46 Correspondence — Sir H. H. Howorth. 



From the junction of the two rivers eastward, slate is seen below 

 Table-mountain Sandstone ; and on the latter is a long stretch of. 

 the Dwyka Conglomerate to the coast, greatly disturbed for the 

 most part, and pierced by two dolerite-dykes, between which a 

 patch of Ecca Shales is preserved. 



The author concludes that the marble was deposited on the granite, 

 and probably on the Malmesbury Slates near by, before they were 

 disturbed : that it does not extend far under the neighbouring hills ;, 

 and that some of its local detritus indicates that the rivers ran at 

 higher levels within relatively recent times. 



ooiiK/EsipoisriDsisroiE]. 



ME. DEELEY AND ME. HAEKEE : <'TWO BIEDS WITH ONE STONE." 

 Sir, — In my view there is no more profitable way of advancing 

 knowledge than by good-humoured controvers}'. I only wish 

 my opponents' banter was a little more playful. Mr. Deeley is 

 mistaken in supposing that I, of all people, can object to his 

 attacking old problems. What I called impertinent, was attacking 

 vert) old problems without first learning what other men had had to 

 say to them, coupled with the assumption that the long life's-work 

 of such patient masters of their craft as Studer, and Forbes, and 

 others in the Alps, was going to be all set right by Mr. Deeley's 

 summer jaunt to Mont Blanc. 



What they proved and what recent experiments in the laboratory 

 have confirmed is the plastic nature of glacier ice. Mr. James 

 Geikie, who formerly advocated Croll's transcendental theory of 

 ice-motion, has completely abandoned it in his new volume on the 

 Ice Age, in favour of Forbes' view. Mr. Deeley, some time ago, 

 had a private transcendental theory of his own on the subject, which 

 I cannot find that anybody understood, much less adopted. I do not 

 know whether he still holds to it, or is now satisfied by the experi- 

 ments of McConnel, Kidd, and others, that Forbes was completely 

 right. I take it from some phrases he uses that, like Mr. Geikie, 

 he, too, has surrendered. If he has not, we are beating the air, 

 for I am bound to say I neither understand the physical nor the 

 mechanical basis of his ice theory. 



If he now holds, as all the world holds, that ice is a viscous body, then 

 he must also hold that it acts like one, and that when it has a sloping 

 back it will not move at all on account of the shearing resistance of 

 the ice, unless the slope of its back is equal to that of a glacier-bed 

 when motion first ensues in a glacier. Forbes showed that this meant 

 a considerable slope. Tlie question for Mr. Deeley (entirely apart 

 from all geological difficulties) is how to secure and maintain such 

 an ice slope as would carry boulders to Britain from the Ohristiania 

 Fjord, and then move on till it terminated in a scarped cliff of ice 

 at the 100 fathom line, and this when the upper part of the 

 Dovrefelds was entirely free from ice as it now is from markings. 

 This is one only of a dozen difficulties surrounding an ice hypothesis 

 which has been evolved apparently without any thought of the 



