460 Notices of Memoirs — Mr. Sudlesfon's Address — 



if a portion of Sheet 2 is tacked on to its southern border we obtain 

 a block of country about 120 miles square, which has not its equal 

 for variety of geological formation in any part of the world within 

 the same space. If Europe is to be regarded as presenting a geo- 

 logical ej)itome of our globe, and if Great Britain be an epitome of 

 Europe, then, without doubt, this particular block of the south-west, 

 which has Bath for its more exact centre, with a radius (say) of fifty 

 miles, may be said to contain almost everything to be found on the 

 geological scale, except the very oldest and the very youngest rocks ; 

 while east of the Severn and south of the Bristol Channel true 

 Boulder-clay is rare or absent. 



It may be convenient to consider a few points which have arisen 

 of late years in connection with the geology of portions of the 

 district now under consideration. 



Palceozoic. 



If we omit the Silurian inlier at Tortworth, the geological history 

 of the country, more immediately round Bristol, may be said to 

 commence with the Old Red Sandstone, whose relations with the 

 Devonian towards the south-west have always presented some 

 difficulty. And this difficulty is accentuated by doubts as to the 

 true Devonian sequence in West Somerset and North Devon. Ever 

 since the days of Jukes that region has been fruitful in what 

 I must continue to regard as heresy until the objectors have really 

 established the points for which they are contending. The un- 

 certainty is to be regretted, since it is through these beds of West 

 Somerset that the system is to be made to fit in with the several 

 members of the Old Red Sandstone. 



There is a mystery underlying the great alluvial flats of Bridge- 

 water which affects more than one formation ; so much so that one 

 cannot avoid asking why there should be Old Red Sandstone in the 

 Mendips and Devonian in the Quantocks. The line which separates 

 the Old Red Sandstone of South Wales and the Mendips from the 

 West Somerset type of Devonian lies here concealed. I have 

 already suggested ^ that, if we regard the Old Red Sandstone of 

 South Wales as an inshore deposit over an area which was deluged 

 with fresh water off the land, we can believe that further out to sea, 

 in a south-westerly direction, the conditions were favourable for the 

 development of a moderate amount of marine mollusca. This view 

 not only does away with the necessity for a barrier, but it also, in 

 a general sense, suggests a kind of gradation between the Old Red 

 and Devonian deposits. Mr. Ussher, whose practical acquaintance 

 with this region dates from a long period, stated a few years ago 

 that, " As far as Great Britain is concerned, the true connections of 

 the Old Red Sandstone beds with their marine Devonian equivalents 

 have yet to be carefully worked out on the ground. " ^ I am not 

 aware that further progress has been made in this direction. 



' Trans. Devonsh. Assoc, vol. xxi (1889), p. 45. 



2 "Prospects of obtaining Coal by boring South of the Mendips" : Proc. Soni. 

 Nat. Soc, vol. xxxvi (1891), pt. 2, p. 104. 



