252 ANNUAL OF SCIENTIFIC DISCOVERY. 



and of rise is not greatly different from that of the magnetic meridian 

 for the district, which is about 11 west, of north." As a general 

 thing, the movement has been surprisingly equable over relative pro- 

 portions of the space. There is a large tract in the south and east of 

 Scandinavia, which is ascertained to be undergoing- an elevatory move- 

 ment, even at the present day. Thus, on the stone at Lofsgrund, 

 which has been marked with the height of the water at various peri- 

 ods, but lastly by Lyell, in 1834, Mr. Chambers found the mark of 

 Mr. L. 2 feet 7 inches below that of 1731, and the sea was already 

 about 6 inches below that of Lyell, or over 3 feet below that made; 

 118 years before. On another stone Mr. C. found a mark made in 

 1820, 11 inches above the present level of the sea, thus indicating- a 

 rise of the land to that amount since that period. 



In Abyssinia. M. d'Hericourt, at the close of a memoir presented 

 to the French Academy, on January 14th, concludes, from various 

 reasons which he gives, that " the Gulf of Arabia and Abyssinia are 

 in a constant state of elevation." 



Subsidence Caused by Drainage. Mr. G. W. Ormerod stated to 

 the British Association, at Edinburgh, that the surface of Chat Moss, 

 in Lancastershire, was shown, by a series of levellings made in the 

 last four years, over an extent of about 200 acres, where drainage 

 was carried on, to have subsided to the amount of one inch per annum. 

 -London Athenaum, Aug. 



SUGGESTIONS ON THE CHANGES OF LEVEL IN NORTH AMERICA 



DURING THE DRIFT PERIOD. 



AT the meeting of the American Association at New Haven, Pro- 

 fessor C. B. Adams presented a communication on the above subject. 

 The objections to the glacial theory lie against the origin of the re- 

 quired glacial sheet rather than against the dynamics of the theory ; 

 while the objections to the other theories lie against their dynamics 

 with a serious, if not with a fatal force. The suggestion, therefore, 

 of a possible cause of a vast glacial sheet, 5,000 feet thick, may not 

 be useless, even if somewhat improbable. The hypothesis is this, 

 that the glacial sheet was produced by a great elevation of land in the 

 northern regions above the present level. Besides the direct refriger- 

 ating influence of elevation, the flow of the tropical waters into the 

 North Atlantic may have been essentially diminished by the contrac- 

 tion of the area of the ocean. This contraction must have been much 

 greater, if, as is highly probable, the similar elevation of Northern 

 Europe was synchronous with that of North America. Whether or 

 not this elevation can account for the origin of the glacial sheet, there 

 is direct evidence of a greater elevation than the present during the 

 drift period, in the continuation of the drift striae beneath the sea level ; 

 for it is well known that glaciers cannot advance into the sea. Un- 

 fortunately, the impossibility of following the strias excludes us from 

 the knowledge of the most important fact, the greatest depth at which 

 striae exist. The passage of drift materials across basins which are 

 now filled with water suggests the same conclusion. Such of the 



