SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, 1891. 635 
The Vertical Forces give a ridge line from Glenfarne to Spiddle in Galway Bay. 
This is completely confirmed by the arrows at some twenty stations. Ballinamore is 
anomalous, and Clifden appears to be asspciated with a submarine region of high 
Vertical Force. 
It is possible that two loci of attraction may intersect in Galway Bay. If not, 
there is an abrupt change of direction, and the ridge runs east to between Portunma 
and Nenagh. 
It passes between the following pairs of stations :— 
Carrick-on-Shannon and Kilfree Junction, 15 miles apart. 
Castlereagh 
,, Ballaghaderreen 
9 
Cong 
„ Maum Bridge 
11 
Oughterard 
10 
Galway 
,, Lisdoonvarna 
19 
Lough rea 
,, Gort 
14 
Portumna 
„ Nenagh 
16 
The average distance of these places is 13 miles, so that the position of the ridge 
is fixed at 7 points with an average uncertainty of less than 7 miles. 
Nenagh Town gives the highest Vertical Force Disturbance in Ireland, south of 
Lat. 53°, with the exception of that measured at the Saltee Islands. 
Two ridge lines, both clearly marked by the Vertical Force, run from this place to 
the neighbourhoods of Wexford and Cork respectively. The effect of the former on 
the Horizontal Forces appears to be entirely subordinate to that of the Slieve Bloom 
Mountains centre of attraction. It is probably a narrow ridge, but it is, as we shall 
see, of very special interest. 
The second line from Nenagh to Cork is also important and is more clearly 
indicated by the Horizontal Forces. 
At both Kilteely and Cromwell’s Hill observations were taken at five stations to 
determine the effect of the basaltic rocks in that locality. As is always the case 
when close to the basalt, the results were irregular. Check measurements were also 
made at Knocklong, about 5 miles away from the basalt, The highest Vertical 
Disturbing Forces in the neighbourhood (w'hich is a region of low Vertical Force) are 
as follows, when expressed in terms of O-QOUl metric, or O'OOOOl C.G.S. unit:— 
Tipperary.+ 6 . 
Knocklong.. . — 47 . 
Cromwell’s Hill. Mean of all 5 stations.— 30. 
,, ,, „ 2 stations furthest from the basalt . . -f- 30. 
Kilteely. Mean of all 5 stations.— 17. 
„ „ 2 stations furthest from the basalt.+ 66 , 
4 m 2 
