xiv Journal of Proceedinys. 



where the Thanet sand had been breached, and was the subject of an 

 exposition from Professor Morris. Its surface showed the mammillated 

 appearance so frequently found in these concretions. (Some very large 

 and characteristic examples are to be seen in the adjacent village, near the 

 wharf of the Grays Chalk Quarries Comj)any.) The Professor pointed 

 out that these rounded appearances were not due to the wear and tear of 

 transport. A thin flake examined by the microscope would show the 

 sandstone to be composed of subangular quartz grains, and not of these 

 grains rounded. Looking at the range of the Bagshot and Thanet sands, 

 which at one time extended all over the valley of the Thames, he was 

 incHned to consider these Greywethers as derived from the indurated base 

 of the latter ; the softer sand had been carried away by denudation. 



On reaching the floor of the pit, wliich is excavated one hundied feet 

 into the chalk, the party examined the fine vertical sections which are 

 there exposed, consisting of upper chalk, with green-flint bed, Thanet 

 sand (in some places twenty-five feet in thickness), and High Terrace 

 Thames Valley drift. Some of the "sand-pipes" here are sixty and 

 seventy feet in depth, partially filled, in some instances, with gravel, and 

 in others with Thanet sand. Sir Antonio Brady, who was present, called 

 attention to one of the more remarkable, which had penetrated below a 

 horizontal band of flint without disturbing it. Mr. Walker gave a 

 general account of the structure and composition of the rocks here 

 exposed ; the chalk, with its marine organic remains, more especially its 

 sponges, corals, " sea-urchins," moUusca and fishes (a large number of the 

 curious palatal teeth of Ptyclwdus and other sharks were shown sub- 

 sequently) ; the Thanet sand, marine but unfossiliferous, near London ; 

 and the "High Terrace Thames Drift" of Professor Prestwich and Mr. 

 Wliitaker (the "Marine Gravel" of Mr. Searles Wood). Prof. Morris 

 followed with a comprehensive re^dew of the history and former range of 

 the chalk, Thanet sand, and other Eocene beds now missing below the 

 gravel, especially descanting upon the great physical changes which had 

 taken place in the face of Euroj^e (such as the elevation of the Alps), in 

 the interval denoted by the absence of the Woolwich beds, Oldliaven 

 pebbles, London clay, and Bagshot sand. Keferring to the Green-flint 

 bed (the "Bull-head bed " of the workmen), Professor Morris called atten- 

 tion to the well-marked concentric structure of many of the flints, 

 probably owing to the presence of iron, which tends to this arrangement. 

 The solvent action of carbonated waters, which formed the "i^ipes," was 

 also seen, the Professor said, in the undulating surface of the chalk, as 

 traced by the course of the green-flints. The depressions in this line 

 were therefore posterior to the elevation and desiccation of the sea-bed. 

 With regard to the absence of Woolwich beds and London tertiaries which 

 once overlay the Thanet sands, he pointed out that the Woolwich beds 

 were found about a mile further inland, at the village of Stifford, and he 

 would suggest to the Essex Field Club an examination of them at that 

 spot, inasmuch as the only instance of a certain shell of the Woolwich 



