Mr Grieve on the Somersetshire Coal Formatioii. 93 



In No. 2 Process, aluminium sulphate is used instead of 

 iron chloride, but otherwise the processes are similar. 



In ]N"o. 3 Process, the effluent water is first treated with acid 

 aluminium sulphate, and then excess of finely-ground barium 

 carbonate. The great beauty of this process, which I should 

 say was first proposed by my friend Mr William Durham, is 

 that in consequence of the barium carbonate being insoluble 

 in water, any excess of it which may be used separates along 

 with the other insoluble matter, and does not find its way to the 

 river, as much of the lime used in the iron process must 

 necessarily do. As aluminium salts do not appear to form a 

 precipitate quite so fast as iron salts seem to do, I have pro- 

 posed a modification of this process, in which I use iron sul- 

 phate and barium carbonate. In this combination very little 

 matter indeed is left in the water. 



[These processes were all carried out at the meeting, and 

 were very successful — the dirty water becoming in a 

 very few minutes almost as clear as spring water.] 



11. — Notes on the Coal Formatio7i of Somersetshire. 

 By David Grieve, Esq., F.K.S.E. 



Having last autumn spent a month at Clifton, near Bristol, 

 the author was much interested in the geology of its neigh- 

 bourhood. There is probably no place in England where, 

 within a very limited area, typical examples of so many 

 different formations occur as round this city. Bristol being 

 the centre of an extensive coalfield, the author considered it 

 necessary, as preliminary to his subsequent remarks, to give 

 some account of the subjacent and superjacent strata. 



Twelve distinct formations may be counted within a radius 

 of ten miles from the centre of the city of Bristol ; in short, 

 there may be readily and easily investigated the Silurian, 

 Devonian, Carboniferous, Triassic, Liassic, Oolitic, and Cre- 

 taceous formations, with igneous rocks of the paleozoic age. 

 The juxtaposition of the rocks is curiously and often very 

 eccentrically arranged, evincing the result of great disturb- 

 ance. In many of the strata fossils abound. The coal 

 measures are interlaced and modified in various ways by the 



