408 R. M. Deeley — Viscous Flow of Glacier-Ice. 



In conclusion, I may refer to a paper read by my esteemed col- 

 league, Mr. D. Pidgeon, to the Geological Society in 1890, in which, 

 on the evidence of the shells and beach materials sent to him, he 

 disputed the genuineness of the Eaised Beaches of Hope's Nose and 

 the Thatcher Rock.^ Mr. Pidgeon, with his accustomed keen eye 

 for important detail, has pointed out certain very significant facts 

 pi'eviously unnoticed, and still unexplained ; but the proof of the 

 genuineness of the beaches lies in evidence quite independent of 

 the minute structure of the beach-material, organic or inorganic. 

 Had my friend been able to visit the beaches, I feel assured he 

 would never have questioned their genuineness ; and think it highly 

 probable he would have found some very satisfactory explanation for 

 the angularity of certain of the inorganic, and for the fractured 

 state of certain of the organic, components of the deposits in question. 

 During the many years over which my own investigations extended, 

 I never gave these two points a thought; and since Mr. Pidgeon's 

 paper was published have not set foot on the Thatcher Rock. 



VI. — The Viscous Flow of Glacier-Ice. 

 By E. M. Deeley, F.G.S. 



ALTHOUGH, ever since the classical researches of J. D. Forbes 

 on the phenomena presented by the Swiss glaciers were 

 jjublished, it has been recognized that glacier-ice behaves like a 

 viscous liquid, and flows from high to low levtls much in the same 

 way as does a river of water, it is apparent that many who have 

 interested themselves in the subject of glacier- flow, and have 

 written rather dogmatically on the sulyect, have not clearly realized 

 the nature of the phenomenon. Very contradictory and erroneous 

 conclusions have consequently been arrived at, with the result that 

 it is now somewhat difficult for those who have not made a special 

 study of the subject to distinguish what may be fairly regarded as 

 ascertained fact from that which is purely matter of opinion. 



I will, therefore, venture to state as clearly as possible the laws 

 of viscous flow (as I understand them) as deduced from experiment, 

 and then inquire to what extent the motion of a glacier approximates 

 to the conditions of such flow. 



Our knowledge of the subject is by no means due to recent 

 discovery. The viscous flow of liquids — and glacier-ice behaves as 

 a veiy viscous liquid — was worked out by Poiseuille and Coulomb. 

 Later, we have Helmholtz, 0. E. Meyer, Graham, Clerk Maxwell, 

 and Osborne Reynolds. The discoveries of these workers are quite 

 sufficient to enable us to work out the more important phenomena 

 presented by glacier-flow from first principles. Indeed, had sound 

 physical theory been adhered to by all writers on the subject of 

 glacier erosion and transport, the mistakes so many have fallen 

 into might have been avoided. Fortunately such investigators as 

 Prof. James Geikie have been able to keep the balance of opinion 

 from inclining in the wrong direction. 



1 Quart. Journ. Geol. Soc, vol. xlyi, p. 438. 



