308 ON THE RED SANDSTONE, MARBLE, 
Cromarty, Sutherland, Caithness, and the Orkney Islands, con- 
sists of exactly the same number of great divisions as this 
system of the western coast. That subordinate Red Sand- 
stone of the western system which has been colored as Old 
Red in every geological map of Scotland ever published, and 
which extends, in an interrupted belt, from Eilan Garbh, be- 
yond Cape Wrath, to the Island of Rum, a distance of more 
than a hundred and twenty miles, corresponds in place to the 
Great Conglomerate of the east coast,—a deposit equally con- 
tinuous. The lower quartz bed which overlies the red sand- 
stone we find occupying exactly the place of a thick arenaceous 
bed, by which, on the east coast, the Great Conglomerate is 
overlaid. The stratified limestones, with their associated flag- 
stones and marbles, occupy exactly the place of the flagstones 
and associated limestones of Caithness, and the stratified, semi- 
calcareous, nodule-bearing clays of Cromarty and Ross. And, 
finally, we see the vast upper quartz deposit of the west occu- 
pying exactly the place of that thick deposit of sandstone, red, 
white, and yellow, which overlies the ichthyolitic flagstones and 
stratified clays of the east, and which may be found immensely 
developed in the Ward-hill of Hoy, and in the promontories 
of Dunnet-head, Cannisbay, and Tarbet-ness. Bed for bed, 
the two systems correspond not only in number, but in charac- 
ter and place; for even the quartz-rock beds that are altered 
most cannot be regarded as other than indurated beds of quart- 
zose sandstone. Let me further remark, that both systems rest 
unconformably on the same ancient rock,—the fundamental 
gneiss of the country. Were the systems not indentical, we 
would have to account for the curious fact, that, resting on ap- 
parently the same rock, the number, character, and relative 
position of their beds should also be the same,—a contingency, 
regarded simply as such, that would exhaust many chances. 
Why, for instance, should the stratified limestone and flagstone 
