— 233 — 
土. 
1 . e °* stringers can rest upon the supporting brackets until it is convenient 
^ lv e them to the beam. Next run out the second pair of stringers putting them 
ce at the far end and supporting them from the lower strut temporarily. 
as .. . len bring out tlie next floor beam, swiug it into place removiug the runway 
1 ftei’fei’es with the work, and so on until the end of the bridge is reached. 
jj .. 8 80011 as the second floor beam is in place the rivetters cau commence cou- 
n、. ハ 1 •气 ie sfcl _i n g ei .s to tlie beams, and follow up the work as fast as these members 
aie Wia place. - 
ei ^ 10 track stringers rest upon the floor beams, quite anoilier method of 
are ^ 0ü mils 也 bo pursued. The stringers must be brought out at the same time as 
lateral struts and rods, both of which pass through holes in tlioii* webs, 
tiou 10 08 mu8 t be large enough to give considerable play, both to allow for cleflec- 
Unc ^ ei Posing loads, and to facilitate the passage of the lateral system. The 
fels ^ ei S ル 011 】(1 be supported temporarily upon blocks from the caps of the lower 
Sf) |- W ° l ^ > au< i can bo made continuous from end to end of span by rivetting on the 
f ates and bracing frames, removing of course, tlie runway, 
floor h Gr SWni g lu g the span, tlio stringers must still rest upon tlie blocks until the 
tlie t earUs aLe i 11 place and screwed np : the floor beams can be run out upon 
by tl 〇 ! 3 ( f も 】 10 8 ^ n o ers - Then the stringers and beams must be rivettud together 
こ 1 r connecting plates and brackets. 
t a i Uec | | X HCrew U P every adjustable rod to the proper tension, which can be ascer- 
y tlio sound they make when tapped with a hammer. 
aia(l • • any mud or other impurity that there may bo on tlie iron-work, 
of i“ w o good coats of paint wlierever the brush will reach. Tlie best kinds 
are al^tl 如〇 如で ^ ea( ^ w ^ ien they can be obtained iinadulterated ; but tJiey 
oxide • 6 Same the most expensive of all the paints used for iron- work. Iron 
s Uc j 1 a g 00 d paint, but requires more frequent renewal. The color should be 
れ sp お も 0 rea ぐ] ily show any sign of rust : various shades of gray are efficient in this 
^ ’ and are at tlie same time pleasing to the eye. 
tioiis • 011 山 0 shims, ties, rails, guard rails and foot planks with their connec- 
I’u 1 功 a “ ei 80 simple as to require no explanation, 
upper f i° n ° Midges of several spans, it may be economical to dispense with the 
pn r p 0g e ' vo i.k by using a travelling derrick, running upon wooden stringers, for the 
如 1)。 二?" 1 う】 1 仙 1 】 g the lieavy sections. Under these circumstances, the whole of 
in 0lle 'l be connectod while lying upon the falsework, then hoisted into place 
The bi)d leCe ’ an (l su PP 0l ^ e ^ there by shore timbers from the first bent of falsework. 
S ^ 10U W be completed as the traveller retreats : otherwise there will be 
bro^j ? 111 Carr ying tho members past tlie traveller. The material should be 
The 0 ] 1 ° aVS reac h of the derrick. 
the bed f ^ to be done is to take down the falsewjrk, and draw the piles from 
the i* 0 p ° ^ 1G s ^ ream - The latter is easily accomplished by a crab on tlio bridge ; 
directiQ 6 6lU ? a ^ ac ^ let l to the head of the pile, which is vibrated transversely in all 
ThT ''仙 6 being lifted by the tension of the rope. 
P°pular idea that au iron bridge wheu once erectctl will last forever without 
