James Geikie — On Changes of Climate. 105 



lY. — On Changes of Climate DURiNa the Glacial Epoch. 



By James Geikie, F.E.S.E. 



District Surveyor of the Geological Survey of Scotland. 



Fourth Paper. 

 {Continued from the February Ntcmher,p. 69.) 



IN my last communication to the Magazine I made an attempt to 

 correlate the Scottish Glacial deposits with the equivalent accu- 

 mulations in Switzerland, Northern Europe, and North America, my 

 purpose being to show that the same order of succession holds good 

 in all those regions where the " Drifts " have been examined, and 

 that in each case there is no proof whatever of any warm period 

 having intervened since the deposition of the clays with Arctic shells 

 and the decrease and disappearance of local glaciers. In the present 

 and a subsequent paper I propose to treat of the superficial deposits 

 of Ireland and England, more especially those of the latter country. 

 It is with some diffidence that I approach this discussion, because I 

 feel that in venturing to dissent, as I must do, from opinions some- 

 what generally received, I lay myself open to a charge of presump- 

 tion. Yet it is just possible that one working in a country where 

 the drift-deposits are neither very complex nor confused, and where 

 the succession of events can be made out with tolerable certainty, 

 may be able to let in some light upon the obscurity which it cannot 

 be denied still clouds the history of the later geological changes in 

 England. At all events it can do no harm to make the attempt. 



So long as the geologist confines his attention to the mountainous 

 districts of England, the sequence of the glacial deposits appears to 

 be sufficiently clear. The lowest member of the series consists of 

 a stony clay, above which, in some districts, come sheets and 

 mounds of sand and gravel and erratics, while in certain valleys 

 there occur heaps of loose moraine matter. Prof. Eamsay long ago 

 interpreted the order of events for Wales thus : a period of vast 

 glaciers, followed by one of great submergence, and this again 

 succeeded in time by re-elevation and a second period of glaciers. 

 But when the geologist continues his researches into the low grounds 

 that sweep outwards from the base of the mountains a number of 

 perplexing details come in to worry him. He finds not one stony 

 clay only but several with intervening stratified deposits ; and in his 

 endeavours to correlate these, bed for bed, with other glacial accu- 

 mulations, many difficulties arise. The day is yet distant when we 

 can hope to see this hard task of correlation accomplished ; and I 

 certainly do not feel myself qualified to decide on a minute or detailed 

 classification of the English drifts. All I mean to attempt is to 

 point out in a general way what appear to me to be the equivalents 

 of those divisions under which I have grouped the Scottish deposits. 

 If the reader will take the trouble to refer to my last paper in the 

 Magazine, he will observe that, in the several tables of Scottish and 

 foreign glacial deposits, a series of marine beds (3) occurs after the 

 Scottish (1) " Till, boulder-earth and clay," and (2) " moraine 

 rubbish," and likewise after the Scandinavian (1) "stony clay, etc.," 



