Trigonometrical Survey. 625 



angle and the sides spoken of, there results the following tri- 

 angle, viz. 



Nine Barrow Down - no" 30' 10" 

 Black Down - 40 6 54,75 



Dean Hill - - - 29 22 55,75 



This, using the side Nine Barrow and Dean Hill, ( 166497 

 feet,) gives 240236,7 feet, for the distance between Black Down 

 and Dean Hill. 



The angle at Dean Hill, between Nine Barrow Down and 

 Dunnose,is 64 50' 19", (see Phil. Trans, for 1795. p. 501,) and 

 the angle between Black Down and Nine Barrow, as just found, 

 is 29 22' 55",75, which, increased by the proper correction for 

 the difference between the chord and horizontal angles, becomes 

 29 22' 57",5. The sum of these angles ,94° 13' i6",5, is the hori- 

 zontal angle between Black Down and Dunnose. 



The angle at Black Down, between Dunnose and Nine Bar- 

 row Down, deduced from observations made in 1797, is found 

 to be 4 30' 25",75 : this, subtracted from the angle between 

 Dean Hill and Dunnose, leaves 35 36' 29", for the angle at 

 Black Down ; which, corrected for the purpose of reduction 

 to their respective chord angles, become 94 13' n",5, and 35° 

 36' 25",75, from whence we get the angle at Dunnose = 50? 

 iq' 22",75. We have, therefore, the following triangle, viz. 



Dean Hill 



- 94 13 ii>5 



// 



Black Down - - 35 36 25,75: 



Dunnose - - - 50 10 22,75 



The distance between Dean Hill and Dunnose is 183496,2 



feet, (Phil. Trans, for 1795, p. 501,) and that between Black 



Down and Dean Hill, according to the foregoing computation, is 



240236,7 feet : these, applied to the angles of the above triangle.. 



