This selection of horizontal distances makes the curves into much more nearly their correct shape than is possible on the Census Office chart, where five-year and ten-year class intervals are shown by equal scale distances.

Perhaps the greatest gain made in clearness in Fig. 145 is due to the placing of the curves for male and female on the same ruled field, so that they can be compared instantly and correctly without need for any right-hand and left-hand measurements such as were necessary in Fig. 144. No claim is made that Fig. 145 is suitable for untrained readers. Since, however, it is doubtful whether many unskilled readers ever refer to the Census Atlas, it would seem desirable to use the general scheme of Fig. 145 for clearness and convenience.

In Fig. 146, also taken from the Census Atlas for the 1900 Census, a right-and-left measurement must be made to compare death rates in two different years, ten years apart. The chart was drawn to bring out the data clearly and, if clearness is not attained, the data might just as well be expressed in columns of figures. Here again the variables have been reversed and the independent variable improperly made the vertical scale.

In Fig. 147 the data of Fig. 146 are redrawn into two curves by which the number of deaths occurring at different ages can be readily

GRAPHIC METHODS

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ISO ISO \tO 120 100 so 60 40 20

20 40 60 aO 100 120 140 IBO 100