The black areas indicate the portion of the ^-t-hour power-house load for which the gasoline engine would be used

The curve looks smooth in this illustration simply because the gauge readings were taken so frequently that the nearness of the many points made the lines joining them appear curvilinear rather than angular. Such a smooth curve would not have resulted if gauge readings had been taken only every six hours and the chart made by connecting with straight lines the points plotted for the data obtained at these longer intervals.

Another flood curve is shoAvn in Fig. 77. The speed with which the water ran off the territory drained can be judged by the shape of the curve. It is not. however, safe to compare the shapes of the curves in Fig. 76 and Fig. 77 without noticing that in Fig. 77 we have one day represented by a space approximately the same as the space used in Fig. 76 for only six hours. If the curve of Fig. 76 were plotted on the same horizontal scale as the curve of Fig. 77, the flood would appear to be much more severe and rapid than it appears from Fig. 76.

CURVE PLOTTING

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Sept.eth Sept.Tth. Sept.ath.

Time in Hours

Engineering Record

Fig. 76. Curve Showing Duration of a Flood, September 16, 1909, in the Canadian River, New Mexico

This curve was first plotted on a paper having co-ordinate lines close together. For ease of reading, the intermediate lines were omitted from the magazine illustration