286 
BATHYMETRICAL SURVEY OF 
parallel to those in the Moine schists ; indeed, in certain localities they 
pass, irrespective of the boundary-line, from the igneous to the altered 
sedimentary rocks. 
On either side of the Sutors of Cromarty, and stretching southwards 
along the sea-cliff to Fortrose, there is a narrow belt of crystalline schists 
rising from underneath the Old Red Sandstone. They belong to the 
group of quartz biotite granulites, and are associated with bands of 
amphibolite. 
Newer granite masses are also represented in the area, as, for 
instance, on the hills north of Ardross Castle above Strath Rusdale, 
and in Glen Orrin west of Fairburn House. They resemble the normal 
types of the newer granite masses of the Highlands, and were erupted 
after the Moine schists had assumed their present crystalline character. 
The strata of Old Red Sandstone age in the basin of the Cromarty 
firth are arranged in the form of a great syncline, whose axis runs in a 
north-north-east and south-south-west direction. The base of the series 
and the order of succession are admirably displayed on the sea-cliffs at 
Cromarty, and on the south-east shore of that firth as described long 
ago by Hugh Miller. The basal conglomerate is there overlain by the 
well-known fish-band, with calcareous nodules, graduating upwards 
into the coarse sandstones that form the centre of the basin. On the 
west side of the firth a similar sequence is observable. The basal con- 
glomerate along the flanks of the hills is usually brought into conjunction 
with the crystalline schists by a fault, evidently of no great amount, for 
the unconformity is visible at certain localities. This horizon is sur- 
mounted by red sandstones and flagstones, calcareous and bituminous 
shales, and occasional intercalations of clays with limestone nodules, 
with fish remains. These are followed by an upper band of conglomerate, 
which is overlain by the coarse sandstones in the centre of the basin. 
Various outliers of Old Red Sandstone, largely composed of con- 
glomerate, and resting unconformably on the highly denuded platform 
of crystalline schists, occur some miles to the west of the main area of 
this formation in the Conon basin. Some of these are met with on the 
plateau between Loch Luichart and Aultguish. By far the largest and 
most important is that still further north in Strath Vaich, where an 
extremely coarse conglomerate, composed largely of blocks of the 
contiguous foliated granite, is found on the crest of Meall a’ Ghrianain 
(2531 feet). 
At the base of the sea-cliff formed by the crystalline schists and Old 
Red Sandstone of the Black Isle and the North Sutor, there are small 
patches of Oolitic rocks which have only a limited development. They 
occur on the beach below high-water mark at Eathie and at Port-an- 
Righ and Cadh-an-Righ near Sandwick. By means of the great fault 
that traverses the line of the Caledonian Canal, and is continued 
north-east along the shore of the Black Isle, these Secondary strata 
have been let down against the older rocks. 
