REVIEW—GEOLOGY OF EAST SOMERSET. 67 
Arcbietvs, 
The Geology of East Somerset and the Bristol Coal Fields. By Horace B. 
Woopwarp, F.G.S. Nine plates, twenty-three woodcuts, 271 pp. 
Price 18s. 
T'u1s Geological Survey memoir contains the results of the re-survey of a 
country which has long been classic ground to geologists. It was first 
mapped about thirty years ago by De la Beche, Ramsay, Phillips, and 
others. The revision of the Dristol area (sheet 35) was done by Mr. 
Bristow in 1864, whilst that of the sonthern part (sheet 19) is chiefly the 
work of Messrs. H. B. Woodward, Blake, and Ussher. 
The area described includes a wonderful variety of formations, 
ranging from the Silurian Rocks of the Tortworth district, which may 
be regarded as a continuation of the Malvern and May Hill ridge, up to 
the Cretaceous Rocks, which come on in the sonth near Chard, and in 
the south-east at Mere, &c. 
The physical features of the country are then described. The 
Severn and Bristol Channel form the wesier1 boundary; while on the 
east we have the Oolitic escarpment, rising to a height of about 800 feet. 
The principal rivers are the Litile Avon, Bcistol Avon, Yeo, Axe, and 
Parret. 
The Old Red Sandstone resis upon the Silurian Rocks near Berkeley. 
Tt also forms the central axis of the Mendip Hills, rising at Blackdown 
to 1,067 feet above the sea-level. 
The Carboniferous system is much more extensively developed. 
The Mountain Limestone has a thickness of 3,000 feet. From the north 
of Bristol, at Chipping Sodbury, it curves round to the west by 
Thornbury and Clifton, where the remarkable gorge cut by the Avon is 
well Imown. Thence it passes southwards by Backwell and Brockley 
Castle ; turning rather abruptly to the east it forms the greater part of 
the Mendip Hills, which may be considered to extend from Uphill on the 
Bristol Channel by Axbridge to near Frome. The scenery of this 
southern portion is bare and rugged, with remarkable combes and ravines, 
as at Cheddar, Burrington, &c. Fossils are numerous, especially 
brachiopods, crinoids, and corals, the latter resembling those which form 
the fringing or shore reefs of the present day. 
The Millstone Grit or Farewell Rock is on an average 1,000 feet in 
thickness, but in the Mendip district becomes: reduced to half this 
amount. The Coal-measures proper comprise one main tract—tvhe 
Bristol and Radstock coal-field—and two smaller basins which lie west- 
ward of it, viz., the Nailsea basin and that of Clapton-in-Gordano, which 
has lately been found to extend northwards under the Severn. Mr. 
Woodward also shows the great probability that a covered-up coal-basin 
exists south of the Mendips, about Wedmore, Glastonbury, &c., whilst 
eastwards such a series of basins probably extends by Oxford and the 
neighbourhood of London to connect with the coal-fields of Belgium and 
the north of France. The Bristol Coal-measures exhibit three ‘well- 
