AND QUARTZ DEPOSITS OF ASSYNT. 359 
bed, which occupies, in Caithness and elsewhere on the east 
coast, the second place in the system reckoned from the top 
downwards, and the third from the bottom upwards, occupy 
exactly the same place in Assynt, and not the place of any of 
the other beds? Or why should the red, rough-grained sand- 
stone, with its included pebbles, which occupies the first place 
in the system of the east coast reckoning upwards, occupy also 
the first place, reckoning upwards, in that of the west coast, 
and not the place of any of the three beds which overlie it? 
Or, further, why should the place of the two great sandstone 
beds of the east-coast system, in their position as second and 
fourth, be occupied in the west-coast system by arenaceous 
beds also second and fourth in the series, instead of being 
occupied by beds not arenaceous? The number of the 
chances against such thorough coincidences as that exemplified 
here, regarded simply as chances, are so great, that they will 
be found to occur in no two British systems not indentical. 
The probability, so to speak, that an unaltered system which 
in one locality is fossiliferous in one of its beds and non-fossilif- 
erous in any of the others, should in another locality be slightly 
altered in all its beds, and, in consequence, non-fossiliferous in 
them all, is a probability which must be regarded as having 
many more chances in its favor. 
Let me also remark, that the Old Red system of the east 
coast, which rests, as I have said, on the unconformable gneiss, 
is overlaid in several localities, as at Eathie and Shandwick, by 
beds of the Liassic formation. A wide gap occurs in the geo- 
logic scale in these northern districts: the Carboniferous, Per- 
mian, and Triassic systems, are wanting; and along the northern 
side of the Moray Frith generally the Old Red Sandstone 
forms the immediate base of the Lias,—a formation which, 
though it barely appears on the edge of the land there, is 
apparently largely developed under the bed of the German 
