Time Zones on Seventeen Highway Routes to and from Corner Parle and Trennont Streets in Boston During the Morning and Evening Rush Hours from June to September 1927.

While most of the traffic maps give the amount of traffic, this map gives the length of time it takes to get into Boston from outlying districts.

GRAPHIC PRESENTATION

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Chapter 28 CONTOUR MAPS

_ ontour maps may be used to show lines of erosion, precipitation, climatic conditions, as well as the topography of the land. Gradations of shading and cross hatching may be used on contour maps to differentiate. For suggestions relative to the arrangement of shadings, see "Suggestions for Making a Chart," pages 367-380.

GENERAL REFERENCES

Raisz, Erwin, General Cartography, McGraw-Hill Book Co., Inc., New York City, 1938

Robert Waril. Cliiiiatts of tht Umtrcl States. " Ginn & Co., Boston and Nrw York, I'liS.

Average Annual Number of Rainy Days in the United States.

1. While the contour map is best known for its use in uivinn the topography of land, it may

also be used to show preci(>itation. temperatures, and erosion.

2. Since no key for the shadinus was nivin with this map. it is rather ditlicult to read

accurately.

GRAPHIC PRESENTATION