4 
MR. GEORGE W. WALKER ON THE MAGNETIC RE-SURVEY OF THE 
cannot well be over-rated. Apart from the fact that it relieved me of the necessity 
of finding my own azimuth by sun observation, it places the magnetic survey on a 
permanent basis, so that in future surveys precisely the same points and reference 
objects will be available, and the scheme is linked up with the triangulation of the 
British Isles. 
The general plan of campaign was worked out by Captain (now Colonel) Winter- 
BOTHAM, D.S.O., Captain (now Major) Henrici, and myself. It was arranged that 
parties from the O.S.O. should travel in advance to select, mark, and fix a suitable 
point of observation and a suitable reference object for use. Wlien a station had 
been so determined, maps and descriptions' to enable me to find the stations were 
sent on. 
The parties had complete instructions as to selecting points not likely to be built 
over in the near future, and well removed from local magnetic disturbances and more 
especially those that might arise from railway or tramway lines. 
At first we aimed at getting the points close to the reputed points used by Rucker 
and Thorpe, but a little experience showed that this was not generally possible. In 
many cases electric tramways had rendered the point unsuitable, in others the 
co-ordinates appeared incorrect, and again other points would have been very 
difiicult for the O.S.O. to fix. It is obvious that the simplest course for the O.S.O. 
was to obtain a suitable “ down trigonometrical point ” for the magnetic station from 
which a suitable “ up trigonometrical poiiH,” such as a spire, could be used as 
reference object. No reasonable objection could be taken, from a magnetic point of 
view, to adopting a course which simplified the work of the O.S.O. Accordingly our 
plan changed to selecting as observing station, if possible, a “ down trigonometrical 
point” as near as possible to Rucker and Thorpe’s point and free from spurious local 
magnetic disturbance. 
The field work started in March, 1914, and after the usual slight difficulties of 
getting the various “ staff” operations to work smoothly, the survey went well away 
throughout tlie summer. The outbreak of war found us working in the North of 
Scotland after having surveyed from Cornwall round the South and East of England, 
right up to Orkney. The O.S. parties, consisting chiefly of Royal Engineers, had to 
be recalled; but Colonel Close kindly agreed to leave with me Surveyor Assistant 
Young, who was grea.tly skilled in finding the “ trig.” points. We therefore worked 
along under considerable difficulties until the end of September, when I decided to 
finish up for the season. Ill stations had been completed out of a programme 
of 120. 
The field work was resumed in April, 1915, but various circumstances arising on 
account of the war interrupted the work. 72 stations were completed by the end of 
October of that year. Thus during the summers of 1914 and 1915, 183 out of the 
original 200 had been completed. These included the whole mainland of Scotland, 
England and Wales and Ireland, along with Orkney and Skye. There remained to 
