GEOLOGY OF THE BRISTOL COALFIELD. 



45 



been collected, the interior of which are lined with splendid 

 crystals of celestine. 



With this mineral, selenite or sulphate of lime is almost 

 universally seen, and is indeed present in all the Triassic and 

 Rhaetic and Liassic beds. 



An analysis of the celestine crystals gives — 



Strontium Sulphate 

 Barium, Sulphate 

 Calcium, Sulphate 

 Ferric Oxide 

 Manganese 

 Silica, Clay and Lias 



99-13 

 .16 



.02 



trace. 



•44 



100.00 



The beds of Triassic or New Red Sandstone, are so similar in 

 lithological appearance and character to those of the Devonian or 

 Old Red that they cannot be distinguished when removed from 

 the quarry, and when their relation to the contiguous strata cannot 

 be observed. Generally they may be known by the New Red 

 beds being horizontal, while those of the Old Red have a 

 considerable dip. This may be well observed in the cutting at Sea 

 Mills, of which Fig. 26 is a sketch. The horizontal beds of the 

 Trias, are seen lying unconformably on the Devonian. 



Fig. 26. — Section at Sea Mills. 



a — Triassic beds. Z*- Devonian Sandstone beds. 

 About the middle of the true variegated marls, occur one or two 



