Chap. XI.] 
OLD EED— OED OF CAITHNESS. 
257 
Let the geologist proceed northwards from the edge of the crystalline 
rocks, and he will clearly see, first, that the lowest strata of conglomerate 
and red sandstone, as made np of the crystalline rocks, alternate with, and 
pass into, deep -coloured, thin-bedded, micaceous red sandstones, as in the 
Cliffs of Trefad and the Old Man of the Ord, which constitute the natural 
and conformable base of the flagstone series of Caithness. 
In order to convey to the reader some notion of the natural features of 
the lower portion only of this fine succession, a small sketch is annexed, as 
taken from the footpath on the northern side of the Ord, at a spot called 
Badna Bae. 
View of the Old Eed Succession, from near the Ord of Caithness. 
The foreground is made up of the rude conglomerate, a of the section at p. 255, 
here chiefly composed of huge blocks of granite (the nearest rock, and of which 
the hut is built), though other smaller materials are of quartz-rock and mica- 
schist. This bottom rock of the series is followed by deep-red sandstones, which 
occupy the next headland, known as the Man of the Ord, b of the diagram ; 
whilst all these strata, inclining to the north, pass beneath the flagstones of Caith- 
ness, which occupy the distant low headlands (c, d, of the long section, p. 255). 
(See description by Sedgwick and myself, Trans. Geol. Soc. 2 ser. vol. iii. p. 139.) 
It would be a difficult task to endeavour to assign an average thickness 
to the accumulations of sandstone and conglomerate (the sandy beds being 
sometimes the lowest) that constitute the lowest member of this group, 
since it is in the very nature of pebbly accumulations which were formed 
either on coasts or in bays washed by the waves of a former sea to present 
the most variable dimensions. Independently of the conglomerates, and the 
associated sandstones, often very finely laminated, these deposits must have 
occupied a long lapse of time in their accumulation. Since the last edition 
of this work, an important confirmation of my view respecting these lower 
sandstones being the equivalents of the Arbroath beds, or the lowest Old Red 
s 
