48 THE KANSAS CITY BRIDGE.

water jet, by which the sand from the more remote parts of the caisson was fed
to the siphon and dredge. To give additional weight, the spaces between the
timbers of the upper section were filled with rubble masonry, which was pro-
tected from injury by an inside sheathing of thin boards. In order to diminish
the external sand friction, a large cast-iron pipe was placed around the caisson
above water, from which a series of small gas pipes extended down nearly to the
cutting edge, thus forming a line of water jets encircling the caisson, and distri-
buting the discharge of a single pump around the whole surface. An nine-inch
Alden pump was attached to this set of pipes, but it proved unequal to the task,
and only half of the pipes, those on one side of the caisson, were ever worked
together ; the force of the stream so widely distributed was also too much
reduced for effective work, and it was generally preferred to use a single
movable jet, which could be taken in turn to every part of the caisson.

The changes in the bottom during the work on this foundation were very
frequent and singular, sometimes causing no small trouble. In November a
scour was noticed around the anchor piles, which was accompanied by a deposit
at the pier site; the elevation of the sand, which was materially lower on the
first of that month than it had been when pile-driving was begun in August, was
raised 1] feet in three weeks. On the 2d of December there were 14 feet of
water outside of the caisson at the upper end, and 22 feet at the lower end ; one
week later this was reversed, when the water was found to be 24 feet deep at
the upper end and only 12 at the lower. Some of the smaller changes, though
less embarrassing, were more remarkable. About the middle of December the
river gouged out a hole in the sand, close to the south-west corner of the caisson,
extending clear to the rock, which was examined by the diver; the sand was
soon filled up to the ordinary level. A. similar hole was washed out about a
week later, and some pieces of floating ice were sucked under the edge of the
caisson and came up inside.

Ou the 10th of January the descent was stopped by coming in contact with
a buried log ; this was cut half through by the diver with a handsaw, and then,
the saw binding so much as to make its farther use impracticable, a large chisel
was mounted with a long handle so as to be worked from above, and the cut
finished by striking repeated blows on it ; only four days were lost by this ob-