1879.] 



of the Parallel Roads of Lochaber. 



7 



portion of the glacier ascended the opposite hill to the Col of Glen 

 Glaster, while another portion passed down the valley blocking Glen 

 Roy, and a third portion travelled up the valley eastward to the Pass 

 of Makoul, and thence into the valley of the Spey. 



The " roads " were, he considers, formed by long-continued shore 

 action at each successive level of the lake, that level being determined 

 by the height of the cols over which the lake waters escaped. In 

 proof of the long duration of the lakes, Mr. Jamleson refers to the 

 dimensions of the "roads," and the large size of the mounds at the 

 junction of Glen Turret and Glen Roy, and of that at the entrance of 

 the Gulban in Glen Spean, which mounds he considers to be deltas 

 formed by the respective streams flowing into the old lakes. 



To these views it has been objected, by Mr. Milne-Home and others, 

 that it is difficult to conceive the glens to the north of the Spean 

 Valley to have been filled with water while at the same time those on 

 the south were filled with ice, and he advocates a detrital barrier 

 formed of clay, sand, and gravel, by marine origin, when the sea stood 

 some 3,000 feet higher than at present. There is, however, a want of 

 evidence of marine action, and it is difficult to imagine that beds 

 of loose clay, sand, and gravel, formed in this way, could be water- 

 tight, while there is a further difficulty in accounting for the origin of 

 the materials and the subsequent removal of such vast barriers. 



Professor ISTicol, also, has pointed out that, had lakes existed in Glen 

 Gluoy, Glen Roy, and Glen Spean for the length of time required to 

 form the "roads" by erosion, and to accumulate the deltas, the cols by 

 which their surplus waters escaped during those periods must have 

 cut a channel in the rocks in the same way that the rivers (which now 

 represent the same drainage, or probably less) have since excavated 

 their channels in the present valleys ; whereas, although there are 

 indications of water-wear in the passes, nothing like a defined river 

 channel exists. Professor Mcol has attempted to explain the facts 

 on the theory of the " roads " being sea beaches. But the absence of 

 corresponding beaches outside those glens — the limitation of the 

 highest "road " to Glen Gluoy — and of the second and third to Glen 

 Roy, and the want of corroboration by marine remains in any of the 

 various drift beds, renders the marine hypothesis inadmissible. 



Sir John Lubbock, looking at the form of the "roads" which has 

 been described by Macculloch as parallel layers applied in succession 

 to the sides of the hills, contends that such a form is incompatible 

 either with the heaping up of materials on a shore line, or with their 

 removal by erosion, as in the one case a notch and in the other a pro- 

 jecting ledge in the hill side would be formed, whereas, with one 

 exception of a superior talus pointed out by Macculloch, no such 

 structure exists. Sir John points out that a parallelism between the 

 slopes may, however, have been formed by wavelet action, in con- 



