(j60 REPORT— 1903. 



7. BepOft of the Committee on Underground Waters oj North-uiest Yorkshire. 



See Reports, p. 192. 



8. Report of the Committee on Geological Photographs, 

 See Reports, p. 197. 



9. On the Practical ValuC. of certain Species of Molluscs in the Coal 

 [Measures. By Wheelton Hind, M.D., F.R.C.S., F.G.S. 



1 0. Report of the Committee on Life Zones in the British Carhoniferoiis 

 Rocks, — See Reports, p. 185. 



11. On some Igneous Rocks near Weston-super-Mare, Somersetshh'e. 

 By W. S. BouLTON, B.Sc, A.R.C.S., F.G.S. 



The Paper dealt with a summary of the results obtained by the author after a 

 study of the basaltic lava flow in the carboniferous limestone at Spring Gove, 

 Weston-super-Mare, the evidence for the contemporaneity of which was first pub- 

 lished in the Summary of Progress of the Geological Survey for 1898. 



After referring to the complex character of the flow, and its relation to the 

 carboniferous limestone beds above and below, with the contact phenomena and 

 the metasomatic changes in the limestone subsequent to the consolidation of the 

 basalt, three characters were emphasised and described : (1) the ' pillow ' struc- 

 ture ; (2) the tuffy or agglomeratic structure within the flow ; (3) the included 

 lumps and masses of limestone. 



In general, the pillowy masses, themselves often compound, are embedded in 

 a tufiy material of the nature of volcanic sand, while in some parts great lenticular 

 bands occur, made up of coarse agglomerate, containing lumps of slaggy basalt and 

 limestone, and with a pronounced fluxional structure. In all cases the tuff, within 

 the limits of the sheet, behaves as a lava and has flowed, and was not the result 

 of sedimentation. 



Illustrations were shown of irregular masses of oolitic and fossiliferous lime- 

 stone up to 12 feet across in between the spheroidal masses of basalt, and evidence 

 was adduced to show that this included limestone was derived from the underlying 

 calcareous floor, when a sea-bottom, probably in a powdery or plastic condition, 

 and was rolled in or picked up by the lava, and was able to accommodate itself in 

 between the moving and distending spheroidal masses. 



In conclusion, reference was made to other pillowy lavas containing sedi- 

 mentary material, and the author emphasised the difficulty of distinguishing such 

 submarine flows from sills or intrusive sheets, where, as Professor Lapworth has 

 suggested, we may get tuffs, lava, and included masses of sedimentary material 

 confusedly mixed and drawn out into lenticles as here described. 



MONDAY, SEPTEMBER 14, 



The following Papers and Keport were read : — 



1. On Dedolomitisation. By J. J. H. Teall, M.A., F.R.S., 

 Director of the Geological Survey. 



The Durness dolomites as they approach the plutonic complex of Cnoc-na-Sroin0 

 become transformed into a white marble -w'hich generally contains one or more of 



