OF THE PARALLEL ROADS OF LOCHABER. 
677 
say, than 3,000 feet, would not have allowed of the maintenance of the large blockading 
glaciers, or else, if even not lower than 1,500 to 2,000 feet, would not have allowed 
of the existence of such large bodies of open water. 
The snow-fields supplying the Alpine glaciers extend over a zone 4,000 to 5,000 feet 
in height. In Norway, this zone is not more than 2,000 to 3,000 feet, but compensa¬ 
tion is found in the great superficial extent of the fields. Notwithstanding this, the 
glaciers in both countries are of much smaller size than those attributed to Glen Treig 
and Glen Arkaig. To furnish such glaciers it is scarcely possible to suppose that the 
difference between the mountain summits and the level of the- snow-line could have 
been less than in the countries referred to, and if not less, instead of open lakes, glaciers 
must have filled all these glens of the mountains alike to the north and the south of 
Strath Spean. 
If on the contrary the lakes were formed during the retreat of the glaciers (as would 
be implied by the retreat of the Glen Treig glacier from Glen Glaster col), then it is 
not possible to suppose that the main ice-barriers, no longer fed by fresh supplies, could 
have existed during the great length of time required on this hypothesis for the for¬ 
mation of the roads by erosion and of the mounds by delta deposition. 
View t s of the Author. 
Although I consider there are the foregoing objections to the exposition of the 
glacial theory so ably propounded by Mr. Jamieson, I believe with him and with 
Agassiz that this theory affords the most satisfactory solution of the problem, but I 
would suggest a somewhat different interpretation in explanation of the build of the 
barriers and the formation of the “ roads.” 
I have before mentioned that Agassiz, after showing the great extent of ice-action 
in Scotland, sought to explain the origin of the lakes of Macculloch and Dick- 
Lauder by a system of glaciers issuing from Glen Arkaig, Glen Treig, and from the 
side of Ben Nevis, and that later observations had led Scotch geologists not only to 
verify the intensity of the first great glaciation of the country, but also to conclude 
that it was succeeded by a milder period, when a great submergence of the land took 
place, and then again by a second cold period during which the chief mountain ranges 
formed centres of local radiating glaciers of limited extent. 
Dismissing, for the reasons before assigned, the hypothesis of local glaciers, I fall 
back upon the original theory with the development given to it by more recent 
research. I would attribute the origin of the Lochaber lakes—not to the incoming 
of a second cold period and to special glaciers damming back the streams, and so 
giving rise to lakes of which the “ roads ” are the old shores formed by the long- 
continued action of the lake waters,—-but to causes of a more transient character con¬ 
nected with a phase of the early or first glacial period.* I feel that this view is not 
* Tf it should be proved that the second glaciation was of extent equal or nearly equal to that first 
