35 



November \th, 1878. 



Captain McDakin, iu addressing the Society on the subject of 

 the gravel beds of the neighbourhood — after briefly explaining 

 the supposed origin and analysis of flint — referred to Mr. G. 

 Dowker's paper on flints (published with the proceedings of the 

 Society) and stated that it would be going over ground already 

 beaten to occupy their attention longer on this portion of the 

 subject. But he proposed directing it to those accumulations of 

 flints originally derived from the chalk, and now constituting 

 the tertiary pebbles and subaugular gravels, the pebbles being 

 the effect of the marine denudation that removed the greater 

 portion of the cretaceous rocks from the Weald, leaving but 

 rolled fragments of the hardest portion of tlie chalk flints and 

 greensand cherts, a slowly advancing sea leaving those rounded 

 jjebbles so remarkably of the same size, form, and colour, now 

 forming the most conspicuous feature of Shottenden Hill, and 

 constituting what are known as the Old Haven pebble beds. 

 The land then sinking into the quieter depths of a deeper sea, 

 the London clay and Bagshot sand were deposited, when 

 ra-elevatiou taking place, the land was covered with the vegeta- 

 tion and animal life of a warm climate, as evidenced by the 

 organic remains of the preglacial period which died out or 

 gradually changed to species adapted to a colder climate, and 

 iinally ceased to exist, being driven southward by the advancing 

 cold, until the mountains of Great Britain sujiported glaciers, 

 and the lower lands were submerged under a sea covered with 

 floating ice. The whole northern portion of the island was 

 in this manner spread over with fragments of rocks and 

 clays, transported by the ice in many instances from long 

 distancus. But south of a line passing westward through the 

 valley of the Thames, all this evidence of glacial action ceases 

 until we reach the south coast, when we find imbedded in the 

 sands and shingle large blocks of granite from a few pounds to 

 three tons in weight, as at Bognor, and Hayliug island, 

 evidently carried by floating ice from perhaps the Channel 

 Islands or far to the west from Devon or Cornwall. This part 

 of the country must then have been elevated above the glacial 

 sea, and have been covered with an ice cap, the result of the ac- 

 cumulated snows of centuries, which, flowing downwards a few 

 feet or inches in a day, pushed before it the loose pebbles left by 

 the former marine denudation and the angular flints arising 

 from the erosion of the chalk, so sweeping bare of gravels the 

 wealden district of Sussex and Kent, leaving in the bottom of 

 old valleys and on the land-locked shore of inlets, confused 

 masses of sand, gravel, and jiebbles. A warmer climate again 

 succeeding (or as Mr. Dawson has put it, the spring time of the 

 Tertiary period) the glaciers melted away, retreating year after 



