1162 The Problem of the Soaring Bird. [ December, 
or was slain before his natural death, so that he could not be 
buried in his own tomb. The high mounds in the valleys served 
both to protect the dead from floods and as watch-towers in time 
of danger. 
One of the remarkable aspects of floods is their influence on 
the formation of valleys. Nowhere is this more clearly shown 
than in the valley of the Mississippi below Cairo, over which the 
floods distribute themselves to a width exceeding forty miles in 
many places. This valley has a bed of alluvial silt deposited in 
past flood times increasing from forty feet at Omaha and Dubuque 
to 300 feet at and below New Orleans. In other words, the flood 
alluvial deposit of the Mississippi covers 80,000 square miles to 
an average depth of 170 feet, a surface equal to Montana. In 
this elastic valley the floods annually work out the destiny of 
the river’s bed, which is often found miles from its previous course 
after high water. 
The ice-gorges which dam up the rivers and hold back the 
waters for hundreds of miles are another destructive factor of 
floods. When they break the resulting destruction is enormous. 
Congress has only to supply its existing snag-boats with dynam- 
ite in order to destroy these before the damage force is accumu- 
lated. The Government signal service along the rivers can give 
warning of their formation. 
A’. 
se 
THE PROBLEM OF THE SOARING BIRD. 
BY I. LANCASTER. 
( Continued from p. 1058, November number.) 
A® soaring is a phenomenon dependent entirely on bird and 
air, which are not connected with the earth, to avoid confu- 
sion it is best to pay no attention to the latter. For instance, a 
bird motionless in regard to a point on the earth facing a five- 
~ mile-per-hour breeze ; the same bird moving in calm air at the 
~ Tate of five miles per ee or going with the wind at the rate of 
_ ten miles per hour, are identical in character so far as soaring is 
concerned. In each case the wind is meeting the bird at the rate 
> five spp pei hour, and the differences of translation over the 
rth a idental, not concerned with the mechanical activities 
