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



It is easy to comprehend that these are the remains of such deltas or 

 alluvia, undermined during the different subsidences of the lake, 

 and remaining as indications of their former existence* 



Having now compared all the appearances of Glen Roy with 

 those which are to be found in existing lakes, and considered the 

 probable changes which the drainage of such lakes would effect on 

 their containing valleys, I shall proceed to point out the difficulties 

 with which even this hypothesis is encumbered. 



It has been seen in the description, that considerable deficiencies 

 may be observed in the courses of these lines, as well in Glen Roy 

 itself, as in the neighbouring glens. Some of these anomalies indeed 

 assist in proving the probability of the hypothesis here considered : 

 the remainder, yet unaccounted for, may perhaps be explained here- 

 after, when observations have been further multiplied. One short 

 line only, is found in the upper valley of Glen Roy ; yet all the sides 

 exhibit a general equality of slope, form, and texture ; nor is any side 

 more than another, subject to the action of a visible wasting cause. 

 A great deficiency of the whole of the lines occurs also towards the 

 bottom of lower Glen Roy, and many partial ones in other places. 

 Of these, some evidently arise from the rocky nature of the margin, 

 and others may perhaps be the consequence of the coincidence be- 

 tween the slope of the hill and the slope of the supposed shore. But 

 these causes will not account for them all, nor are there sufficient marks 

 of the action of posterior waste to explain them. The anomalies of 

 Glen Gloy and Glen Spean in particular, which I have described at 

 length in the commencement of this paper, seem at present to baffle 

 all explanation, and in this unsatisfactory state must the argument 

 remain. It were well if there were no further difficulties to en- 

 counter in adopting this hypothesis, but it is necessary to enumerate 

 them. 



