388 Dr. Mac Cuij.och on the Parallel Roads of Glen Roy. 



point out as in itself constituting a sufficient distinction between the 

 transported and untransported alluvia ; the last of which, indepen- 

 dently of its rounded and heterogenous fragments, alternates with 

 deposits of sand and gravel, and even of clay, but seldom or never 

 exhibits the same irregular admixture of fine clay which is found 

 in the former. The lines at the lower part of the glen are formed 

 in the transported alluvium. 



If we consider the first case alone, that of the untransported 

 alluvium, we are led to enquire into the length of time required 

 for its accumulation before the lines were formed in it. We see 

 from the small changes these have undergone, that scarcely any 

 wearing of the hills, and consequently no material deposition of 

 rubbish has taken place since their formation, wide as that interval 

 is. Yet the depth of this deposit being so great, while its accu- 

 mulation is thus tedious, we are unavoidably carried back to an 

 incalculable period of time previous to the existence of the lines, 

 during which it must have been accumulating. 



Let us now remark, that as no disturbances of the sharp alluvium, 

 at least to a degree capable of producing the rounding of these 

 fragments has taken place, it is plain that the waters which acted 

 on this alluvium so as to produce the lines, had not been subject to 

 violent motion. If there was no violent motion fn the upper part 

 of the glen, there could be none in the lower, since there is a con- 

 tinuity between these two parts. Yet these portions of the lines 

 which are found in the lower part of the glen are formed in a 

 rounded and transported alluvium of pebbles, sand, and gravel. 

 This alluvium therefore was not thus rounded by the action of the 

 water which produced the lines, since if it acted at all, it must have 

 acted in a similar manner throughout the whole valley. We must 

 consequently suppose that a rounded alluvium had been by previous 



