1861.] On the Origin of the Parallel Roads of Lochaher, 341 



its own specific law of variation of inductive capacity with respect to 

 distance. With air it varied as the distance, inversely ; but with 

 gutta-percha it was more nearly as the square root ; with India-rubber 

 and white wax it was intermediate between the two ratios, and the 

 law of variation was different with every substance tried. From 

 which it would result that observers who deduced the specific inductive 

 capacity of any material from experiments on half-inch plates, would 

 arrive at very different results from others who operated on inch 

 plates, 



[L. C] 



WEEKLY EVENING MEETING, 



Friday, March 22, 1861. 

 The Rev. John Barlow, M.A. F.R.S. Vice-President, in the Chair. 



Professor H. D. Rogers, F.R.S. F.G.S. &c. 



On the Origin of the Parallel Roads of Lochaher (Glen Roy)^ 

 Scotland. 



The speaker prefaced his account of these curious features in the 

 scenery of Lochaber, by stating that he was induced to recall attention 

 to them from having, during four recent visits to the ground, discovered 

 certain phenomena not hitherto noticed or theoretically considered by 

 any of the able and distinguished observers who have preceded him. 

 Though nearly all the more prominent peculiar characters of the scene 

 have been very skilfully described and discussed by Dr. MacCulloch^ 

 Sir Thomas Dick Lauder, Charles Darwin, Esq., David Milne Home,. 

 Esq., Professor Agassiz, Sir George S. Mackenzie, Robert Chambers, 

 Esq., and others, Professor Rogers has been led by a careful study of 

 the structure of the so-called Parallel Roads, and a perusal of the 

 views of those eminent geologists, to reject all the hypotheses thus far 

 offered in explanation of the terraces as inadequate, and to recognize 

 in the facts about to be developed, a key to a solution of the problem 

 of their origin, which he thinks may prove satisfactory. 



The geographical area of the parallel roads may be defined as 

 embraced between Loch Laggan and Loch Lochy, east of the Great 

 Caledonian Valley. They are chiefly restricted indeed to Glen Spean, 

 Glen Roy, and two or three immediately adjacent smaller glens. One 

 belt of them ranges from near Spean Bridge up the Spean Valley, to 

 beyond the head of Loch Laggan ; another up Glen Roy to the water- 

 sheds at its very head, and a tliird through Glen Gluoi to its head. 



