030 PHILOSOPHICAL TKANSACTIONS. [aNNO 1795. 



A similar circumstance occurred at Brightling. For these reasons, lamps are 

 greatly preferable to white lights, when the distances are not too great. At the 

 different stations, after the observations had been made, large stones, from 14. 

 to 2 feet square, were sunk in the ground, generally 2 feet under the surface, 

 having a hole of an inch square made in each of them, the centre of which was 

 the precise point of the station. Immediately after this are registered all the 

 angles taken in the year 1 TQI, which it is not necessary here to be reprinted. 



From an opinion, that triangles, whose sides are from 12 to about 18 miles 

 in length, are preferable for the general purposes of a survey, to those of greater 

 dimensions, we have endeavoured to select such stations as might constitute a 

 series of that description. In those which were chosen to the eastward of 

 Bagshot Heath, Hind Head, and Butser Hill, we have in some degree suc- 

 ceeded; but, from local circumstances, we have not been equally fortunate with. 

 those to the westward. Instead of Dean Hill, it was hoped that the ground on 

 which Farley Monument stands, might have suited our purpose; but the wood 

 to the west of the hill was found to be so high, that even with the whole stage, 

 the instrument would not be sufficiently elevated. There remained therefore 

 no other expedient but fixing on Dean Hill, which is the highest spot near 

 Farley Monument. It must be also observed, that Highclere is the only situa- 

 tion which affords the means of carrying on the triangles from the side Bagshot 

 Heath and Hind Head, without forming a quadrilateral. 



The interior stations which, were selected for the use of the small instrument, 

 were Bow Hill, near Rook's Hill; Portsdovvn Common, on the road to Ports- 

 mouth ; and Sleep Down, near Steyning. To the first and last of these the 

 instrument was taken, for the purpose of fixing such objects as could not be 

 intersected from the principal stations. The points on the coast were particularly 

 wanted, for the construction of some maps which were making for the use of 

 the Board of Ordnance. Those places so fixed will be given hereafter; but it 

 must be observed, that (gvj opportunities were lost of searching for church 

 towers, and other objects whose situations were to be determined. That the 

 bearings of those might be taken with precision, the observations were made 

 either in the morning or evening, when the air was free from vapour, and with- 

 out that quivering motion, which in summer it generally has in the middle of 

 the day. 



Towards the conclusion of the operation in 1792, it was found that the axis 

 of the instrument, by the frequent use of it, was considerably worn, and whicli 

 was perhaps increased by the motion of the carriage, as the arch could not be 

 clamped with tightness sufficient to prevent the circle from moving within the 

 limits of the bell-metal arms, and the upright part of the travelling case. The 

 consequence was, that it sometimes became necessary to let the circle lower by 



