THE DOCTRINE OF ISOSTATIC COMPENSATION 701 



large corrections for topography. It has been found, however, 

 that in the great triangle Kamiensk-Podolsk, Kazan, Astrakhan, 

 which relatively to the surrounding country is very unstable in a 

 seismic sense and is bordered by dislocations, the measurements 

 of gravity made by General Stebnitzki 1 have shown a notable 

 deficit of gravity to characterize this marginal zone. A like three- 

 fold correspondence of seismic instability, of zones of dislocation, 

 and of abnormal gravity has been proved for a number of other 

 regions, notably Southern Italy and Sicily, 2 the Indo-Gangetic 

 plain to the southward of the great protuberance of the Himalayan 

 Highland, the North German plain, and a district in Hungary. 



Evidence from India. — As the Russian province is of interest 

 because the topographic correction is small, so the Indo-Gangetic 

 plain at the southern base of the Himalayas offers a contrasted set 

 of conditions and presents the best possible opportunity for testing 

 the influence upon deflection constants of a huge protuberance of 

 the lithosphere whose volume and probable density may be sub- 

 jected to computation. It is thus of interest to find that Colonel 

 Burrard 3 is led to ascribe the deficit of gravity in the Indo-Gangetic 

 plain to the known zone of dislocation in correspondence with the 

 zone of seismic instability; his view being that a great rift in the 

 subcrust filled with material of low density extends to considerable 

 depths beneath this zone. 



Colonel Burrard is exceedingly favorable to the Pratt-Hayford 

 conception of isostasy and has made computations based upon 

 Hayford's earliest figures for the surface of compensation, yet he 

 does not find that the residuals are thereby decreased, but, on the 

 contrary, that they are enhanced. For the entire distance of 25 

 miles separating Kurseong in the outer Himalayas and Jalpaiguri 



1 M. A. de Lapparent, " Sur la signification geologique des anomalies de la gravite," 

 ibid., CXXXVII (1903), 827-31. 



s Annibale Ricco, "Determinatione della gravita. relativa in 43 luoghi della 

 Sicilia orientale, della eolie, e della Calabria," Mem. della Soc. degli spettroscopisti 

 Italiani, XXXII (1903), 173-296. 



3 Col. S. G. Burrard, "On the Origin of the Himalaya Mountains, a Considera- 

 tion of the Geodetic Evidence," Prof. Paper No. 12, Survey of India (Calcutta, 1912), 

 pp. 1-26. See also by the same author, "The Origin of Mountains," Geol. Mag., 

 Dec. V, Vol. X (1913), pp. 385-88; and "On the Origin of the Indo-Gangetic Trough, 

 Commonly Called the Himalayan Foredeep," Proc. Roy. Soc, A, XCI (1915), 220-38. 



