Rev. E. Hill — Questions and Answers on Ice-Motion. 79 



Lizard district, the schists of the Start, the granites of Cornwall or 

 Dartmoor, the Devonian limestone, the Palgeozoic slates (perhaps 

 hardly to be expected) or their associated grits of the south-west 

 region. Among the quartzites and quartzitic rocks a few might be 

 Devonian, and some others probably represent the quartzites (earlier 

 Palaeozoic) of southern Cornwall,^ but the majority did not quite 

 correspond with any of the rocks which I have seen in situ in the 

 South-west of England, and, though my knowledge is nothing like 

 complete, I have sampled a fair number. Moreover, I was not 

 reminded at Budleigh Salterton of the fragments in the Meneage 

 conglomerate. The felstones may represent some of the w^estern 

 elvans, but, as already said, they are comparatively rare; the other 

 igneous rocks, still more rare, are not characteristic. 



The materials, then, seem not generally to represent the rocks 

 now exposed in Cornwall and Devon. I had expected to find 

 a large proportion of rocks from this region, as in the case of the 

 breccias, which are so fully exposed further west. I was surprised 

 to observe a very marked difference in this respect, and a much 

 closer correspondence with the lithological character of the Midland 

 pebble-beds. The fragments are far better rolled than those of the 

 breccia beds, and thus very probably have had a much longer journey. 

 I do not, however, suppose that they are derived from the same 

 source as the pebbles in the Midlands. The ascertained facts as to 

 the distribution of the Trias, which it is needless to recapitulate, 

 make this practically impossible, and the fairly constant direction 

 of the false bedding indicates the action of currents from a more or 

 less western quarter. But the presence of the curious quartz-felspar 

 grits, and of quartzites resembling those of North-west Scotland, 

 including even the peculiar liver-coloured type, suggests the pos- 

 sibility that the ancient mass of Archsean crystallines, which once 

 swept round from the Scoto-Scandinavian region to North-western 

 France, may have been fringed in more than one district with rocks 

 of Torridonian and Durnessian types.* 



A 



V. — Questions and Answers on Ioe-Motion. 



By Key. E. Hill, F.G.S. ; late Tutor of St. John's College, Cambridge. 

 PASSAGE in Mr. Deeley's letter in the December Number 



suggests to me that some readers may like an opportunity of 

 clearing their thoughts on some points connected with the motion 

 of ice. After a tutor's fashion, I will ask some questions. Let any 

 reader consider the answers he would give, and then compare with 

 mine which shall follow. 



If ice be a viscous body, how can the Antarctic ice stand "pre- 

 senting a vertical wall to the ocean, 1£0 feet high " ? So, in a better 

 known case, how can the walls of crevasses in a glacier retain their 



' Mr. Pengelly (Geol. Mag. 1878, p. 238) considered the fossiliferous quartzites 

 to be practically identical with those of Gorran Haven. 



2 See a very suggestive paper by Mr. Ussher, Quart. Journ. Geol. Soc. vol. 

 XXXV. (1879), p. 245. 



