524 Correspondence — Mr. Dugald Bell. 



than the figures, not much weight will be placed on the remarkable 

 statements as to the distribution of these forms in the Mexican beds 

 as compared with those in Russia. 



This memoir is an important contribution to the Geology of 

 Mexico, and it may be hoped that it is the first of a series which 

 will make known the geological characters of that country in detail. 



G. J. H. 



ooi^ie-DESiPOisriDZBiNrozE:- 



EEPLY TO PEOFESSOR HULL ON THE GLACIAL DEPOSITS OF 

 ABERDEENSHIRE. 



Sir, — Anything Prof. Hull writes is sure of respectful attention 

 in many quarters — not least in that part of the West of Scotland 

 where he laboured during an early stage of his geological career, 

 and where he still has some good friends. From the lettered retreat 

 in which he fitly " cx'owns a youth of labour with an age of ease," 

 the Professor emerges (in your last Number) to rebuke and exhort 

 a " neo-glacialist " for his errors and " fanciful views " regarding 

 non-submergence and the Glacial period. May the heretic be allowed 

 a few words by way of reply ? 



The Glacial deposits of Aberdeenshire consist, it may be repeated, 

 of the following, in ascending, i.e. chronological, order : — 



1. Lower Grey Boulder-clay, derived from the rocks of the district. 



2. Beds of Gravel and Sand, with water- worn pebbles and frag- 

 ments of shells. 



3. Upper Red Clay, with boulders and a few marine forms. 



No. 1 is admitted to be the moraine profonde of an ice-sheet which 

 once extended seaward from the mountainous region on the west. 

 The only questions are regarding 2 and 3. Under what conditions 

 were they formed ? Do they indicate submergence up to, or some- 

 what beyond, the highest level at which they are found ? Or are 

 they also due — under certain changing conditions — to land-ice? 

 The answers to these questions are various: — 



Dr. Jamieson says No. 2 does not, but No. 3 does indicate sub- 

 mergence. 



The Geological Surveyors say No. 2 does, but No. 3 does not. 



Professor Hull says both do. 



The only other possible view is also held, viz. that neither indicates 

 submergence. 



Now, as Dandie Dinmont used to observe, " that makes an unco 

 difference " ; and in such a divided, not to say disorderly, state of 

 opinion on the subject, it seems hardly fair to say, or imply, that 

 anyone trying to throw additional light upon it is animated by an 

 " innate love of change." 



After laying down the grand " rational " rule or principle that 

 " deposits diff'ering in composition and structure from each other 

 should have been formed under different sets of conditions," Prof. 

 Hull goes on to state the "evident succession of conditions " of these 

 three differing superimposed deposits in Aberdeenshire, viz. : 



