G34 
i\rR. A. W. RtrCKER AND DR. T. E. THORPE ON A MAGNETIC 
a firm spot on alluvium near a stream, but in all cases such precautions as were 
possible wei’e taken. 
ikt man_y stations also the observations v'ere repeated at two neighbouring places 
to distinguish as far as possible between regional and local attractions. The disturb¬ 
ances were very great and the results were often in bad accord. 
riius at each of the pairs of stations at Dunloy and south of Ballymena, the two 
Horizontal Disturbances are in opposite directions. At the two stations north of 
Ballymena, which were about a mile apart, the Vertical Disturbing Forces were 
— 0'00274 and + 0 01233 C.G.S. unit respectively. Under such circumstances we 
can arrive at no certain conclusions. Taking, however, the results as they are, and 
proceeding as usual, we find from the Vertical Disturbances a short ridge line from 
Carnioiigh to the neighbourhood of Ballymena, surrounded by a horseshoe-shaped 
valley line, which in turn is enclosed by a ridge line which runs from Larne to 
Sperrin. Its continuation northwards is suggested by the high Vertical Force at 
Coleraine. 
If these lines are drawn, the Horizontal Disturbing Forces fit in with the scheme 
in a surprising way. Putting aside the results at Dunloy and at the stations south 
of Ballymena, the directions of the Horizontal Forces at Cookstown Junction and 
Balymena, at the two stations north of Balymena, at Carnlough and AVaterfoot are 
all explained by the central ridge line. 
The external ridge is suggested—quite apart from the Vertical Forces—by the 
Horizontal Forces at the follovvung pairs of stations : Larne and Carrickfergus, 
Belfast and Templepatrick, Sperrin and Draperstown, Coleraine and Ballycastle 
(Antrim). A general attraction towards it is also indicated at nearly a dozen 
external stations, which would be unexplained if a region of high Vertical Force 
were not interposed between these places and the region of negativ’e disturbance near 
Ballymena. 
One blanch of the external ridge points in the direction of the centre of attraction 
neai Islay, thus sugesting a connection between it and the magnetic system of 
Scotland. 
On the wnole then, while giving our conclusions as to Antrim with all reserve, 
we think the solution of this vmry difficult problem, which is suggested by the 
A eitical Forces alone, (l) fits in very well with the results arrived at in Scotland, 
and (^) explains the direction of the Horizontal Disturbing’ Forces in Antrim better 
than could havm been expected. 
District 19. —Mid-Ireland. 
Nearly two-thirds of Ireland are included in this District, the central point of 
which seems to be the meeting point of several ridge lines near the Slieve Bloom 
Mountains, at a place the approximate position of which is Lat. a3°, Long. 8°. 
