310 



Status of the Theory of Isostasy. 



Region. 



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New England 1 58 35-60 2-76 008 



New York 2 65 21-86 2-25 0-10 



New Jersey-Eastern Virginia 3 56 35-67 3-36 009 



Southern Appalachians 4 73 22-42 2-48 011 



Wisconsin-Michigan 5 52 8-96 3-73 ■ 0-42 



Ohio Basin 6 67 17-77 2-40 0-14 



Missouri-Eastern Utah 7 46 16-92 2-17 013 



Great Basin 8 42 32-23 3-57 0-11 



Northern California 9 60 60-50 2-93 0-05 



Coast Range, Southern Calif ornia 10 57 65-44 3-91 006 



Florida-Georgia 11 44 21-32 2-84 013 



Minnesota-Nebraska 12 36 8-23 2-17 0-26 



Texas-Oklahoma 13 40 19-23 3-23 0-17 



Washington-Oregon 14 37 53-68 3-37 006 



All combined 733 30-37 2-91 010 



"From the evidence shown in the table it is safe to conclude 

 that the isostatic compensation is so nearly complete on an aver- 

 age that the deflections of the vertical are hereby reduced to 

 less than one-tenth of the mean values which they would have if 

 no isostatic compensation existed. One may properly charac- 

 terize the isostatic compensation as departing on an average less 

 than one-tenth from completeness or perfection. The average 

 elevation of the United States above mean sea level being about 

 2500 feet, this average departure of less than one-tenth part from 

 complete compensation corresponds to excesses or deficiencies of 

 mass represented by a stratum only 250 feet (76 meters) thick on 

 an average." 17 



This quotation appears to contain two fundamental 

 errors ; one in the comparison of topographic deflec- 

 tions with the residuals of solution H, the other in the 

 use of sea level as a datum for interpretations of excesses 

 or deficiencies of mass. The latter error was pointed 

 out and discussed by the writer in 1914. 18 In so far as 

 the relief between continent and ocean floor is concerned, 



17 J. F. Hayf ord, Supplementary investigation in 1909 of the figure of the 

 earth and isostasy, 59, 1910. 



18 Joseph Barrell, The strength of the earth's crust, Jour. Geology, 22, 

 297-301. 



