S56 Dr. Mac Culloch on the Parallel Roads of Glen Roy. 



amined 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 moun- 

 tain torrents, and which I have fully described in other parts of 

 this paper. By these it is proved that the torrents existed pre- 

 viously 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 



