440 WILLIAM BOWIE 



would be offset almost entirely by the effect of the compensation 

 if this lighter material were compensated for by an excess of 

 material lower down in the lithosphere. 



The mean anomaly with regard to sign for the Cenozoic stations 

 in the United States was —0.007 dyne. In India it was —0.017 

 dyne. There were 31 stations in India on this formation and 20 

 had negative anomalies and 11 had positive ones. The positive 

 anomaly in every case was comparatively small, the largest being 

 0.033 dyne. There were 10 of the negative anomalies larger than 

 0.032 dyne. 



Since the publication of the results of the recent investigation 

 of gravity and isostasy, data have become available in regard to a 

 number of gravity stations established in the Pacific Coast states, 

 during the summer of 19 16. Of 13 stations established in southern 

 California, each one has a negative anomaly, and the mean with 

 regard to sign is —0.037. The largest one is —0.081. This is 

 only slightly smaller than the anomaly of —0.093 a t the Seattle 

 station. Each of these stations in southern California is located 

 on Cenozoic material. 



There were 9 stations established during 1916 close to Seattle 

 with 8 of them on the shores of Puget Sound. Eight of these 

 stations were on Cenozoic formation, and 7 of these had negative 

 anomalies. The mean anomaly with regard to sign for the stations 

 in this vicinity which were established in 19 16 is —0.033 dyne. 



The writer does not wish to be understood as asserting that the 

 Cenozoic or the pre-Cambrian material is the cause of the anomaly 

 at the stations located on those formations. He does believe, how- 

 ever, that the abnormal density of the material of those two forma- 

 tions is the cause, or rather the principal cause, of the tendency of 

 the gravity stations located on them to have anomalies of one sign. 

 As was stated earlier in this paper, it is not possible from the data 

 now at hand to tell whether or not the area covered by a Cenozoic 

 or pre-Cambrian formation, where the sign of the anomaly agrees 

 with the density of the surface material, is in isostatic adjustment. 

 This is due to the fact that the compensation, if present, is so far 

 from the station that its attractive effect is very small in comparison 



