VIII 



THE PAEALLEL ROADS OF GLEN" ROY* 



THE first published allusion to the Parallel Eoads of 

 Grlen Roy occurs in the appendix to the third vol- 

 ume of Pennant's "Tour in Scotland," a work 

 published in 1776. "In the face of these hills, " says this 

 writer, "both sides of the glen, there are three roads at 

 small distances from each other and directly opposite on 

 each side. These roads have been measured in the com- 

 plete parts of them, and found to be 26 paces of a man 

 5 feet 10 inches high. The two highest are pretty near 

 each other, about 50 yards, and the lowest double that 

 distance from the nearest to it. They are carried along 

 the sides of the glen with the utmost regularity, nearly 

 as exact as if drawn with a line of rule and compass." 



The correct heights of the three roads of Glen Roy 

 are respectively 1,150, 1,070, and 860 feet above the sea. 

 Hence a vertical distance of 80 feet separates the two 

 highest, while the lowest road is 210 feet below the 

 middle one. 



These "roads" are usually shelves or terraces formed 

 in the yielding drift which here covers the slopes of the 

 mountains. They are all sensibly horizontal and there- 

 fore parallel. Pennant accepted as reasonable the ex- 



^ A discourse delivered at the Royal Institution of Great Britain on June 9, 

 1816. 



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