TWO GLENS AND THE AGENCY OF GLACIATION. 201 



the road from Inveraray to Lochgilphead has been made, in order to avoid ground which 

 is too precipitous at some places on the shores of Loch Fyne. The summit level 

 of the easier gradients afforded by this glen is only 300 feet above the sea, and 

 along its floor there are stretches of land which lie very low. These are generally occu- 

 pied by mosses, and they are almost entirely free from boulder-stones. But the top and 

 sides of the somewhat sudden rise, which conducts us to the summit level, are, on the 

 contrary, loaded with transported blocks of stone — some of them more or less rounded, 

 but many others presenting rough and angular outlines. The accumulations of these 

 which have been left on the more prominent knolls and elevations have all the appearance 

 of having been stranded where they now lie by floating ice, which came from the N.E., 

 and, in passing, grounded on the first obstructing rocks and shoals which arrested their 

 progress through the straits. The same explanation, and no other, is suggested by a 

 series of similar blocks which lie on a hill some 500 feet above the same glen. That hill 

 happens to be so situated as to break and obstruct a parallel hollow behind the first 

 ridge to the north, and it raises its steep front exactly in such a position as to front and 

 arrest any agency, whether water or ice, which could have moved south-westward along 

 the hollow. Accordingly, this obstructing hill is covered with great angular blocks of 

 stone, just as it would naturally be if it stood directly in the way of a current from the 

 N.E., which carried along with it floe-ice laden with stones from the N.E. Many 

 years ago I took the late Sir David Milne Home to see this remarkable example 

 of the transported boulders, to which he devoted so much attention, and he was much 

 struck by its significance and its only possible interpretation. 



But even more decisive than all other facts, in my opinion, of the nature of the 

 agency which carried the blocks, are the cases of what are called " perched boulders," on 

 the very tops of many of the lower ridges, and even of the highest ridge between Loch 

 Fyne and Loch Awe. Some of those are very remarkable, both as to great size, as to 

 angularity, and as to position. They are so situated that it is impossible to conceive how 

 any other agency than floating ice can have placed them where they are. They 

 cannot have rolled down from higher ridges behind — because their material is generally 

 different, and also because they would have had to roll up steep slopes, and the impetus 

 which would be required for this cannot be supposed to have stopped exactly at the top. 

 Moreover, many of them are not rolled at all, and some are conspicuously angular. On 

 the other hand, such situations are precisely such as would be the natural places, or 

 points, of deposit by ice floating on a sea over an emerging land. Every prominence 

 which is now a ridge must have been a shoal, or ledge of reef, in such a sea at some 

 given time in the process of emergence. Floes, or bergs, stranded on such reefs would 

 necessarily drop their burdens upon these when they melted, and such deposit would 

 always be upon the very top, or close to it. 



There is yet another very clear indication of the nature of the glaciating agency in the 

 appearance presented by the hills on the tops of which these perched blocks are situated. 

 In one conspicuous instance, not far from the town of Inveraray, a hill which is crowned 



VOL. XXX VII [. PART I. (NO. 4). 2 D 



