400 T. F. Jamieson — Oscillation of Land in Glacial Period. 



III. — On the Cause of the Depkession and Ee-elevation op the 

 Land during the Glacial Pekiod. 



By Thomas F. Jamieson, F.G.S. 



N a paper published in the Quarterly Journal of the Geological 

 Society for January, 1865, p. 178, I drew attention to the re- 

 markable fact that in various parts of the world the presence of 

 glaciers had been attended bj'' a submergence of the land, and I 

 suggested that the enormous weight of ice laid upon the surface of 

 the country might have caused a depression, while the melting of 

 the ice would also account for the rising again of the land which 

 seems to have everywhere followed some time after the ice dis- 

 appeared. 



The paragraph in question, if it did no other good, was of service 

 in so far as it attracted the attention of the thoughtful mind of Dr. 

 James Croll, who in a letter dated 22nd Aug. 1865, addressed to 

 Professor Eamsay, and published in the pages of " The Eeader " of 

 the 2nd Sept. in the same year, commented on the suggestion I had 

 made. But, while admitting the fact that submergence had generally 

 accompanied glaciation, he doubted the sufficiency of the cause I 

 had assigned, and maintained that the circumstance would be better 

 explained by the influence of a great polar ice-cap whose mass 

 would effect a slight shifting of the centre of gravity of the earth 

 and thus draw the waters of the ocean northward or southward, 

 according as either pole happened to be under ice at the time. This 

 theory had previously been advanced by M. Adhemar and developed 

 by him at considerable length, in a volume entitled " Eevolutions 

 de la Mer." 



Dr. Croll's letter gave rise to a lengthened correspondence and 

 controversy in the pages of the periodical called "The Eeader," in 

 which a part was taken by Mr. S. V. Wood, jun., Mr, 0. Fisher and 

 others ; but so far as I remember, no further notice was taken by 

 any of them of the cause I had suggested. 



Dr. Croll's maturer views on the subject will be found set forth 

 in his remarkable work called " Climate and Time," and also in a 

 paper published in the Geological Magazine for July and August, 

 1874, " On the Physical Cause of the Submergence and Emergence of 

 the Land during the Glacial Epoch." He there assumes that the 

 Antarctic contingent is at present covered by a cap of ice 2800 miles 

 in diameter and six miles thick at the pole, with an average depth 

 of about two miles all over ; and he maintains that the submergence 

 of the northern lands during the Glacial period was caused by the 

 transference of this great mass of ice from the southern to the 

 northern hemisphere. 



It seems to me that we have no sufficient proof of the present exist- 

 ence of a south polar ice-cap of the dimensions Dr. Croll assumes ; 

 and the evidence, so far as I can judge, seems to be decidedly against 

 the notion that there was any such ice-cap at the North Pole during 

 the Glacial period ; but without meaning to question the adequacy 

 of a great polar ice-cap, supposing it did exist, to affect the centre 



