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 origin of Parallel Boads. 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 (C 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 

 featitres of the country indicate that, while a portion of such a vast sea-tide 

 entering the Firth of Limine 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 Boy and Glen Gluoi, into the valley of the Spey, and so across 



