Correspondence — R. M. Brydone. 527 



that evaporation equals precipitation on the plateau leads one to 

 infer that it is likely that the ice-cap there is quite thin. If the 

 upholders of the 5,000 feet ice-sheet will produce the record of 

 a tabular iceberg more than 1,600 feet thick, or if they will show 

 that there is a valley 5,000 feet from crest to trough running under 

 the flat ice-cap of Greenland — the observations at present available 

 tending to show, on the contrary, that the deep valleys on the coast 

 go but a short way inland and end abruptly on the edge of a plateau 

 — then I will believe that physical laws have been suspended in 

 their operation for the special benefit of glacialists. 



Ernest H. L. Sohwarz. 

 Ehobes University College, 



Grahamstomtst, Cape Colony. 



THE TRIMMINGHAM CHALK, 



Sir, — It seems desirable to make a few comments on Professor 

 Bonney's paper in your September number. On the question of 

 " western and eastern " or " northern and southern " bluffs, 

 I cannot see what the trend of the coast, ever varying from point 

 to point and as you take it at the base or top of the cliff, can have 

 to do with the relative position of two fixed points. A line drawa 

 from bluff to bluff runs by the compass 5^-10° S. of S.E., so that 

 I and any earlier writers who used magnetic bearings are accurate 

 in speaking of " northern and southern " bluffs. Can it be that 

 Professor Bonney is treating our magnetic bearings as if they were 

 geographical, and supplying an instance of the very confusion 

 I sought to forestall by a note obviously addressed to the general 

 public. (Professor Bonney affects to regard it as addressed to him 

 personally, but 1 can assure him that the paper by him and Mr. Hill 

 gave rise to no alteration in the form or substance of mine.) On the 

 East Coast it is in any case natural (and not inaccurate) to speak of 

 points along the coastline as north and south, while they are no 

 nearer due east and west than 10°-15° E. of S.E indicates. 



I am less fortunate than Professor Bonney in having only found 

 one place where the foreshore chalk has a skin of boulder-clay, the 

 plastic clay having, under pressure from the cliffs above, crept over 

 the chalk for a few yards in a depression. It seems a very natural 

 thing to happen. 



Professor Bonney has not fully grasped my theory as to his blocks 

 A, C, and E. I believe that the eroded surface, unconformable to 

 the lines of flint, of the Ostrea Innata chalk in these three blocks 

 was formed in Cretaceous times, and then still in Cretaceous times 

 the grey chalk was deposited on it, most thickly in the hollows, 

 e.g. between C and E, and in the pocket in the seaward face of A 

 shown by my figs. 13 and 13. On this theory no twisting of the 

 grey chalk is required, nor is there any difficulty in its occurring 

 still at the top and bottom of the sloping face of C. (As I have 

 stated, it formerly covered the whole of this sloping face and was 

 continuous above the sand with the grey chalk in E.) 



