CHAPTER V. 
孔〇 Oß SYSTEM PEOPEß, RE-EilLLHG & DITCHING APPARATUS. . 
Tlie floor system proper, or the arrangemeut of ties and guard rails, liei’e 
^ocommemlecl is not tl ie one in common uso in America, bat is a modification of 
that proposed by W. Howard White, Esq. C.E., in tlic Transactions of the American 
Societu of Civil Engineer^ Nov^ f 88, the changes being tlie substitution of angle 
iion for tho wooden guard rails, tlio sliorteniug of tlie ties, tlio diminution of the 
spacea b etwoen them, aud the providing of a place of safety for auyeme wlio nmy ヤ 
upon the bridge wlien a truiu is passing. Tlio usual American floor system is much 
heavier than tho one proposed by Mr. White, and consequently is not only move 
costly i u itself, but by increasiug tlie dead load of tlie bridge necessitates tlio use of 
デ 〇 1 〇 iron for the trusses. For short spans tliis might be considered advantageous, 
111 that it tends to lessen vibration, but for long spans it is decidedly tho conti aiy. 
Tlle employment of long tics and outside guard rails necessitates tlio use of two 
extra stringers to sustain a portion of the live load in case of clerailmeiifc, because 
tho guard rails being higher than the rails must bo placed at such a distance outsiilo 
0 “he latter, in order to permit of tlio passage of snow-plouglis, that tho unaiclec 
ties would not be strong enough to uphold a derailed locomotive. • 
Because of tlie flanges on tlio wheels an inuor guard rail of tlie same liciglit n,s 
tlie rail is fully as efficient as an outer guard rail two in dies Iiiglier, aiul li^-s the 
advautago that it may bo placed closo to tho rail, tlius preventing excessive lateral 
movement of a derailed carriago or locomotive. 
Tlie floor system recommended by the author is illustrated on Plates I [I 娜 
IV * Most of tho ties are of T x 8 ;, x G ; oak, laid on tlicir flats, and spaced not more 
で lian twelve inches centre to centre, tlius leaving an opening of no more than four 
inches, "whicli will not causo excessive jolting of derailed wlicels. Every sixth or 
seventh tie in single track bridges is twelve foot long, so as to support at each end a 
3 x 12 r pino planlf, extending ffom end to end of bridge, in order to nilou-1 a yUc し 
of refuge from passing trains. Each foot plank is to bo spikod to eacli long tie y 
two 7" cut spikes. 
• エ 11 double track bridges the long ties arc to be twenty- two feet in length, extend 
ing clear across tlio bridge, and supporting a run of plank at each end fl»ncl another 
at tlie middle. The latter serves merely as a stepping place to pass from one tiack 
to tliG other, the outer runs only being intended for places of safety. 
