PRESIDENTIAL ADDKEftS. 555 



regretted iu view of the curious circuuistauce, already couuuouted on, lliat not 

 a single iuterglacial peat-bed has ever been detected iu all tbe length of our 

 unrivalled coast sections. As the matter stands, we are, I think, justified in 

 regarding these Scottish land deposits as an insecure foundation for the wide- 

 reaching conclusions which have been drawn from them. 



The hypothetical Helvetian submergence of Scotland rests on similar evidence 

 to that which has been already discussed in the case of the English and Irish 

 drifts. Its limits are not marked by any shore-line, and, indeed, are acknowledged 

 to be uncertain by Professor Geikie himself. Some patches of marine sediments, 

 containing a molluscan fauna that is generally distinctly boreal, have been found, 

 sometimes beneath, sometimes above, and sometimes intercalated with the boiilder- 

 clay ;_ but it is especially noteworthy that these patches all occur along the outer 

 margin of the country, contiguous to the sea-basins, and that a belt of shelly 

 boulder-clay, denoting the dispersal of pre-existing marine deposits, occupies a. 

 similar position in many places. From my knowledge of the conditions under 

 which the patches of marine detritus occur in the Basement Clay of East Yorkshire, 

 I think it most probable that the shell-beds at Clava, Inverness-shire, and in 

 Kintyre,' which lie at or near the base of the boulder-clay, represent the disturbed 

 sea bottom of early glacial times ; while that at Chapelhall, near Airdrie, appears 

 to have been a very small isolated patch iu the boulder-clay, as no further trace of 

 it was found in the search carried out by a Committee of the Association. These 

 beds are certainly inadequate as proof of a mild interglacial submergence. 



In_ Eastern Aberdeenshire and the neighbouring coast-lands the drifts have 

 been indefatig,ably studied by that honoured veteran among glacialists, Mr. T. F. 

 Jamieson.2 The general succession of the drifts is remarkably similar to that in 

 East Yorkshire, and the evidence for the mild Helvetian Epoch is almost exactly 

 that which we have already considered in England, Ireland, and the Isle of Man, 



' Neudeckian' {Third Interglacial)/ Mecklenhiirgian' {Fourth Glacial), 'Lower 

 Forestian ' {Fourth Interglacial), ' Loioer Turharian ' {Fifth Glacial), ' Upper 

 Forestian ' {Fifth Interglacial), and ' Ui)per Turbarian ' {Slclh Glacial) Epochs. 



According to the terminology usually adopted by British geologists, the Glacial 

 Period came to an end with the final disappearance of the confluent ice-sheets 

 from our lowlands, and the events which followed are classed as Post-glacial. 

 But the latter period has been sufficiently long to cover some extensive changes 

 in the relative distribution of land and sea in Western Europe, accompanied"bv 

 modifications of climate tending on the whole toward progressive amelioration. 

 To classify these changes into a further series of three interglacial and three 

 glacial epochs, as Professor J. Geikie has done, is, so far as the British evidence is 

 concerned, mainly a question of personal opinion as to the arrangement of the 

 sequence and the application of terms. As we have already seen, the interpreta- 

 tion of the North European sequence, on which Professor Geikie greatly depends 

 for proof of these later epochs of glaciation, has been challenged abroad even by 

 geologists favourable to the general principle of interglacial epochs ; and we are, 

 therefore, the more fully entitled to question its application in this country. 



In Scotland, Professor Geikie claims that the ' Alecklenburgian ' glaciation was 

 marked by the reappearance of glaciers in the mountain valleys, and by tlieir later 

 extension over part of the neighbouring lowlands iu the form of ' district ice- 

 sheets.' After these had melted away during the 'Lower Forestian ' intero-lacial 



' ' Report on tlie Character of tlie High-level Shell-bearing Deposits at Clava, 

 Chapelhall, and other Localities.' Rep. Brit. Assoc, for 1893 (Clava), pp. 483-5U : 

 ibid, for 1894 (Chapelhall), pp. 307-315 ; ibid, for 1896 (Kintyre), pp. 378-399. 



•^ Mr. Jamieson's latest papers : ' The Glacial Period in Aberdeenshire and the 

 Southern Border of the Moray Firth,' Quart. Journ. Oeol. Sac., vol. Ixii. (1906), 

 pp. 13-39, and ' On the Raised Beaches of the Geological Surrey of Scotland,' Geol. 

 Mag., dec. v., vol. iii, (1906), pp. 22-25, contain an excellent descriptive summary and 

 discussion of the glacial sequence. 



