THE OLD RED SANDSTONE. 19 
the north of the Friths of Forth and Clyde, together with the 
southern flank of the Grampians and the northern coast of 
Sutherland and Caithness, appear to have been girdled at 
some early period by immense continuous beds of Old Red 
Sandstone. Ata still earlier time, the girdle seems to have 
formed an entire mantle, which covered the enclosed tract from 
side to side. The interior is composed of what, after the 
elder geologists, I shall term primary rocks —porphyries, 
granites, gneisses, and micaceous schists; and this central 
nucleus, as it now exists, seems set in a sandstone frame. 
The southern bar of the frame is still entire: it stretches 
along the Grampians from Stonehaven to the Frith of Clyde. 
The northern bar is also well nigh entire: it runs unbroken 
along the whole northern coast of Caithness, and studs, in 
three several localities, the northern coast of Sutherland, 
leaving breaches of no very considerable extent between. 
On the east, there are considerable gaps, as along the shores 
of Aberdeenshire.* The sandstone, however, appears at 
Garnrie, in the county of Banff, in a line parallel to the coast, 
and, after another interruption, follows the coast of the Moray 
Frith far into the interior of the great Caledonian valley, and 
then running northward along the shores of Cromarty, Ross, 
and Sutherland, joins, after another brief interruption, the 
northern bar at Caithness. The western bar has also its 
* The progress of discovery has shown, since this passage was 
written, that these gaps are not quite so considerable as I had sup- 
posed. The following paragraph, which appeared in July, 1843, in an 
Aberdeen paper, bears directly on the point, and is worthy of being 
preserved : — 
‘6 ARTESIAN WELL. 
“The greatest of these interesting works yet existing in Aberdeen 
has just been successfully completed at the tape-works of Messrs. 
