2i8 SCIENCE PROGRESS 



islands are not isostatically compensated, and invariably show 

 a positive anomaly of gravity. Hence their bases must yield, 

 and they sink slowly down into the crust under the influence 

 of gravity. This suggestion of local subsidence is regarded 

 by Davis as an important contribution to the coral-reef pro- 

 blem (" Isostatic Subsidence of Coral Islands," Proc. Nat. Acad. 

 Set. 191 7, 3, 649-54); but the phenomena of uplifted reefs 

 and atolls show that other processes than isostatic subsidence 

 are in operation. 



The recent diastrophism of North-East America excellently 

 illustrates the theory of isostasy (" Post-glacial Uplift of North- 

 eastern America," H. L. Fairchild, Bull. Geol. Soc. Amer. 191 8, 

 29, 187-238. See also " Glacial Depression and Post-Glacial 

 Uplift of North-Eastern America," Proc. Nat. Acad. Set. 191 8, 

 4, 229-32). The amount and area of land depression beneath 

 the latest continental ice-sheet (the Labrador glacier) is fairly 

 proportionate to the thickness and extent of the ice. When 

 the ice melted the land was much below its present altitude, 

 which it has since attained by a tilting movement with the 

 hinge south of New York. Ancient estuary features are trace- 

 able to a height of 800 feet in Vermont, and it has been found 

 possible to map the isobases over a considerable part of the 

 area. 



Regional and Stratigraphical Geology. — J. F. N. Green ad- 

 vances reasons for believing that the red Mell Fell Conglomerate 

 of the Lake District, hitherto regarded as the basal division 

 of the Carboniferous, is really of Devonian age (Proc. Geol. 

 Assoc. 1918, 29, pt. 3, 117-25). Its characters are those of a 

 torrential deposit formed at the foot of a mountain range in 

 an arid climate ; whereas the Carboniferous Limestone indi- 

 cates deposition in a sea bordering a low-lying land whence 

 little clastic detritus was derived. 



In a study of the structural relations of the Skiddaw granite, 

 J. F. N. Green presents evidence suggesting that the intrusion 

 is earlier than the cleavage, the Devonian faulting, and the 

 minor folds of the surrounding rocks (Proc. Geol. Assoc. 191 8, 

 29, pt. 3, 126-36). It is therefore believed to be connected 

 with local folding towards the close of the Borrowdale volcanic 

 episode. 



O. Holtedahl, Bidrag til Finmarkens Geologi (Norges 

 Geol. Unders. 191 8, No. 84, 314 pp.). This is a full account 



