internal Structure of the Magnesian Limestone. 71 



in the coastruction of the Stockton raiUroad. The mineralogical character of this sandstone, its 

 great elevation, and its apparent want of conformity to some parts of the limestone terrace, might 

 seem good reasons for placing it in the carboniferous order. The sections presented at Houghton. 

 le-Side in the quarries on the east side of Brussleton Tower Hill, and in the quarries near East 

 Thickley on the north side of the rail.road, made me however doubt the propriety of such a con- 

 clusion, and induced me to regard a portion, at least, of the sandstone hills in question, as an un. 

 usual development of the lower red sandstone. The part of the terrace extending by Eldon 

 Cowndon, &c. to Ferry Hill, does not in any way assist in clearing up these difficulties : for in 

 two or three places when the escarpment is not disguised, we find a light grey sandstone imme. 

 diately inferior to the limestone, which by some may be regarded as one of the most ordinary 

 members of the coal.measures ; by others, as an exhibition of the inferior red sandstone thout^h 

 under an unusual form. 



In the range of the escarpment from the north-east side of Ferry Hill to the banks of the 

 Wear, there is a formation of sand and sandstone, about the true relations of which it seems im. 

 possible to doubt ; for, notwithstanding its very variable thickness, it is seen at so many places 

 under the limestone, that it must form a nearly continuous mass stretching obliquely over the 

 successive portions of the Durham coal-field*. It must therefore be unconformable to them and 

 can only be referred to the lower red sandstone. 



Notwithstanding the absence of a continuous terrace, and the want of numerous natural sec- 

 tions, there can be little doubt that the same sandstone is continued from the banks of the Wear 

 to Tynemouth Castle Hill : for it is well exhibited in the hill near Hilton Castle, under West 

 Bolden, and in the cliff under Tynemouth Castle f; and two quarries of micaceous sandstone on 

 the road from Westoe to Jarrow belong apparently to the same formation. 



Its mineralogical character in this part of Durham is, as before stated, very different from the 

 more usual type of the same formation in Yorkshire. It is most usually seen under the form of 

 a yellow micaceous sand ; or of a yellow sandstone so imperfectly coherent, that it falls to powder 

 under the shock of a blast, or the blow of a heavy hammer. Traces of red sandstone and the 

 subordinate marls are not, however, altogether wanting. For example, in the escarpment at 

 Rough.dean near Houghton-le-Spring, the following beds are exposed. 



1. At the bottom a strong grey freestone. About twenty feet are visible; and near the top it 

 passes into a soft slaty micaceous variegated sandstone. 



2. Yellow and light blue unctuous clay, four feet. 



3. Red and black clay, about one foot. 



4. Yellow incoherent sand, twenty feet. 



5. Over the preceding are marl beds, and the yellow limestone ; but they are not exhibited in 

 this section. I was not able to determine tlie true place of No. 1. with certainty : the other 

 beds evidently represent the lower red sandstone. 



Again, there is at Clack's Heugh, on the south bank of the Wear, a magnificent natural 

 section of the deposit, in the form of a yellow sand, of a great but unknown thickness, supporting 

 the limestone, and in consequence of a fault abutting against the coal.measures +. But on the 

 opposite bank of the river it is exhibited under a more complex form in a succession of beds of 



* In proof of what is stated above, I may refer to the following localities, where the inferior 

 sandstone is well exhibited, Thrislington Gap, Coxhoe Hill, Quarrington Hill, in the various 

 coal-pits near Hetton-le-Hole, Houghton.le-Spring, Painshaw Hill, and the sections on the 

 banks of the Wear near Clack's Heugh. (See Plate VII. fig. 3. and Plate V. fig. 1.) 



t See Plate V. fig. 2. + See Plate VII. fig- 1- 



