86 Reports and Proceedings — 



scopically and microscopically, and of eight chemical analyses are 

 given. It appears better to call one a porphyrite and two diorites 

 (micaceous varieties). The remainder are all characterized by 

 abundance of mica (biotite). Augite also appears to have been 

 generally a constituent ; but it has almost invariably been replaced 

 by secondary products, calcite, dolomite, viridite, etc. Three are 

 crystalline in structure ; one of these is named minette, the others 

 kersantite. The remaining eleven show a microcrystalline or crypto- 

 crystalline base. It is proposed to call eight of them minette- 

 felsite, the rest kersantite-porphyrite. These rocks commonly occur 

 in rather narrow dykes ; they are intrusive in Silurian strata, and, 

 in the authors' opinion, are undoubtedly true igneous rocks. 



2. " Pleistocene Notes on the Cornish Coast near Padstow." By 

 W. A. E. Ussher, Esq., F.G.S. 



In this paper the author described certain deposits seen in a small 

 bay near St. Enodock's chapel, and known as Daymer Bay, and in 

 section at Greenway cliffs. The former included a portion of raised 

 beach, and a reef of consolidated old beach and a peaty deposit below 

 high-water mark, the raised beach indicating a depression of from 

 5 to 10 feet and a subsequent elevation of more than that amount, 

 during a pause in which the lower beach was formed. The further 

 elevation of the coast was sufficient to favour the growth of forests 

 furnishing the peaty bed, which a subsequent subsidence has brought 

 down to its present level. Greenway cliffs consist of grey slates, 

 resting against which, in two places, are old consolidated blown 

 sands ; about 5 feet above high-water mark is a raised beach, near 

 which the face of the cliff consists of " head " capped by gravel. 

 The author discussed the relative ages of these deposits, and inclined 

 to regard the gravel as a fluviatile deposit, and the stony loam or 

 '" head " as an ancient talus or flood-gravel, both deposited before 

 the raised beach. 



3. " The Pleistocene History of Cornwall." By W. A. E. Ussher, 

 Esq., F.G.S. 



In the first part of this paper the author, from his own observa- 

 tions and the writings of other geologists, gave detailed descriptions 

 of the various superficial deposits of Cornwall as exposed in nume- 

 rous coast-sections. 



In the second part he discussed the relative ages of these deposits, 

 for which he proposed the following classification : — 



1. The oldest beds described are patches of quartzose gravel, 

 found up to 400 feet above the present sea-level ; these are regarded 

 by the author as of fluviatile origin, and as being possibly rede- 

 posited Tertiary beds. Their age may be any thing between Cre- 

 taceous and Glacial. 



2. Boulder-gravels, from 40 to 50 feet above sea-level. 



3. Baised beaches, up to 15 feet above sea-level. 



4. Old blown sand closely associated with the raised beaches. 



5. "Head" or talus of angular fragments lying upon the raised 

 beaches, and therefore of younger date than the latter. 



6. Stream tin-gravels, evidently older than the forest stratum. 



