Murehisori s Silurian System. 47 



with the Rothe-todte-liegende, our geologists made use of the best 

 evidence with which they were acquainted. But the New Red Sandstone 

 group is now better understood ; and in future comparison with conti- 

 nental deposits of the same age, we should use as our types those sec- 

 tions which are most complete, instead of the Bristol or Exeter overlying 

 groups, in which more than one half of the series is absolutely wanting. 

 " The trappean ridges of Malvern, Abberley, and Clent, will be described 

 in the sequel; but in the mean time it may be observed, that as the red 

 conglomerates on their flanks contain angular and rounded fragments 

 of the trap composing those hills, the rocks from which such debris was 

 derived must have been in existence before the conglomerate was form- 

 ed. Now, the rupture between the New Red Sandstone and the car- 

 boniferous deposits, as marked by the dislocations along the line of the 

 Abberley Hills, would certainly lead us to suppose, that the eruptions 

 which gave rise to these hills took place, either during the accumulation 

 of the upper coal measures, or of the Lower New Red Sandstone ; for, 

 without anticipating explanations which are to follow in the ensuing 

 chapter, it may be asserted, that nothing is more consistent with mo- 

 dern and ancient analogies, than that such volcanic eruptions should 

 have been mere local phenomena, which in the tracts where they 

 prevailed (Devon, Abberley, Clent, &c.) may have occupied the place of 

 the Lower New Red Sandstone, by interfering with its deposition, while 

 in the tracts not visited by these outbursts, the formation would natu- 

 rally be fully developed, and would there exhibit the unbroken con- 

 nexion between the New Red and Carboniferous Systems which has been 

 detailed in the previous pages." 



Before going into the description of the coal measures, 

 Mr. Murchison devotes a chapter to Trap Rocks. Ninety 

 years have scarcely elapsed, he observes, since two French 

 academicians collecting plants among the hills of central 

 France, were astonished by discovering numerous cavities 

 resembling the craters of volcanoes. From the lips of these 

 cavities currents of lava, as fresh in aspect as if they had 

 flowed yesterday, were traceable into the neighbouring val- 

 lies, following their sinuosities and stopping their ancient 

 water-courses, and moulding themselves into the inequali- 

 ties of the actual surface. To complete the analogy with 



