ALUM SHALE. 127 



may be more correct to say, that in these hills it loses its conglomerate 

 character, and passes into common sandstone. 



Having described the series of strata intervening between the 

 blue limestone and the aluminous schistus, we might notice the 

 remarkable undulations and breaks in these strata ; but it will be most 

 proper to defer our account of these phenomena, till we have taken 

 a view of the next member of our strata, viz. 



THE GREAT BEDS OF ALUM SHALE. 



The aluminous schistus, as has already been intimated, forms a 

 most important feature in the three ranges of hills in the northern 

 part of our district, which we have therefore denominated the alum 

 hills. This schistus forms beds of immense thickness, intei-stratified 

 with seams, or thinner beds, of various descriptions. It begins to rise 

 above the level of the sea towards the northern extremity of the 

 Stainton Dale cliffs, nearly a mile to the south of the Peak ; and is 

 continued along the coast, with a few interruptions which will be 

 noticed, to Saltburn and Redcar, at the mouth of the Tees. On the 

 western side of the hills, it first makes its appearance at Thimbleby, 

 near Osmotherley, where it rises from under the north-west skirts of 

 the Hambleton hills ; and from thence it proceeds along the western 

 and northern fronts of the Cleveland hills to the mouth of the Tees ; 

 leaving, however, a considerable plain, between the fronts of the 

 hills and the river Tees, where no alum rock is found. 



To give a more distinct view of the aluminous strata, and the 

 beds subordinate to them, it will be best to describe them as they 

 appear in the lofty cliffs at Boulby; where these strata are more entire 

 than in almost any other spot, and at the same time are of easy access. 

 The whole series of beds, fi-om the summit of the cliffs down to the 

 beach, may be thus enumerated : 



