1863.] JAMIESON' — PARALLEL ROADS OF GLEN ROY. 235 



resemblance to those described and figured by Mr. Salter, from the 

 Lingula- flags, as the trail of Hymenocaris vermicaudat* 



The track of an apparently smaller Crustacean (?) (fig. 4) consists 

 of ovate prints, stamped in a more regular serial order. In none of 

 these is there any evidence of tail-markings, in the existence of any 

 central rib or ridge, like that which appears in the trail of the Cli- 

 mactichnites of the Potsdam Sandstone, or in that of recent Limuli. 

 Long, slender impressions also appear upon the sandstone-surfaces, 

 having coriaceous interiors, and being probably the casts of Sertu- 

 larian zoophytes. 



The Bouldon quarry is certainly the richest exposure of these 

 track-bearing sandstones, and should therefore be carefully worked ; 

 for in the absence or, at least, paucity of organic evidence as to the 

 Crustacean fauna of the Old Red Sandstone, we are forced to content 

 ourselves with the examination of secondary and indirect witnesses. 



3. On the Parallel Roads of Glen Roy, and their Place in the 

 History of the Glacial Period. By Thomas F. Jamieson, Esq., 

 F.G.S., Fordyce Lecturer on Agriculture in the University of 

 Aberdeen. 



[Plate X.] 



Contents. 



1 . General appearance of the ' Roads.' 



2. The different theories. 



a. General review of the theories. 



b. The marine theory. 



c. Agassiz's theory. 



3. Place of the Parallel Roads in the history of the Glacial period. 



a. Relation to the period of chief submergence — Eskers and Osar. 



b. Relation to the 40-feet Raised Beach of Argyleshire and to the 



' Raised Beaches ' of Norway. 



4. Height and horizontality of the Parallel Roads. 



5. Difficulty as to a dam of ice. 



6. Central Asia during the Glacial period. Its glacial lakes and inland 



seas. 



7. Intensity of glacial action in the West Highlands 



8. Recapitulation. 



§ 1. General appearance of the Roads. 



In the Highlands of Scotland there is a district called Lochaber, 

 embracing a range of bare hilly country in the south-west of Inver- 

 ness-shire. In this district lies the little valley of Glen Roy, famous 

 for certain curious features in its scenery. 



High up on both sides of this glen three lines appear, one above 

 another, and some distance apart. They are perfectly level, strictly 

 parallel, and run along the bare mountain-sides as neatly as if drawn 

 with a ruler and pen. They sweep round the shoulders of the hills, 

 wind into their side-recesses, and encircle all the upper part of the 

 valley, everywhere preserving the same rigid parallelism and the 

 same undeviating horizontality. A sight so curious and unusual 

 * Quart. Journ. Geol. Soc. vol. x. p. 208. 



