452 BUTE. GEOLOGY. 



short courses of the streams, necessarily limit these to 

 mere brooks, incapable of producing any conspicuous 

 effects on the form of the surface. This island is indeed 

 remarkable for the almost total absence of alluvial matter, 

 except in the two places formerly mentioned. One or 

 two banks of gravel are visible on each opposed shore, 

 near the northernmost point; but whether these have 

 been thrown up, under some former state of things, by 

 the action of the tides, being afterwards deserted as 

 the water has found a deeper channel ; or whether they 

 are the remains of more considerable deposits, now nearly 

 removed by its gradual corrosive power, it is impossible 

 to determine. No rolled stones of large size are any 

 where to be seen; nor are there any deposits of loose 

 materials in the interior valleys, except those which appear 

 to have resulted from the wearing of the present surface. 

 These, consisting of clay and sand, are found chiefly in 

 the sandstone district ; and are precisely similar to those 

 which are seen in similar situations in Arran, and indeed 

 every where else on the surface of this rock. It is 

 unnecessary to take further notice of the flat tract 

 near the Garroch head; and it is equally superfluous 

 to describe the marly deposits which are found among 

 the clay, as they evidently owe their origin to the occa- 

 sional presence of calcareous rocks among the sandstone 

 beds. 



As the general boundaries of the primary rocks have 

 already been described, and as they are particularly de- 

 tailed in the map, it is unnecessary to dwell on them ; 

 the more so, as they do not present any irregular portions 

 incapable of being specified in that map, and requiring 

 verbal description. The dip of the strata is toward the 

 east, as already mentioned, at various, but commonly at 

 considerable, angles, the ordinary extent and irregularity 

 of which have been noticed in the description of the 

 mountain range. Any further remarks on the bearings 



