72 Proeeedings. 



and wearing by the waves upon a sea-beach until their 

 present rounded form was attained. Descending Croham- 

 hurst on the other side, the party proceeded to the conspicuous 

 water-towers, where other members of the Club as well as a 

 good many members of the Croydon Microscopic and Natural 

 History Society and their friends had assembled. Under the 

 guidance of their former President, Mr. John Flower (who, 

 as probably most present are aware, has since been removed 

 by death, greatly to the loss of the Croydon Club and of 

 Science generally), the party then walked along the Combe 

 Lane as far as the point where it is crossed by a bridge of 

 the new line of railway now being made to connect Woodside 

 with the main line of the South Eastern Eailway not far from 

 South Croydon Station. Proceeding along the line in a 

 southerly direction, in order to inspect first the challicutting 

 through which the line runs, Mr. Flower pointed out several 

 good examples of what are known as " pockets" in the chalk, 

 /. e., holes of various sizes and shaj)es filled with surface-clay 

 or gravel, usually having a thin baud or layer of similar clay 

 communicating with the surface. He explained that these 

 pockets were probably formed by the action of water which 

 had become charged with carbonic acid, and thus converted 

 the chalk in some places into a bicarbonate of lime. This is 

 readily soluble in water ; and had doubtless become dissolved, 

 and the surface-soil had gradually washed down and filled up 

 the space so left. In some of these pockets rounded flints, 

 evidently from the Oldhaven Pebbles, were observed, some of 

 them of considerable size. Walking from the chalk-cutting 

 northward, soon after recrossing Combe Lane we again came 

 into a cutting where a remarkable variety of strata was dis- 

 played. The lowest in the series was the Thanet Sand, a 

 bed of a pale yellowish colour ; next above this came the 

 Greensand of the Woolwich and Eeading Beds, a marine 

 deposit by no means to be confounded with the Upper Green- 

 sand or Lower Greensand with which we are so familiar in 

 the neighbourhood of Eeigate, from which it is separated by 

 a vast interval of geologic time. In the lowest two or three 

 feet of this Greensand large quantities of Sharks' teeth have 



