XXXIV PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



In this paper the rocks described are classified in the Wernerian 

 order in two grand series : the first beginning with the transition 

 rocks of old times, and ending with the coal formation ; the second 

 beginning with the newer red sandstone, and ending with the oolite, 

 thus — 



No. I. No. 2. 



1. Greywacke. 1. Newer red sandstone, compri- 



2. Transition limestone. sing — 



3. Old red sandstone. a. Dolomitic conglomerate. 



4. Carboniferous or mountain h. Red sandstone. 



limestone. c. Red marl. 



5. Coal measures. 2. Lias. 



3. Oolite. 



The leading physical difference, namely want of conformability, 

 between these two sections of rocks is pointed out by the authors ; 

 the first or lowest section being usually highly inclined, and the 

 second or newer approaching more to horizontality ; the authors 

 deducing from this circumstance a caution for those who expect to 

 find a coal deposit under every patch of new red sandstone, by point- 

 ing out that an envelope of this kind may spread over every or any 

 member of the underlying inclined strata. The authors also ex- 

 plain that, though these two great series of deposits usually include, 

 when complete, the members enumerated, it must not be expected 

 that all should be found in every natural section, as one or other may 

 be wanting, and thus a particular deposit may be brought into im- 

 mediate connexion with another, from which, in a normal section, it 

 would be separated by many others. In fact, the teaching of geology 

 is, that when a mineral deposit has been linked to some definite epoch 

 of the earth's history by the organic relics it contains, it ceases to be 

 a mere crude mass of matter, and becomes a speaking page of that 

 history. Other pages may be torn out or obliterated in the various 

 copies of this history, but yet the still remaining pages will occupy 

 their original and true position. 



The principal basins of the district, which include as many import- 

 ant coal-fields, are thus classed : — 



1 . That of Somersetshire and South Gloucestershire as the basin 

 of Bristol. 



2. That of the Forest of Dean. 



3. The great coal-basin of South Wales. 



The boundaries of each of these coal-fields are traced, the distri- 

 bution of the rocks described in the fullest detail, the phsenomena of 

 the faults investigated, and most remarkable they are, as, in the Bristol 

 basin the limestone has been at one place thrown up to such an ex- 

 tent as to appear to re-emerge in the midst of the coal measures ; 

 whilst at another, the coal measures have subsided to such an extent 

 as to appear to dip beneath the mountain limestone " on which they 

 in fact repose." The paper is illustrated by numerous detailed 

 tabular sections of the strata, in which the positions of the several 

 seams of coal are exhibited, &c. so that the paper will always continue 



