300 
THE GEOLOGIST. 
ordinary sea-beaches. Indeed, this feature is of itself enough to suggest an 
origin due to a strong current sweeping inward from the Atlantic, and across 
the water-shed of the island to the opposite sea. 
The speaker next proceeded to examine the hypotheses of his predecessors in 
this inquiry respecting the orijin of Parallel Roads. They all assume the 
agency, in one form or another, of standing water, either the ocean in its 
ordinary state of repose, or lakes pent within the glens. 
The notion that a quietly resting sea has fashioned these level shelves is 
refuted by the fact that they are not true marine beaches ; they exhibit none 
of the distinctive features of genuine sea-shores, not a vestige of any marine 
organic remains, no rippled sands, no shingle, and no sea-cliffs. They display 
in like manner a total absence of the distinctive marks of lake sides ; not one 
lacustrine organism, neither fresh-water plant, nor animal having ever been 
discovered imbedded in them. A further difficulty attends the lake-hypothesis 
in the necessity it imposes of discovering a feasible cause of blockage of 
the glens at different stations above their mouths, to pond the waters to the 
respective heights of the terraces. Though much ingenuity has been expended 
upon this part of the problem, no suggestions yet offered of barriers of gravel, 
accumulated by currents or glaciers from Ben Nevis, can be regarded as ad- 
missible, inasmuch as there are no traces of any such in any of those localities 
where alone we can assume them to have existed to produce the required 
embaying of the waters. In this entire absence of all remnants of the sup- 
posed natural dams across the glens, it is most unphilosophicul to take for 
granted their total obliteration, where no cause has or can be assigned which 
can have so effaced them. 
On the other hand, the hypothesis of successive "sea-margins," or sea- 
levels, is overthrown by the now well-established deduction from the professor's 
own recent measurements, that none of the several shelves, or " roads," of 
Glen Roy correspond in level with any of those seen in the adjacent valley 
Glen Gluoi, a marked discrepancy separating the two groups of terraces into 
two independently produced systems. It can be shown, moreover, that these 
discordances of interval between the shelves of the glens respectively, are such 
as cannot be accounted for on any supposition of " faults," or dislocations of 
the earth's crust, in the ground between the two glens. Equally incompatible 
are all the facts of the relative levels of the shelves, with the notion that they 
are possibly sea-beaches which may have undergone an unequal amount of ele- 
vation by an oblique secular rise of the land, such as is known to be very 
gradually taking place on some coasts at the present day. The individual 
terraces are too nearly level to admit of this explanation, since so wide a 
warping of the crust from horizontality within so limited a space as separates 
the two glens, would have left them conspicuously sloping. Besides, the two 
systems of shelves are wholly insulated from each other, and the notion of 
their origin as sea-beaches gradually elevated implies a continuity between 
them, together with certain agreements in their directions of derivation from 
levelness which we wholly fail to perceive. 
In conclusion, the speaker proceeded to sketch the action to which he 
ascribes the formation of all these shelves or parallel roads. He supposes the 
several terraces to have been cut or grooved in the sides of the hills by a great 
inundation from the Atlantic, engendered by some wide earthquake disturbance 
of the ocean's bed, and forced against the western slope of Scotland. The 
features of the country indicate that, while a portion of such a vast sea-tide 
entering the Eirth of Linnhe rushed straight across the island through the 
deep natural trench, Glen Mor, or the great Caledonian valley, a branch 
current was deflected from this, and turned by the Spean valley and its tribu- 
tary glens, Glen Roy and Glen Gluoi, into the valley of the Spey, and so across 
