South-western Coal District of England. 313 



The connexion of these calcareous bands with those of the Forest of Dean 

 and of the neighbourhood of Bristol is likewise suggested. A third line is 

 also traced to the north of the northern calcareous band in Pembrokeshire^ 

 along which Owen supposes another continuous band of limestone to extend. 

 Along this line^ however,, the calcareous masses which occur^ are discon- 

 tinuous^ and are in truth detached portions of transition limestone subordinate 

 to grey-wacke slate, which very generally along that line contains a mixture 

 of calcareous matter. 



At the same time that Owen lays down correctly the general fact of the 

 regular arrangement and continuity of mineral masses, he appears to have 

 had confused notions of their position below the surface of the earth. He 

 calls these masses indiscriminately veins; is ignorant of the distinction be- 

 tween veins and beds ; neglects entirely the dip of the beds, and seems not 

 to have entertained any suspicion that the two bands of limestone, the northern 

 and the southern, had a subterraneous communication, and thus formed a 

 great basin containing the superincumbent coal-measures ; — a doctrine after- 

 wards so ably developed in the paper of Mr. Martin. We do not find in 

 Owen's memoir any notice of the organic remains of the several strata. 



The Bristol coal-basin has been rendered remarkable by a memoir on its 

 structure by Mr. Strachey, published in the Philosophical Transactions for 

 1719, which, though later by a century than that of Owen, is yet entitled to 

 very particular mention. This essay was followed by another, containing 

 some supplemental diagrams and observations, published in the Phil. Trans, 

 for 1725. The author gives a clear description of the collieries in the neigh- 

 bourhood of Brislington and in other parts of the central coal-tract of the 

 Bristol basin ; enumerates the seams of coal there worked ; traces them to 

 some distance along their line of drift ; explains the nature of the faults by 

 which they are deranged ; particularly notices the inclined position of the coal- 

 measures, specifying the degree and direction of their dip ; and states the im- 

 portant fact, that these inclined strata are partially covered by other strata, 

 which differ from the former in being horizontal : — a distinction not suffi- 

 ciently kept in view by several distinguished geologists of a more recent date. 

 These horizontal strata are also described as consisting of lias with its accom- 

 panying marl, and of red and yellow earth ; in which we clearly recognise 

 the lias and newer red sandstone formations. These descriptions are illus- 

 trated by engraved sections, which convey an adequate, though somewhat 

 rude, representation of the coal strata, of their faults, and of the overlying 

 horizontal formations. Mr. Strachey has appended to his second paper, dia- 

 grams representing the manner in which he conceives the mineral masses to 



2s3 



