ABSTRACTS 



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GRAVITY. — Investigations of gravity and isostasy. William Bowie. 

 U. S. Coast and Geodetic Survey, Special Publication No. 40. 

 Pp. 196, with 18 illustrations. 1917. 



For a number of years the U. S. Coast and Geodetic Survey has been 

 carrying on geodetic investigations of isostasy with special reference 

 to the effect of isostatic compensation upon the deflection from the 

 vertical and upon the intensity of gravity. Four reports on these 

 investigations have appeared previously. The first one was in 1909 

 and the last one in 1912. 



The present report has as its main features: (1) The observed value 

 of the intensity of gravity at the stations in the United States, Canada, 

 India, and Europe, and at a few scattered stations. (2) Discussions 

 of the relations between the gravity anomalies and the topography, 

 the large areas of erosion and deposition, the geological formation as 

 indicated by the surface rock, and the elevation of the station. (3) 

 So-called regional versus the local distribution of the isostatic com- 

 pensation. (4) The determination of a gravity equation and of the 

 earth's flattening and the depth of compensation upon each of several 

 assumptions. (5) Summaries of the results of the field observations 

 with the pendulums, and descriptions of the gravity stations. (6) Illus- 

 trations, in the pocket at the back of the volume, showing graphically 

 much data resulting from the investigation. 



The results of the investigation may be summarized briefly as follows : 



1. The most probable depth of compensation derived from gravity 

 observations alone is 95 kilometers. As the author believes that the 

 best value determined by Hay ford from deflection data is 97 kilometers 

 and that each of these two values should have equal weight, the re- 

 sulting best value from all geodetic data is 96 kilometers. 



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