52 0. P. Hay — Deposit of the Glacial Drift. 



The above analysis obtains for a friction less bearing. From 

 the discussion of relative sensitiveness, we have found that 

 with equal friction, a spread vane is more sensitive than a sim- 

 ilar straight vane; consequently, for two vanes of equal sensi- 

 tiveness, the spread vane will have the greater friction and will 

 come to rest more quickly. 



Art. YII. — On the manner of Deposit of the Glacial Drift ; by 



0. P. Hay. 



The events of the "Great Ice Age," that period of the 

 earth's history during which the deposits known as the 

 "Drift" were scattered over a great portion of the Northern 

 Hemisphere, have left many problems to perplex and to 

 reward geologists, physicists, and astronomers. Some of these 

 problems have already been solved ; many yet await solution. 

 That the principal agent concerned in performing this vast 

 work was glacial ice ; that its general direction of movement 

 was from the north toward the south; and that it bore along 

 with it, often from very distant localities, the materials of the 

 Drift, are conclusions that are now pretty generally conceded. 

 A problem whose solution has not yet been effected, is that 

 relating to the manner in which the great glacial ice-sheet has 

 deposited upon the older rocks its burden of materials that it 

 had wrested from the strata and mountains farther north. 

 There seems by no means to have been any dearth of theories 

 on the subject, but none of them have been able to command 

 general assent. 



Prof. J. D. Dana has held the view that the materials of the 

 drift were gathered up during the Glacial period, and for the 

 most part deposited by the melting of the ice during the Cham- 

 plain. His language is as follows : 



" The earlier part of the Champlain period was the era of the 

 melting of the great glacier and of most local glaciers .... and 

 of the deposition of the sand and gravel of the glacier, except 

 the relatively small part which had been earlier dropped," etc. — 

 Manual, 1876, p. 542. 



Prof. James Geikie appears to adopt the hypothesis that the 

 Drift deposits accumulated under the glacier, but I am not 

 aware that he has anywhere attempted to tell us how.' His 

 language in various passages seems to imply that these mate- 

 rials thus lying beneath the glacier were either constantly 

 being pushed along or, at least, liable thus to be acted upon by 



