2'dti PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Jail. 21, 



strongly arrests the attention of the spectator. These lines look all 

 too mathematically regular for the work of nature, and yet they 

 seem on too grand a scale to have been traced by mere mortal hands. 

 One might fancy he had wandered into fairy -land, and caught the 

 genius loci practising geometry on the hill-sides. No wonder then 

 that the imaginative Highlanders ascribed them to the ancient heroes 

 of their race, and saw in these lines the hunting-roads of Fingal and 

 his companions, that they had made for chasing the deer. In their 

 native language they call them ' Casein,' or i the footpaths ' ; for, on 

 climbing up to them, they are each found to consist of a green ledge, 

 or narrow terrace, jutting out from the face of the hill ; so that they 

 actually serve as convenient tracks for walking on. 



Pennant, I believe, was the first to draw attention to these sin- 

 gular appearances, and, before they were well known, various con- 

 jectures were started to account for them ; but an attentive ex- 

 amination of the district by Dr. Macculloch* and Sir Thomas Lauder- 

 Dickf at once showed that these " Parallel Roads" must have been 

 formed by water that had once filled the glen to the height of the 

 uppermost line, and had subsided step by step till it • reached the 

 lowermost, leaving its water-mark in these shelves as the traces of 

 its ancient shore. But then arose the difficulty, how to account for 

 the water. As you walk down the glen and draw near its lower 

 extremity the two upper lines vanish, and no sign of them again 

 appears ; in like manner the lowest line, which now becomes more 

 faint, after being traced into the larger valley called Glen Spean, of 

 which Glen Roy is a branch, also vanishes before reaching the mouth 

 of the Spean valley, leaving no trace of any barrier to account for 

 the retention of a lake to the necessary height ; and so deep and 

 wide is the gap that would have to be filled up, that any attempt to 

 account for the gradual wearing down, or wasting away, of any mass 

 of earth or rock that could have occupied the void strikes one at 

 once as utterly hopeless. Another little valley, called Glen Gluoy, in 

 the immediate neighbourhood, and branching off from the Great 

 Valley of the Caledonian Canal, is also marked in a somewhat simi- 

 lar though less striking manner. Here only one decided line is 

 seen, although there are likewise some faint traces of a lower one. 

 This Glen Gluoy line is a little higher than any of those in Glen Roy, 

 and towards the mouth of the long narrow valley, which resembles 

 a profound trench cut among the hills, it seems to reach the very 

 brow of the ridge, and then ceases ; but the flanks of the hills on 

 either side show not a vestige of any protruding mass that could 

 have filled up the deep gulf between. There is no narrow rocky 

 gorge, no mound of earth, nothing, in short, but the smooth slopes 

 of grass and heather, with the sheep nibbling quietly on the hill- 

 side. Had any barrier of earth or rock existed here in times so 

 recent as these shelves would appear to indicate, it is incredible it 

 could have been so completely cut away as to leave no trace what- 

 ever of its former existence. The question then occurs, If these 

 are the marks of old lakes, what could have retained them ? 



* Gcol. Trans, ser. 1. vol. iv. p. 314. t Eclin. Roy. Soc. Trans?, vol. ix. 



