REPORT OF THE COUNCIL, cxix 
Major C. F. Close submitted for the approval of the Council a draft 
letter addressed to the Secretary of the Board of Agriculture, to be 
signed by the President. This letter, with emendations, was approved, 
and ordered to be transmitted. It read as follows :— 
British Association for the Advancement of Science, 
Burlington House, London, W. 
November 14th, 1908. 
Sis Tuomas Henry Euiort, K.C.B., 
Secretary of the Board of Agriculture and Fisheries, 
4, Whitehall Place, S.W. 
Sir,—I desire, on behalf of the Council of the British Association for 
the Advancement of Science, to represent to you, for the information of 
the President of the Board of Agriculture and Fisheries, that the Council 
have been requested by the Association to approach Lord Carrington, 
with a view to ascertaining whether it may not be possible for the 
Director-General of the Ordnance Survey to undertake the remeasure- 
ment of the two principal British arcs, meridional and longitudinal, as 
part of the current work of the Ordnance Survey. 
The reasons which induce the Council to suggest the remeasurement 
are these :— 
The principal triangulation of the United Kingdom, which is an 
excellent piece of work, considering that its mean date is about 1835, is, 
as compared with modern triangulations, below the standard now re- 
quired for use in determining the Figure of the Earth. Making allow- 
ance for the fact that the triangulation is in the form of a net-work and 
not of a chain, it is thought that the errors in length and position are 
about twice as large as those of modern chains. It is not, however, easy 
to predict the magnitude of the errors of the British triangulation as 
compared with those of modern work; and the Council would suggest, 
for Lord Carrington’s consideration, that it would be well, before 
definitely assuming that a remeasurement is desirable, to cause a 
section of the older portion of the triangulation, forming part of the 
meridional arc between the Shetland Islands and the Straits of Dover, 
to be remeasured with modern instruments. 
The Council would further suggest that the experimental measure- 
ment should be undertaken by the existing staff of the Ordnance Survey, 
as opportunity offers; and, if Lord Carrington approves of the sug- 
gestion, the Council may be in a position to offer his Lordship the loan 
of a modern theodolite suitable for use in refined geodetic operations. 
The Council desire to point out that their motive in venturing to put 
forward these suggestions is solely tne scientific value of the remeasure- 
ment. They are aware that, for all practical map-making purposes, the 
existing triangulation is of quite sufficient accuracy ; whilst they realise 
the high character of the work of the old observers and the importance 
of Colonel Clarke’s discussion of that work. 
IT am, Sir, 
Yours faithfully, 
(Signed) Francis Darwin, 
President of the British Association. 
