918 
Proceedings of the Royal Society 
The detritus had assuredly not fallen from the adjoining hills, by 
the natural decay of the rocks composing them. 
The late Dr Macculloch, who was eminent as mineralogist, 
geologist, and chemist, visited Lochaber, to seek for data to 
enable him to try and solve the problem of the parallel roads ; 
aud wrote an elaborate paper on the subject, which was published 
in the Transactions of the London Geological Society for 1817, 
vol. iv. 
He particularly studied the nature of the gravelly materials 
lying on the surface of the country, and he found that these 
were of two descriptions. He observed that the debris of the rocks 
were angular in shape : — The other class he called “ transported 
alluvium of pehhles^ sand^ and gravel and these, he observed, 
generally differed in mineralogical composition from the rocks of the 
hills on which they lay. “ The alluvium (he says) was not thus 
rounded by the action of the water which prodmced the lines {i.e., 
the parallel roads). We must suppose that this rounded alluvium 
had been, by previous causes, accumulated. If this took place from 
the action of water {aQid to what other cause can ive assign it .?), it 
must belong to an epoch prior to the deposits of sharp matter in 
the upper parts ” (page 330). 
Again he says : — “ The conoidal hillocks, occurring between Glen 
Fintec and Glen Glastrie, consist of deposits of fine sandy clayy and 
rolled stones of different sizes, — disposed in a manner irregularly 
stratifiedy and in a direction more or less horizontcd. The terraces 
and hillocks, which occupy positions much inferior to these, all the 
way along the course of the SpeaUy are of the same materials^* 
(page 339). 
The hillocks in Glens Fintec and Glastrie, here mentioned as 
examples of '•transported alluviumfi occupy positions exceeding 
1200 feet above the sea, and are (Macculloch says) the same kind 
of deposits as those along the course of the Spean, referring, no 
doubt, to the kaims described in this paper. 
Examples of these detrital deposits occur in all the Lochaber 
glens. In Glen Roy and its lateral valleys, there are cliffs of 
boulder clay, exceeding 200 feet in depth. Along the course of the 
Spean at Murlaggany on the east bank, there are cliffs of sand, par- 
tially stratified horizontally, above 80 feet deep; and on the west side, 
