Trigonometrical Survey. 635 



fore, the latitude of Hensbarrow is 50 23' 3",3, and its longi- 

 tude, west of Butterton, 55' 2o",2 ; consequently, its longitude, 

 west of Greenwich, is 3 52' 47",5 + 55' 20 "' 2 = 4° 4 8 ' 7">7 



art xxii. Directioji of the Meridian at St. Agnes Beacon. 



On the 2 2d of May, in the forenoon, the angle 

 between the Pole Star, when at its greatest 

 elongation from the meridian, and the staff 

 near Peranzabulo, was observed, and found 

 to be - - - 38° 26' i",5 



And on the 2 2d, in the afternoon - 44 o 33,25 



Half their sum is the angle between the meri- 

 dian and staff - - - 41 13 17,5 



The angle between the staff at Peranzabulo and the station 

 Hensbarrow, was also observed at the same station, and found 

 to be 31 50' 55", 5 ; wherefore, 41 13' if ,5 -f 31 50' 55",$ 

 = 73 4' 13", is the angle between Hensbarrow and St. Agnes 

 Beacon. 



art. xxiii. To find the Latitude and Longitude of St. Agnes 



Beacon. 



In Plate XXX. Fig. 3. Let A be the station at St. Agnes, P 

 the pole, H Hensbarrow, and B the point where the parallel to 

 the meridian of St. Agnes cuts that meridian, BHP being a 

 right angled spherical triangle on the earth's surface. 



PH has been already found = 39 36' 56", j ; and, as BH, the 

 distance of Hensbarrow from the meridian, =92878, and AB, 

 the distance from the perpendicular, = 28271 , we get BH =15' 

 iC',9, and AB = 4' 38",8 ; which arcs are found by using 

 61182 and 60845 fathoms, for the length of their respective 



