Map of Credit and Sales Conditions in the United States in July 1938.

Since interest is chiefly in the "active-and-up" cities, the choice of a solid black symbol to represent them was a logical one.

Chapter 27 FLOW MAPS

Jflow maps may be used to show both qualitative and quantitative flow of goods, persons, automobiles, etc. When a flow map is used to indicate the number of persons or automobiles on streets and highways, it is generally called a traffic map.

See Cosmographs in "Flow Charts" on pages 73-80. cy^ r'

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National Resources Board. "Report of Water Planning Committee, Part III," 1934.

SCALE .8

A. Generalized Spring and Autumn Stornn Paths in the United States.

1. Although spring and autumn storms

may not always follow these paths, it is more than likely that they will.

2. The use of a flow map to show the

path of a storm is not an uncommon one.

3. The lines here show the center path

and the outlying borders. For comparison see 216B and 218.

American Mutual Liability Insurance Co., Boston, Mass., "Watch," 1939. SCALE .6

B. A Map of Hurricanes Which Have Occurred Between September 16 and 30 During the Last Fifty Years in the Eastern Part of the United States.

1. During the half-century ten hurricanes

have struck inland in the latter half of September.

2. Hurricanes usually originate off the

northern coast of South America, move west from Africa, and travel toward the West Indies and Florida, moving about 300 miles per day.