30 
MR. A, RUCKER AND DR. T. E. THORPE ON A AfAGNETlC 
Number of Stations. 
Scotland . ... ■ 
r1886 . 
[1891. 
..... 190 
England and Wales < 
[1886 . 
[1891. 
.107* 
.345 
1 
1 
Ireland, . ... < 
[1886 ...... 
[1891 ...... 
.44 
.142 
Total. 
. 882 ! 
Number of Separate Observations. 
Epoch of 
survey. 
Dips. 
Deflections. 
Vibrations. 
Geographical 
meridian. 
1 
Magnetic j 
meridian. 
1886 
422 
186 
259 
344 
362 
1891 
1.368 
521 
944 
928 
958 
Total . 
1790 
707 
1203 
1272 
1320 
Positions of Stations. 
In our earlier survey we determined the positions of our stations by making notes 
while in the field and by marking them on such maps as we carried with us. The 
latitude and longitude were determined in the case of some of the Scotch stations 
from the Admiralty charts, but generally from the Ordnance maps, which were lent 
to us for the purpose when we returned to London. This was the best course then 
open to us, but it was probable that the latitudes and longitudes would be affected 
with greater inaccuracies than if the stations had been marked on the Ordnance 
maps when we were actually on the observing ground. In our later work we have 
been able to adopt the latter plan. The Board of Agriculture has been good 
enough to present to us an entire series of the Ordnance maps, on condition that 
on completion of the survey they shah become the property^ of the Boyal Society. 
Our best thanks are due to the Board and to Colonel Sir Charles Wilson, 
K.C.B., F.B.S., the head of the Ordnance Survey, for this valuable and useful 
gift. 
Messrs. Gray and Watson have observed at about 26 stations included in the 
* Inclusive of five supplementary stations along the Valley of the V’’ye, at which Dip Observations 
only were made in 1889. 
