the 'Trigonometrical Operation . 
out the extent of the ifland till it fell into the Murray Frith. 
A new meridian might then be taken more to the weft ward, 
perhaps that of Inyernefs, or fome hill near it, whereby the 
feries would be extended to the North Sea, bounding the coafts 
of Sutherland and Caithnefs. 
It is unneceffary here to enter into any minute detail of what 
fliould be the fucceeding parts to be carried preferably info exe- 
cution, as things of this fort would naturally prefen t them- 
feives, in the. courfe of fuch important operations,, to thofe 
entrufted^ with the direction. It is however fufficiently ob- 
vious, that having, as above fuppofed, obtained the meafure of 
a portion of the meridian amounting nearly to fixteen degrees 
of latitude in continuity, .between' the Pyrenean mountains 
and the northern extremity of Britain, or more than one*fixth 
part of the diftance between the equator and the pole ; the 
things of the next confequence to be obtained would be, the 
meafures of the radii of the vertical and parallel in the low- 
lands of Scotland, that is, in the latitude of Edinburgh, and 
again at the northern coaft. In each of thefe fituations it is 
evident, that about three degrees of longitude might be mea- 
fured with great exadtnefs. At the north, for inftance, Cape 
Wrath being made the central ftation, from thence the Orkney 
IJlands to the eaftward and Butt of the IJland of Lewes to the 
weftward, being diftindtly feen, would confequently become the 
ftations to the right and left. 
With regard to the ufe of white lights, fo indifpen.fably ne« 
ceffary in all operations of this fort, no opportunities have yet 
offered of afcertaining with precifion the immenfe diftance to 
which they may be feen in favourable circumftances of the 
weather, and with fufficient elevation of theftations above the 
fea. Thofe commonly ufed in the recent operation were only 
Vol. LXXX. 
M m 
three 
