There is a chance that the man who has advertising to place may feel

CURVE PLOTTING

that the chart has been drawn in too optimistic a manner because it does not show zero at the bottom of the scale. It would have given a much more conservative impression if the excellent record of circulation growth had been plotted in curves having the zero line shown at the bottom of the chart, so that the relative growth could be accurately judged visually.

In Fig. 89 a large amount of information has been condensed into a small amount of space, yet the chart is fairly clear and easy of interpretation. Several ingenious combinations have been included as, for instance, the arrows that show the prevailing direction of the wind each day. The chart gives unusually complete information in a most convenient form for any ventilating engineer or power-plant manager who wishes to keep careful track of his cost of coal in different months of the year as dependent upon weather conditions.

DAY OF MONTH g 10 II 12 13 14 15 16 17 18 19

24 25 26 a? g6 80 30 al

S R 3CRRCPCSSCPCC PCS: PC R R Fi PC PC S S Sn S Sf? C S R S

Heating and Ventilating Magazine

Fig. 89. Record of the Weather in New York City for December, 1912

The heavy line indicates temperature in degrees Fahrenheit The light solid line shows wind velocity in miles per hour

The dotted line depicts relative humidity in percentage from readings taken at 8 a.m. and 8 p.m. Arrows portray the prevailing direction of the wind