OLD RED ‘SANDSTONE OF WESTERN EUROPE. 44]. 
shore-line, sometimes leaning directly against the Highland slopes, sometimes 
running up into bays worn out of them, sometimes retiring and exposing a con- 
siderable breadth of the older sandstones and conglomerates with their earlier 
shore. Some of these phenomena did not escape the observant eye of Dr Mat- 
€OLMSON, who believed that “great denudations were in progress during the 
whole period of the deposition of the Old Red Sandstone, by which different 
superior members of the system were placed in contact with the inferior rocks,”* 
and who specially points out the rapid disappearance or attenuation of the 
massive conglomerate as inconsistent with the notion that this formation merely 
thins off or appears in a degraded form. I have not found, however, any evidence 
of such extensive denudation of the Old Red Sandstone of Morayshire, except 
at the great interval between the lower and upper divisions of the system. The 
rapid diminution of the great conglomerate of Cawdor, which Dr MAtco_mson 
cites as proof of these changes, is almost certainly due to the circumstances 
under which the deposit was accumulated and not to subsequent denudation, 
as will be pointed out further on.t 
4. From the Nairn to Inverness.—¥or the present, therefore, I shall 
omit further description of the upper or Holoptychius sandstones of Moray 
and Nairn, seeing that neither stratigraphically nor paleontologically can 
they be classed with the true Caithness flags. This latter series runs, as 
I have said, in a gradually widening strip along the base of the Highland 
hills to the south-west of Nairn. In that part of its course it presents 
| many of the lithological peculiarities which mark its occurrence in the 
country to the eastward. A band of grey clay and shale, full of calcareous 
nodules containing plates and scales of Coccosteus and other characteristic 
ichthyolites, forms a recognisable horizon, and was traced for many miles up the 
_ Nairn valley by Matcotmson. The remarkable changes which occur especially 
in the thickness of the basement conglomerates cannot be better displayed than 
in the four vertical sections which my colleague in the Geological Survey, Mr JoHn 
_ Horne, has been good enough to prepare for me. (See Plate XXII., columns 
Y., Vi., vii. and viii.). They are arranged to show the variations along the strike 
of the beds as we proceed from south-west to north-east. In section viii. 
| the strata consist almost entirely of sandstones and sandy shales. About 180 
feet above the base lies the thin zone of grey shales and clays, with calcareous 
nodules and seams, which occurs at Knockloan and is well-known for its fossil 
fishes. Even at a glance one can see the close similarity of these concretions 
to those of the Banffshire sections ; and on closer examination this similarity is 
3 
| BIOp, cit. p. 338. 
; ar [Since this was in type Mr Horne has extended the work of the Geological Survey into the . 
Findhorn district, and has traced the unconformable overlap of the Upper Old Red Sandstone. | 
VOL. XXVIII. PART IL DY 
