somewhat greater amount of photographic reduction had been used in making the hne engraving or if the proportions between the horizontal- and vertical-scale distances had been changed somewhat. There is really no necessity for using the wavy line for the bottom of Fig. 245 since the chart would have been better made with the zero line showing the bottom. Fig. 245 will serve, however, as an example to illustrate how the wavy line can be drawn to any chart where it is really inconvenient to extend the chart itself so that the zero line may show.

Death Rate Per lO.OOO

leso

1S90

oTuberculosis

I910

mmmimm Degenerat^ive Diseases (Heart-, Kidney, etc.^

Data of Elmer Rittenhouse

Fig. 247. Comparison of Death Rates in the United States, Showing Reduction in Death Rate for Tuberculosis and Increase in Death Rate for Degenerative Diseases

This chart is made from the same data as Fig. 246. Here the zero line is shown and the changes in death rate appear much less rapid than they do in Fig. 246. See also Fig. 248

GRAPHIC METHODS

Fig. 246 gives another example where neglecting to show the zero line may cause an entirely erroneous impression regarding the facts which the chart is intended to bring out. The failure to show the zero line at the bottom of a chart is so common a fault, found in nearly all publications, that some typical examples are shown here in the hope that a bad practice may be somewhat reduced.

Fig. 247 gives the data of Fig. 246 redrawn so that the zero line is shown at the bottom of the chart. It is believed that this illustration will prove conclusively how great an error may be made if charts are read hastily on the assumption that the bottom line of the chart is the zero line.