374 PROFESSOR GEIKIE ON THE 
2. Order of Succession among the Strata. 
It is now necessary to show the order and the lithological and palzonto- 
logical characters of the Caithness flagstones as obtainable from a comparison 
of the various natural sections which have just been described. For the sake 
of clearness the following general table may be prefixed to this section of 
the memoir, as it shows the subdivisions which I have been able to make out, 
their thicknesses, and the localities where they are best seen, and where the 
characters to be afterwards described were observed in the field. 
TABLE showing the Order, Thickness, and Typical Localities of the leading 
Subdivisions of the Old Red Sandstone of Caithness in descending order.* 



Thickness Localities where the Rocks 
Subdivisions. Strata. in’ Feet. occur. 

John o’ Groat’s Sand-| 9. Red sandstones, with occa-}| 2000 | John o’ Groat’s House, | 
stone and Flagstone sional bands of flagstone, on the shore. 
Group. thin impure limestone, and 
shale. 
Huna Flagstone Group. | 8. Flagstones, shales, and thin} 1000 | Shore at Huna. 
impure limestones. 
Gill’s Bay Sandstones. | 7. False-bedded red sandstones. 400 | Gill’s Bay, on Pentland 
Firth. 
Thurso or Northern | 6. Dark-greyandcream-coloured | 5000 | Coast-line of Caithness 
Flagstone Group. flagstones, grey and blue from Reay to Dunnet | 
shales, and thin limestones ; Bay, and from Brough } 
some beds strongly bitumin- to Gill’s Bay. Stroma | 
ous. This group more fissile, and the Orkney Islands. | 
shaly, and calcareous than 
No. 5. 
Wick or Eastern Flag- | 5. Dark-grey flagstones, often} 5000 | Coast on either side of} 
stone Group. thick - bedded, thin shales Wick, and inland to} 
and limestone bands passing Banniskirk. 
down into red shales and 
sandstones. 
Lower Red Sandy and | 4. Dull red sandstones and occa- | 2000 | Coast south and north of | 
Conglomeratic Groups. sional red shales and bands Berriedale Water, Sar- | 
of fine conglomerate passing clet, Braemore, Morven, | 
inland into conglomeratic &e. 
sandstone. 
Do. 3. Brecciated conglomerate. 300 | Coast at Badbea. 
Do. 2. Dull chocolate-red sandstones 450 | Berriedale Water around 
and sandy shales or clays. Braemore. 
Do. 1. Coarse basement conglome- 50 | Berriedale Water below 
rate. Braemore, and mouth 
of Ousedale Burn. 

* In the field observations from which I have plotted this table, I was materially aided by Mr 
B. N. Peacu, whose active and helpful co-operation I would again heartily acknowledge. 

