220 Geological Society: — 



there are indications of the close proximity of land and of the 

 access of fresh water. Two types of faunas are to be recognized, 

 namely those of the Calcaire Grossier and the London Clay, the 

 latter indicating more temperate climatal conditions. The former 

 is represented in England by the Bracklesham series. The areas of 

 these two faunas were separated by land forming an isthmus, as 

 each formation is bounded by a shore-line and separated from its 

 neighbours by freshwater formations ; but this isthmus probably 

 shifted its position to the north and south without ever being broken 

 through. A vast Eocene river existed, draining a great continent 

 stretching westward ; the indications of this river in Hampshire and 

 Dorsetshire would show it to have been there 17 or 18 miles wide. 



The Lower Tertiaries have been divided by Prof. Prestwich and 

 the Survey into the marine Thanet Beds, the fluviatile, estuarine, 

 and marine "Woolwich and Eeading Beds, and the marine Oldhaven 

 Beds. The mode of occurrence of these was described by the 

 author, with especial reference to the section between Heme Bay 

 and the Beculvers, from his investigation of which he was led to 

 the following conclusions : — The Thanet Sands were probably depo- 

 sited by a rough sea outside the estuary of the great Eocene river, 

 but within its influence. This area became silted up, rose above 

 the surface, and became covered with shingle and sand. The Thanet 

 Beds closed with a period of elevation, during which the Pveading 

 Beds were formed ; and this was followed by a subsidence during 

 the Woolwich period, which finally ushered in the Oldhaven and 

 London- Clay deposits. The formation of the Oldhaven Beds may 

 be compared with that of the modern beach at Shellness ; and during 

 the period of depression the beaches would advance steadily over 

 the flat area of Sheppey, and the earlier formed ones would sink 

 and become covered up by the silt of the great Eocene river. These 

 beaches, forming vast aggregations of sand and shingle between 

 the Thanet Beds and the London Clay, form integral portions of one 

 or other formation, and cannot be recognized as forming a separate 

 formation at all equivalent to the other divisions of the Eocene. 



2. " On Mr. Dunn's Notes on the Diamond-fields of South Africa, 

 1880/' By Francis Oats, Esq., E.G.S. 



The author referred to the hypothesis put forward in 1880 by 

 Mr. Dunn (Quart. Journ. Geol. Soc. vol. xxxvii. p. 609), that the carbon 

 for the production of the South-African diamonds was furnished by 

 the black carbonaceous shales found throughout the district, and the 

 conclusion drawn by him therefrom that therefore diamonds would 

 not be found below the level of these shales. The author stated 

 that the shales, so far as he knows, do not occur below 270 feet, 

 whilst the ground is successfully worked for diamonds at a depth of 

 350 feet. He maintained that the carbonaceous shales have nothing 

 to do with the origin of the diamonds, and stated that the " craters " 

 containing the diamantiferous rock, at an earlier date erupted quite 

 different material ; and he instanced the occurrence in the Kimberley 

 mine of a mass of " dolerite " between the diamantiferous ground 

 and the surrounding shales. 



