10 PEOCEEDIK^GS OF THE GEOLOGICAL SOCIETY. [NoV. 8, 



in supporting it, yet they differ so much respecting details that they 

 mutually weaken their cause*. He then considers the specific 

 objections to the theory, especially the existence of terraces similar 

 to the Parallel Eoads, though less perfect, at all levels round our coasts, 

 as well as inland, along every fjord in Norway, and across the whole 

 of Sweden ; these, he says, cannot be accounted for by the ice-dam 

 theory, which therefore treats them as something distinct, whereas 

 they are specifically the same, differing from the Glen Eoy Roads 

 only in being less perfectly preserved. Mr. Watson also remarks 

 that, even in Lochaber, there are banks of water-sorted gravel at 

 various heights and unconnected with any " col" — a fact which 

 cannot be accounted for by the ice-dam theory ; and he mentions 

 particularly two short lines between the two highest roads in Glen 

 Roy, and one in Glen Gluoy at 960 feet, which do not correspond 

 with any " col," also several instances in and near Glen Collarig. 

 He then describes an extraordinary series of terraces on Ben Clinaig, 

 and draws attention to certain gigantic flat-topped heaps of water- 

 sorted gravel, whose levels do not correspond with those of any of 

 the terraces. Mr. Watson therefore asks. What can the ice-dam 

 theory do with all these ? He also states that if the cold was 

 severe enough to supply the ice needed for such a dam, it was too 

 cold in Lochaber for lakes, and vice versa. Glaciers, he remarks, 

 are mere tongues of ice projecting beyond the snow-liae, and the 

 area which these tongues occupy is minute compared with that 

 occupied by the body — the snow-field which contains them ; but 

 the ice-dam theory reverses this relation, and makes the snow-body 

 minute and the tongues gigantic. Mr. Watson also considers that 

 it was impossible for tbe ice to be present at the places indicated, 

 as no glacier from Ben Nevis could reach Glen Roy, and no inde- 

 pendent glacier could be formed in Glen Spean. Another objection 

 is, that no place can be found for the ice-dam theory between the 

 glacial epoch and the present day — a consideration which the author 

 discusses in detail, and he concludes his objections by urging that, 

 as the sea has been all over the Lochaber district to a height of 2000 

 feet, there is no reason for seeking any other agency for the forma- 

 tion of the terraces, nor for introducing such a complex machinery 

 as the ice-dam, where none is needed. 



In supporting the " Marine" theory, on the grounds that the sea 

 has been on the spot, and is capable of performing the work re- 

 quired, Mr. Watson gives the following sketch of the manner in 

 which he conceives the " Parallel Roads " to have been formed : — 

 " We have the land standing probably, in the first instance, rather 

 higher than now, but gradually sinking, though perhaps with 

 pauses. The climate resembled that of North Greenland. The 

 land was swathed in thick ice, which was ever settling downwards 

 to the sea, under that law of regelation which gives to ice its true 

 viscid or plastic character. The whole surface of the rock was being 

 moutonneed and striated. The boulder-clay resulting from the 

 destruction of the earlier soils and looser weathered rock-surfaces was 

 * See Eeader 1864, p. 301 (September 3). 



