Trigonometrical Survey. 



607 



the following triangle, in which the distance between St. Ann's 

 Hill and Bagshot Heath, viz. 46955,3 feet, (see Phil. Trans, 

 for 1795, p. 496,) is used for the base. 



No, of 

 triangles 



L1X. 



Names of stations. 



St. Ann's Hill 

 Bagshot - - 

 Pen Tower - 



Observed 

 angles. 



80 43 48 

 70 30 37 



Diff. 



Spheri- 

 cal 

 excess. 



Error. 



Angles corrected 

 for calculation. 



80 43 48 



7° 3° 37 

 28 45 35 



Pen Tower from 



J St. Ann's Hill 

 I Bagshot Heath 



Distances. 



Feet. 



92000,5 

 96318 



The distance from St. Ann's Hill to Hanger Hill Tower is 

 68895,8 feet : this is derived from the mean length of the base 

 on Hounslow Heath. This side, together with St. Ann's Hill 

 and Pen, using the included angle at St. Ann's Hill, as found 

 above, give 94640,5 feet, for the distance between Pen and 

 Hanger Hill Towers. 



The angle at St. Ann's Hill, between Bagshot Heath and 

 Hanger Hill Tower, is 151 7' 24^25 : this, with the sides 

 Bagshot Heath and St. Ann's, St. Ann's and Hanger Hill, 

 give 17 13' 48", for the angle at Bagshot Heath, between 

 Hanger Hill Tower and St. Ann's Hill : hence we have the 

 following triangle. 



Bagshot Heath - - 16 45' 43" 

 Hanger Hill - - 103 18 23 

 Stanmore - - 59 55 54 

 I 2 



