430 Correspondence — 3Ir. G. TI. Morfon. 



Mr. Mellard Reade states that " Blown-sand of sand-dunes is not 

 distinguishably more worn than the sand of the shore from which it 

 is derived." I do not know what particular dunes are referred to, 

 but I must say that my experience is quite the reverse of this. 

 Blown-sands of deserts and dunes procured from many parts of the 

 world have never yet failed to provide me with characteristically- 

 rounded grains in great abundance. 



Of course much will depend on the particular spot from whence 

 samples are procured. Grains freshly blown up from the shore on 

 to the surfaces of dunes would not become appreciably rounded until 

 they had travelled some distance inland, and had been whirled 

 about in hollows and depressions for some length of time. The 

 places to find rounded grains of blown-sand would be, therefore, in 

 such depi'essions some distance from the shore, and I feel sure that 

 anyone collecting samples from such spots will confirm my opinion. 

 It must be clear that the action of the wind in time, by hurling the 

 grains one against the other, would produce (in the case of quartz) 

 sphericity through abrasion, and numerous sands prove this. 



A fact that does not appear to be known in connection with grains 

 of blown-sands is that many of the grains exhibit the mastoid 

 markings so frequently seen on flint pebbles, and these markings 

 clearly show with what force the grains have collided. I have 

 never found these markings on wave-borne sand grains, simply 

 because in the denser medium — water — the grains do not collide 

 with sufficient force to enable them to become developed. Some 

 years ago, at St. Agnes, in Cornwall, I found a deposit of white 

 quartzose sand (probably Pliocene), the larger grains of which were 

 covered with these markings, and these alone, I considered, pointed 

 to the Eolian character of the deposit. 



Before we can base any conclusion — as to the locating agent of a 

 particular deposit — upon the rotundity of certain sand-grains con- 

 tained therein, we must satisfy ourselves that such grains were not 

 already i-ounded and polished in the parent rock from which they 

 were derived. 



In reference to Mr. Pittman's letter on " Flexible Sandstone," it 

 does not appear to have been noticed that nearly thirty years ago 

 Dr. Wetherell published an opinion that the flexibility was due to 

 the grains being " arranged in definite groups separated from one 

 another by intervening cavities." Cecil Carus-Wilson. 



Bournemouth, July 11, 1892. 



SUBTERRANEAN EROSION OF THE GLACIAL DRIFT, A PROBABLE 

 CAUSE OF SUBMERGED PEAT AND FOREST-BEDS. 



Sir, — In December last a paper under this title was read before 

 the Geological Society by Mr. William Shone, F.G.S., and more 

 recently a resume of it was given to the Chester Natural Science 

 Society. The author desci'ibed a section at Upton, near Chester, cut 

 by two streamlets through Boulder-clay resting on a considerable 

 thickness of sand. The clay sloped towards the sides of the streams. 



