28 



NEW RED SYSTEM. 



gland, however, where the lower members of this system are much more fully developed, 

 the subsequent researches of Professor Sedgwick have thrown a new light on these re- 

 lations, proving that a great thickness of sandstone is there interpolated between the 

 magnesian limestone and the carboniferous strata; and further establishing the important 

 fact, that the coal measures of that region sometimes pass conformably into the lower 

 New Red Sandstone 1 . I now proceed to show, that in the central counties, where its 

 structure was once deemed " obscure to the most acute geologists 2 ," this system may 

 also be subdivided into formations, representing those of the North of England ; an ac- 

 quaintance with which, will be found of great practical importance, in the neighbour- 

 hood of the underlying coal fields. In the descending order these formations are— 



1 . Saliferous Marls, fyc. 



2. Red Sandstone and quartzose Conglomerate. 



3. Calcareous Conglomerate = Magnesian Limestone. 



4. Lower Red Sandstone, 



5. 



a. Lower Lias. b. Saliferous Marls, &c. c, Red Sandstone and Quartzose Conglomerate. 



d. Calcareous Conglomerate. e. Lower New Red Sandstone. /. Upper Coal Measures. 



Before describing these deposits, it is desirable to cast a glance over the map, and 

 consider their geographical position as a whole. To the south-west of Gloucester they 

 occupy a mere band, which after many contractions and expansions between Newent, 

 the Malvern Hills and the Severn, finally spreads out in the plains of Worcestershire. 

 Thence the Lias and Oolite rapidly receding in a north-easterly direction, the area of the 

 New Red Sandstone is greatly enlarged; and finally where the Silurian and Cambrian 

 rocks terminate abruptly near Shrewsbury, the Red Sandstone wrapping round their 

 edges, is extended over a large region, the greatest width of which, from the coal-field of 

 Chirk and Oswestry on the west, to the Lias of Leicestershire on the east, is not less 

 than seventy-five miles. The following observations apply to the western portion of this 

 area, and to some of those central districts where the coal-measures and older rocks 

 protrude through the younger deposits. 



1 Professor Sedgwick, Geol. Trans., vol. iii., thus identified this Lower New Red Sandstone with the "Rodte- 

 todte-liegende " of German geologists ; see account of this rock, in the next Chapter. 



2 Bucklandand Conyheare, Geol. Trans., vol. i. p. 299. New Series. The passage alluded to, is, — "The 

 Newer Red Sandstone exhibiting throughout its whole course an identity of character and composition, is ab- 

 solutely continuous from the points in this district (Bristol and Tortworth) where it rests unconformably on the 

 coal measures, to the plains of Salop, where its relations to the coal measures have appeared obscure to the most 

 acute geologists." (1825.) 



