internal Structure of the Magnesian Limestone. 73 



In the preceding details I have frequently mentioned the irregular thick- 

 ness of the lower sandstone. The fact is proved by the general details already 

 given in the description of the escarpment : but as the fact is one of import- 

 ance, it may be expedient to place it in a stronger light by specific reference 

 to one or two extreme cases. 



1st. On Bramham Moor (in the denudation which extends into the south-east corner of the 

 park) there is a quarry which exposes a few beds of yellow limestone, and about twenty feet of 

 the lower red sandstone, without reaching the coal-measures. In a second quarry, a few hundred 

 yards further west, the upper beds agree with those of the preceding locality ; but the inferior 

 sandstone is represented by an irregular bed not two feet thick, resting on a coal-grit with vege- 

 table impressions. 2nd. The three great shafts of Eppleton, Hetton, and EUemore are within 

 two miles of each other. In the first, the equivalent of the lower red sandstone was found to be 

 126 feet thick ; in the second, only four or five feet; and in the third, about sixty feet thick. 

 3rd. In the cliff under Tynemouth Abbey, the same sandstone does not appear to be more than 

 twenty-five feet thick ; while at Clacks Heugh, and some other places on the Wear, the whole 

 thickness is perhaps not less than two hundred feet*. 



It is unnecessary to accumulate more examples. We may, however, natu- 

 rally inquire whence arises this extraordinary irregularity ? It has been pro- 

 duced by three causes. 1st. The beds on which the lower red sandstone rests 

 do not always present an even surface. For example, in the two quarries 

 above mentioned on Bramham Moor, the coal strata, probably in consequence 

 of the intervention of a fault, appear at different levels. Under such cir- 

 cumstances it is not possible that superior unconformable strata should preserve 

 an uniform thickness. 



2nd. The deposit appears to have been produced by the irregular action of 

 mechanical forces ; and, consequently, to have presented an uneven surface at 

 the commencement of the more tranquil formation of the magnesian limestone. 



the rate of 48,000 gallons an hour. In the hopes of reducing this, they were, in the summer of 

 1826, constructing pumps capable of lifting 54,000 gallons an hour. 



3. In the new water-works at Bishop Wearmouth, after passing through 108 feet of limestone 

 and 36 feet of indurated sand, they reached a very copious spring of water. 4. In a well sunk on 

 the property of Mr. Grimshaw in the same neighbourhood, the following beds were cut through. 

 (1.) Limestone, 3 fathoms. (2,) Dark blue clay, 1 foot 6 inches. (3.) Brown and yellow 

 indurated sand, 3 fathoms. (4.) Quicksand and water. — Similar results are given in the wells 

 sunk near the Wear by the proprietors of the Hetton coal-works. 



At the present time a pit is sinking on the north bank of the Wear, between Southwick and 

 Sunderland Bridge : but the success of the attempt must be extremely doubtful ; because the 

 lower sand (which they must pierce through before they descend to the coal-measures) passes 

 under the bed of the river, and is proved by all the neighbouring sections to be of incoherent 

 texture, and of great thickness. The interior part of it may therefore probably contain such an 

 enormous quantity of water, that no engine will be found capable of keeping it under. — N.B. The 

 preceding remarks apply to the state of the works in 1826. 



* Some details connected with the preceding sections will be given in a subsequent part of this 

 paper. (See Plate V. fig. 3.) 



VOL. III. — SECOND SERIES. L 



