Sftetcb of tbe (Beological Ibistor? of tbe 
Bristol District/ 
By C. Lloyd Morgan, LL.D., F.R.S., & S. H. Reynolds, M.A., F.G.S. 
B ristol is situated in a district of most varied geological interest. 
Within the limits of an afternoon’s excursion almost every geo- 
logical horizon from the Llandovery to the Chalk, with the exception 
of the Permian, is readily accessible. The picturesque and diversified 
scenery of the Bristol district not only delights the eye of the lover of 
natural beauty, but affords admirable examples of sculptured relief, 
leading on the thoughtful observer to enquire into their mode of origin. 
For geological purposes the Bristol area may be taken as bounded on 
the west by the Severn and Bristol Channel, and on the north by a 
line drawn from Tite’s Point on the Severn to the Stroud Valley. On 
the south it may be regarded as including the Mendip Hills, and on the 
south-east as limited by the edge of Salisbury Plain. Further to the 
north its eastern boundary may be drawn across the hilly country from 
Bradford-on- Avon, through Box and Badminton, to Nails worth and 
Stroud. 
THE SILURIAN ROCKS.2 
These, the oldest rocks of the Bristol district, are exposed in two 
somewhat widely separated areas, forming the well-known inlier 
of Tortworth, and that recently discovered in the eastern Mendips. 
These two areas agree with one another, and differ from all other 
Silurian regions in Great Britain in the fact that they include a 
development of contemporaneous igneous rocks with well-marked lavas 
and tuffs. In the Tortworth area these igneous rocks form two bands 
associated with the Llandovery strata, which are remarkably fossil- 
iferous. In addition to the lava, which is andestic or basaltic in 
character, a band of highly fossiliferous tuff occurs overlying the upper 
lava band. The Llandovery rocks of Tortworth are succeeded by a 
1 For general accounts of the Geology of the Bristol District see T. Weaver, 
“Geological Observations on Part of Gloucestershire and Somersetshire”, 
‘Trans. Geol. Soc.’, Ser. 2, I., Pt. ii., p. 317 (1824) ; W. Buckland and W. D. 
Conyheare, “Observations on the South-Western Coal District of England”, 
ibid., p. 216; H. B. Woodward, “The Geology of East Somerset and the 
Bristol Coalfields ”, ‘ Memoirs of the Geological Survey of England and 
Wales,’ 1876 ; W. J. Sollas, “ On the Geology of the Bristol District”, ‘ Proc. 
Geol. Assoc.’, VI. (1880), p. 378 ; T. Wright, Presidential Address to Section C 
of the British Association, Bristol, 1875 ; H. H. Winwood, “ Geology of the 
Bath District ”, British Association Handbook, Bath, 1888 ; AY. H. Hudleston, 
Presidential Address to Section C of the British Association, Bristol, 1898, re- 
printed in the ‘ Geol. Mag.’, New Ser., Sec. iv., Vol. A^. (1898), p. 458. 
^ For the Silurian rocks see the papers by AA^eaver and by Buckland and 
Conyheare quoted above ; also by R. I. Murchison, “ The Silurian System ” 
(1839), p. 454; J. Phillips, ‘Memoirs of the Geological Survey of England’, 
II., pt. 1 (1848), pp. 190—198 ; also papers by C. Lloyd Morgan and S. H. 
Reynolds in the ‘ Q. Journ. Geol. Soc.’, LVII, 1891, p. 267 ; by S. H. Reynolds, 
ibid., LXIII, 1897, p. 217 ; and by F. R. C. Reed and S. H. Reynolds, ibid., 
LXIV, 1898, p. 512. 
