834 Correspondence — D. Mackintosh. 



GLACIATION OF WEST SOMERSET. 



Sir, — In the article under the above heading in your last Number, 

 Mr. Lucy does not seem to be aware that the grooves on the banks 

 of the Exe, supposed by Professor Jukes to be ice-marks, were after- 

 wards clearly shown by Mr. Whitley to be a development of rock- 

 structure by weathering (Quart. Joum. Geol. Soc., vol. xxiv. p. 3). 

 In West Somerset there is a greater display of curved-back slaty 

 laminee than anywhere else in South Britain ; and in endeavouring 

 to account for the phenomena, I mentioned land-ice as one of several 

 competing agencies in an article in the above Journal for November, 

 1867. The direction of the curvature is from about N.N.W. to 

 S.S.E,, and great blocks of quartz imbedded in angular drift have 

 been transported in the same direction. The curvature may be well 

 seen on the flat summit of Brendon Hill, and must have been pro- 

 duced by some cause assailing the high ground of West Somerset 

 from the IS.N.W., and not moving down the hill-slopes towards the 

 north. Though not in any way doubting the validity of Mr. Lucy's 

 discovery of ice-m-arks near Ashley Lodge, I may state that during 

 several years' successive residences in different parts of the south- 

 west of England, I never once saw any certain trace of the action of 

 land-ice, nor have I seen such trace anywhere in England to the 

 S.E. of a line drawn from about the mouth of the Tees, by Ilkley, 

 to Hope Mountain (on the east side of which there is an extensively 

 rounded and strikingly striated rock- surface), n^ar Wrexham. Mr. 

 Croll, in your last Number, does not seem to be aware of the exist- 

 ence of a beautifully-planed, polished, and striated rock-surface on 

 the north cliff-line of Eombald's Moor, west of the headland called 

 the Calf, near IIkle3^ When I saw it in course of being exposed by 

 the quarrymen, I was under the impression that it had been pro- 

 duced by an iceberg (see Proc. of Geol. Soc. of West Eiding for 

 1870) ; but I now believe that it was caused by land-ice, and that it 

 approximately marks the S.E. boundary or sea-wall of an ice- 

 sheet which never extended any farther. Professor Eamsay believes 

 that the apparent ice-marks on the Bloody Stone near Matlock (dis- 

 covered by me, and afterwards described by Mr. A. H. Green, and 

 the Eev. J. M. Mello), are not reliable. 



Mr. Lucy refers to Boulder-clay and Gravel in West Somerset. 

 For several years I devoted attention to the drifts of many parts of 

 the South and South-west of England, but refrained from publishing 

 much on the subject^ until I had examined the Glacial drifts of the 

 North-west of England and North Wales. I now believe that com- 

 paratively little progress will be made in arriving at certainty con- 

 cerning the sequence of events during the Glacial period in South 

 Britain, until some geologist has given several years' undivided 

 attention to the task of correlating the Glacial drifts of the North 

 with the non-Glacial drifts of the South, that is, the drifts which 

 contain truly glaciated stones in a matrix ground up by ice, with the 

 drifts in which no certain trace of either the one or the other can be 

 detected. The task could only be accomplished by one person 



1 See Geol. Mag. Vol. IV. p. 390. 



