OLD RED SANDSTONE OF WESTERN EUROPE. 407. 
on one or more sides to a sandy beach. The cliffs are repetitions of those of 
Caithness, down even to the minutest details of form and colour. It is only 
on these sea-walls that any angular outlines, or, indeed, any considerable ex- 
posed faces of rock can be seen. Back from the edge of the precipice, the 
ground spreads out into a great plain, ora gently undulating surface, only varied 
now and then by some higher swell, or by the conical outline of a “ Wart 
Hill.” This monotony of external configuration affords a good indication of 
the sameness of the geology. Orkney is in fact simply a prolongation of the 
north of Caithness. 
These northern islands have, long been of geological interest, from the 
number and variety of ichthyolites which they have yielded. Probably the 
earliest geological examination of them was that of JAMESon (1800), who, with 
characteristic method and perseverance, traversed their rocks, but grew weary 
of their monotony. “It required,” he says, “nearly six weeks to traverse the 
Orkney Islands, and that journey proved the most uninteresting I had ever 
made.”* He makes no mention of organic remains, and does not attempt to 
connect the rocks with the formations of other regions. Professor TRAILL, of 
Edinburgh University, made a large collection of the fossil fishes from the flag- 
stones. He supplied some of the species named and described by Agassiz, 
whose works called more special attention to this tract. In later years (1850) 
' the Stromness flagstones became widely known from HucH MIL.Er’s chapters 
on “The Footprints of the Creator; or the Asterolepis of Stromness.” Other 
collectors added to the number of species, some of which were described by 
Professor M‘Coy.t From the general similarity of organic remains, it had long 
been known that the Orkney Old Red Sandstone belonged to the same division 
of the system as the Caithness flagstones. The first attempt, however, to 
ascertain the structure of the islands, and to connect them stratigraphically 
with the mainland, appears to have been that of Sir R. Murcuison, who visited 
Orkney in 1858, and passed rapidly through the islands.{ His observations 
went to show that two divisions of the Old Red Sandstone occur in Orkney— 
the flagstones, and certain overlying yellow sandstones, which he assigned to 
the upper member of the system.§ He believed that the base of the whole 
flagstone series was to be seen at Stromness, where certain conglomerates rest 
upon a ridge of crystalline rocks, and that this series passes upwards, confor- 
mably into the yellow sandstones of Hoy. In both of these inferences he was 
mhistaken, as will be pointed out further on. 
* “Mineralogy of the Scottish Isles,” vol. ii. p. 252. See also P. Nurx’s “Tour in Orkney and 
Shetland,” 1806. 
t “ Synopsis of Classification of British Paleozoic Rocks,” &c., 1855, p. 579, et seq. 
$= “Quart. Journ. Geol. Soc.” xv. 410. ; 
§ These subdivisions had been noticed before by Dr Matcoumson (1839, “Quart. Journ. Geol. 
Soc.” vol. xv. p. 336) and by Huew Minuzr (“ Footprints of the Creator,” p. 2). 
