492 Prof. K. Busz — Corundum on Dartmoor. 



That this in outline is what geological history tells has happened 

 in the neighbourhood of Liverpool, I have no manner of doubt. 

 Similar movements of the land, not necessarily in this order or of 

 the same frequencj', are registered all round the coasts of England 

 and Wales, Scotland* and Ireland, as shown by dock or other 

 excavations where the submarine geology can be explored. 



Whether my hearers agree with me or not in the details of these 

 land movements, he would be a bold man who would deny that 

 the}'' have occurred on a large scale during the periods named. 

 Admitting the fact, the interesting question remains, what is the 

 cause of these frequent oscillations of level. One favourite explana- 

 tion at the present time is that it is the effect of isostacy, of a loading 

 and unloading of the earth's crust by sedimentation and denudation. 

 Let us examine this : the glacial deposits cannot average so much as 

 200, probably not 100, feet in thickness; the effect of such a loading 

 would be inappreciable on the earth's crust, whatever view we take 

 of the constitution of the earth's interior. If the addition of the 

 glacial deposits cannot affect the foundations of the earth, still less 

 can their partial denudation create a rise of land. The same 

 reasoning applies with greater force to the post-Glacial deposits, 

 as they are neither so extensive nor so massive. Alterations of the 

 sea-level seem to me out of court, simply because such fluctuations 

 must arise from gravitation to land masses, thus creating a greater 

 difficulty to account for a lesser one, as the land masses have to be 

 moved first before the water of the sea can follow. 



Mr. Shone has suggested that the subsidence of the peat and 

 forest beds has been due to subterranean erosion, but they occur at 

 too regular levels and in too many places to render this a feasible 

 explanation. Ice in the Glacial Period accumulating in great 

 thicknesses on the land has been appealed to as a cause of 

 submersion, and its melting of emergence. This is a more plausible 

 suggestion, because thei'e is nothing to bind us in our idea of the 

 load, which we can pile up in imagination to any extent, but unfor- 

 tunately it does not explain post-Glacial movements which are 

 demonstrated to have taken place, not only by the facts I have laid 

 before you, but by the shore terraces found in various places around 

 our Islands. 



It appears, then, that these pulsations of the land are not due to 

 external causes, but to causes hidden from us in the earth's interior. 



VI. — On the occurrence of Corundum produced by Contact- 



METAMORPHISM ON DARTMOOR. 1 

 By Professor K. Busz. 



SOME three years ago, when travelling in Devonshire, I had the 

 opportunity of visiting some places on Dartmoor, and of 

 collecting on the border of the Dartmoor Granite some specimens 

 of rocks, which on closer examination seemed to be of general 



1 An abstract of this paper was read before tbe British Association, Li\ 

 September, 1896. 



