152 



THE AMEKICAN MONTHLY 



[August, 



quartz ; in a slide made of it the few 

 intrusions of flint are about three or 

 four. 



Let us now come back to our south- 

 ern coast, and one of the facts that 

 first attracted me in relation to this 

 subject was that organisms using sand 

 for building purposes always choose 

 quartz. It is so with that curious 

 spone Dysidea fragilis ; it is so also 

 with the ovisacs of one of the mollus- 

 ca, which at first look so much like 

 a sponge. These are completely built 

 up of quartz sand, and although other 

 fragments are sometimes used, and 

 even foraminifera, yet it is rare to 

 find anything of chalk flint. Dysidea 

 is common at Brighton, where the 

 shingle is of chalk flint, and one 

 might think sand also ; but it is quartz 

 that is used. 



What then becomes of the flint 

 sand .? We see the rounded pebbles : 

 abrasion must produce powder, /. <?., 

 sand. What then can become of it.'* 

 Does the flint change to quartz } Is 

 it possible that any molecular meta- 

 morphosis can take place, or, if not, 

 what becomes of the abraded dust of 

 chalk shingle that it is always found 

 in such small quantities.? Then 

 whence proceeds this very abundant 

 and ubiquitous quartz sand.'' The 

 set of the current of the English Chan- 

 nel is, I believe, from west to east ; 

 that of the German Ocean from north 

 to south. 



We must think of all the conditions 

 existing to account for the prevalence 

 of quartzose sand. On our southern 

 coast there is a large gap between the 

 chalk cliffs of Dover and that of Beachy 

 Head, in which the Wealden deposits 

 make their appearance, consisting of 

 sandstone grit, shaley laminated sand 

 rock, and the like — all of fluviatile 

 origin — remains of the delta of a 

 mighty river, equal, at least, to that • 

 of the Ganges. This sand is of pure 

 quartz, or nearly so, and as the Weal- 

 den outcrop crosses the English Chan- 

 nel, though not represented on the 

 opposite shore, here is necessarily an 

 abundant supply of quartzose sand. 



Still we I'nust note that the coasts, all 

 along this gap, have the usual beach 

 of chalk flint shingle. Indeed, it is 

 represented in enormous quantities, 

 often a mile and more in diameter at 

 the closed-up ancient estuaries re- 

 ferred to. First, there is that of Pe- 

 vensey, where the old Roman castrum 

 is in a more complete condition than 

 is found elsewhere, and which once 

 defended its entry against our ances- 

 tors the Saxon pirates. Let us be 

 proud of our Saxon forefathers, of 

 whom the Roman historian pitifully 

 says, ' Pras ceteris hostibus Saxones 

 timentur.' Then let us go to Rom- 

 ney Marsh, where is the same phe- 

 nomenon on a grand scale, and an- 

 other ancient estuary closed up, the 

 ' Tortus Lemanis ' its fortress, which 

 once defended it, a shapeless, dis- 

 rupted ruin. Here the rolled shingle 

 covers many a square mile. Where 

 then is the detritus of all this mass, 

 if it is not found in the sands adja- 

 cent .'' 



There is still to be brought into the 

 account the upper and lower green- 

 sand, the Shanklin sand which must 

 furnish a part of the ocean bed as it 

 crops up by Folkestone at Copt Point. 

 But we have to consider whence these 

 are derived. The more we seem to 

 go into the matter the more intricate 

 or extended does the problem appear ; 

 and yet its solution ought to be with- 

 in a small circle, for what we are 

 seeking to know is, what becomes of 

 the detritus of chalk flint.'' 



Let us now proceed to examine the 

 geological deposits of the tertiary pe- 

 riod, formed within the large depres- 

 sion 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 abund- 

 ant about and in London. Washing 

 a portion of this, taken from the 

 neighborhood of Hampstead, after 

 getting rid of extraneous matter, there 

 remains a portion of sand, which ap- 

 pears to be in part or wholly of quartz, 

 though much comminuted. Amongst 

 it, however, are some, though few, 



