626 I'HILOSOPHICAL TRANSACTIONS. [aNNO WQS. 



In addition to this reason, there was another which offered itself, and that was, 

 the prospect of being able to obtain the length of a degree of longitude in an 

 early stage of the survey; for it had been suggested, and on inquiry was found 

 to be true, that Dunnose in the Isle of Wight was visible, in particular moments 

 of fine weather, from Beachy Head on the coast of Sussex: but attention was 

 at the same time given to the recommendation of General Roy, in the selection 

 of Shooter's Hill and Nettlebed, as places for observing the directions of the 

 meridian; and it was resolved, whatever preference might in future be given to 

 those on the coast for this important operation, that at all events such observa- 

 tions should be made, as might determine the distance between the stations 

 recommended by the General. 



Having therefore formed an outline for the operation of the year ] 7Q2, on the 

 approach of spring, Captain Mudge and Mr. Dalby explored the country over 

 which it was intended to carry the triangles, and visited such stations in the series 

 of General Roy as were judged to be proper for the above purpose. In the 

 choice of those stations which were about to be selected, instructions had been 

 given by the Duke of Richmond to avoid towers and high buildings, as getting 

 an instrument on them had, by the experience which the former operation 

 afforded, been found difficult and dangerous; such of them therefore as were 

 thus circumstanced were avoided, and near the most proper ones, stations were 

 chosen on the ground. From these directions the points of junction were neces- 

 sarily confined to St. Ann's Hill, Botley Hill, and Fairlight Down, because the 

 pipe sunk near Hundred Acre House was found destroyed; but this was consi- 

 dered immaterial in its consequence, as it would have been improper to have 

 chosen it for a principal station, because the high ground near Warren Farm 

 took off the view of Leith Hill. 



A disadvantage however, which seemed to result from this resolution of avoid- 

 ing high buildings for stations, occurred in the difficulty which offered itself of 

 proceeding from Hanger Hill and St. Ann's Hill, with a mean distance of that 

 side as given by General Roy ; for the station chosen at the former place being on 

 the ground, there was scarcely a possibility of erecting a staff at King's Arbour, 

 sufficiently high to afford a view of its top from Hanger Hill : a quadrilateral 

 therefore, similarly posited, could not be fixed on; but as a proper substitute, a 

 station was chosen on the elevated ground near Banstead, which was visible from 

 St. Ann's Hill, King's Arbour, and Hanger Hill; and this, together with St. 

 Ann's Hill and Hanger Hill, formed 2 triangles, which would give the distance 

 between St. Ann's Hill and Banstead, independent of each other. 



On the return of Captain Mudge and Mr. Dalby from their expedition, in 

 which they had selected many of the principal stations, and by examining the 

 face of the country had formed some judgment of the future disposition of the 



