181,';.] Geological Society. 391 



Swaffham, on the edge of the fen. This place has for ages sup- 

 plied the surrounding country with the chalky lime-stone called 

 clunch, in con-^cquence of which extensive excavations have heen 

 formed', which h^e laid bare a large mass of a lenticular shape 

 imbedded in the clunch. The greatest thickness of this mass is" 

 ahoiit ei'xlit feet, and its length and breadth from '60 to '10 yards. It 

 is comnnsed of kidney-shaped masses, about tiie size ot a walnut, 

 of ochre-yellow lime-stone, covered superficially with a thin coat of 

 green oxide of iron. It contains a few spifies of an echinus com- 

 pletely converted into spar, and also vegetable impressions seemmgly 

 belonging to plants of the tribe of gramina. 



At tliiii meeting the reading of Mr. Horner's paper on the south- 

 western part of Somersetshire was concluded. 



Hie most elevated ground in the district here described is Exmoor 

 Forest and the Quantock Hills. This tract is composed for the 

 most part of a grey-wacke formation ; the strata ot which present 

 more or less coarsely-tjranular mixtures of quartz and clay, some- 

 times consideraoly calcareous, alternating with slaty beds, which 

 often are not to be distincuiihcd by external characters from primary 

 clav-slate. Within thest^ latter beds are included thick short beds 

 of 'lime-stone full of madrepores, and containing veins and nests of 

 erev copper malachite and haematite. In the ground of Hester- 

 combe occurs a wall (probably a vein) of fine grained grey granite; 

 the slate rises up towards it at a very high angle, is conside.ably 

 indurated, and at the plane of junction appears to be more or less 

 penetrated by the granite. 



Wliere the hills of grey-wacke sink down into the lower country 

 their sides are covered with beds of conglomerate passing into red 

 sand-^tone, which extend to a considerable distance. These beds 

 appear to consist of the same materials as the grey-wacke formation, 

 but decomposed to a considerable degree. They are traversed by 

 veins of calcareous spar, sometimes of so great a thickness as to be 

 quarried for lime-stone. . 



The conglomerate, with its accompanying sand-stones, is covered 

 in many places by a red aigillnccous sand-stone, containing a 

 variable proportion of calcareous matter, but bemg principally 

 characterized by spots and stripes of a gretnish-grey colour. It is- 

 of an uniformly fine texture, never contains any tragmcnts either 

 angular or rounded, is in places traversed by veins ot gypsum, and 

 appears to be the same rock as that in which the salt-kf/i oi 

 ^Chfsbire and Droitwich are situated. 



To this rock succeeds the strata of Lyas lime-stone, which with 

 their accompanying beds of slate-clay are sometimes seen distinctly 

 resting on the red gypseous rock, and sonuthues m very broken and 

 disturbed stratification appear to alternate with it. 



On the sea coast about three miles westward of the river Farrett, 

 in the cavities formed by the curvature of the l.yas strata, is a stjft 

 blue clay, covered with peai, iu which me imbedded trunks of 



