Newfoundland and Nova Scotia. 389 



the element measured by the amount of post-Glacial 

 uplift was, during the application of the ice-load and the 

 subsequent lag, represented by subsurface matter com- 

 pressively condensed by the load. If the earth 's compres- 

 sibility varies according to the law deduced from seismo- 

 grams, the center of gravity of the excess mass thus 

 developed in depth may have l3een many hundreds of kilo- 

 meters below the surface. The horizontal component of 

 the attraction exerted by the element, at the earth's 

 surface, would therefore be less than that exerted by the 

 same mass when expanded because of unloading. A mod- 

 erate rise of sea-level near and within the glaciated area 

 should be expected.' 



Drowning in the belt outside the zero isobase may also 

 result from the isostatic restoration of crustal equilibrium 

 after unloading. Jamieson, Munthe, Barrell, and the 

 writer have found some evidence that the weight of an 

 ice-cap produces a centrifugal, viscous flow of subcrustal 

 material and consequent low bulges along the margin of 

 the glaciated tract.^ After the melting of the ice a return 

 viscous flow toward the center of the glaciated tract should 

 be expected. Barrell pointed out that, during the process 

 of attaining final equilibrium, the crust underlying the 

 marginal bulge should be lifted somewhat too high ; and 

 that, after the central region had nearly reached its final 

 position, the bulge would slowly subside. Any coastal 

 part of this belt would undergo progressive drowning 

 for some time after the purely elastic deformation was 

 completed. 



Thus, in the marginal belt the shore contour at sea-level 

 would be first affected by the return of water to the. sea, 

 a process accompanied by an immediate elastic uplift of 

 the glaciated tract, with concomitant effect on mass attrac- 

 tion; then by the delayed uplift due to elastic after- 

 working and by accompanying viscous inflow, with further 

 change in mass attraction; lastly, by slow subsidence in 

 the bulged, marginal belt, entailing a positive movement 

 of the sea in any coastal part of that belt. This third 

 cause of drowning would persist long after the action of 



' Cf. J. H. Pratt, The Figure of the Earth, 4th ed., London, 1871, p. 214; 

 G. H. Darwin, Scientific Papers, Cambridge, England, 1910, vol. 3, p. 29, 



«T. F. Jamieson, Geol. Mag., vol. 9, p. 461, 1882; H. Munthe. Geol. 

 Foren. Stockholm Forhandl., vol. 32, 1910 — reprinted as Guide-book No. 2-5, 

 Cong. Geol. Internat., Stockholm, 1910; J. Barrell, this Journal, vol. 40, 

 p. 13, 1915; E. A. Daly, Bull. Geol. Soc. America, vol. 31, 1920, p. :503. 



