P. MACNAIR ON ROCKS OF HIGHLAND PERTHSHIRE. 175 
succession of the altered clastic rocks of the Highlands. In a sum¬ 
mary of the Rocks of Highland Perthshire, read by Mr. H. Coates 
and myself^ before this Society in January, 1891, we gave an account 
of what we supposed to be the order and succession of these rocks as 
seen in Perthshire. In that paper we placed at the top the great 
arenaceous series of Schiehallion, Blair-Atholl, and Ben-y-Ghloej then 
the mica-schists and quartz-schists of Ben Lawers and Loch Tay, 
with their limestones, and, below these, the arenaceous and argillaceous 
groups of the marginal Highlands. Subsequently, but in the same 
year (1891), in his Presidential Address to the Geological Society 
of London, Sir Archibald Geikie,^ as the result of the work of the 
Geological Survey, arranged the altered rocks of Highland Perthshire 
in the following descending order :— 
17. Dark schist, calcareous schist, and limestone (Blair-Atholl). 
16. Quartzite (Ben-y-Ghloe, Schiehallion). 
15. Graphite schist. 
14. Calcareous sericite schist. 
13. Sericite schist with bands of quartzite (Canlochan, Glen 
Isla). 
12. Garnetiferous mica-schist and schistose pebbly grits. 
II. Limestone (Loch Tay). 
1 o. 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 phyllite (Trossachs, Ben Ledi, 
Ben Vorlich, etc.). 
5. Schists and shales, with occasional bands of pebbly grit 
(Loch Achray). 
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 (Aberfoyle). 
2. Pebbly rusty-coloured greywacke and grit (Pass of Leny). 
I. Black shales and flags, with lenticular bands of limestone 
seen against the great fault at Callander. 
The above is supposed to be a perfectly conformable series, the 
highest member, the dark calcareous schists of Blair-Atholl, being 
placed at the top, while the black shales and limestones of Kilmahog, 
