AUSTEN — EXTENSION OF THE COAL-MEASURES. 51 



inasmuch as they dip away under the cretaceous series of WestphaHa, 

 — beneath which they are worked, — they have a considerable width 

 beneath the sands of Aix-la-Chapelle, but from this point they con- 

 tract rapidly. This diminution across the Belgian area is not owing 

 to any falling off in the thickness of the component beds, but results 

 from the complicated folding of the masses, whereby they are caused 

 to assume a deep trough-shaped arrangement, accompanied by an 

 endless succession of zigzag folds. This part of the Belgian coal- 

 band, if restored to its original horizontal position, would occupy 

 more than four times its present surface-breadth. 



From the expansion which the mountain-limestone takes west of 

 Mons, it is evident that the whole series expands again ; from which 

 it may be inferred that the coal-measures beneath the chalk of the 

 north of France will be found to have wider dimensions than has 

 been generally supposed : that such is the case is already indicated 

 by the extent which they have been proved to have west of Bethune ; 

 and it becomes an important consideration as to their western ex- 

 tension. 



All dislocations of the earth's crust having been produced by the 

 action of some force acting in the plane of the disturbed beds, such as 

 that of contraction, any movements producing ridges such as those 

 of the Rhenish-Ardennes System would be attended by the greatest 

 amount of dislocation at any point where it had a pre-existent trans- 

 verse range. 



Such are the considerations by which we are enabled to sketch out 

 some of the earlier physical arrangements of Western Europe. 



The Carboniferous Series. 



§ 1 . Old Bed Sandstone. 



An early condition of the surface of part of the European area ftt 

 this period is very clearly indicated by the arrangements and com- 

 position of the typical Old Red Sandstone formation. 



Much confusion in the chronology of geological changes has been 

 caused by the reference of this formation to the marine series. If 

 due weight be allowed to the facts of an accompanying terrestrial 

 and fluviatile vegetation, to the occurrence of the genus Cyclas, 

 together with air-breathing oviparous quadrupeds and terrestrial 

 Chelonians, the early suggestion of Dr. Fleming, though based on 

 other considerations, will surely be adopted ; and the Old Red 

 Sandstone of Scotland will be referred to the lacustrine series of 

 formations. The " Old Red Sandstone" Fishes offer a subject well 

 worthy of special treatment, with reference to the conditions of the 

 area of water in which they lived ; but the coliciusions would pro- 

 bably be in accordance with those of Dr. Mantell * — that these con- 

 ditions were such as those of the Lepidosteus and Polypterus. 



Of the three divisions into which Sir R. Murchison divided the 



* Quart. Jouin. Geol» Soc. vol. viii. p. 108. 



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