476 Reports and Proceedings — 



Kent, and is altogether an unique geological memento in the county. 

 On leaving Well Hill, the excursionists felt they had seen the great 

 sight of the day. At Shoreham the conductor pointed out some 

 notable sand-pipes in the chalk by the side of the high road to 

 Sevenoaks, between the eighteenth and nineteenth milestones ; a very 

 fossiliferous bed of chalk with Inoceramus near the first shaft at the 

 north entrance to Halstead tunnel, and a dry upper valley of the 

 chalk (south branch of the Timberden Valley) with six feet thick- 

 ness or more of flints, the water standing at a level below the valley 

 fully 100 feet deeper than it once stood ; and, lastly, the trumpet- 

 mouthed valley of the Darent, opening out into the Weald, but 

 draining in the opposite direction into the Thames. The party, 

 numbering between 40 and 60, were subsequently entertained by 

 Mr. and Mrs. Prestwich at their mansion, Darent Hulme, where a 

 cordial vote of thanks was presented to the conductor through Mr. 

 Henry Walker and Professor Hughes. 



IV. — July 3rd. — Henry Woodward, P.E.S., President, in the Chair. 



1. " On the Deposits now- Forming in British Seas." By G. A. 

 Lebour, F.G.S., etc. 



The author limited his present task to a brief description of the 

 principal constituents of British Sea Bottoms, with particular re- 

 ference to their distribution and its causes. The materials are of 

 meclianical, chemical, or organic origin. The agencies by which 

 these three kinds of sediment are distributed include rain, rivers, 

 winds, tides, currents, and the composition of sea water, but all are 

 subordinate to the configuration of the sea floor. The area under 

 consideration is situated on the westernmost margin of the Old 

 World plateau. 



Boclc Bottoms. — In some places no deposit occurs, the bare rock 

 being left. The largest of these bare spots, in British seas, occurs 

 in the western half of the Channel A^alley. Tlieir distribution is 

 directly connected with that af currents, and this is strikingly proved 

 by their being limited to no relative depth ; for, in the Channel, 

 their range extends entirely across the valley, and reaches in one 

 place, north-west of Alderney, a depth of more than 86 fathoms at the 

 deeper end of a curious longitudinal oblique depression, called by M. 

 Delesse the fosse centrale of the Channel. Another bare area exists 

 at the point where the Atlantic cable enters the yet deeper region 

 of the Atlantic ooze, in 500 fathoms water. The specimens brought 

 up by the sounding instruments from such places consist of weathered 

 and rotten stone, pointing to chemical rather than mechanical dis- 

 integration, even where powerful currents are present. 



Marine Deposits. — These consist chiefly of sand, with occasional 

 islands of clay, mud, gravel, and shell detritus. The broader the 

 sea, the greater the pi'oportion of sand : thus the North Sea bottom 

 is especially a sandy one, though towards the centre the sand becomes 

 muddy over a co-nsiderable region. Sandy bottoms also largely pre- 

 vail in the north-western seas, and on the west coast of Ireland ; but 

 south of Ireland a large expanse of fine mud and muddy sand 

 extends in a south-easterly direction. As submarine deposits, gravels 



