A series of magnetic and gravitational measurements at 7-mile intervals was made across the continent from Sea Bright, New Jersey, to Morro Bay, California. For the most part the data were complementary indicating a common control, although this varied with the regions crossed. In the eastern half of the country lithologic variations in the basement apparently controlled; in the western part of the country, structure was reflected in the gravity values due to the large density contrast between the sediments and the crystalline and consolidated formations. The magnetic variations for the most part reflected lithology.
Large anomalies in both sets of data must originate from deep-seated sources. The marked regional effect upon which the above variations were superimposed apparently reflects in the gravity value the elevation of the stations, and the amount of the anomaly is approximately that of the isostatic correction. For the magnetic values the regional effect is believed to be primarily related to inadequate longitude corection. In general no corelation could be made between the reduced data and the large regional geologic structures.