― 230 — 
He should be also provided with a plan of the bottom chord packing, the trans- 
verse dimensions being exaggerated so that the size of each piece may be written 
thereon ; a bill of bolts giving the number and position of each kind, and a clear 
statement of the system of marking the iron. 
Before starting to erect the bridge the foreman should study carefully all tlio 
plans so that lie will have a clear picture of the bridge in liis mind’s eye, and will 
not have to be continually referring to tho drawings daring the erection. On a work 
of any magnitude there should be kept on hand a few standard nuts of each size 
ordinarily used, so that the loss of a nut or two will, cause no delay : for the same 
reason there should be a few extra bolts of each size. 
The material as a general rule is all piled on one side of the stream, the raising 
should therefore be commenced at tlie other side so that the passage of the material 
will not interfere with tlie work. If there be no objection, the far end of tlio bridg 6 
should be the fixed one, so as to start from something permanent, but this is not 
absolutely necessary. ' 
To illustrate the method of raising take for example the bridge treated iß 
Chapter XVIII. , and assume that tlio foundations with their anchor bolts and false- 
work, are in place. Tlie first tiling to bo done is to lay out the centre line of tl ie 
bridge upon the falsework caps, marking it with a small-lieaded tack on each cap» 
then the centre lines for the trusses in tlie same way. This can be done either witli 
a transit, or with a carpenter's chalk-line ; care being taken to make the transverse 
measurements to the outer lines exactly perpendicular to the central lino. A test 
the accuracy of the perpendiculars can be made by the three, four, and five method 
using a tape-line. Next, mark tlie exact positions of the panel points upon tho 
longitudinal beams under the trusses, and place tlie camber blocks, levelling over 
them so as to make tlie lines joining the central points of their upper surfaces 
parallel to the curve of tlio chords. It is better to have the blocks a trifle high, say , 任 
quarter of an inch near the centre, and au eighth of an inch near the ends, or iuo 1 '®» 
it on account of tlie height of the falsework, a greater settlement be anticipated. It 
better to liavo tlio height too great than too little ； for, if on account of too much 
cambre the last chord connection cannot bo made, it is only a few minutes， wort to 
tap the blocks a little, so as to lower them tlie requisite amount. 
Foui* small nuils will 110 Id each pair of camber blocks from slipping during tliß 
work, and they can be left so as to be easily extracted before swinging tlie brid^ 0. 
Next transfer the centre lines of the trusses to the tops of the camber blocks, ^ 
mark accurately the first panel points from the fixed end, then, starting there, pack 
the chord bars of both chords. It might bö convenient to have a few hard- wood 
pins to fit tlie 110 les pretty tightly, so as to aid in getting the bars properly placed 
longitudinally. 
After tlie chord packing has made some progress, run out the two baiter braces» 
and hoist them into place by means of pulleys attached to the cap of the first bent of 
falsework, which bent should have been previously guyed and braced so that it 
cannot possibly be disturbed by the effect of the pulleys. As soon as each battel* 
