CHAPTER XXII. 
ERECTION AND MAINTENANCE. 
如 The immbev of men required to erect an iron railroad bridge will vary from a 
to a hundred and fifty or even more according to the length of span, location 
1 11 the time to be occupied in erection. 
any one bridge, there is a certain number of men which will be more econ- 
t 11 广 ^ lan an y other number ； and it is only experience which will enable one to 
6 e | ， °i , ehaiicl what this number is. 
^ r 1 tliei’e are too few liands, the work will lag, and difficulty will be experienced 
iKUing heavy pieces : on the other hand, if there are too many men, they will 
lu ea °h other’s way, and the total aräounfc of effective work done by each man 
^ day W ill j 10t bo a maximum. If, for any reason, there be need of haste, it will 
economical to have a large force of men, notwithstanding the last mentioned 
consideration. 
g 如 1 〇が叫 to certain well known peculiarties of Japanese workmen ifc is very dif- 
h 1 to say how many men will be needed in any particular case : this matter will 
も 0 be left almost entirely to tlie judgement of the engineer. To such as have 
foil 丨 'o ex P er i ence in bridge erection, the author offers with much diffidence the 
0 wh]g tables as a mere guide. 
FOR RAISING SINGLE TRACK BRIDGES 
SPAN 

No. OF MEN EEQUIRED 
Plate Girders 
From 12 to 18 
Pony Trusses 
” 20 25 
T^ro. Spans under 10 O' 
>* »， 30 
ioo f to ia5’ 
，， 30 ，， 35 
>y 150' 
，， 35 ,, 4 。 
ゆ ， ， ， 175, 
，， 40 ，， 45 
175’ •,， loo. 
，， 45 >» 5 ° 
20 O, „ 22 s' 
，， 50 ，， 60 
叫’《 25 〇 ; 
,, 60 „ 75 
2 5 〇 ’ ，， 275 ， 
” 75 ，， 9 0 
^7 S' » ? 。〇， 
,, 90 110 
