Vol. 69.] IN THE MAGNESIAN LIMESTONE AT HARTLEPOOL. 191 



Limestone. The experience of all workers in this formation in 

 Durham is that brachiopods die out and disappear before the 

 deposition of any of the upper beds. 1 



We are, therefore, driven to the conclusion that the greater part 

 of the Upper Magnesian Limestone Series, and apparently also 

 a considerable portion of the middle beds, are here represented 

 and replaced by an included mass of anhydrite of uncertain shape 

 and size, occupying in its present condition a strictly limited area 

 in the Hartlepool district. 



Eig. 1 (p. 192) is an attempt to represent diagrammatically the 

 boring through the anhydrite, aud side by side with it the most 

 reliable boring records obtainable in the immediate vicinity, with 

 the view of showing the beds which are replaced by the anhydrite. 



The discrepancy in the limestone in the various borings will be 

 noticed, and, indeed, the absence of any bed having anything like 

 a, stratigraphical continuity over an extended area is a marked 

 feature of the Upper Magnesian Limestones in Durham. 



The boring near Hart Railway-Station is 2| miles north-west 

 of the Warren Cement-Works boring. The limestone was met 

 with at 37 feet below the surface and completely pierced. It had 

 a thickness of 708 feet, from which fact aud the outcropping of 

 Upper Limestones not far away, one may reasonably infer that all 

 the great divisions are represented. No fossils were recorded, and 

 the cores are now lost. 



The boring at Howbeck is situated near the Hartlepool Union 

 Workhouse, about a mile away from the anhydrite boring. The 

 boring was still in limestone at 324 feet, and a good supply of 

 water was obtained. 



At West Hartlepool Waterworks, whenever borings are sunk, a 

 good supply of water is obtained, and constitutes the household 

 water of the two towus. It has been supposed, though it is by 

 no means certain, that the water is held np by the mass of 

 impervious anhydrite a little to the eastward. 



South of the West Hartlepool fault a boring was sunk at the 

 West Hartlepool Cement- Works (Casebourne's Boring). Under 

 30 feet of Glacial drift the red beds were encountered, having a 

 thickness of 575 feet 6 inches, following which the Upper An- 

 hydrite Series (1.8 feet 6 inches), red and blue marls representing 

 the here-absent salt-bed (28 feet 6 inches), and the Lower Anhydrite 

 Series (77 feet 6 inches thick), occur in descending order. 



Beneath this, the Magnesian Limestone with gypsum was met 

 Avith at a depth of 730 feet from the surface, and was pierced to a 

 depth of 40 feet, the total depth of the boring being 770 feet. 



The boring was not continued far enough into the limestone to 

 show Avhether any extensive bed of anhydrite existed in it, and the 

 cores having, by a great misfortune, been recently thrown into a 

 pond and buried up, I was unable to examine them for fossils. 



1 This feature seems to be common to the Upper Limestones over the whole 

 of North-Western Europe. 



