PHYSICAL GEOLOGY. 187 



between the period of the rock-grooving and the deposition of the over- 

 Ipng marine clays. C. E. De R. 



Reusch, H. H. En notis til Kundskaben om Strandlinjer. [Note on 

 Coastlines.] Forh. Vid.-Selsk. Christiana for 1874, pp. 284, 285. 



Ricketts, Dr. C. The Cause of the Glacial Period, with Reference 

 to the British Isles. Geol. Mag. dec. ii. vol. ii. pp. 573-580 ; and 

 Proc. Liverpool Geol. Sac. vol. iii. pt. 1, pp. 49-52. 



The alternations of mild and very low temperature during the Glacial 

 Period have been thought to be indirectly due to astronomical causes ; 

 but the author thinks that a series of oscillations of level in Central 

 America, whereby the Gulf Stream would be from time to time diverted, 

 would give rise to the same phenomena, and might at the same time 

 afford an explanation of the occurrence of Boreal shells in Tertiary 

 deposits. J. G. G. 



Rogers, J. J. Remarkable Sea-waves observed in Mount's Bay, 

 Cornwall, April 24th, 1868. Trans. Ii. Geol. Soc. Cormvally 

 vol. ix. part 1, pp. 74-77. 



Although the wind was off shore, the sea was violently agitated for 

 some hours on the coast near Helston. There was a succession of great 

 waves differing from ordinary waves by their size and the distance 

 inland to which they penetrated. Much damage was done to the coast, 

 the sea-waves eroding the soft earth at points rarely touched. The 

 author supposes that recent encroachments of the sea near Porthleven 

 must be attributed to a subsidence of Mount's Bay. C. L. N. F. 



Sexe^ S. A. Angaaende Jaettegryders opkomat. [Origin of Giant's 

 Kettles.] Extract from an unprinted paper by Capt. L. Adlerstam. 

 Forh. Vid. Selsl: Christiania for 1874, pp. 187-189. 



Shaler, Prof. N. S. Some Considerations on the possible means 

 whereby a Warm Climate may be produced within the Arctic Circle. 

 Proc. Boston Nat. Hist. Soc. xvii. pp. 332-337. 



To solve the question raised by the occurrence of fossil forest- 

 vegetation about the N. Pole, the author imagines an easier access for 

 warm equatorial currents to the Arctic Regions, especially that the 

 Japan current was enabled to flow over what is now the land about 

 Behring's Strait. The admission to the Arctic Regions of another 

 current equal to the Gulf Stream would make the temperature nearly 

 equal to that of the Ohio Valley. The subsidence is supposed to have 

 occurred during the glacial period, and to have taken effect at its close. 

 The bearing of the theory on the changes in Greenland and Iceland 

 within the historical period is also discussed. F. D. 



. Notes on some points connected with Tidal Erosion. Proc. 



Boston Nat. Hist. Soc. vol. xvii. pp. 465, 466. 



The erosive action of tidal waves is greatest where, as in the Bay 

 of Fundy, there is a wedge-shaped arrangement of the shores, and a 

 closure at the far end. As soon as a passage is worn open to another 



