YORKSHIRE NATURALISTS IN UPPER TEESDALE. 287 



this time without the friendly aid of a bridge, into Yorkshire. 

 Here, where the Maize Beck enters the Tees, is the junction of the 

 three counties, although the exact spot in the bed of the stream 

 would be somewhat difficult to fix upon. The way was now taken 

 along the Yorkshire bank of the river, under the frowning heights of 

 Cronkley, picking their path slowly over the talus at its base, and ever 

 and anon pausing to admire the weird grandeur of the scenery around. 

 Shortly they were upon some beds which have occasioned some 

 discussion among geologists, the soft shales known as the Pencil 

 Mill Beds, which were formerly used for the manufacture of slate 

 pencils. These beds arc claimed by Messrs. Gunn & Clough, of 

 the Geological Survey, to be Silurian, and they argue that the 

 important fault known as the Great Burtreeford Dyke (which crosses 

 the river near this point, and also crosses the great Teesdale fault) is 

 the cause of these lowest beds being brought up. The total 

 displacement caused by this fault, which crosses over through 

 Weardale to Allenheads, in Northumberland, is thought to be, near 

 the Pencil Mill, about 350 feet. To judge from a specimen of this 

 shale obtained in situ, without knowing the position it was obtained 

 from, we should certainly pronounce it to be of Silurian age. In 

 some places veins of quartz run through, and a dyke of igneous rock 

 crossing the river and passing through this bed was also noted. 

 This dyke seems different in character from the basalt seen during 

 the day, and partakes more of the nature of a mica-trap. This point 

 was the most interesting noticed, and it occasioned some discussion. 

 From thence Cronkley Bridge was passed, and the return made to 

 the High Force Inn for rest and refreshment, both grateful to the 

 party, wet and weary as they were. 



On Sunday there was no programme, and members could if they 

 chose rest after the fatigue of the previous day, or betake them- 

 selves to study some matter in detail still further, or again, by brisk 

 walking in the bracing air, add to their stock of health. Some of 

 the party spent a few quiet hours in the charming and well-wooded 

 grounds connected with the High Force, and thus were enabled to 

 examine more closely the majestic waterfall and the surrounding rocks. 

 At High Force the Tees leaps over the basalt in a direct fall of 72ft. 

 into a deep pool below. The river was much fuller from the rains of 

 the previous night, and the scene was impressive beyond description. 

 The peat-stained waters of the swollen river were hurled with a 

 deafening roar over the ledge, and from the pool rose spray and foam 

 almost to the top of the fall. On the sides of the pool the rushing 

 waters had formed miniature caves in the limestone at the base, and 

 wherever a chink or crevice occurred in the sides of the ravine there 



Sept. 1889. 



