SURVEY OP THE BRITISH ISLES FOR THE EPOCH JANUARY I, 1891. 621 
magnetic region. A clearly-marked ridge line runs a little to the north-west of 
Callander and Crieff, and a little to the south-east of Dunkeld. Our last survey left 
us in some doubt as to the exact relation of Crieff to the surrounding magnetic 
districts. Additional stations in the neighbourhood have now completely cleared 
the matter up. The Crieff region of high Vertical Force is not only, as we surmised, 
separated by a valley line from the Great Glen District, but, as the direction of the 
Horizontal Disturbing Force at Crieff suggested, it is also independent of the 
important Scotch Coalfield District on the other side. 
The prolongation of the Crieff ridge line eastwards is not made obvious by the 
Vertical Forces alone. The Horizontal Disturbing Forces, however, clearly support 
the view that a narrow attractive region runs E.N.E. from Dunkeld, then bends 
nearly due east, and finally enters the sea between Bervie and Montrose. 
If this is so, the district contains a secondary ridge line which runs from a point 
between Montrose and Arbroath, nearly parallel to the first, Dundee is a magnetic 
col, the Vertical Disturbing Force being — 23 as against — 132 at Perth, and — GO 
at St. Andrews. 
Immediately on the other side of the valley line there are high Vertical Forces at 
Kinross and Cupar, with clear indications that a centre of attraction lies between 
them. This appears to be a peak in a region of high Vertical Force, and to be 
separated by a very slightly-maiked secondary valley line from the important ridge 
line which traverses it further to the south. This peak is connected by a magnetic 
col between Perth and Dundee with the Arbroath ridge line. 
District 7, —The Scotch Coal Field and the Cheviots. 
We now come to a district of the first rank, which, although comprising several 
centres, appears to be a connected whole extending from the Tees to the Tay, 
and from Canty re to the coast of Northumberland. 
The main feature of this region, as delineated after our earlier survey (‘‘1890 
Memoir,” Plate 13), was a ridge line from the neighbourhood of Edinburgh to Arran, 
intersected by a clearly-marked col near Glasgow. This result has been completely 
confirmed, and the position of the ridge has been determined at six points within 
narrow limits and with far greater accuracy than we had previously attained. 
Thus in 1890 we placed it between two chains of stations, of which the northern 
comprised Dundee, Edinburgh, Stirling, Glasgow, and Cumbrae, while the southern 
consisted of Berwick, Hawick, Carstairs, and Ayr. These lines run about 30 miles 
apart, except at their easterly terminations, where the distance from Berwick to 
Dundee is more than 60 miles. 
We have now fixed the position of the easterly half of the line between three 
pairs of high level stations, viz., Berwick and Grant’s House (13 miles apart), 
Edinburgh and Leadburn (ll), and Falkirk and Whitburn (10). 
