MACKIE THE PARVLLEL ROADS OF GLE^ ROY. 
127 
junction of the Spey and the Truim takes place, it is uot difficult to 
conceive that it was worn down by the action of the waters of the Spey, 
causing tlie drainage of the highest level in Grlen Eoy ; or else after 
that drainage had taken place by the failure of some other barriers. 
The flow of the Spey and the Eoy would then follow the directions of 
the intermeduite ground, and the present courses of these rivers, as far 
as they were then free, would be established. If we now turn to the 
western side of Glen Eoy, and examine tlie elevation and direction of 
the ground at its junction with the vale of the Lochy, we shall see 
that both Glen Eoy and Glen Spean bear one common water-mark or 
* line,' and unite in one common wide valley before they join the vale 
of the Lochy. The imaginary barrier must therefore be removed at 
least to that part of this valley where the ' lines ' terminate, whicli 
is to a point beyond Teindrish. . . . But the form of tliis ground and 
the gradual dilation of the valley into that of the Lochy is such thut 
no barrier could have existed here without occupying the whole of the 
present valley of the Lochy." MaccuUoch therefore proposes to re- 
move this barrier to an indefinitely distant point towards the sea. 
" If . , . Glen Gloy was dammed by a barrier of its own, indcpen- 
•dently of that which occupied . . . the common opening of Glen Eoy 
And Glen Spean, we multiply our difficulties without necessity. A 
continuous lake must therefore be supposed to have existed among 
the present valleys of the Eoy, the Spean, the Gloy, and Loch Lochy, 
independently of a portion of Strathspey." Ma'ccuUoch then gives 
a map of the quantity of water he presumes under these circum- 
stances must have occupied the surrounding country, but the po- 
sitions he assigns to the barriers, and the condition he depicts for the 
country, are not entirely such as the glacier theory, hereafter to be 
noticed, will require. A considerable portion of Glen Lochy mus^t 
therefore, he thinks, have formed a part of this common lake, and al- 
though he cannot determine its boundary in this direction, it must, 
accordinfj to his views, have extended at least to the noith of the 
opening of Glen Gloy. But that valley opening into what would 
have been the middle of this lake, and being constantly diminished 
from the deposit of alluvial matter from the streams, while the per- 
manence of the ' lines ' upon the hills shows that they have under- 
gone no violent changes, Macculloch does not incline to put any bar- 
rier there. If he attempts the great Caledonian valley, he gets en- 
tangled in a series of similar difficulties ; in short, he does not find it 
possible to " fix upon a point which shall satisfy the requisite condi- 
