1884.] 



MICROSCOPICAL JOURNAL. 



151 



sands, of which Hampstead Heath 

 gives us an example easy for exami- 

 nation. Proceeding downwards, we 

 pass thi"ough the vast mass of the 

 London clay, and come to the Pebble 

 bed, well represented at Blackheath, 

 and well named for its small rounded 

 pebbles, like marbles of various sizes, 

 and mixed v\^ith this is sand. All 

 these pebbles are of chalk flint. De- 

 posits, more or less mixed with sand, 

 succeed these, until we arrive at the 

 ' Thanet sands,' laying on the chalk. 

 Of what material, then, are all these 

 sands, and wherein derived is the 

 question proposed to this Society. 



Of course the prima facie view is 

 that they naturally arise from the at- 

 trition of the flint. Nothing is more 

 apparently obvious. Away from the 

 region of the chalk flint, our coast 

 sand is mostly composed, as we might 

 imagine, of the debris of the adjacent 

 cliffs or rocks, or from other prolific 

 but neighboring sources of supply, 

 such as shells of molluscs, or calca- 

 reous particles of the remains of vari- 

 ous zoophytes, as, for instance, at 

 Land's End, and other parts of Corn- 

 wall. After we pass westward of the 

 estuary of the Exe, chalk flint is of 

 rare occurrence on our coasts, al- 

 though an outlier of the chalk debris 

 may be seen w^est of but close to the 

 Teign. 



Now then we will proceed to see 

 how far this question belongs to us 

 as a Microscopical Society. Let us 

 take a pinch of sand out of a ^vashing 

 down of a road paved with gravel, 

 after storms of rain, and submit the 

 same to the microscope ; or, to be 

 certain in our experiments, let us 

 pound up some chalk flint finely. 

 Our examination of it will show us 

 that the flint has a granular appear- 

 ance, and does not polarize.* Let 

 us now take a piece of quartz and 

 reduce it to powder, and submit this 

 to the microscope, and we find it to 

 be translucent and clear, and it polar- 

 izes brilliantly. Moreover, the frac- 



* It would be more correct, perhaps, to say that it 

 does not give any prismatic colors. 



tui'e of the quartz is diflerent from 

 that of the flint. These conditions 

 understood, we are now prepared for 

 the problem to be solved, one which 

 belongs to the geologist, if not to the 

 phvsicist. 



Our eastern counties have beaches 

 of chalk shingle and sand, and the ^ 

 cliflfs are mainly a tertiary deposit, ^^ 

 consisting of clays, sands, and flint 

 gravel. These counties are devoid 

 of building stone, so all their ancient 

 churches are built of flint, and much ^ 

 ingenious workmanship is therein 

 sho"wn. Little stone is seen but that 

 which belongs to the upper green- 

 sand, locally known as ' clunch,' 

 sometimes oolite in small quantities, 

 which must have been brought round 

 by sea, and occasionally sandstone, 

 which, belonging to the Wealden sys- 

 tem, could not have been obtained 

 nearer than Hastings. Consequently 

 there is no material whatever on the 

 coast capable of furnishing any quartz 

 sand. Still one must al^ways remem- 

 ber that the operations of nature are 

 large, and our views of them small. 

 The visitor to Yarmouth must remark 

 the deep sand deposits on its shore. 

 Let us cross to the other side of the 

 German Ocean, and large dunes or 

 hills of sand are found all around the 

 coasts of Belgium, leading into France 

 as far as Boulogne. Does it come 

 from chalk flint? 



I have examined sand from Lowes- 

 toft, and I find it all to be of quartz ; 

 in a slide made from its sand only 

 one piece of chalk flint is seen. Dr. 

 Matthews gave me some sand from 

 Aberdovey, Wales ; it is mostly of 

 quartz, with some intrusions of other 

 substances, but none, of course, of 

 chalk flint. Indeed, no one could 

 discover any difference between the 

 two, although one is on the eastern 

 side of our island, amid nothing but 

 chalk debris, whilst the other is on 

 the western side, in the L-ish Chan- 

 nel, where no chalk or chalk flint 

 exists at all. Let us travel higher up 

 our eastern coasts as far as Yorkshire, 

 and at Bridlington the sand is again 



