38 THE KANSAS CITY BRIDGE.

is believed to have been entirely novel, is admirably adapted to use in places
where piles cannot be driven, and posts merely braced together are not to be
trusted ; it is effective, can be put in rapidly, and may be used where the rock
is overlaid with several feet of sand, the posts being sunk by blowing away the
sand with a stream of water forced through the central hole.

After the removal of the screws the caisson was sunk two feet farther to
the rock by means of a water jet, directed by a diver working on the outside ;
a single day proving sufficient to bring it to its permanent bearing. The water
jet used on this, as well as on subsequent occasions, consisted of a copper or
iron nozzle attached to a three-inch flexible hose, and sufficiently loaded to be
handled with ease under water ; through this a stream of water was driven by
either a centrifugal or reciprocating pump, the former being used on the founda-
tions first put in, but the latter being found the more efficacious. The attempt

_to fit the rock by shaping the bottom of the caisson proved a failure, and a good
joint was only secured by means of the sheet piles ; these were driven by a light
ringing engine, and by bruising against the rock secured an accurate fit. The
caisson was then surrounded on the outside by a double row of gunny bags filled
with clay, which were carefully placed by the diver in a trench excavated by
him with the water jet. These bags were further surrounded with hay, which
was again covered with a bank of clay, protected from the water by a canvas
tarpaulin, and the whole covered with a layer of clay and stones.

On the 10th of October these preparations against leakage had been com-
pleted, and the work of pumping out the caisson was begun. The joints were
found to be admirably tight, a nine-inch Alden pump, driven by a twelve-horse
power engine lowering the water five feet in an hour. Additional braces were
placed within the caisson as the water was lowered, to resist the increasing out-
side pressure. The small amount of sand and mud remaining on the rock was
cleaned off, and removed in boxes, when two beautiful springs of clear water,
contrasting strongly with the muddy Missouri, were found issuing from the
fissures in the rocks, and the rough and jagged surface was quarried to an even
bearing, suitable to receive the masonry. The solid character of the rock was
also proved by drilling into it.

To facilitate handling the stone a trestle bridge was built, extending from