394 PROFESSOR GEIKIE ON THE 
exists between them gradually to bring in higher parts of the group as we 
proceed westwards. Thus the strata of Sandside Head lie on a platform 
several hundred feet higher in the flagstones than those of Holburn Head, 
This is a point of considerable importance with reference to the overlap already 
spoken of. On the east side of Sandside Bay an admirable section exposing | 
every bed may be traced from the outer reefs to the line of sandy beach at the 
mouth of the Isauld Burn.* Dark-grey and blue shaly flagstones and “ calmy” 
or calcareous shales dip out to sea (N.N.W.) at 12°-15°. Harder bands, varying 
from less than an inch to a foot or more in thickness, are intercalated with 
them and project as ribs from their weathered surfaces. These are underlaid 
by about 70 feet of white and yellow sandstone, below which lie some calca- 
reous shales, flagstones, and an impure limestone band. After a short space 
obscured by blown sand and other superficial accumulations, the section is 
resumed in the channel of the Isauld Burn by flaggy yellow pebbly sandstones, 
becoming more conglomeratic till they rest upon an uneven surface of dark 
granite full of black mica. Similar sandy conglomeratic strata with occasional 
bands of limestone continue to emerge from under the Isauld beds, with a dip 
to N.N.W. ; but eastwards on the line of strike they pass into the flagstones, | 
as already explained. (See map, fig. 4.) The thick yellow sandstone, with its 
underlying limestone band and shales seen in Sandside Bay, strikes westward 
and comes against the granite beyond Sandside house. ‘This sandstone is | 
quarried for building purposes, and, with its well-defined beds and occasional | 
false-bedding, could hardly be distinguished from one of the ordinary Carboni- | 
ferous sandstones. It is well exposed in the quarry and in the water-course 
to the north of Sandside house, where a deep goe also affords an excellent 
section of the overlying flagstones and shales. At the mouth of this inlet the 
shaly calcareous flagstones, with their nests of sand, concretions of bitumen, 
rippled and sun-cracked surfaces, present all the typical characters of the 
group; yet only a quarter of a mile inland they pass down into the sandy beds 
which rest upon the crystalline rocks. 
Three quarters of a mile westwards from the Sandside Goe, the prevalent dip | 
to N.N.W. having continued undisturbed through that interval on a bold rugged 
projection of the cliff-line, a portion of the uneven platform of crystalline rocks : 
rises up through the later deposits. Bosses of gnarled gneiss and dark mica- 
schist, traversed with pink granite veins and with an easterly dip at high 
angles, appear on the shore-reefs and rise up to the summit of the cliff. The 
singularly unequal surface presented by these ancient rocks when the Old 
Red Sandstone began to be laid down on them is well shown by this part of 
the coast. A pink granitic breccia with intercalated seams of green sand- 
* Munrcuison, “Quart. Journ. Geol. Soc.” vol. xv. p. 403. 
mae 

