmission from

one  or two  well placeri  central stations, with  or without

siatic transíormers.

     Motor-dynamo sets, or  rotary converters at a number

of conveniently placed stib-stations, to convert high pres-

stire currents into continuous currents of about 600 volts

pressure.

     Storage batteries of  quick charge and discharge ca-

pacity, gcnerally at the same sub-stations as the motor con-

verters, to equalize their duty and to prevent sharp varía-

tions in the gcneral plant as well as the  sub-station.

     A system  of feeders and main conductors.

    A power  rail or trolley wire supplying  continuous

current, but ordinarily without any swítching of currents.

     Individual transportation units  with a multiple  unit

control, so that combinatîon of  cars without  regard to

sequcnee or  end relation can be madc up at any portion of

the linc independently, and controlled from any selected

poĩnt.