DISCOVERY OF SILURIAN BEDS IN TEESDALE. 



31 



in them consists chiefly of quartz. There is, indeed, besides quartz, 

 usually something corresponding to " douk;" but the quartz is by 

 far the most prominent element. In places, ribs of quartz 8 or 9 

 inches thick may be found ; and thinner ribs abound on all sides. 

 Our colleague Mr. J. G. Goodchild informs us that the number of 

 quartz veins is quite a characteristic feature in the Silurian shales 

 under Cross Fell, when compared with Carboniferous shales in the 

 same country. This difference has also been noted by Prof. Phillips 

 (Geol. Yorksh. part ii. p. 4). 



(e) Apparent Unconformity between this bed and the Carboniferous 

 beds above. — The next beds seen on the banks of the Tees higher up 

 the river than the Pencil-bed occur under theWhin Sill at Falcon Clints. 

 The section here is described at length by Sedgwick in his paper on 

 the " Geology of High Teesdale " (Cambr. Phil. Trans. 1824, vol. ii. 

 p. 174), and is alluded to by Phillips (Geology of Yorkshire, pt.ii. p. 78). 

 Phillips was struck by the resemblance of the beds to the basement 

 Carboniferous beds in Eibblesdale ; among other things, he says : — 

 " A few seeming beds occur of a quartzose compound almost exactly 

 like grauwacke, and closely resembling some local beds which cover 

 the slate deposit in Eibblesdale." The lowest bed seen here, ap- 

 pearing just above the Tees, is a conglomerate made up mainly of 

 quartz and clay-slate pebbles of a subangular character, the larger 

 pebbles being sometimes several inches in length. Somewhat similar 

 conglomerates can, however, be seen nearer the Pencil-mill than 

 this, and in equally distinct exposures. Some time ago we had an 

 open cut made in the bank above and a little to the west of the 

 Pencil-mill, in order to discover, if possible, the upper limit of the 

 Pencil-bed, and we succeeded in finding it readily. In this cut we 

 have exposed at the bottom the Pencil-bed of exactly the same 

 character as at the Mill, and resting upon it 5 feet of breccia com- 

 posed of angular fragments of shale like that it is resting upon ; 

 for the next 8 feet we get alternations of quartzose conglomerates, 

 more or less coarse, and mostly hard, but with some finer and softer 

 sandstones. Above this the section is obscure. The next 17 feet 

 appear to be made up of shales and more or less shaly conglo- 

 merates. 



We wish to call special attention to the fact that in this open cut 

 the Pencil- bed is of exactly the same character as at the Mill : 

 specimens from either locality being placed before you, it would be 

 impossible to say which specimen came from which locality, while 

 the conglomerate beds are not altered at all. It is true that beds 

 composed of coarser material seldom or never do show cleavage so 

 well as finer beds, shale &c. ; but in these conglomerates, whether 

 coarse or fine, there is never the slightest approach to cleavage, nor 

 do they show any sign of any other alteration such as ordinarily 

 takes place in the neighbourhood of whin dykes &c. The finer- 

 sandstone beds interbedded with the conglomerates have nothing 

 approaching the character of quartzites ; and the more shaly bands 

 are like simple unaltered Carboniferous shale. 



