138 Reports & Proceedings — Geological Society of London. 



The character of the flints in the gravels indicates that they have 

 heen derived from surface-soils which have been winnowed and shifted 

 by soil- creep, rain, and streams, until arrested on the terraces and 

 flats of the valleys. 



The dry land of Miocene age was the first over which the flints 

 of our gravel beds could have received that subaerial treatment which 

 they all seem to have undergone. There was then no Boulder-clay 

 to protect and obscure the Chalk -with-Flints. 



Then came the submergence which let in the Crag sea. This 

 rapidly invaded the land, not giving time to reduce the flints to 

 pebbles, but burying remains of animals and plants in coarse subangular 

 gravel. In time the subsidence affected more distant shores, and 

 compensating rises of mountain regions far away began to modify 

 climatal conditions ; ice floated southwards, stranding at various 

 depths according to size, ploughed up and crumpled the shore-deposits, 

 and dropped masses of far-transported material. It is not difficult to 

 distinguish the old shore-deposits, even when they have been crumpled 

 up, from the foreign material introduced by the floating ice. 



When the land had sunk so low that the wind- and tide- waves 

 could not sort the material, it remained, as brought, a boulder-clay, 

 which is therefore widely spread over the peneplain of the East 

 Anglian heights, and is generally above the gravel and sand of the 

 advancing sea. 



Where the sea was able to work longer at pounding and rolling the 

 flints, immense beds of pebbly shingle or of sand are the result. 



The Plateau Gravel is traced from section to section across the 

 country, and the characteristics by which it can be recognized are 

 pointed out. 



Since an irregular land-surface was thus depressed beneath the 

 sea, one might expect that in some of the deeper valleys deposits 

 older than the submergence might be detected. Also, seeing that the 

 land has slowly risen again many hundred feet, we ought to have 

 evidence of the subaerial denudation which has been going on since 

 the land began to rise. 



Thus the author starts with the definition of three important ages 

 of long duration, and proceeds to refer some of the best exposed 

 gravel deposits of East Anglia to one or other of them. 



They are, in descending order — 



(1) The stage of which the Barnwell Gravel is taken as a type. 



(2) The stage of which the Plateau Gravel is the most important 



representative. 



(3) The stage to which he suggests that the Barrington Beds may 



belong. 



The rest of the paper consists of descriptions of sections and 

 discussion of evidence derived from fossil remains. 



2. "The Pitchstones of Mull and their Genesis." By Ernest 

 Masson Anderson, B.Sc, M.A., F.G.S., and E. G. Radley. 



The pitchstones here discussed occur with extraordinary frequency, 

 intruded into the Tertiary plateau-lavas of the eastern portion of 

 the Ross of Mull, as well as in less number in other parts of the 

 island. 



