i! 

 Geological Society. 30$ 



— (7) Brecciated structure. This modification abounds on the coast 

 of Durham. — (8) Small concretionary structure. — (a) Irregular. — 

 (b) Regular or oolitic. — (9) Large globular concretionary structure. 

 — Of this, four principal modifications are described with minute de- 

 tail. All these several subdivisions of structure are supposed to have 

 been produced by great internal movements, after the mechanical 

 deposition of the formation. 



§ 4. Lower Red Marl and Gypsum. — This extends from the 

 edge of Nottinghamshire to the banks of the Wharf; thins off at the 

 two extremities ; attains its greatest thickness (perhaps nearly 100 

 feet) on the right bunk of the Ain ; — but has not been discovered in 

 Durham or the northern parts of Yorkshire. 



§ 5. Upper thin-bedded Gray Limestone. — Near Ferry Bridge this 

 contains very little magnesia. In other places it contains subordi- 

 nate dolomitic beds. It commences at Carlton near Worksop, and 

 ranges without interruption to the left bank of the Wharf. Further 

 north it reappears in several places, under a modified form : and the 

 highest beds on the coast of Durham may perhaps be referred to it ; 

 but the classifications are made obscure by the absence of the lower 

 red marl. 



§ 6. Great Subdivisions of the new red Sandstone which are supe- 

 rior to the dolomitic series. — In Nottinghamshue these consist of two 

 principal deposits.* — (a) Upper red sandstone. — (b) Upper red marl 

 and gypsum. — The same subdivisions may be traced near the mouth 

 of the Tees. In the central parts of Yorkshire they are obscured by 

 diluvium. 



By way of conclusion, — the deposits described in § 1 and § 2, are 

 supposed to be the equivalents of the rothe-todte-liegende, the kupfer 

 schiefer, and zechstein. — The ore described in § 3, 4, and 5, are in 

 like manner supposed to be the equivalents of the rauchwacke, asche, 

 foliated stink stein, breccias, and gypsum, which compose the upper 

 part of the Thuringerwald system. The coincidence, in order, mi- 

 neralogical character, and organic remains, seems to be nearly per- 

 fect. In like manner the two divisions described in § 6. are taken 

 as the respective , equivalents of the bunter sandstein and keuper j 

 and, the enormously thick deposits between the coal measures and 

 the lias, with the exception of the muschel-kalkstein, are thus found 

 to admit of the same natural subdivisions in England and in central 

 Germany. Finally, the author speculates about the origin of the do- 

 lomitic deposits, and adopts in part the theory which derives them 

 from the mechanical destruction of the rocks of the carboniferous 

 order. He states however two facts ( 1st, the greater abundance of 

 magnesia than could have been supplied by the dolomites of the 

 carboniferous limestone ; 2ndly, the fact that some beds contain a 

 greater proportion of magnesia than is found in true dolomites), 

 which seem to imply that the waters of the ocean had a power of 

 separating carbonate of magnesia from the preexisting rocks, in a 

 manner which is not explained by the mere mechanical hypothesis. 

 Whatever may have been the origin of the whole system j its extent, 

 regular subdivisions, and characteristic organic remains, seem to 



prove, 



