The Parallel Roads of Glen Roy. — Upham. 295 
(excepting that Glen Gloy and Glen Spean have each only 
one), which were the chief geological attraction and object of 
pilgrimage for me in the British Isles. 
Traditionally called roads of the mythical hero Fingal and 
his hunting parties, these mysterious, delicately traced, level 
lines far up the valley sides were long ago examined by Alac- 
culloch, Dick Lauder, Milne-Home, and others, who ex- 
plained them as shores of lakes once held in these narrow 
mountain glens by barriers of detrital m.atter which afterward 
Vv'ere washed away. (3n the other hand. Chambers, Darwin. 
Nicol, and others, from their examination, thought them to 
be marine shore lines. 
Agassiz, in 1840, visiting the district with Dean lUickland, 
supplied the key of the true interpretation of these shores in 
the suggestion that lakes were held at the levels of the Parallel 
Roads because the lower parts of the glens were obstructed 
by glaciers. This view has been elaborated by Jamieson, 
Prestwich, James Geikie, and others, ascribing these lakes to 
local glaciers of the mountain valleys, as in the case of the 
Merjelen See on the east side of the Great Aletsch glacier in 
the Alps. To my mind, however, this seems an inadequate 
expression, far less acceptable than the latest discussion and 
explanation given by Jamieson in 1892, in which the Lochaber 
glacial lakes are referred to the barrier of the waning and 
southwestwardly receding remnant of the general Scottish 
ice-sheet.* 
The glacial lakes Roy and Gloy (as I may name them for 
the present description) are the earliest recognized examples 
of their class, which comprises many anciently ice-dammed 
lakes now known and partially mapped in the great valleys 
and basins of Scandinavia east of its mountainous watershed 
but west of the ice-shed during the Glacial period. In Amer- 
ica, on ^ much grander scale, we have the glacial lakes Agas- 
siz, Saskatchewan, Souris, and Minnesota, whose drainage 
was turned by the waning ice-sheet into the upper Mississip])i 
river; and the complexly interrelated glacial lakes Duluth, 
Chicago, Saginaw, Maumce, Whittlesey, Warren, Algonquin, 
♦Quart. Jour. Geo!. Soc, XLVIII, 5-28. This paper has many biblio- 
graphic, references to the extensive literature of the Parallel Roads, for 
which also consult William Jolly, in Nature, XXII, 68-70, May 20, 1880. 
