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BATHYMETRICAL SURVEY OF 
Notes on the Geology of the Nokth-east Part of the Ness Basin. 
By B. N. Peach, ll.d., f.r.s., and John Horne, ll.d., f.r.s. 
Only a small portion of the Ness area has been mapped by the 
Geological Survey. It is situated in the north-east part of the basin, 
and includes the tract at the mouth of Loch Ness and on either side of 
the river issuing from that loch. It comprises a small part of Loch 
Ness, Loch Dochfour, Loch Ashie, Loch Abban, and Loch Laide. 
The geological structure of the northern part of the Ness basin is 
well defined. The basin is traversed by the great fault that runs along 
Loch Ness, which is continued north-eastwards to Tarbat Ness, thus 
giving rise to the prominent cliff bounding the Moray firth in the 
Black isle. This powerful dislocation, which has been a line of weakness 
in the earth’s crust at successive geological periods and is evidently 
related to the earthquake movements that periodically affect the Inver- 
ness district at the present time, has a marked downthrow to the 
south-east. The exact position of the line of fault in the Ness valley 
is concealed by superficial deposits, but its course probably extends 
from near the western shore of Loch Ness at Lochend, north-east by 
Loch Dochfour, Dunean cottage, and Kinmylies, to the Beauly firth 
east of Kessock ferry. 
The effect of this great dislocation in the Ness valley is to let down 
the Old Red Sandstone strata on the south-east side against the 
crystalline schists and gneisses of Dochfour hill, the Abriachan granite, 
and the basal conglomerates and sandstones of Dunean hill and 
Craig Leach on the north-west. The schistose rocks of Dochfour hill, 
which are pierced by the Abriachan granite, consist of quartz-biotite 
granulites and felspathic gneisses traversed by numerous veins of 
pegmatite. Occasional lenticles of garnetiferous hornblende-schist 
are associated with the gneisses, and a band of limestone also 
occurs in the schistose series at Blairnahenachrie, west-north-west of 
Dochgarroch. From their lithological characters, these crystalline 
schists have been referred to the Moine series of the Geological Survey, 
the members of which are regarded as altered representatives of 
sedimentary deposits. 
The triangular area of Old Red Sandstone on the west side of the 
valley of the Ness, extending from Dochgarroch north-east to Clachna- 
harry, and west to the Bunchrew burn, consists of coarse conglomerates 
and grits that dip to the north-west, and are overlain by sandstones, 
flags, and shales. Along their western margin they are bounded by a 
fault, with a downthrow to the east, which is probably a branch of the 
great dislocation running along Loch Ness. 
