84 



PROF. T. M'KENNY HUGHES ON THE 



Mr, Shone, in his excellent paper (Quart. Journ. Geol. Soc. vol. 

 xxxiv. 1878, p. 384) " On the Glacial Deposits of West Cheshire, 

 together with lists of the Fauna found in the Drift of Cheshire and 

 adjoining Counties," discusses the difficulty of explaining the mixture 

 of northern and southern forms in the drift. He says (p. 389) that it 

 is " more than probable that the Scandinavian shells of the Middle 

 Sands and Gravels have been derived from the Lower Boulder- 

 clay ; " and again, after pointing out that the Upper Boulder-clay 

 rests upon an irregular surface of the Middle Sands and Gravels, he 

 says, " what, therefore, more likely than that the southern forms, 

 which are very rare in the Upper Boulder-clay, should have been 

 derived from the Middle Sands ? " I would only go a little further in 

 the same direction, and ask whether the Upper Boulder- clay may 

 not have been derived, together with its Scandinavian shells, from an 

 earlier Boulder- clay, to which they properly belonged. 



It is shown by Dr. Bicketts that flints occur in the Boulder- clay 

 near Birkenhead (Quart. Journ. Geol. Soc. vol. xli. 1885, p. 597). 

 Mr. Mackintosh, id his paper " On the Limits of Dispersion of the 

 Erratics of the West of England and East of Wales notices the 

 occurrence of flint in the marine deposits of sand and gravel along 

 the eastern borders of Wales ; and other writers, many of whom 

 are referred to in the course of this paper, notice the occurrence of 

 flint on Moel Tryfan and in the drift of Lancashire and Cheshire. 



Aitken records that flint has been found on Holcombe Hill, near 

 Manchester, at an elevation of nearly 1000 feet above the sea 

 (Trans. Geol. Soc. Manchester, vol. vii.). 



If shore-ice is needed to explain a few exceptional groups of 

 boulders in the drift or on the hills, that does not involve glacial 

 conditions. I have seen shore-ice in the estuary of the Dee that 

 would float any boulder in the Yale of Clwyd. I have seen at 

 Connahs Quay vessels frozen up in pack-ice 12 feet thick, which 

 broke away in icebergs 50 yards across : and Mr. Alfred Walker 

 has seen the boulders shifted by shore-ice along the same coast. 



The St. Asaph Drift falls to lower levels as we trace it down the 

 vale to the north. This is probably due chiefly to the original nor- 

 therly slope of the valley in which it was throw d down, but also 

 may have been increased by an unequal movement of elevation, and 

 probably more by the greater denudation near the mouth of the estuary* 



It occurs in bosses and ridges of red sandy drift near Bhuddlan, 

 the last place where I have seen anything that could be referred to 

 it being a sand and gravel, with bits of red shale and clay, in a 

 ditch-section \ mile N.W. of the village, and the upper beds passed 

 through in the Aberkinsy borings. It was probably represented in 

 the Eoryd boring also t. 



* Quart. Journ. Geol. Soc. vol. xxxv. 1879, p. 446; Trimmer, Proc. Geol. 

 Soc. vol. i. 1831, p. 331 ; Journ. Geol. Soc. Dublin, vol. i. 1838; Mackintosh, 

 Quart, Journ. Geol. Soc. vol. xxxiii. 1877, p. 736 ; Buckland, Proc. Geol. Soc. 

 vol. iii. 1841, p. 584 ; ' Athenaeum,' 1842 ; Darwin, Lond., Edinb., & Dubl. Phil. 

 Mag. vol. xxi. 1842. 



t " Notes on the Geology of the Vale of Clwyd," Proc. Chester Soc. Nat. 

 Sci. 1884, p. 36 



