74 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



A great mass of epidiorite and 

 hornblende-schist, ascending in 

 places into the quartzite, but 

 apparently not descending below 

 No. 13. 



Lenticular bauds of hornblende- 

 schist. 



Rests on a sill of hornblende-schist. 



Hornblende-schist locally abundant. 



Hornblendic sills begin on this plat- 

 form, and increase in number 

 upwards. 



various subdivisions which have been recognized by my colleagues of 

 the Geological Survey in the Highlands of Perthshire : — 



17. Dark schist, calcareous schist, and 



limestone (Blair Athol), 

 IG. Quartzite (Ben-y-Glo, Schiehallien). 

 1.5. Graphite-schist. 

 14. Calcareous sericite-schist. 

 13. Sericite-schist, with bands of 



quartzite (Canlochan, Glen 



Isla). 

 12. Garnetiferous mica - schist and 



schistose pebbly grits. 

 11. Limestone (Loch Tay). 

 10. Garnetiferous mica - schist and 



schistose grits. 

 9. Upper group of " green schists." 

 8. Garnetiferous mica - schists and 



schistose grits with pebbly bands. 

 7. Lower group of "green schists." 

 6. Thick group of massive grits, often 



abundantly pebbly, with partings 



of mica-schist and phyllite (Tro- 



sachs, Ben Ledi, Ben Yoirlich, 



&c.). 

 5. Schists and shales, with occasional 



bands of pebbly grit (Loch Ach- 



ray). 

 4. Band of conglomerate, with pebbles 



as large as a pigeon's egg (ridge 



between Lochs Achray and Ard). 

 3. Pale green, grey, and blue slates, 



with purple and red shales and 



bands of sandy flags (Aberfoil). 

 2. Pebbly rusty-coloured greywacke 



and grit (Pass of Leny). 

 1. Black shales and flags, with lenti- 

 cular bands of limestone (seen 



against the great fault at Cal- 

 lander). 



On any estimate these metamorphic rocks must be enormously 

 thick. They are prolonged north-eastward across the Grampian 

 range to the shores of the ISTorth Sea and Moray Firth, and south- 

 westward through Argyllshire into the north and west of Ireland. 

 Some of the belts of limestone are almost continuously traceable 

 across Scotland — a distance of 250 miles ; and if, as is probable, the 

 Donegal, Mayo, and Galway limestones are a further prolongation of 



