460 PEOCEEDINGS OF THE GEOLOGICAL SOCIEXr. [May 20, 



blowing, it took two and a half minutes to bring the ashes from the 

 crater as far as our ship, a distance of 1400 yards. 



It is impossible to predicate anything at present with regard to 

 the cessation of the eruption, although if its present state is com- 

 pared with that of 1866 it will be found to have changed several 

 times, and to have diminished in intensity. The apparent slowness 

 of the advance towards the south is due to the depth of water, which 

 is more than 30 fathoms. Por some years the Santorin eruption will 

 reward observers. I must postpone to a future day my numerous 

 notes, observations, and measurements, and at present only offer this 

 general notice of the present state of the volcano. 



Discussion. 



Capt. Spratt pointed out that this was only one of the many peaks 

 in the centre of the large crater of Santorin, which have risen up 

 since the historical period. In the position in which he had anchored 

 but six or seven years ago there is now a hiU upwards of 300 feet in 

 height, according to the latest Admiralty survey of the new land at 

 Nea Kaimeni, dated October 1867. 



Sir Roderick: Murchison referred to the communications to the 

 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 (respectively 

 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 men- 

 tioned 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, and of which only three copies 

 were taken on a larger scale than the published maps. 



2. On the Structure of the Crag-beds of N'orfolk and Suefolk, 

 with some Observations on their Organic Remains. — Part II. 

 The Red Crag of Suffolk. By Joseph Prestwtch, Esq., F.R.S., 

 F.G.S. 



[The pubHcation of this paper is unavoidably deferred.] 

 (Abstract.) 



The superposition of the Red Crag to the Coralline having been 

 clearly shown by previous writers, the author confines 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 is described as occupying an excavated area in the 

 CoraUine, wrapping round the isolated reefs of the latter, filling up 



