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General Electric Review
Fig. 193. Location of Water-Power Developments of 1,000 Horse Power, and Over, and Power Sections of Streams in the United States
The original of this map would have pins in two different colors. The photograph taken from the map
would be retouched by the use of a pen so that squares would replace dots for one of the two colors
of pins. The illustration shows a contrast of dots of two shapes rather than dots of two colors
