288 PROF. T. G. BONNET ON THE [May I9OO,. 



as I think, on insufficient grounds), but I have collected my facts 

 and drawn my conclusions from them as far as possible in an 

 independent spirit. 



The following is a very brief summary of past work: — The 

 Bunter Pebble-beds occupy nearly all the northern part of Cannock 

 Chase (till lately a wild moorland, but now to a great extent 

 enclosed), often practically forming the surface of the ground. 

 Pits, opened for road-metal and gravel, are fairly numerous, some 

 shallow, others 20 feet or so in depth. Those which I have 

 examined are scattered about from Beaudesert Park to the Satnall 

 Hills, a zone about 5 or 6 miles long and 2 or 3 broad. 



Thus I have tested a fairly large area. 1 Moreover, during the 

 earlier part of my work these pebbles were used in making new 

 roads on the Chase, and thus fragments in plenty were spread out 

 to view. The pebbles vary much in size. Those from a horsebean 

 to about 2 inches in diameter are abundant ; very many are larger, 

 from 3 to 4 inches long being a common size ; a few run still larger, 

 up to 6 inches, and occasionally exceed that by an inch or two. 

 In a very few pits they appear to be generally either above or 

 below the average ; but as the deeper excavations sometimes show 

 beds of coarser, alternating with those of finer materials, I cannot 

 venture to draw any inference from this observation. 



They lie in a matrix of sand, composed almost entirely of quartz- 

 grains, not conspicuously rounded, and more or less coated with 

 reddish iron-oxide ; they are very commonly in contact ; indeed, I 

 think that a large one is usually touched by two or three others. Not 

 seldom they are indented, the ' pits ' in the hardest quartzite-pebbles 

 being as a rule extremely shallow, often barely perceptible, while on 

 some of the mudstones they are conspicuous. 2 Beds or seams of 

 sand are intercalated, though as a rule rather sparingly. These are 

 lenticular in habit, generally thin, 3 and they may be seen in- 

 osculating with the pebbly layers. In short, whatever may be the 

 origin of these Bunter deposits, they are -wonderfully like the 

 gravels in the lower valleys of the great Alpine rivers. 



II. Petrography of the Pebbles. 



Some of the more conspicuous rocks occurring as pebbles in the 

 Bunter Conglomerate have been already described, but since 1 883 I 

 have paid more special attention to two groups — the fel stones and 

 the dark green to nearly black pebbles. It may be well, however, 



1 I have also seen something of the pebble-beds in Trentham Park, in the 

 region of the Lower Mersey, at Nottingham and still farther north, besides 

 examining collections from Lancashire made by the late Mr. G. H. Morton 

 and Mr. Bolton, of Owens College, and from Nottingham by Mr. J. Shipman, 

 to whom I return my best thanks. 



2 See T. Mellard Eeade, Geol. Mag. 1895, p. 341, for an excellent plate of 

 the pitted pebbles and a discussion of their mode of formation. See also Proc. 

 Liverpool Geol. Soc. vol. vi (1892) p. 418. 



3 I do not remember to have seen them exceed 4 feet in thickness. 



