﻿146 Geological Society : — 



French Academy relative to the chemical products of the eruption, 

 and their relation to those of Vesuvius and other volcanoes. 



Mr. Forbes directed attention to the fact alluded to in the late 

 President's anniversary address, that the lavas of this volcanic out- 

 burst were, at its commencement, trachytes, or of highly silicated 

 character, but afterwards were basic lavas — thus proving that rocks 

 of totally different characters and chemical composition (respec- 

 tively analogous to the granitic and trappean rocks of former 

 periods) might proceed from a volcanic focus during an eruption. 



Prof. Ansted called attention to the probable connexion of the 

 eruptions in these islands with those of Vesuvius and Etna, and 

 mentioned that Baron von Waltershausen had presented to the 

 Society photographs of his magnificent original drawings of the 

 whole region of Etna, which were upon the table, of which only 

 three copies were taken on a larger scale than the published maps. 



2. " On the Structure of the Crag-beds of Norfolk and Suffolk, 

 with some observations on their Organic remains. — Part II. The 

 Red Crag of Suffolk." By Joseph Prestwich, Esq., F.R.S., F.G.S. 



The superposition of the Ked Crag to the Coralline having been 

 clearly shown by previous writers, the author confined his paper to 

 those questions on which differences of opinion still exist, namely, 

 the structure of the Red Crag, its affinities with the Coralline, and 

 its exact relation to the Mammaliferous Crag of Norfolk. The 

 Red Crag of Suffolk was described as occupying an excavated area 

 in the Coralline, wrapping round the isolated reefs of the latter, 

 filling up the hollows between them, and occupying a similar, and 

 sometimes a rather lower level than the summits of these older reefs. 

 It forms such an extremely variable series of beds, that the author 

 had been unable to observe any definite order of succession in the 

 greater part of it ; but he remarked that oblique lamination is most 

 strongly developed in the lower and central portions, and that 

 almost everywhere there occurs at the base a bed of phosphatic 

 nodules, although deposits of that nature are by no means confined 

 to one level. Old sea-cliffs of Coralline Crag, and remains of old 

 sea-beaches at their base, were described by Mr. Prestwich as oc- 

 curring at Sutton ; and he also gave detailed descriptions of nume- 

 rous pits in the Red Crag of Suffolk, where the phenomena which 

 he described may be observed. Dividing the Red Crag into an 

 upper, frequently unfossiliferous, member (the fossils of which, being 

 most frequently in the position in which they lived, may be re- 

 garded as truly representing the fauna of the period), and a lower 

 fossiliferous portion (in which the shells are found mostly in a broken 

 and comminuted state and mixed largely with fossils derived from 

 the older Coralline Crag), the author described their distribution in 

 Suffolk, and their mode of occurrence on the eroded Coralline Crag, 

 referring more especially to the difficulty in drawing the line be- 

 tween them in many cases. 



In treating of the Organic Remains of the Red Crag, Mr. Prest- 

 wich gave lists of the shells found at the different localities, which 

 had been prepared with the aid of Mr. Gwyn Jeffreys. Taking 



