In choosing shadings be sure they are distinctive.
GRAPHIC PRESENTATION
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CROSSHATCHED AND COLORED MAPS
NUMBER OF
PEOPLE PER
SQUARE MILE
E2a Under Z
^2-6
Over 6
U S Department of Agriculture, Bureau of Agricultural Economic*.
Population of a Section of the United States in 1810 and 1920.
1. A comparison of these two maps shows at a glance the sections in which the greatest
growth of population had taken place in a period of 110 years.
2. In view of the 1920 map, see 179A.
182i
GRAPHIC PRESENTATION
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National Association of Motor Bus Operators, Washington, D. C, "Bus Facts for 1938."
A. Rafes of Gasoline Tax Per Gallon in the Various States as of January I, 1938.
Compare this method of presenting gasoline tax information with the method used in 195A.