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C. F. TOLMAN 
along the bed of the stream, and between the layers, as shown in 
Surrere beloceties. 
The throw of the bottom whirls is indicated by the arrows a, 0. 
1.—The current velocities are indicated at the right. 
Fic. 
The small intercurrent whirls have balanced action and receive material from the bottom whirls, and are not important. 
Fig. 1. The bottom whirl can prob- 
ably be considered of primary im- 
portance, because (a) at the bottom 
there is the greatest friction, and 
therefore, the greatest difference of 
velocity; (6) the bottom whirl has 
an unbalanced upward velocity: 
(c) the higher whirls have equal 
upward and downward components, 
and can affect only the material 
they have received from the bottom 
whirls. They will accelerate the 
upward motion of some particles 
and retard others to the same extent. 
Therefore in this preliminary inspec- 
tion the action of the bottom whirls 
only is considered. Although the 
motions will be complex, assume a 
certain whirl which represents the 
average upward throw of the stream. 
Increase the velocity of the stream 
and the subcurrents will increase 
presumably approximately directly 
as the velocity of the stream. 
Following the course of events as 
they commonly occur in arid regions, 
let us assume that the sudden shower 
or cloudburst picks up a great load 
of both coarse and fine. Let this 
shower be on the rock slope of 
a bolson. There is no dropping 
of coarse and picking-up of fine 
material as is postulated for the 
ordinary stream, because mountain- 
slope and torrential concentration 
give a great excess of energy, so 
