1867.] LUBBOCK PARALLEL ROADS OF GLEN ROY. 85 



which no explanation has yet been afforded. In those placeS, how- 

 ever, where the roads are narrower than usual, their inclination is 

 also more considerable *. 



The shelves " contain fewer well-rounded pebbles at the greater 

 heights than would be expected on any theory of their origin " f. 



For several miles " these three lines pass along both sides of 

 Glenroy with scarcely any interruption "X- 



^' The lines are not grooves " § ; they resemble sections of parallel 

 layers applied in succession to the face of the hill" ||. This is a 

 point of great importance. " In only one instance," says Maccul- 

 loch, "is there a slope resembling a superior talus, .... 

 while in no instance did I perceive the marks of an inferior one." 

 The true relation of the shelves to the hill is shown in the accom- 

 panying diagram, which was given by Dr. Macculloch, and has 



Fig. 1. — Section of the Parallel Roads of Glen Bx)y, after 

 ** Macculloch. 



a h, present slope. 



been accepted and copied by Mr. Darwin, Mr. Chambers, and Sir C. 

 Lyell. It will be observed that the general slope of the hiU^is the 

 same above and below the road. In fact there are but two slopes, one 

 that of the hill, the other that of the roads. Both vary somewhat 

 in different parts of the glen, preserving, however, about the same 

 ratio to one another. 



Finally, the lines " entirely disappear when crossing any part 

 which is gently inclined " ^. 



* Macculloch, p. 320, t Darwin, p. 41 . 



X Chambers, Ancient Sea Margins, p. 97 ; Darwin, p. 75, 

 § Jamieson, Quart. Journ. Greol. See. vol. xix. p. 233. 

 II Macculloch, p. 337. ^ Darwin, p. 40. 



H 2 



