supported meanwhile by blocking at least every 6 ft., and the stringers
and planking were shoved into place. Excavation was next made between
the caps to a depth of about 5 ft. below them, needle-beams being placed
under the caps, one or two at a time, and supported on posts erected in
these excavations; the material on line of the bents was excavated to
the depth of the intermediate caps, which were then set, together
with the posts and bracing for the upper deck of the structure. This
operation was repeated for the lower deck, about 10 ft. being gained for
each change of posts, and three shifts, therefore, were required.

At the beginning of the train-transportation period, May 22d, 1905, two
shifts of 10 hours each were inaugurated, and the earth was handled at
the rate of from 85,000 to 90,000 cu. yd. per month; but, by the end of
August, when a little more than 60% of the total earth had been disposed
of, the rock began to interfere very greatly with the progress. The
strike of the rock was almost directly north and south, and its surface
formed broken ridges running in that direction, with deep valleys
between. The dip was almost vertical near Ninth Avenue, and about 70°
toward the west near Seventh Avenue. This condition made it necessary to
turn the shovels parallel to the ridges in order to strip the rock for
drilling; and, as the ridges were very broken, the shovels continued to
bump into them on all occasions, making it necessary to move back and
start other cuts or stand and wait for the rock to be drilled and
blasted. One small Vulcan steam shovel, with vertical boiler and ¾-cu.
yd. dipper, had been brought on the work to be used in stripping rock,
and was moved from place to place so much more easily than the large
ones that an Ohio shovel of the same general type was purchased in
October, and thereafter the stripping was done largely by the two small
shovels and by hand, the large shovels being used almost exclusively in
handling rock.