PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 1 25 



rocks and the overlying carbonaceous shales of Silurian age. On 

 the other hand, he finds similarities between the containing rocks 

 in Borrowdale and the diamond-bearing rocks of South Africa, and 

 considers that the conditions under which the graphite was formed 

 in the Lake District approached much more closely to those which 

 gave rise to the Kimberley diamonds than to those which originated 

 the graphitic deposits in North America, though there is great dis- 

 similarity in the chemical composition of the intrusive rocks in the 

 two cases, especially with regard to the quantity of magnesia pre- 

 sent. He suggests that the molten magma in its upward course 

 passed through a deep-seated stratum of highly carbonaceous mate- 

 rial, and tore off numerous fragments, the bituminous matter in 

 which became acted upon by heat, a further alteration being subse- 

 quently caused by the intrusion of the diorite. 



Discussion. 



Prof. Seelet was not aware of any satisfactory description of the 

 Kimberley diamond-mines, which contained rocks of an essentially 

 brecciated deposit, and therefore, as he considered, very different 

 from the rocks of which the Author had given a description. 



The President believed there were two possible sources of supply 

 for diamonds and graphite, viz. derivation direct or indirect from 

 organic matter, and (as, e. g., in the Archaean rocks and meteorites) 

 as an original mineral. 



2. "Notes on the Yalley-Gravels about Eeading, with especial 

 reference to the Palaeolithic Implements found therein." By 0. A. 

 Shrubsole, Esq., F.G.S. 



The following specimens were exhibited : — 



Specimens exhibited by J. Postlethwaite, Esq., E.G.S., in illustra- 

 tion of his paper. 



Palaeolithic Implements and Mammalian remains, exhibited by 

 0. A. Shrubsole, Esq., E.G.S., in illustration of his paper, 



