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of ft pencil- line will often cause a great deal of mconvenieiice. A piece of emerj 
paper or a fine file will be found useful for sharpening pencils. The tracing-paper 
will be convenient in transferring drawings of similar chord heads, etc. : its function 
is merely tbo saving of a little time. 
It is generally better to have both a long aud a short scale. The long one may 
be divided into feet only, the inches and fractions of inches being taken from a dia- 
gonal or other small scale. If tho draughtsman be not provided with a suitable 
scale, lie can easily prepare a very fair one for himself on a strip of the roll of 
paper upon which the drawing is to be made. 
Tlie method of projecting one view of a piece from another view will not do for 
working- drawings, owing to tho liability of the triangles to slip. All measurements 
should be transferred by the dividers ; and, if there bo any probability of the points of 
the dividers having been moved, the distance between them should be tested by 
laying it off once more upon tlie original length. Thoro should be no more than a 
single tran sferrence of any one distance, for errors often increase, instead of balancing. 
The general arrangement of a working- drawing consists merely in laying out a 
plan and elevation of one-lialf of the span, leaving at least a foot of space at each 
end, and six or eight inclies above the elevation and below the plan, if there be room 
to spare, with the same distance, or a little more, between. As it is immaterial if 
different portions of the drawing cross each other, provided that such intersection 
cause no conflicting of the measurements, the various members may be shown in 
several views alongside of tlieir respective positions in plan and elevation. 
Thus the top chord may be represented in an under and an upper view above 
the elevation of tlie truss, and tlie batter brace may be shown in a similar manner 
above and to ono side of the elevation. Projections of the posts on planes transverse 
to tlie bridge may bo drawn alongside and a little below the elevation of these mem- 
bers, the amount of lowering being sufficient to bring tlie ends of the strut clear of 
the chords. Attached to the projections of the posts can bo shown the iutermediate 
struts and vibration rods, with their connections ; and shortened views of tbe chord 
bars and diagonals can be placed alongside their elevations in order to represent the 
heads clear of all other members. Passing to tlie plan, on 0110 side is drawn the 
packed lower chord, and attached thereto the lower lateral rods and struts in half- 
length ； -while alongside the latter can be represented an elevation of tlie same with 
the floor beams beneath, and an end view of tho beams near by. The stringers can 
also be represented in this neighbourhood. At the other side of the plan, can be 
shown half-lengths of the upper lateral rods and struts in two views, and a pro- 
jection of tlie portal bracing on tho plane of tho batter braces, and on planes 
right angles thereto. Each detail can bo delineated to any required extent in the 
neighbourhood oi its position in plan, elevation, or both. If necessary, the 
points on one side of the plan may be brought opposite the middle of the panels on 
the other side, in order to avoid too much intersection. 
This arrangement, although a good one, is by no means the only one, and 
some cases might not be the best. For instance, in skew bridges it would be well to 
show the whole of the lower lateral system in the plau, and the whole of the upp^' 
