CiRC. No, 63. 



Physical Features. 



Upper Nidderdale, one of the most secluded and sequestered of 

 the Yorkshire dales, is closed in at the dale-head by a sweep of moun- 

 tain wall which for nearly forty miles attains a continuous and un- 

 broken elevation of more than a thousand feet, and on Great Whern- 

 side reaches its maximum altitude of 2,310 feet. The physical 

 configuration of the dale shares the general uniformity of its geological 

 structure, which is for the most part millstone grit, except for the very 

 limited tracts where the most easterly outcrops of the mountain lime- 

 stones occur. At the dale-head the mountain pastures sweep down 

 in broad grassy declivities or slopes from the summit ridge to the 

 river banks, and some portion of the watershed is capped by undu- 

 lating plateaux of heatherland much broken up by peat-ravines. Down 

 the mountain pastures trickle the innumerable rills which by their 

 union form the head-waters of Nidd and its tributaries. The river, 

 which rapidly acquires force and volume from the numerous tributary 

 streams which feed it, runs a course due east for about six miles before 

 turning southward. About Angram it is margined by numerous 

 escarpments of shale of considerable height, and fringed by a slight 

 growth of wood and coppice. The outcrop of mountain limestone 

 above Lofthouse is the cause of beauty and picturesqueness in the 

 scenery of the dale and of its chief tributary, the How Stean Beck, 

 the lower part of whose course lies through a deep and imposing gorge 

 in the limestone, the remarkable scenery of which can hardly be ex- 

 celled for grandeur and interest. Two miles above Lofthouse the 

 liver Nidd disappears entirely, precipitating itself into the pot-holes 

 called Manchester Hole and Goydon Pot, to reappear in volume be- 

 low Lofthouse after a subterranean course of a couple of miles in ex- 

 tent. Not that the visible bed of the stream is dry throughout, for 

 the feeders from the mountain slopes are sufficient to keep the stream 

 running above ground as well as below. 



Geology. 



Mr. B. Holgate, F.G.S., furnishes the following : — As we approach 

 Lofthouse a thick mass of impure limestone gives rise to the canon 

 and waterfall in How Stean Beck. This is a very good example of 

 the manner in which a stream by the act of running through it wears 

 down limestone quicker than the action of the weather upon the sur- 

 rounding surface, and thus cuts through the rock a water-course with 

 vertical sides. We have also here an example, in the case of the 

 manner in which underground streams cut their way through lime- 

 stone. In the Blayshaw beck to the left of this, the beds of limestone 

 may be seen to form waterfalls or rapids, and a little way up the stream 

 a tramway brings one to the quarry where the well-known encrinital 

 marble is got from, of which so many mantel-pieces are made. 



Returning to the main course of the Nidd, we find it issuing from 

 a hole in the rock beneath the bridge which we cross before entering 

 Lofthouse. Notwithstanding that its main course is free and open 

 the river disappears in the Goydon Pot Hole, some distance higher up, 

 and it is only when the rains are so heavy that this underground 

 river cannot carry off the water that the old river bed on the surface 

 carries off the water. 



