ALUM SHALE. 151 



In attempting to trace the progress of the break to the south and 

 west, we find ourselves lost amidst the irregularities of the strata. It 

 appears sometimes to follow the course of the Esk, and sometimes 

 not. The strata, which form high cliffs at the mouth of the river, dip 

 rapidly to the south or south-west on both sides ; those on the right 

 bank sinking or disappearing in Bagdale, and those on the left at Spital 

 beck, a little further up. Immediately beyond the harbour, the strata 

 rise again on both banks, and as the sandstone cliffs on the opposite 

 sides appear to correspond, we see no vestige of the slip. Proceed- 

 ing about half a mile further, we find the beds on both sides discon- 

 tinued, or receding from one another, and the fine circular vale of 

 Ruswarp, about half a mile in diameter, left in the midst. This vale, 

 like the middle of the large vale of Pickering, seems to be a kind of 

 centre of subsidence, the strata dipping towards it from every side, 

 and rising all around it in the form of an amphitheatre. Here the strata 

 on the south-east bank seem to have sunk deeper than those on the 

 opposite side ; for the blue limestone, that occupies so high a position 

 at Gnipe-houe, is here found in the low ravines below Sneaton, as for- 

 merly noticed ; and to what was stated on that subject we can now 

 add, that it is found in a position still lower, in Cockmill wood, imme- 

 diately below the mill-dam, and not many yards above the level of 

 the sea. 



The depression of the strata on the left bank appears to continue 

 till we arrive at Sleights, where the beds rise to a great height, and 

 the alum shale is discovered in a lofty position at Blue-bank, so named 

 from the blue colour of the shale. The vale of Ybiirn dale, which 

 opens on the left into the vale of the Esk, appears to have derived its 

 origin, partly from the washing away of the sti'ata, and partly from 

 their subsidence: for though we find the aluminous beds, both at 

 Littlebeck on the Sneaton side of the vale, and at Godeland banks on 

 the Sleights side, they are more elevated at the latter than the former. 



