: 



12 MR. W. WHITAKEIt ON THE [vol. lxXV, 



been used by man. This rarity is further emphasized by the fact 

 that all the quartzite-pebbles found are of fair size, all I think 

 more than 2 inches long, so that they are the more easily seen. 

 They are usually rather natter than flint-pebbles of corresponding 

 size. The late Dr. G. J. Hinde, with the help of his children, 

 collected far more of these pebbles than anyone else in the Croydon 

 district, and in his family they got the name of ' penny-stones,' 

 from the monetary reward to be gained by finding them. 



The origin of this quartzite is unknown, and, of course, also the 

 number of formations through which the pebbles may have passed 

 before reaching their Eocene resting-place. At first thought, one is 

 inclined to consider them as having been pebbles or boulders in 

 the Chalk ; but then one would have expected them to have been 

 accompanied by pebbles of granite and other hard rocks which 

 have been found in the Chalk. Can it be that the}' are the only 

 derived rock in the Chalk that could stand the long pounding to 

 which the pebbles of the Blackheath Beds were subjected ? And 

 have the} T been found in the Chalk ? 



The obvious conclusion from the composition of the pebble-beds 

 is that the water in which the pebbles were rolled touched no other 

 formation of firm rock than the Chalk, with its comparatively 

 indestructible flints, the quartzite-pebbles being presumably second- 

 hand articles. But, as was pointed out in the Geological Survey 

 Memoir of 1872, the absence of unworn or partly-worn flints shows 

 that the deposition of the beds did not take place along a Chalk- 

 coast, where subangular flints would far outnumber finished pebbles. 

 The flints must have been carried along in shallow water and the 

 well-rolled pebbles deposited in shoals far away from the Chalk 

 from which they came. 



Then the distribution of these pebble-beds is peculiar : they are 

 almost confined to a limited area, for in mass they are present only 

 in the eastern margin of Surrey and in the western part of Kent. 

 Other occurrences are of small extent and in scattered positions. 



The western boundary in Surrey is the Valley of the Wandle 

 (generally dry) from Croydon southward, no sign of the Blackheath 

 Bjds having been found along the southern outcrop of the Lower 

 London Tertiaries in the London Basin farther westward, through 

 Surrey and Hampshire. 



Eastward the pebble-beds are a marked feature in the country, 

 up to the Valley of the Cray, and they continue to occur up to 

 that of the Med way ; but beyond this pjbbles form but a small 

 part of the division, which takes on the sandy Oldhaven character, 

 and is better described under that name. In East Kent there is 

 n small mass of pebbles, forming two tiny outliers, at Shottenden 

 Hill, Selling; but elsewhere the Oldhaven Beds consist almost 

 wholbr of sand, with only a thin bed of pebbles at the bottom. 



Along the northern outcrop of the Lower London Tertiaries in 

 the London Basin there is little trace of anything that can be 

 referred with any certainty to the uppermost division, unless the 



