3 io THE POPULAR SCIENCE MONTHLY. 



Lochaber, Inverness-shire. On both, sides of tbe steep, narrow glen 

 through which the Roy runs, there are three perfectly horizontal and 

 parallel roads, directly opposite on each side, those on one side corre- 

 sponding exactly in elevation to those on the other. They are re- 

 spectively 1,150, 1,070, and 860 feet above the sea, and are formed as 

 shelves in the yielding drift which covers the sides of the mountains. 

 They usually slope somewhat from the hill, and vary in width from 

 one to twenty yards. The two highest stop abruptly at different 

 points near the mouth of Glen Roy, although no barrier now remains 

 to show any reason for it. At some points the grass on the shelves 

 differs from that which is above and below, and, as the roads lie in the 

 midst of heather-covered hills, the absence of the dark shrub from 

 them adds greatly to their conspicuousness. 



The terraces were originally supposed to have been made for the 

 heroes whose deeds have been sung by Ossian. A less romantic view 

 was that " they were designed for the chase, and were made after the 

 spots were cleared in lines from wood, in order to tempt the animals 

 into the open paths after they were roused, in order that they might 

 come within the reach of the bowmen who miffht conceal themselves 

 in the woods above and below." In 1816 Playfair believed them to be 

 aqueducts for artificial irrigation. In 1817 Dr. MacCulloch discussed 

 the probability of there having been lakes embosomed in Glen Roy 

 at one time, and supposed that these roads were the margins of the 

 lakes. It remained, however, for Sir Thomas Dick-Lander to bring 

 forward the facts of the subject, and place them in a scientific light. 

 Adjacent to Glen Roy is Glen Gluoy, along the sides of which there 

 is a single terrace or road, having the same elevation on each side of 

 the valley, and similar in all respects to the roads of Glen Roy. 

 Wishing to see whether these two sides would be united at the head 

 of the glen, and in what manner, he followed them into the mountains. 

 As the valley gradually rose, he observed the shelves approaching 

 each other more nearly; and finally, at the head of Glen Gluoy, he 

 discovered a water-shed of exactly the same elevation as the road 

 which swept around the glen. This height was found to be 1,170 feet, 

 or 20 feet higher than the upper road of Glen Roy. From this water- 

 shed he passed through a lateral branch-valley to Glen Roy, de- 

 scended to the highest road, and followed it up the glen as he had 

 pursued the previous road. In the same manner he came upon a 

 water-shed looking into Glen Spey, and of precisely the same eleva- 

 tion as the road. After this he dropped clown to the lowest shelf, 

 and followed it to the mouth of the glen. It did not end here, how- 

 ever, but doubled around the hills, and ran along the sides of the 

 mountains which flank Glen Spean. Continuing eastward, he observed 

 the Spean Valley gradually approaching the road until the two were 

 on a level, when, as in the other cases, he discovered a water-shed. 



From these facts, convinced that water alone could have produced 



