Curve patterns should be so selected that the curves can be distinguished readily from each other.

2. In general, the simplest patterns ore most effective and most economical.

3. In selecting curve patterns, it Is well to bear In mind the drafting difficulties and disturbing optical effects of complicated patterns.

COMPARISONS WITH TWO CURVES

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Standard Stattitici Co . Inc , N. Y. C , "Standard Trade and Securitiei," May 29, 1936.

SCALE .7

A. Building Contracts Awarded for Residential, Commercial, and Industrial Use in the United States for 1928. 1935, and 1936.

For explanation of cumulative curves, sec 2 79.

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National Aitociation of Motor Bus Operators. Washington, D. C, "Bus Facts for 1938." SCALE .9

B. Comparison of the Number of Cities Using All-Rail Transportation, Combined Rail and Bus Transportation, and All Bus Transportation in the United States from 1912 to 1937.