Geological Society, 303 



negroes; conceived that the want of civilization contributes 

 to make the people black ; and referred to various South-sea 

 islanders and others, to sanction this singular fancy. The 

 length of these conjectures prevented the'reading ot a vaki- 

 able paper by Professor Berzehus and Dr. Marcet, which 

 was in consetpience postponed till the next meeting of the 

 Society after the holidays, on the SQth of April. 



GEOLOGICAL SOCIETY. 



^pril Qd, 1813. W. H. Pepys, Esq. Treasurer, in the 

 chair. 



The reading of a memoir by Mr. John Farey, Sen. on 

 the Ashover denudation in the county of Derby, was be- 

 gun. The first part of this paper consists of minute local 

 observations, incapable of abridgement, relative to the in- 

 osculation ridges, the basset ridges, the partial incurvation 

 ot the beds, and the ascertained'or supposed faults. 



-y^pril 23d. The President in the chair. 



Thomas Gregory, Esq. of Bays water— Thotnas Botfield, 

 E>q. of Hopton Court nearBewdJey — were severally elected 

 members of the Society. 



A notice by the Rev. J. J. Conybeare, M. G. S. relative 

 to the slate ofTlntagel in Cornwall, was read, and thanks 

 were voted for the same. 



The slate quarries of Tintagel are situated close (o the 

 sea, about six iiules N. VV. of Camelford : they are worked 

 on a large scale, and are celebrated for the excellent quality 

 of the roofing slate which they afford. No dykes of irranite 

 or of porphv ry have been observed in this rock ; but there 

 are veins which afford quartz, rock-crystal of great trans- 

 parency and beauty, calcareous spar, chlorite, and in some 

 instances adularia. The slate of Tnitagel appears to bear 

 a near resemblance to that of Sno-vdon, and like it 

 occasionally presents the impressions of bivalve shells. 



The reading of Mr. Farcy's paper on the Ashover denu- 

 dation was concluded, and thanks were voted for the same. 



This portion of Mr. Farcy's paper contains a detailed ac- 

 count of the several strata represented in the maps and sec- 

 lions, beginning from the lowest of those that are known. 



The tuiidamemal rock of Derbyshire is the fourth lime- 

 stone. It is supposed to lie at the depth of about 350 yards 

 below the level of the river Amber in Ashover valley. It 

 rises towards the surface under Matlock vallty, and actually 

 bassets in Griff-dale. 'I'he thickness of this bed is un- 

 known ; but as the deep vale of the Dove is entirely exca- 

 vated in it, without discovering the bottom of the bed, its 



thickness 



