226 



THE GEOLOGIST. 



Hill, about half-a-mile out of Mitcheldcan, where the complete 

 sequence of the beds is to be seen, as iu the following diagram 



}tIillstone-grit. Carboniferous Limestone. Old Red Sandstone, 



1 2 3 4 5 6 7 8 



1. Sandstone vein of Iron Ore. 2. "White Head Limestone. 3. Limestone vein of Iron Ore. 



4, Grey and Red Limestone. 5. lilack rock Limestone. G. Foreline Limestone. 7. Grey Sand- 

 stone. 8. Conglomerate. 



In t^YO thin and nearly vertical bands of shale, so rotten that it is 

 difficult to secure a whole square foot of it, which repose respectively 

 on beds of about a foot thick of very hard, partly crystalline, limestone, 

 charged with a considerable per centage of sand, so thick do the ossicula 

 lie, that in dry weather a little gentle crumbling will detach them 

 by hundreds. Eesides the trochites, portions of encrinital stems or 

 entrochites, three, four, and even live inches long, are often to be 

 obtained, as well as the plates of the pelvis, and a great number more or 

 less perfect terminal branches or arms. The most common species is 

 the Platycrinus triakonta-dactylus, or thirty-fingered encrinite, but 

 remains of the Actinocrinus or nave-encrinite " are also very abundant. 

 Mingled with the Crinoidea, in the shale beds, are vast numbers of 

 shells of Brachiopoda, including two species of Spirifer (S. striatus and 



5. cuspidatus), and one of Terebratula (T. hastata). 



Perhaps the most interesting circumstance connected with these fossil- 

 beds is the lesson in physical geology which may be learnt from them. 

 We find the stems of the crinoidea attached to the bed of limestone, 

 and growing, as it were, out from it ; we find the lower portions of the 

 stems projecting a short distance into the shale ; and then v/c find the 

 upper parts of these same stems broken into pieces, and the disconnected 

 ossicula scattered about in every conceivable position, many of them 

 crushed, and all more or less exhibiting evidence of the violence of 

 the forces causing their destruction. 



The recurrence of this condition of things, in two separate sets of 

 beds of shale and limestone, as seen in the Plump Hill quarry, would 

 show a return to the same condition of sea-bottom, and probably a 

 lepetiliouot the same physical agencies at long separated intervals of time. 

 [To be coniinucd.) 



