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4 
XIX. An Account of the Mode propofed to he followed in deter- 
mining the relative Situation of tide Royal Obfervatori s of 
Greenwich and Paris. By Major-General William Roy, 
F. R. S. and A. S. 
Read February 22, 1787. 
T W O years have nearly elapfed fince an account of the 
meafurement of a bafe on Hounflow-Heath was laid 
before the Royal Society, being the firfr part of an operation 
ordered by his Majefty to be executed for the immediate pur- 
pofe of afcertaining the relative fituations of the Royal Obfer- 
vatories of Greenwich and Paris ; but whofe chief and ulti- 
mate object has always been confidered of a ftill more impor- 
tant nature, namely, the laying the foundation of a general 
furvey of the Britifh Ifiands. 
When the operation commenced in 1784, it was not doubted, 
that in 1786, at latefl, we fhould have been able to have pro- 
ceeded with the feries of triangles from Hounflow-Heath to the 
neighbourhood of Dover; but the contrivance and conflrudtion 
of an inftrument, new of its kind, propofed to be made ufe of, 
and more particularly the nicety of its divifion, whereby it is 
hoped the angles may be determined to a degree of preciflon 
hitherto unexampled, have required much more time than Mr. 
2 Ramsden 
