76 Professor Bonney — Pebbles in the Trias. 



of the English Midlands.^ For this purpose I recently spent a short 

 time at the former place, and think the results worth placing on 

 record. I select for comparison the pebble-bed on the more northern, 

 part of the wild Staffordshire moorland called Cannock Chase, with 

 which I happen to be especially familiar. The points of resemblance 

 shall be noted iirst, those of difference afterwards. 



The outcrop of the Devonshire pebble-bed is usually a hilly 

 moorland, naturally overgrown with bracken, gorse, heath, and ling. 

 There are scattered copses of Scotch firs (planted). That is the 

 characteristic scenery of Cannock Chase. The pebbles are numerous, 

 and lie in a sandy matrix. They vary from subrotund to well 

 rounded, the larger specimens being sometimes almost subangular. 

 They seldom exceed a foot in the longest diameter, are very 

 commonly from 3 to 5 inches, and smaller specimens are abundant. 

 Here and there are intermittent beds of sand, nearly or quite free 

 from pebbles, in thickness from a few inches to two or three feet ; 

 false-bedding is often distinct ; the pebbles are occasionally impressed 

 one by another, though rather less frequently than in Staffordshire, 

 for they are not, I think, quite so closely packed. But the general 

 resemblance of the two deposits is very marked. 



Where I had the best view of the relation of the Budleigh 

 Salterton psbble-bed to the underlying and overlying deposits, 

 I found it pass rather quickly, and apparently regularly, into the 

 marl below, the pebbles, perhaps, generally being a little smaller 

 than usual for the last few inches, and the matrix more marly. 

 The pebbles also run rather small at the top, for any larger than 

 a duck's egg are rare in the last four feet ; the upper surface of the 

 bed is usually even, and it is succeeded by a thick deposit of false- 

 bedded red sand, which has a general resemblance to the Bunter 

 sand of the Midlands. 



Next as to the materials of these pebble-beds. Vein-quartz is 

 common in both. Quartzites of more than one variety are yet more 

 common. Speaking in general terms, the same types occur in both 

 deposits, though not in the same proportion. 1 reserve, however, 

 further particulars till I come to mention the differences, merely 

 observing that in both a fairly hard quartzite, the surface of which 

 has a somewhat speckled look, due to the presence of very small 

 grains of felspar, is rather common. But I was surprised to find 

 at Budleigh Salterton specimens of the moderately coarse hard 

 quartz-felspar grit, which so closely resembles the Torridonian of 

 Scotland, to the presence of which in the Midlands I have already 

 called attention. Specimens of a dark-green to almost black rock 

 occur in both deposits, which will presently receive a fuller notice. 

 Both also contain some felstones, with more basic rocks of compact 

 structure and purplish colour ; also granitoid rocks in a very rotten 

 condition. The last are rare in the Midlands ; still rarer and more 

 obscure at Budleigh Salterton. In neither region are fossiliferous 



1 A very full description of the pebble-bed, with notes on the pebbles by Mr. 

 Carter, and references to literature up to 1880, is given by the late Mr. T. Davidson. 

 " Palseont. Soc." vol. xxxv. (1881). 



