west to the east, or from the present lowest level of the country to the highest one, it will be seen in the course of the argument, that many of the facts bear equally against the possibility of this supposition; to such an extent indeed as to render it quite unnecessary to enter into a formal refutation of it.
The cause of such a deluge or torrent as is here supposed, is generally assumed to be an elevation of a portion of land, elevating at the same time the superincumbent waters. I shall as far as possible simplify the phenomena, and thus give all the assistance I can to this hypothesis by supposing that with one line only, no other valley but Glen Roy exhibited that appearance. A single elevation of the site of Loch Spey would therefore be the only change required to produce the effect. But the fall of the country to the east, and the present course of the Spey show, that a wave produced by this cause must have equally tended to flow in the contrary direction or into the present valley of the Spey, and consequently to leave its impressions to the eastward as well as to the westward of its origin, on the supposition that the form of the surface was then similar to its present one. But no such impressions exist, although the form of the present valley of the Spey is fully as capable of receiving them as that of the Roy; and there are no reasons to suppose any material changes in the shape and disposition of that valley. No water courses either antient or recent, nor any agents are to be seen, capable of destroying these remains if they ever existed. Nor is it possible to comprehend by what means a wave produced at the present elevation of Loch Spey could have formed the first line which is visible in the upper Glen Roy. It is evident that the quantity of water carried by the assumed wave must have been sufficient to have filled the whole of Glen Roy for a course of twenty miles or upwards. It must have consequently
