THE KANSAS CITY BRIDGE. 27

comes the mountain rise from the upper river, which usually attains its greatest
height early in July ; it is the most certain, and except on rare occasions the
highest flood of the year. By the 1st of August the river has begun to subside,
and it continues to fall, with few or no disturbances, till the low winter stage is
reached. The best working season is from the middle of August to the middle
of December, the winter work being made extra hazardous by the dangers from
ice, and the spring freshets greatly curtailing the amount of work which can be
done before the end of the summer.

Observations taken to determine the speed of the current showed a mini-
mum velocity in the channel of two miles an hour—this being in the early part
of February, 1868, when the river was frozen and the water extremely low.
The greatest velocity accurately observed was in April, 1867, being at the rate
of 12.7 feet per second, or a little more than eight miles and a half an hour.
As the speed of the current is largely dependent on the rapidity with which a
flood rises, and as the river has been known to rise at other times and places
much more rapidly than was observed at Kansas City during the building of the
bridge, it is likely that the maximum speed is considerably in excess of that
given above, and it may be as great as 12 miles an hour.

The unstable condition of the river bottom was fully confirmed by sound-
ings taken in the spring of 1867, at four successive times, from which cross-
sections of the river were carefully plotted.* Changes continued to take place
with equally marked effect during the two following years, but as their very
frequency made each individual change unimportant no record was kept of the
subsequent changes, beyond the soundings taken from time to time at the sev-
eral pier sites and for special purposes.

In selecting a location for the bridge, it was necessary not only to place it
where it should best fulfil its commercial requirements, and to see that it formed
as slight an obstruction to navigation as was possible, but also to locate it at a
point where a moderate amount of artificial shore protection would suffice to
hold the channel permanently at the draw. As the bridge was designed to
accommodate the high way travel as well as the railroad, it was necessary that
it should be opposite the city, and a very favorable location four miles below

 

* See Plate IL _