SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY 1, 188G. 
63 
j 
Stations. 
Dips. 
Deflections. 
Vibrations. 
Geog’rapbical 
meridian. 
Magnetic 
meridian. 
Scotland .... 
64 
120 
57 
66 
89 
93 
England and Wales 
102 
213 
94 
135 
171 
185 
Ireland .... 
44 
89 
35 
58 
84 
84 
Total . 
200 
422 
186 
259 
344 
362 
Most of these observations were taken by one or other of us. We have, however, 
to thank Mr. A. P. Laurie, now Fellow of King’s College, Cambridge, for observa¬ 
tions of Dip at 8 stations in Scotland. The stations on the West Coast of Scotland 
were, for the most part, visited in Dr. Thorpe’s yacht “ Coventina.” During the 
first year (1884) we generally observed together. Afterwards, in order to save time, 
we ti'aveiled separately. 
Method of Taking the Ohservations, 
The conditions and time of the observations necessarily varied, but the greatest 
number were made as follows:—Shortly before 10 a.m. we visited the post-office to 
correct our GhroRometers by the time signal from Greenwich. We then drove to the 
station which had been selected the night before or earlier in the morning, The first 
observation taken w^s the solar azimuth, which was finished about an hour before 
noon. This was followed by the declination, vibration, and deflection in this order. 
The dip was then determined, and, if time and weather allowed, we often repeated 
the azimuth and declination. The Sun observations were hardly ever taken within 
an hour of nooii. 
In a variable climate like that of the United Kingdom the weather often presents 
a serious difficulty. We carried with us a small tent, in which the dip and vibration 
observations could be made, and we were also provided with waterproof covers for the 
Magnetometer and Dip Circle. We were thus able to make the Dip observations, for 
example, during showers, while the Magnetometer, though outside the tent, was pro¬ 
tected by its covering. The case coRtaining the dip needles was carried in a box 
filled with soda-lime to prevent the axles being injured by rust. 
During sunshine we shaded the deflecting magnet in the deflection experiment by a 
cardboard case, or by throwing a light piece of cloth over it. At 42 principal and 
subsidiary stations the force was determined by means of the vibration experiment 
only, the deflection being omitted and the moment of the magnet deduced from the 
values obtained at neighbouring stations. 
The only part of the observations which recjulres special comment is the use of the 
mirror employed in the sun observations. The adjustment can be effected by means 
of the reflected image of the cross wires in the telescope. We found, however, that 
