Trigonometrical Survey. 543 



themselves as fit places for these observations, Dunnose in the 

 Isle of Wight presents itself as highly eligible, not only because 

 it is removed the necessary distance from the meridian of 

 Greenwich, but also because it commands a most extensive 

 view of the western coast : therefore, as the direction of the me- 

 ridian was observed on this station in 1793, (see Philosophical 

 Transactions for 1795, p. 517.) it became necessary to fix on 

 three places only. 



In the selection of these stations, it was our wish to have 

 found such as should lie nearly in the same parallel, each inter- 

 mediate one being visible from those east and west of it ; by which 

 means, the differences of latitude between their respective paral- 

 lels would be accurately determined. 



When the party was at Dunnose, in the year 1 793, a hill at a 

 very considerable distance, in a direction very nearly west, was 

 seen just rising out of the horizon. It then occurred to us that 

 this spot would, at some future period, be a very proper one for 

 a station whereon a new direction of the meridian might be ob- 

 served. Experience, in the Survey of 1795, led us to believe 

 this hill was actually Black Down in Dorsetshire; therefore it was 

 determined that our operations should commence at that station, 

 and the event verified the truth of our suppositions. 



The party took the field early in April, as observations on the 

 Pole Star, for the purpose in question, are made with superior 

 advantage at this season of the year, because the star comes to 

 its greatest elongations from the meridian at those times, when 

 the sun produces little tremor in the air, by which means, the 

 staff to which the Pole Star is referred, in good weather, is easily 

 perceived. 



As the high land in the vicinity of Teignmouth, in Devonshire, 



4A 2 



