For Fig. 251 an assumption was made that the chart would be printed on exactly the same size page as was used for Fig. 249. The scales for Fig. 250 were, however, arranged in the other direction on the page and the co-ordinate ruling was made so that some space would be allowed for extension of the curve in future years. As seen from Fig. 251 the growth in the telephone business does not appear nearly so rapid as would be thought from observing Fig. 250. Each of these charts is, however, plotted to exact scale and the difference in the impression obtained is caused only by the proportions of the vertical and the horizontal scales. The appearance of less rapid growth in Fig. 250 is assisted somewhat by the fact that the large-type title of the chart is arranged horizontally instead of in the form of a square as seen in Fig. 250. The heavy black type with much greater spread horizontally than vertically tends to overshadow the curve itself and causes for the curve a more distinctly horizontal impression than would otherwise be obtained. A person reading charts must take great care that he does not give too much weight to the actual appearance of the curve on the page, instead of basing his conclusions on the percentage increase or decrease as judged from the figures of the vertical scale. The proper choice of scales for curve plotting is largely a matter of judgment, and

GRAPHIC METHODS

Courtesy of the Grolier Society