Dr. Mac Cul LOCH on the Parallel Roads of Glen Roy. 389 



causes accumulated in the lower part of the glen. If this took place 

 from the action of former waters flowing through the valley, (and 

 to what other causes can we assign it?), it must belong to an epoch 

 prior even to the deposits of sharp matter in the upper part ; as 

 these must have been otherwise necessarily removed by that cause 

 which deposited the rounded materials in the lower. Here there- 

 fore we are again carried back to an sera marked by the action of 

 water, and prior even to the very distant time which appears to 

 have been required for the tedious deposition of the sharp alluvium. 



Such are the complicated views derived from a consideration of 

 these appearances, nor is it easy to see how we can avoid the con- 

 clusions which must be drawn from them. Although some of 

 them should have their foundation in error, there are still enough 

 remaining to excite our industry in the observation of analogous 

 phenomena, and to stimulate us to seek for a theory of these facts 

 less incumbered with inexplicable results ; if indeed it be possible 

 to discover one which shall not be attended with most of the various 

 consequences I have pointed out. 



It follows yet, from a general view of these alluvia, that many of 

 them are probably of a formation more ancient than the last great 

 changes which produced the present state of the surface, if we con- 

 sider the drainage of Glen Roy to appertain to those changes. 

 But we are in danger of being bewildered in the views which open 

 on us when we pursue the operations of Nature so far beyond the 

 limits of our immediate observation. 



I have thus, as distinctly as is in my power, stated the whole of 

 the arguments, as well as the difficulties and objections which bear 

 on this question in all the several lights in which it has yet been 

 considered, suppressing nothing which has occurred to me as an 



Vol. iv. 3 d 



