Siratificalion of Glamor gansli'ire. 427 



tected either m the air or limestone, tlie potassium must either 

 be contained in a free state in the atmosphere or in the lime- 

 stone, which from its remarkahle attraction for oxygen is inad- 

 missible : or it must be a component principle of some one of 

 the elements present ; or Lastly, it must be itself a compound of 

 two or more of the princi])les of those elements, or of two or 

 more of the elements themselves. 



But I am aware that the saltpetre may be considered as an 

 educt of the process, and that it may possibly exist already 

 formed in the atmosphere in a state of minute division : yet, 

 when we consider the comparatively fixed nature of that salt, 

 and that no experiments have yet detected its presence in at- 

 mospherical air, or in the moisture precipitated from atmosphe- 

 rical air ; and lastly, when we reflect on the probability that 

 the metals, of which potassimn is one, are compound bodies, 

 the former supposition seems upon the whole preferable to the 

 latter. 



Fcbrimry, 1811. 



LXVI. Stratlfical'wn of Glamorganshire*. 

 ]\lomHa'm Lime. 



J. Hrs rock forms the whole of the peninsula of Gower, westward 

 of a line drawn S.S.E. through Penclawold, Gellyhir, Littlehills, 

 west side of Clgne Moor to Blackpill ; appears again near Pgle 

 Inn, Cenfig, Skerr, Cornely, Nottage, Newton Down, Cevn 

 Cribbor, r^ses through tlie 'lias at Ewenny, forms Ewenny and 

 Ogmore Downs, (ioldcn Mile, Saint Mary Hill, Coed y Mwstor 

 near Covcburch, Newforest, Llan!)lethian, Pealline, Trecastle, 

 Lanchaciir, Stalling Down near Cowbridge, Saint Lythians 

 Down, Courtgrala, Bolston, covered by aUuvia at St. George's 

 and elsewhere in that valley. . Very hard variety at Saint Fagaas. 

 Hills near Lantrissant E. and W. Lower Garth, Castell Coch, 

 Lisvane towards Caerphilly, Ruddrey, v/hence at Machen it 

 runs into Monmouthshire. ' This last named range bounds the 

 great coal basin which will he presently described. I have 

 observed no fossil madrepores, but abundance of entrochi ; ga- 

 lena is found in various places. A shallow bed of coarse sand- 

 stone rests on the mountain lime at St. Hilary and Lantrytbid ; 

 beds of white calcareous slate have been cut through in the lead 

 mines tlsre. Manganese has been worked on Newton Down. 

 Cherty blocks may be observed there and on St. Mary Hill. — 



* For the localities mentioned in tliis sketch, see tlie excellent Map of 

 GhunoPL-Hiisliirc, published froai liic Survey of G. Yates, by Gary, 181, 

 Jjlrand, London. 



A grey 



