Geological Society of London. 135 
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 
Caleaire 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 forma- 
tions; 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 indica- 
tions of this river in Hampshire and Dorsetshire would show it to have 
been 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 Reading Beds, and the Marine Oldhaven Beds. 
The mode of occurrence of these was described by the author, with 
especial reference to the section between Herne Bay and the Reculvers, 
from his investigation of which he was led to the following conclu- 
sions:—The Thanet Sands were probably deposited by a rough sea 
outside the estuary of the great Eocene river, but within its influence. 
The 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 Reading Beds were formed, and this was 
followed by a subsidence during the Woolwich period, which finally 
ushered in the Uldhaven 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 Hocene 
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., F.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 ‘‘do- 
lerite’’ between the diamantiferous ground and the surrounding shales. 
Il.—January 24, 1883.—J. Gwyn Jeffreys, LL.D., F.R.S., Vice- 
President, in the Chair.—The following communications were read :— 
