whatever, nor is there any indication that either of the three ever
existed in the western half of the valley. When I first visited the
region, these phenomena had already been the subject of earnest
discussion among English geologists. The commonly accepted explanation
of the facts was that these terraces marked ancient sea-levels at a time
when the ocean penetrated much farther into the interior, and Glen Roy
and the adjoining valleys were as many fiords or estuaries. And though
the present elevation of the locality made such an interpretation
improbable at first sight, the first or highest of the terraces being
eleven hundred and forty-four feet above the present sea-level, the
second eighty-two feet below the first, and the third and lowest two
hundred and twelve feet below the second, or eight hundred odd feet
above the level of the sea, it was thought that the oscillations of the
land, its alternate subsidences and upheavals, proved by the modern
results of geology to have been so great and so frequent, might account
even for so remarkable a change. There are, however, other objections to
this theory not so easily explained away. There are no traces of organic
life upon these terraces. If they were ancient sea-beaches, we should
expect to find upon them the remains of marine animals, shells,
crustacea, and the like. All the explanations given to lessen the
significance of this absence of organic remains are futile. Again, why
should the lower terrace alone be continued into the eastern end of the
valley of Glen Spean, while there are no terraces at all in its western
part, since both must have been as fully open to the sea as Glen Roy
valley itself? This seemed the more inexplicable since all the terraces
exist on the valley-wall opposite the outlet of Glen Roy, showing that
this sheet of water, wherever it came from, filled the valley itself and
the space between it and the southern wall of Glen Spean, but failed to
spread, on either side of that space, into the eastern and western
extension of Glen Spean. It is evident, that, at the time the water
filled Glen Roy, some obstruction blocked the valley of Glen Spean, both
to the east and west, leaving, however, that space in the centre free
into which Glen Roy opens, while, by the time the water had sunk to the
level of the lowest terrace, one of these barriers, that to the east,
must have been removed, for the lowest terrace, as I have said, is
continuous throughou