240 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 21, 



little map, would not serve his purpose, inasmuch as the lowermost 

 line extended beyond it. 



Here then was no approach to agreement ; and Sir Charles Lyell, 

 in summing up his lucid sketch of the controversy, correctly ex- 

 pressed the state of the case when he said, " This problem, like many 

 others in geology, is as yet only solved in part \ a large number of 

 facts must be collected and reasoned upon before the question can 

 be finally settled.''* 



These words will serve as an excuse for reopening the discussion. 

 The matter is one of interest, not merely as a local curiosity. It is 

 so connected with the history of the last great geological changes 

 that to leave it unsettled is not only an opprobrium to our geologists, 

 but is also a confession of our inability to give any clear account of 

 these events. Unsolved it is a source of perplexity and confusion, 

 whereas, if once fairly understood, it would help us much in unra- 

 velling the history of the great ice-period. 



Accordingly Sir Charles Lyell suggested to me, when in London in 

 1861, to visit the district in order to get more evidence on the sub- 

 ject ; and this was further urged by Mr. Darwin, who candidly ad- 

 mitted that, not having glacier- action in view when he was there, he 

 had since, to some extent, doubted his own observations. He fur- 

 nished me with some useful maps and memoirs bearing upon the 

 problem, and likewise indicated several points worthy of particular 

 attention. 



Having myself been long desirous of seeing these curious lines, I 

 took the first opportunity I had of carrying out these suggestions ; 

 and to that intent devoted a holiday ramble to Glen Roy in August 

 1861, and another in July of the following year. 



b. The marine theory. — The first good sight I had of the parallel 

 roads was from the shoulder of Bohuntine Hill, in the lower part of 

 Glen Roy, near a place known as " the Gap." Looking up Glen 

 Roy from this station, the three lines are beautifully seen, running 

 along both sides of the glen with unbroken regularity. Here I was 

 much impressed with the extreme neatness and precision of the 

 markings. These clear narrow lines seemed to me altogether too 

 fine and neat for the effect of a sea-margin, subject as it is to a 

 continual rise and fall of tide. On the west of Argyleshire there 

 is a fine old coast-line, about 40 feet above the present, which 

 every one admits to be due to the sea, but it has a very different 

 character from these Roads of Glen Roy. 



Here are no cliffs, no caves, no banks of well-rolled shingle, no 

 rude notching of the rock. Wherever the lines pass across a rocky 

 face of gneiss, they die out or become so faint that they can scarcely 

 be traced. This fact has been allowed by all the visitors who have 

 attended to it, by Macculloch, Lauder-Dick, and Darwin. In the 

 narrower land-locked parts, where the water had been least ruffled 

 by the prevailing south-west wind, the little terraces, of which these 

 lines consist, jut sharply out from the hill, almost perfectly flat and 



* Manual of Geology, 3rd edit. p. 89. 



