Yol. 69.] IN THE MAGNESIAN LIMESTONE AT HARTLEPOOL. 185 



Survey maps as extending in a straight line from West Hartlepool 

 to a point south of Darlington. The lovels of the limestone in 

 horings north and south of this fault at West Hartlepool show 

 a difference of about 700 feet, and so the southward throw of the 

 fault is probably of this magnitude. Its exact point of contact 

 with the sea-coast would seem to be where the road from Seaton 

 Carew to West Hartlepool crosses the railway near the saw-mills 

 and engine-shed. 



The Red Beds, well exposed at Long Scar and Seaton Carew, are 

 not touched upon in this paper, except as the protective covering of 

 the underlying Magnesian Limestone. 



To the west and north-west the typical sections of Magnesian 

 Limestone on the coast and in the various ravines and isolated 

 outcrops are described as far north as Castle-Eden Dene, and as 

 far west as the limit of the Magnesian Limestone in that dene. 



The whole south-western portion of the area is hidden by 

 Glacial drift, and does not concern this paper. Glacial action has 

 brought about an intense deformation of the limestone in parts ; this 

 is especially noticeable in some of the Upper Limestones of the 

 coast-section, and makes a detailed mapping of the coast an almost 

 impossible task. The effect seems, however, to be a comparatively 

 superficial one. 



As may be supposed, on account of the internal collapse of 

 parts of the Magnesian Limestone, the dip of the beds is a very 

 variable one ; but the prevailing dip is a few degrees eastwards 

 or south-eastwards, corresponding to the general slope of the 

 country towards the sea. 



The work on the outcrops and sections in the area is based 

 chiefly on palseontological evidence. 



II. The Mass of Anhydrite in the Magnesian Limestone 

 at Hartlepool. 



The observations here detailed deal primarily with a large mass 

 of anhydrite and the associated gypsum, which is proved by a boring 

 and other indications to occur in close proximity to the Upper 

 Magnesian Limestone upon which the towns of Hartlepool and 

 West Hartlepool are built. To the subsequent denudation and 

 -erosion of this mass the harbour of Hartlepool owes its existence. 



Had the Magnesian Limestone extended without an interruption 

 from its occurrence on Hartlepool foreshore to its second outcrop 

 at the gasworks at West Hartlepool, it is clear that the inter- 

 vening ' slack ' or valley which accommodates the harbours of the 

 two towns could not have existed under the given conditions. 

 Thus the harbour of Hartlepool, situated as it is in a somewhat 

 anomalous and unexpected position on the coast, proves to be in 

 respect to its mode of origin in many ways a very interesting and 

 unusual phenomenon. 



The presence of gypsum in the harbour might have been inferred 

 without the evidence of any boring, from the fact that masses of 



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