624. The Account of a 



SECTION SECOND. 



Determination of the Latitudes and Longitudes of the Stations on 

 Black Down, in Dorsetshire, Butterton, in Devonshire, and St. 

 Agnes Beacon, in Cornwall. 



Art. xvi. — Calculation of the Distance between Black Down and 

 Dunnose in the Isle of Wight. 



To complete this distance, I shall have recourse to thexxvith 

 and xxvuth triangles, published in the Philosophical Transac- 

 tions of 1795, and Lind and Livth of the Trans, for 1797, 

 together with the observations made at Black Down, in the 

 latter year. (See also PI. XXX. Fig. 1.). 



The most eligible method of calculating with these data, 

 seems to be that of first finding the cross-distance between 

 Black Down and Dean Hill. To do this, we have the angle at 

 Nine Barrow Down, between Black Down and Dean Hill, and 

 the respective distances from the first to the latter stations, 

 together with the newly observed angle between Dunnose and 

 Nine Barrow Down ; from which we obtain the angles of a tri- 

 angle, constituted by Dunnose, Nine Barrow Down, and Black 

 Down. 



The distance from Nine Barrow Down to Dean Hill is 

 166497 feet, and, from the same station to Black Down, the dis- 

 tance is 126782 feet, (see Phil. Trans, for 1795, p. 502, and for 

 1 797> P- 455') an d the angle comprehended by those distances 

 = 110° 30' 13" ,25. The difference between the horizontal angle 

 and that formed by the chords is 3",25, which, substracted from 

 no 30' 13",2,5, leaves 110 30' 10" : computing with this 



