Status of the Theory of Isostasy. 313 



mum for the United States, and the residuals of solu- 

 tions E, H, and G- are only one-fourth those of solution B. 



It would appear, therefore, that continents rest nearly 

 in isostatic equilibrium with respect to ocean basins, and 

 that the larger features of the continents also show very 

 considerable adjustment between regional elevation and 

 density, but the evidence from deflections of the vertical 

 as presented by Hayford does not prove, as he thought 

 it did, a close local isostatic relationship. On the con- 

 trary, it shows the importance of density variations 

 unrelated to topography. It is clear that geodetic inves- 

 tigations pursued with competent geologic cooperation 

 are capable of revealing the larger and deeper structures 

 of the crust to a degree which has heretofore never been 

 appreciated, and this should be recognized as a new and 

 important means of geologic research. 



It is impossible, however, to utilize to a large extent 

 for geologic problems the geodetic data as now pub- 

 lished, since, in the published results, the items which 

 enter into the topographic deflection and the effects of 

 various depths of compensation are not listed except 

 for a few illustrative stations. A complete publication 

 would make a volume of perhaps a thousand pages, but 

 the size of a work has not customarily been an argu- 

 ment against publication in the government printing 

 office and such a volume would make a valuable perma- 

 nent record of source material. 



If such details were given, one page of tabulated 

 figures for each station, it would be possible to try out 

 various hypotheses. For example, in the Lake Superior 

 region, group 5, it might be found, by comparing vari- 

 ous stations, to what degree the compensation was local 

 or regional and something further in regard to the loca- 

 tion of masses of excessive density. The outstanding 

 masses are so large, and the distance from the ocean 

 basins so great that the data do not show strong evidence 

 of isostasy. Just for that reason, however, they would 

 serve as a means for determining the larger irregulari- 

 ties of crustal density in a region where knowledge has 

 become of high theoretic and economic importance. 



There remains to be mentioned the interpretation of 

 gravity anomalies. This was discussed by the writer in 

 1914 and that detailed analysis need not be repeated. 

 Hayford and Bowie estimated that the mean anomaly 



