464 T. F. Jamieson — Oscillation of Land in Glacial Period. 



formed by the ei'osive action of glaciers, and which has been so ably- 

 expounded by that excellent geologist ; for I have always thought 

 there was a large measure of truth in that theory, and in a paper of 

 my own which was written, before Eamsay's famous article appeared, 

 I had, in fact, maintained that the bottoms of valleys and lakes 

 in Scotland had been powerfully eroded and deepened b3'^ the long 

 grinding of the ice,^ an opinion which I have never seen any reason 

 to change. But allowing Sir Andrew Eamsay to be right in his 

 contention, I see no reason why we should not avail ourselves of 

 this additional mode in which glaciers may have contributed to the 

 formation of lakes, as it may help to get over some of the difficulties 

 that have been felt by Lyell and others in applying Eamsay's 

 explanation to many of the larger and deeper lake-basins. 



We should have thus three different ways in which glaciers have 

 contributed to the formation of lakes, viz. by moraine-dams, by 

 erosion, and by depression. 



In those lakes which are due, or partly due, to depressions caused 

 by the ice in the way I have mentioned, it seems likely that in 

 general they would incline to be deepest towards their upper end, or 

 side next the centre of depression ; and this is a feature that many 

 fjords and Alpine lakes still exhibit, notwithstanding that a long 

 period of silting up has been going on, which has had the effect of 

 filling their upper extremity. Some of the larger lake-basins may 

 be partly due to local depressions caused by the long-continued 

 pressure of the ice in these basins, if special areas of weakness had 

 existed in the strata beneath them, 



I shall conclude with the following quotation from Dr. Croll, in 

 reference to the question I have been considering : — 



" It is a circumstance of some significance that in every part of 

 the globe where giaciation has been found, along with it evidence 

 of submergence of the land has also been found. The invariable 

 occurrence of submergence along with giaciation points to some 

 physical connexion between the two. It would seem to imply, 

 either that the two were the direct effects of a common cause, or 

 that the one was the cause of the other ; that is, the submergence the 

 cause of the giaciation, or the giaciation the cause of the submer- 

 gence." ..." The simple occurrence of a rise and fall of the land 

 in relation to the sea-level in one or in two countries during the 

 Glacial epoch would not necessarily imply any physical connexion. 

 The coincidence of these movements with the giaciation of the land 

 might have been purely accidental ; but when we find that a succes- 

 sion of such movements occurred, not merely in one or two countries, 

 but in every glaciated country where proper observations have been 

 made, we are forced to the conclusion that the connexion between 

 the two is not accidental, but the result of some fixed cause." 



Addendum. 

 Since the foregoing pages were written I have seen another very 

 ingenious attempt to explain the evident connection that exists 

 1 Quart. Journ. of the Geol. Soc. vol. xviii. p. 179, Feb. 1862. 



