l*h'i><toc<'iie l\ipii'x a.f flii'AVii><hi iKjioii Mirt'nKjx. 237 
<lepression. within Xeolithic time, was probably only a few thou- 
sand years ago. 
Mnir ifhtciir and its luclulfij. By H. P. CrsHiNO. An iuter- 
•esting description, with lantern illustrations. The rate of glacial 
motion near the border, according to >Ir. Cushing"s measurements, 
is four to eight feet per day. Ijeing much less than the rate deter- 
mined Ijy Wright for the more central portions of this famous 
Alaskan glacier. [See this paper. \). 207.] 
The present stdndimj of the sevnal hypotheses of the enuse of 
the GhieiaJ period. By Thomas C. Ch.\mberlix. The restric- 
tion of the great areas of Pleistocene glaciation to one side of 
the northern hemisphere forbids our receiving the ingenious 
astronomic theory of the late Dr. Croll as an adequate explana- 
tion of the causes of the Ice age. Also, from the line of argu- 
ment employed by the speaker in his previous paper before the 
American Association, the theory of high uplifting of the land 
to account for the ice accumulation seems e([ually untenable. 
An elevation of 10.000 or 15,000 feet would prol)ably be re- 
([uired. and this great uplifting must be shown to have been con- 
temporaneous and co-extensive with the glaciation. Therefore, 
finding no evidence of such continental elevation, the most prob- 
able theory is believed to be that of changes in the position of 
the earths axis and its poles, liringing the glaciated countries into 
high latitudes with arctic climate. A paper presented before the 
astronomic section of the American Association at this meeting 
by Prof. George C. Comstock. on --The secular variation of ter- 
restrial latitudes. "" shows that a slow change in the place of the 
north pole is now in progress and has amounted to four and a half 
seconds during the past century. Such movement of the i)ole 
may have been more rapid during the (Hacial period. If thi' 
north pole were transferred fifteen or twenty degrees toward the 
south end of Greenland, the drift-covered areas of North America 
and Europe woidd be brought into latitudes ftivorable for their 
envelopment by ice. 
Prof. ('. 11. TIiTciicocK. in discussion, suggested that the sun's 
heat may have l)een variable, being considerably diminisheil dur- 
ing the glacial epochs. 
Prof. N. S. Sif.vi.KR distrusted the exphination liy movement of 
the earths axis, and inclined instead to l)elieve that geographic 
■c-hanges during the (Jlacial period induced cool and humid cli- 
