702 WILLIAM HERBERT HOBBS 



upon the plains, the difference in deflection is 45", instead of 26", 

 which it should either equal or exceed on the conception of support 

 by rigidity without compensation, and 15", as it must be according 

 to Hayford's hypothesis. 1 In a separate monograph of the Indian 

 Survey, Major Crosthwait has discussed the application of Hay- 

 ford's theory to the Himalayan area and has found that whereas 

 for the United States as a whole the mean residual is i''86 and for 

 all save the western section 1". 15, for the Himalayas it is more than 

 eight times this amount. 2 Dr. Hayden has shown that to secure 

 compensation the depth of the equilibrium surface must be in- 

 creased from Hayford's figure of 122 km. to 330 km. 3 Applied in 

 the region where it is most crucially tested, the Hayford hypothesis 

 thus receives less support in the facts than does the doctrine of 

 non-compensation . 4 



Mutual relationships of abnormal gravity, abnormal earth mag- 

 netism, dislocations, and seismicity. — In at least three widely sepa- 

 rated provinces the coincidence of anomaly of terrestrial magnetism 

 with that of gravity, and with that of dislocation zones, has been 

 proved by the data from official surveys. In the earthquake prov- 

 ince of Calabria and Sicily this result has been reached by a Royal 

 Commission under the direction of Professor Ricco. 5 



A close correspondence between anomaly of gravity and that 

 of terrestrial magnetism has likewise been brought out to special 

 advantage within a province in Hungary which is relatively small, 

 but one provided with an especially large number of stations, so 



1 Burrard, op. cit., p. 4. See also Sir Thomas Holland, "The Origin of the Hima- 

 layan Folding," Geol. Mag., Dec. V, Vol. X (1913), pp. 167-76. 



'Major H. L. Crosthwait, R. E., "Investigation of the Theory of Isostasy in 

 India," Prof. Paper No. 13, Survey of India (Dehra Dun, 1912), pp. 1-123. 



3 H. Hayden, "Notes on the Relationship of the Himalaya to the Indo-Gangetic 

 Plain," etc., Geol. Surv. India, XLIII (1913), 138-67, Pis. 3, 4. 



* The stations discussed by Bowie from the Indian district to indicate harmony 

 with the Hayford doctrine are far removed from the Himalayas (W. Bowie, "Isostasy 

 in India," Jour. Wash. Acad. Sci., IV [1914], 245-49.) 



s A. Ricco, "Anomalie del magnetismo terrestre in relatione alle anomalie della 

 gravita nella Sicilia orientale," Boll, dell' Accad. Gioenea di Scienze Naturali in Catania, 

 Fasc. 80 (1904), pp. 1-3. See also "Anomalie della gravita e del magnetismo terrestre 

 in Calabria e Sicilia," Annali dell Ufficio Centrale Meteorologico e Geodinamico Italiano, 

 XIX (1897; separate printed at Rome in 1907), 1-10, plate; also, "Anomalie della 

 gravita e del magnetismo terrestre in Calabria e Sicilia in relatione alia costituzione 

 del suelo, Boll, della Soc. Sism. Hal., XII (1907), 393-407. 



