fractions of a division at both beginning and end of the component to be measured. The best thing in charts of this kind is to use unruled paper, and specify the scale. The reader, if he wants the exact data, can take his measurements with a ruler. The engineer's scale has its subdivisions in decimals and hence is the most convenient scale for chart work. An engineer's scale should be part of the equipment of every person who has charts to make.
Another method of showing the relative size of the divisions and subdivisions of a unit or group is shown in Fig. 6. In this case we have the total population of the United States split into its component groups according to the condition in regard to marriage. The subdivision bars, given below the total bars, show the conjugal condition in each of the main groups which enter into the total population. Each of these main-group bars is cross-*hatched to show the conjugal condition within the group. The combined length of the four bottom bars is equal to the length of the total-population bar shown at the top. These same data could have been presented by the method shown in Fig. 5. It will be noted, however, that in Fig. 6 all the figures have been included, and are available for reference purposes without detracting from the utility of the chart itself. The lettering was done by hand and shows the possibilities for neatness resulting from hand work when a skilled draftsman is employed. In many ways the method of Fig. 5 is preferable, but it is probably true that Fig. 6 would be more readily understood by the average untrained reader.
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United States Statistical Atlas for the Census of 1900
Fig. 5. Elements of the Population of the United States in 1900
Here the components of the total population
are shown in their relative sizes on the
vertical scale. Each component is also
divided into different subdivisions whose
percentage size may be read from the
horizontal scale. This is an admirable
method of presentation if components
must be subdivided
Where there are a large number of items to be compared and the
components of each item are given, the method of Fig. 7 is a very
convenient one. The Census Atlas for the 1900 Census contained
many pages of charts of this type for its comparisons of different States.
By placing bars for all the States on one page, the total for the country
is shown as 100 per cent in the vertical direction. No vertical scale
