(2) It implies also a corresponding survey of the ground intermediate between the Wall and the river. Now the intervening ground along the banks of the Clyde, from Chapel Hill to the Pointhouse at Glasgow, is a low-lying flat with a gradual rise inland, at the present moment, of not more than 25 or 30 feet. But according to Professor Geikie's latest survey, the Clyde must have been about 25 feet higher in the time of the Romans than it now is--and Professor Geikie, we presume, is an authority on such subjects, who may be quoted along with Hugh Miller and Smith of Jordanhill:--therefore the whole of that strath, and the strath on the opposite side, from Renfrew to Paisley, on this assumption, must have been submerged at the same time; and there could be no dwelling-place for human beings--neither local habitation nor a name--within the entire compass of that now fertile and populous region. But two or three Gaelic names survive on the northern verge of it, which not only indicate the presence of the sea there, but fix the very limits of its tide. Dalmuir, for example, which means the Valley of the Sea; and Garscadden, which means the Bay of Pilchards or of foul herring, must, in fact, have carried the waters up their respective streams to within less than a mile of the Roman Wall at Duntocher and Castlehill. It was in such retreats, then, that both salmon and herring (as the name of one of them imports) would take refuge in the spawning season; it was into such retreats also, they would be pursued by the seals; it was on the shore of such inlets the seals themselves would bask, when the Romans saw them; and it is at the two forts respectively at the head of these inlets--Duntocher and Castlehill--that they have been actually represented in Sculpture. Could anything be more conclusive as to the proximity of the tide, and very character of the shore, within a bowshot or two of the Wall in that neighbourhood, where there is now a distance of more than two miles between it and the river? and yet even more conclusive, in connection with this, is the fact that on the southern verge of the strath, right opposite to these, are other Gaelic names equally significant--such as Kennis, the Head of the island; Ferinis, the Hero's island; and Fingal-ton, which speaks for itself--at the same or a similar level with Dalmuir and Garscadden, that is from 100 to 200 feet above the present level of the Clyde, which seems to demonstrate beyond doubt that the whole intervening space of seven miles in breadth, with the exception of such small islands as those named above, was then an arm of the sea to the depth of 50 feet at least, if not more.