58 J. G. WALLER ON SAND. 



Let us now proceed to examine the geological deposits of the 

 tertiary period, formed within the large depression scooped out of 

 the chalk, called the London basin. And we will take them in 

 order, and first the brownish loam or brick earth, which is abundant 

 about and in London. Washing a portion of this, taken from the 

 neighbourhood of Hampstead, after getting rid of extraneous 

 matter, there remains a portion of sand, which appears to be in 

 part or wholly of quartz, though much comminuted. Amongst it, 

 however, are some, though few, intrusions of chalk flint. The 

 main fact is the general quartzose character of the whole. 



Next in order comes our familiar gravel, with its sand layers of 

 that deej) ferruginous hue, prized for our garden walks. Of this I 

 took samples from a section on Epping Forest, near Loughton, 

 made for a supply of fine gravel. Here, one would have thought, if 

 anywhere, being in the midst of a chalk flint debris, rolled together 

 to all sizes, that a vein of sand must show the same form of silex. 

 My specimen was taken four feet from the capping of loam, firmly 

 compacted together, and of a deep rusty colour. On submitting a 

 slide made from this to the microscope by polarized light, I was 

 astonished to find it so uncompromisingly of quartz. There were 

 other substances, yet extremely few in number, and I am not able to 

 pronounce upon them, but not the smallest atom of our familiar 

 flint of which every pebble around was composed. But not satisfied 

 with one specimen of the sand, I took another from a vein of a pale 

 grey tint close by, and the same results ensued, as indeed one might 

 have expected, only in such investigations one should never assume 

 anything, but resort to experiment. 



We now come to the series of the Bagshot sands, to which I have 

 alluded, and testing a specimen from Hampstead Heath, after 

 washing it, quartz is found to be the largest basis of the deposit. 

 Other particles, however, are seen in it, some of which look like 

 amber, and some fragments remind one of the colour of the 

 Cairngorm, yet it requires a mineralogist to pronounce upon them. 

 The character is also special in the presence of dark specks and 

 nearly black bodies, and we must certainly seek in another direction 

 than flint shingle, of which few signs are to be seen, as the factor of 

 the Bagshot sands. 



The vast mass of the London clay, that deposit of estuary mud of 

 a tropical sea, has its layers of sand represented at White Cliff and 

 Alum Bays, Isle of Wight, and of these I have examined several 



