Mr. J. Prestwich on the Phenomena of the Quaternary Period. 409 



The author next proceeded to notice the raised beach at the Bill 

 of Portland, in which he had, with the assistance of Mr. Jeffreys, 

 determined 26 species of shells, two of them not now living in the 

 British Channel, and one new. This beach contains pebbles of the 

 Devonshire and Cornwall rocks. 



The raised beach Mr. Prestwich found to abut against an old cliff 

 that had been swamped at a later geological period by a land-wash, 

 which had levelled it and the old sea-land with the adjacent land- 

 surface. The mass which had thus swamped the cliff and buried 

 the beach consisted of loam and angular debris, the latter being in 

 larger proportion at top. In the loam he found several species of 

 land and freshwater shells and fragments of bones. The angular 

 debris consisted of pieces of the local rocks, together with a number 

 of specimens which by their organic remains were shown to belong 

 to the Middle Purbecks, a part of the series not now existing in 

 Portland. A similar bed, but much thicker, was then described at 

 Chesilton, in the north of the island. It is there 60 feet thick, and 

 contains large blocks of Portland stone and Portland chert, the 

 greater number of which are in the upper part of the deposit, which 

 is here on the sea-level, and 400 feet lower than the Portland 

 escarpment which rises above it. This loam and angular debris the 

 author was disposed to attribute to a temporary submergence of the 

 land to a depth exceeding the height of Portland, by which the 

 land as it emerged was swept and its debris carried down to the 

 lowest levels, with the remains of its land-animals and land and 

 freshwater shells, which latter, where protected by large masses of 

 loam and suddenly entombed, have been preserved uninjured. To 

 this deposit, which is common over the raised beaches on the south 

 coast, the author proposed to apply the term " Land-wash." 



The paper concluded with a short notice of the drift-beds formed 

 subsequently to the denudation of the Weymouth district, and there- 

 fore never on the high-level Portland drift. Among these was one 

 near Weymouth of singular character, consisting almost entirely of 

 subangular fragments of Greensand chert, which could not have 

 been derived from beds nearer than Abbotsbury. The lower drift of 

 the district is the valley-gravel of Upway and Radipole, in which 

 the remains of Elephas primigenius have been found. 



2. " On the Character of the Diamantiferous Pock of South 

 Africa." By Prof. N. Story Maskelyne, F.P.S., P.G.S., Keeper, 

 and Dr. Plight, Assistant, of the Mineralogical Department, British 

 Museum. 



In this paper the authors confirmed certain statements made by 

 one of them from a superficial examination of specimens brought to 

 this country by Mr. Dunn. The specimens examined and analyzed 

 *y Dr. Flight were obtained from various diggings and from different 

 depths, down to 180 feet in the case of one mass from Colesberg Kopje. 

 Their characters throughout are essentially the same. 



The rock consists of a soft and somewhat pulverulent ground- 

 mass, composed of a mineral (soapy to the touch) of a light yellowish 



