THE PARALLEL ROADS OF GLEX ROY. 227 



panding knowledge upon the intellectual organ itself. 

 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 contempt 

 tion of these facts so strengthens and expands the in- 

 tellectual powers, that where truth once could not find 

 an entrance it eventually finds a home.* 



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 LAUDEB DICK (afterwards SIR THOMAS DICK-LAUDEK, 



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



Trans. 1818, vol. is. 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. 



* 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, con- 

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

 (Men 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 Glon Spey, Glen Glaster, and Glen Spean, were nil 

 represented. The successive shiftings 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. 



