T1IK AUfll.LAN l:OCKS 



45 



v.-in 4ii.i'i/., quartzite, grit, chert, and jasper; and Dr. Teall lia 

 found from microscopical examination that the felaites and por- 

 hries are i'lrntuval in all - 



phyries are i'lrntuval in all essential respects with tin- felsites 

 [i.e. devitritied rhyolites] belonging to the Uriconian S.-ries of 

 Shro]isliiiv." 



In these pebbles, therefore, we seem to have traces of a 

 vanished formation, of later date than the Hebridean gneiss, from 

 which the component materials of the Torridonian deposits were 

 principally derived. It would be interesting to coin par 

 volcanic rocks with the felsites and porphyries which occur in 

 Sweden and seem to occupy an intermediate position between tin- 

 equivalents of the Hebridean and Torridonian Series. 



In the extreme north between Cape Wrath and Loch Inchard, 

 the Torridonian is not more than 1200 to 1500 feet thick, but 

 farther south the beds not only thicken but another set of beds 

 come in at the base, till round Loch Maree and Loch Torridon ite 

 thickness amounts to more than 8000 feet. The whole formation 

 lias been divided into three groups by Messrs. Peach and Home, 

 ;is shown in the following table. 



Still farther south in Skye Mr. Clough finds that the lowest 

 or Diabeg Group expands in a remarkable way, and that it then- 

 attains a thickness of about 7000 feet, BO that although in that 

 island the Aultbea Group is not represented there are 12,000 feet 

 of Torridonian deposits, and may have been as much as 16,000 feet 10 



Mi. Clough has made the following subdivisions of the 

 Torridonian of Skye in descending order : 



e. Applecross Group. Red and chocolate arkoses with lobbies of various 



rocks ; estimated at 5000 feet. 

 d. Kinloch Beds. Alternating beds of dark-grey sandy shale and fin*- 



grey or butr grit ; about 3500 feet. 

 c. Seamraig Beds. Greenish-grey grits with gome beds of sandy shale ; 



2600 feet. 



b. Loch na Dal Beds. Sandy shales and fine grits ; 600 feet. 

 a. Rpidotic grits and conglomerates. About 300 feet. 



