SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, 1886. 303 
there can be no donbt that in this district the ridge line passes through the region of 
greatest Vertical Force disturbance. It obviously does so in the east. In the west the 
region of positive disturbance is defined by a single station only, and its boundaries are 
uncertain. If we included Welsh’s observations at Ardrossan they would be pushed 
further south. In the central region there are clear indications of a maximum dis¬ 
turbance, though the largest values are negative. Thus at Row and Stirling the 
Scotcli Coal-field District. 
Vertical Force disturbances are —•0188 and —•0002; at. Glasgow and Carstairs 
'—•0080 and —‘0079 ; and at Ayrand Hawick —'0145 and —^0099. The two central 
stations which are nearest to the ridge line have algebraically the largest values. 
The convergence of the Horizontal disturbing Forces towards the ridge line is 
unmistakeable. The isogonals (Plate V.) give evidence of a subsidiary centre of 
attraction near Lochgoilhead, 
