392 Dr. Mac Culloch on the Parallel Roads of Glen Roy, 



fully proved by the relative state of the lines and of the furrows of 

 the torrents on the faces of the hills ; namely, that its waters had 

 once occupied a lower level, or that the valley had actually been dry 

 before it was the receptacle of a lake. It is undoubtedly possible that 

 the ocean might have had its various periods of elevation and sub- 

 sidence, but the supposition is attended with difficulties at least as 

 great as those which follow that hypothesis which attributes the 

 confinement of the waters to solid and local obstacles. 



It is time to conclude this subject. To those to whom even that 

 theory which I have adopted shall appear unfounded, these reason- 

 ings can only be superfluous. To others whom such physical dif- 

 ficulties cannot appal, considering our limited knowledge of the 

 present and former state of the globe, and of the actions and causes 

 by which its present form has been produced or modified, their 

 omission would have been unpardonable. To those who, in con- 

 sidering the lines of Glen Roy as works of art, are inclined to cut 

 this knot of difficult solution, and to repose in a tacit acquiescence 

 on motives which they are unable to appreciate, and on a state of 

 society and manners of which history affords us no information, 

 the whole discussion may appear unnecessary. Yet in the trust 

 that future examinations of the earth's surface may throw future 

 lights on this subject, and that its physical origin may be established, 

 I shall make no other apology for the length of this paper than 

 the extreme importance of a phenomenon which exhibits a register 

 of revolutions in this globe of which no other similar example 

 has yet been discovered. 



