onstruction,
except roadway, about two and one-half hours; extra time to be allowed
for difficult footings.

The width of gap is measured, the position of footings determined, and
the length of standards from butt to transom determined and marked as
before.

The inclined frames in this case are built of equal widths, launched
as before, and held by guys just above their final position. Two
stringers are launched out from each bank to the main transom. The
distance pieces, Fig. 6, are put into position inside the standards,
using tackle if necessary, and the road transoms are placed and lashed
to the distance pieces at the places marked. Both frames are now
lowered until they jam.

=1115. Roadway of spar bridge.=--For infantry in fours crowded the
transoms should have a diam. of not less than 9 ins. for a span of 15
ft. Five stringers 2 ft. 3 ins. c. to c., and 6 ins. diam. at the tip
will suffice. If the sticks vary in size, the larger ones should be
notched down on the transom so as to bring the tops in the same plane.
The stringers should be long enough to overlap the transoms, and
should be lashed together at each tip. The floor is held down by side
rails over the outside stringers and lashed to them. If lumber can not
be obtained, a floor may be made, of small spars, the interstices
filled with brush, and the whole covered with loam or clay; Figs. 7
and 9.

Corduroy Roads

=1116. Corduroying= is done by laying logs crosswise of the road and
touching each other. The result will be better if the logs are nearly
of the same size. The butts and tips should alternate. If the logs are
large the spaces may be filled with smaller poles. The bottom tier of
logs should be evenly bedded and should have a firm bearing at the
ends and not ride on the middle. The filling poles, if used, should be
cut and trimmed to lie close, packing them about the ends if
necessary. If the soil is only moderately soft the logs need be no
longer than the width of the road. In soft marsh it may be necessary
to make them longer.

The logs may be utilized as the wearing surface. In fact this is
usually the case. They make a rough surface, uncomfortable for
passengers and hard on wagons and loads, but the resistance to
traction is much less than would be expected, and the roughness and
slightly yielding surface make excellent footing for animals. Surface
corduroy is perishable and can last but a short time. In marshes,
where the logs can