■332 TranmctlonH.— Geology. 



evidence of the fact might be found in excavated moraines, 

 such as has been described in the Nelson Province. Be this 

 as it may, the cessation of the work of pihng up the terminal 

 moraines clearly points to the occurrence of marvellously 

 sudden ameliorations of climate. The absence of marks of 

 slow retreat — in morainic matter — of the ice from the low- 

 lands appears to tell a similar tale of an earlier age. How 

 such sudden changes were brought about is a question on 

 which I can offer no opinion ; but I think the condition of the 

 alpine lakes, with their high and steep moraines, clearly 

 proves that the ice retreated from them with great sudden- 

 ness. If this were so, as it appears, the lesser changes regis- 

 tered by the loess may likewise have been sudden changes — 

 that is, occupying but a brief time compared with the dura- 

 tion of each fixed phase. 



Art. XXXII. — On Glacier-motion. 

 By J. Hardcastle. 



^Rcad before the PJdlosophical Institute of CanterburTj, 2nd October, 



1890.] 



The latest authoritative deliverances on the subject of the 

 mode of motion in glaciers of which I am aware state that 

 "the problem of the cause of glacier-motion cannot yet be 

 considered to be satisfactorily solved," and "the solutions 

 accepted are not perfectly satisfactory." Whilst endeavour- 

 ing some time ago to work out a particular case of the pro- 

 blem, using as a principal factor a physical property of ice 

 which underlay some interesting experiments of Professor 

 Tyndall's — viz., its plasticity under pressure — I obtained 

 W'hat appeared to me to be a full, clear, and simple solution 

 of the whole problem of ice-motion. When, however, I again 

 referred to articles on the subject I found that my solution 

 <lid not fit the alleged facts to be explained, in one important 

 particular. It is asserted that " the top of a glacier moves 

 faster than the bottom." The conclusion at which I had 

 arrived was generally incompatible with this. There is no 

 ground for impeaching the correctness of the observations 

 from which that generalisation was drawn, yet the generalisa- 

 tion may be erroneous. It may be true of a part or parts 

 only of a glacier that the top moves faster than the bottom ; 

 and, if this is so, a true theory, in order to explain those 

 observations, should show to what limited extent, and under 

 what circumstances, the surface of a glacier does move faster 

 than the bottom. 



