1863.] CURLEY GRAVEL OF LUDLOW, ETC. 179 



have gradually drained away, the rain-water of the catchment-basin 

 scooping out the beds of the Eivers Terae and Corve, — the courses of 

 which, however, had then dissimilar directions, as is shown by the 

 high terraces behind Burway, leading to Broomfield. Similar changes 

 are now going on, slowly and imperceptibly, though probably not 

 more so than the former ones. 



Hereford. — The city of Hereford is 158 feet above the sea-level, 

 and stands upon a gravel-deposit 900 acres in extent. The materials 

 of this bed appear to have been transported from a great distance, 

 being well rounded and water-worn. In addition to pebbles of Old 

 Red Sandstone and Cornstone, it contains Silurian pebbles from the 

 upper part of the Valley of the Wye, and fragments of trap-rocks 

 from Builth. This gravel is seen to be the lowest of three terraces of 

 drift, and has an average thickness of 30 feet. At a level of 30 feet 

 above it we meet with a second deposit, a belt of gravel perfectly 

 level, and evidently forming the edge of an old lake. Forty-two feet 

 above this, a gravel-bed of small extent exists as a capping to 

 Broomy Hill. 



I am inclined to consider that the denudation of the Old Red 

 Sandstone over the area of the Hereford valley was comparatively 

 rapid ; the present River Wye, which flows through it, discharging, 

 in ordinary dry weather, 1650 million gallons daily. These three 

 gravel-zones are very similar in their appearance and mineral con- 

 stituents. The quantity in the lowest, or City-of-Hereford bed is 

 25 million cubic yards — sufficient to gravel a walk, 10 feet wide, 

 round the globe. 



Skipton. — The plan and sections of the town of Skipton exhibit a 

 somewhat similar condition of things. The lower portion of the 

 town is situated on a lacustrine deposit, lying in a basin of Moun- 

 tain-limestone, containing gravel composed of the debris of this rock 

 and the adjacent Millstone-grit. 



Under this gravel there occurred, on the south side of the canal, 

 and in the excavations for the main sewer, a black deposit of silt of 

 the consistency of tar, which caused great trouble to the contractor ; 

 for straw had to be introduced behind close boarding to keep out this 

 treacherous material, which appeared to be composed of pulverized 

 coal-shale, derived from stratified layers in the neighbourhood. In 

 the sewer-cutting, opposite Christ Church, a thick bed of dark marl 

 was cut through, full of the shells of Physa fontinalis. In the 

 cutting of the sewer north of the canal, opposite Yictoria Mills, the 

 skull, tibia, and other bones of a species of Bos were met with in fine 

 sand, below 8 feet of peat and gravel-drift. Large boulders, about 

 3 1 tons in weight, were found in the gravel opposite the Devonshire 

 Hotel. 



The section along the line of the main sewer has been extended to 

 include the contorted stratification of the Carboniferous Limestone on 

 which the Castle stands, and the anticlinal axis of Storem's Lathe. 



n2 



