The arrangement of Fig. 82 is not as objectionable as Fig. 81, for the upper half of the illustration sliows quite clearly in pictorial form that the subject under consideration is a stream having a channel shaped as shown, with widths and depths as indicated by the two scales. In the bottom portion of the diagram the scale of depths downward relates very definitely to the upper portion of the illustration so that the reader cannot easily go astray. Notice that the curves for the velocity of the water are each plotted on a separate vertical line which serves as zero line. The curves for velocity begin at various points depending upon the thickness of the ice, as will be seen from the upper portion of the chart. There is, of course, no velocity in that portion of the stream which

CURVE PLOTTING

Distances in feet 40 50

CURVES OF EQUAL VELOCITY

VERTICAL VELOCITY CURVES Note Numbers at to|5 of curves indicate measuring points Numbers at bottom of curves indicate mean velocity in the vertical

Horizontal divisions represent one foot per second velocity

Enginecriny Nev:s

Fig. 82. The Velocity of Water in Different Portions of a Stream Flowing under Ice

The horizontal scale at the top of the illustration shows points where velocity measurements were made through holes in the ice. Velocities at different depths are indicated by the curves in the lower half of the chart, each curve being plotted to the right of a vertical zero line which corresponds with some hole in the ice. Lines are drawn in the upper portion of the chart showing different points in the stream where velocities are the same