THE PAKALLEL ROADS OF GLEN BOY. 279 



At first, as in the case of ancient glaciers, through 

 sheer want of .capacity, the mind refuses to take in 

 revealed facts. But by degrees the steady contem- 

 plation of these facts so strengthens and expands the 

 intellectual powers, that where truth once could not 

 find an entrance it eventually finds a home. 1 



A map of the district, with the parallel roads shown 

 in red, is annexed. 



LITERATURE OF THE SUBJECT. 



THOMAS PENNANT. A Tour in Scotland. , Vol. iii. 1776, p. 394. 

 JOHN MAcCuLLOCH. On the Parallel Roads of Glen Roy. Geol. 



Soc. Trans, vol. iv. 1817, p. 314. 

 THOMAS LAUDER DICK (afterwards SIR THOMAS DICK-LAUDER, 



Bart.) On the Parallel Roads of Lochaber. Edin. Roy. Soc. 



Trans. 1818, vol. ix. p. 1. 

 CHARLES DARWIN. Observations on the Parallel Roads of Glen 



Roy, and of the other parts of Lochaber in Scotland, with an 



attempt to prove that they are of marine origin. Phil. Trans. 



1839, vol. cxxix. p. 39. 

 SIR CHARLES LYELL. Elements of Geology. Second edition, 



1841. 

 Louis AGASSIZ. The Glacial Theory and its Recent Progress 



Parallel Terraces. Edin. New Phil. Journal, 1842, vol. xxxiii. 



p. 236. 



1 The formation, connection, successive subsidence, and final 

 disappearance of the glacial lakes of Lochaber were illustrated in 

 the discourse here reported by the model just described, constructed 

 under the supervision of my assistant, Mr. John Cottrell. Glen 

 Gluoy with its lake and road and the cataract over its col ; Glen 

 Roy and its three roads with their respective cataracts at the head 

 of Glen Spey, Glen Glaster, and Glen Spean, were all represented. 

 The successive shif tings of the barriers, which were formed of plate 

 glass, brought each successive lake and its corresponding road into 

 view, while the entire removal of the barriers caused the streams 

 to flow down the glens of the model as they flow down the real 

 glens of to-day. 



