SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, 1891. 619 
and Forsinard. The Horizontal Disturbing Force at Loch Eriboll points northwards, 
while from Forsinard it tends to the west. Hence the ridge line runs north of Loch 
Eriboll and probably near to Forsinard Itself. This latter surmise is strongly 
supported by the directions of the Horizontal Disturbing Forces at Altnabreac and 
Kinbrace. These places are only about twelve miles apart, but the Horizontal 
Disturbing Forces tend in opposite directions towards the ridge line just described. 
A well marked attraction northwards is also exhibited at three stations on or near 
the valley line which bounds this district on the south. 
Altnabreac is, however, tire only place at which a southerly attraction towards the 
ridge line is indicated. Even at Bettyhill, which is very near the ridge line, as we 
have drawn it, the Horizontal Disturbing Force is directed away from it. It is, 
therefore, possible that the ridge line may not be clearly marked in that neighbourhood. 
The connection of the Cape Wrath Sub-District with the north of the Hebrides is 
suggested, but is certainly not proved. 
The chief feature in the Loch Broome Sub-District is the region of high Vertical 
Force indicated by the results at Scoraig, Ullapool, and Braemore. A general 
attraction towards this centre is exhibited at neighbouring places, but the exact form 
of the ridge line is doubtful. At Overscaig in the north the Vertical Force is high, 
but the Horizontal Disturbing Force points north, away from Loch Broome. As the 
direction of the Horizontal Disturbing Force at a point of maximum Vertical 
Disturbing Force is indeterminate (“ 1890 Memoir,” p. 293), it is possible that the 
short ridge line which we have drawn curves northwards to Overscaig, and the 
directions of the Horizontal Disturbing Forces at the station on Loch Shin support 
this view. 
The connection of this district with the south of Lewis is very doubtful. 
Districts 4 and 5. — No7'th and South Aherdeenshire. 
The Great Glen District is bounded on the north-east by two sub-districts, with the 
more northerly of which it appears to be in connection. The valley line between 
them is marked approximately by the Biver Dee. 
We tried to fix the points at which the ridge lines intersect the east coast by 
running a chain of stations north and south of Aberdeen. 
Thus, between Aberdeen and Ellon, which are only about 15 miles apart, we inter¬ 
polated three stations, numbered respectively as 2, 3, and 4. The middle station (3) 
was near Belhelvie. It showed a well-marked maximum of Vertical Disturbino’ 
Force and the Horizontal Disturbing Forces at the two more northerly stations 
(Ellon and (2)), and at the station to the south all tended towards it. 
Directly to the west of this centre are three stations of high V^ertical Force. The 
disturbance is a maximum at Inverurie, and the Horizontal Disturbing Forces at 
Inverurie and Kennethmont indicate a peak to the west of the former and south of 
4/^2 
