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IV. — Two Glens and the Agency of Glaciation. By His Grace 

 The Duke of Argyll, K.G., K.T. (With a Map.) 



(Read 1st April 1895.) 



The group of questions which are connected with the Glacial Age seem to me to be 

 among the most interesting and the most difficult in the whole science of geology. 

 They include the question of Time — since, perhaps, the only hope we have of even reach- 

 ing any unit of time in geological changes lies in the phenomena of the Glacial Age # 

 The question of the comparative slowness or suddenness of great physical changes is not 

 less directly involved. Bound up with this again is the question of the sudden or slow 

 destruction of the extinct forms of life, and the introduction of new forms to replace 

 them. The connection between Cosmical and Terrestrial causes of change comes directly 

 into our view, and then the nature and operation of the terrestrial forces which were 

 brought into play. I am very sceptical as to many of the solutions which have been 

 proposed for most of these questions, and still more for the theories which profess to 

 answer them as a whole. There is nothing to be done but to accumulate evidence in 

 detail — to observe facts well, that is, completely — and avoid looking only at such of them 

 as tell in favour of some preconceived hypothesis. 



It is one of the great delights of the physical sciences that the questions they concern 

 are inexhaustible. I do not mean only that each one of those questions always leads on 

 to some other. I mean that even each question in itself is always turning up in some 

 new light, or new aspect, even when we may have been long familiar with the phenomena 

 which suggests it. The truth is that the very fact of such familiarity is perpetually the 

 cause of some fresh departure, because it extinguishes that sense of surprise, and puts 

 even that natural curiosity to sleep, out of which all intelligent questioning of Nature 

 comes. Things which we see every day are precisely those which are most apt to conceal 

 their lessons from us — and it is only, perhaps, some accidental suggestion that awakes us 

 to obvious interpretations which we had never thought of before. Such, I confess, is 

 the experience I have lately had concerning a question in geology which I have long- 

 regarded as of the highest scientific interest. I refer to the physical agency, and the 

 physical conditions under which what is known as the glaciation of our West Highlands 

 was effected. The science of geology presents no more perplexing problem. Living, as 

 I do, in a country where the marks of glaciation are abundant, but at the same time far 

 from universal over the whole surface, I have long come to the conclusion that one agency 

 widely believed in cannot possibly have been the producing cause. It cannot have been 

 what is called an Ice Sheet, or an Ice Cap, or ice in any form, under whatever name it is 



VOL. XXXVIII. PART I. (NO. 4). 2 C 



