Mem — Drift Deposits of the Eastern Counties. 279 



tion, and to ignore those complications of arrangement wliicli might 

 result from repeated periods of submergence, and the fresh distri- 

 bution and reformation of the materials composing the earlier 

 deposits. There are two obvious difficulties in the way of working 

 out a uniform sequence on lithological evidence. 1st. The constantly 

 varying character of each individual bed, clays and sands passing 

 into each other, through gradations of clayey sand and sandy clay, 

 which, unless you have an absolute continuity of section, renders 

 certain identification impossible. 2nd. That after the coast line is 

 left, the various levels at which the same bed may occur (following 

 an irregular basement line, as pointed out by Mr. Hull, in his paper 

 on the Manchester drifts), complicates the difficulty, rendering it 

 impossible to pronounce with certainty to which division an isolated 

 mass may belong. 



The following particulars of a few drift sections with their range 

 of altitude above the sea, will illustrate the extreme difficulty of 

 identifying the individual sub-divisions in distant localities — 



Strethill, near Ironbriclge, Severn Valley. — From 100 to 310 feet above sea; 210 

 feet thick. A stratified hill of drift, consisting of 70 feet of sand and gravel at 

 its base, 70 feet of Boulder-clay, and capped by a further bed of sand and gravel 

 70 feet thick. 



Buildwas, near Ironbridge, Severn Valley. — From 100 to 270 feet above sea, and 

 a range of altitude of 170 feet. Within about a mile of Strethill, on the opposite 

 side of the Severn Valley. Sands and gravels lying against the sloping side of the 

 valley. No distinct bed of Boulder-clay. 



Bridgnorth. — St. James' Gravel Pit, Severn Valley. — Eight miles below Strethill. 

 70 to 250 feet above sea level, and range of altitude of 180 feet. Terraces of gravel 

 and shingle, with no distinct Boulder-clay. At Q,uat, two miles lower down the 

 valley, the drift is almost wholly made up of the detritus of Bunter Sandstone, and 

 in the cuttings of the Severn Valley Railway, at the same level on the west side of 

 the valley, the drifts consist of loamy gravel of constantly varying character. 



Ryden Hill, Benthall, Shropshire. — From 530 to 600 feet above the sea ; range of 

 altitude and thickness 70 feet. An isolated knoll of clean sand and fine gravel. 



Gravel-hole, JVilley Bark, near Broseley. — 350 to 400 feet above sea; range of 

 altitude, 50 feet, sand and gravel. 



Burton, near Much TFenloch. — 750 to 800 feet above sea ; range of altitude about 

 50 feet. Loamy sand and gravel, with transported boulders, but no tenacious 

 Boulder-clay. 



Middletown Railway Station, Montgomeryshire. — Cutting west of station, 310 to 

 630 feet above sea; thickness 120 feet, consisting of 65 feet of tough clay, overlain by 

 45 feet of gravel and pebble beds, intermixed with clay and boulders. 



Growfield, near Coddenham, Suffolk. — From 100 to 200 feet above sea, thickness 

 100 feet, consisting of about 45 feet of sand and gravels, resting on the Chalk ; over- 

 lain by 55 feet of tough Boulder-clay. 



Moel Tryfan, Carnarvonshire. — Alexandra Slate Quarries. — 1270 to 1320 feet 

 above sea, range of altitude 50 feet, consisting of from 20 to 30 feet of clean sand 

 and gravel beds, containing shells, overlain by from 6 to 15 feet of Boulder-clay, 

 containing transported stones or boulders, some of large size. 



Moel Tryfan, Carnarvonshire (foot of the hill). — From 500 to 600 feet above sea- 

 level, range of altitude about 150 feet. Boulder-clay skirting the base of the hill, of 

 similar character to that near its summit. 



This list of examples might be extended ad infinitum, but will 

 suffice to show the extreme difficulty of disting-uishing on any 

 certain basis, and identifying in distant localities on mere litho- 

 logical character, the individual subdivisions of the Drift series. 

 K compared with the sections, enumerated by Mr. Hull in his 



