Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/366

 may not always exist. The investigation moreover is that of a subject but little attended to, and consequently admitting some prolixity of illustration.

It is plain that a set of changes acting through a considerable space of time posterior to the present disposition of the ground had taken place before the water marks were impressed on its sides. This evidence consists in the marks of the lines which are traced to a certain depth on the furrows now possessed by mountain torrents, and which I have fully described in other parts of this paper. By these it is proved that the torrents existed previously to the causes which produced the lines, and, from what we may see of the actions of similar torrents in this or in other places, we are assured that a long period of time had elapsed between their original flow and the subsequent changes which produced the marks of the lines now visible in them. It is equally clear that the formation of these furrows must have been posterior, even though they had been produced in a short space of time, to the great changes, such as the breaking up either of the crust of the globe or of portions of it, which must be assigned as the cause of these deluges; and it is impossible that a series of such violent actions as would generate a deluge of this nature, could have taken place in the immediate vicinity of Glen Roy without obliterating these furrows and deranging all the signs of a previous state of repose.

The intermediate marks which are found at the upper part of the glen afford another argument against the hypothesis of a deluge. Supposing that three torrents consisting of very different quantities of water had flowed with such equable force as to have produced the three principal lines, we have, between the two upper ones, another so slightly marked that it must needs have resulted from a force very inferior to that which generated those below it. Yet it