Comparison of Daily Electrical Output and Daily Coal Consumption of a Power Plant for the Same Month in Two Succeeding Years

There is a relatively small quantity of power needed on Sundays. In order to make possible a comparison of the two curves for different years the horizontal scales for days were so placed that the Sundays would coincide. With curves thus arranged, the low points caused by Christmas do not fall on the same vertical line, since Christmas is fixed by the day of the month instead of by the day of the week

COMPARISON OF CURVES

in this chart that the December points have not been repeated at the left and the reader is forced to glance between left and right in order to make certain in his own mind just what changes occurred from December to January each year. It can be seen that the January figures for "Operating Revenues" are all considerably lower than the December figures, but even so the reader has no clear idea of the slope of the lines which would be most typical to portray the changes from December to January in each year. This question of repeating one point for curves of different years superinlposed is referred to also in Chapter XIII, Fig. 204.

Fig. 105, Fig. 106, and Fig. 107 are selfexplanatory. They show some interesting applications of curves to special problems, and demonstrate the great convenience which might result if curves could be more generally used for presenting every-day facts to nontechnical readers.