242 PHILOSOPHICAL TRANSACTIONS. [ANNO 1797. 



After these occurs a long series of the secondary triangles, in which 2 angles only 

 have been observed ; unnecessary to be reprinted. Then follow triangles for ascer- 

 taining the distances of the Eddystone Light-house, from the Flagstaff of Plymouth 

 garrison, and the Rame-head. The ball on the lantern of the light-house was ob- 

 served from the stations on Butterton, Kit Hill, and Carraton Hill ; and as much 

 uncertainty has heretofore existed, with respect to a knowledge of its true distance 

 from any point in the neighbourhood of Plymouth, observations were made on 

 various arcs of the circle of the instrument, at the first 2 stations. Whence it re- 

 sults that, with the distance of the Eddystone Light-house from Kit Hill, and also 

 that of the Flagstaff in Plymouth garrison from the same station, we find the dis- 

 tance from the Light-house to the Flagstaff = 7 306l feet;* the observed angle 

 being 29 42' 34" : and, computing with the data obtained from the last triangle, 

 and the 223d, with the observed angle at Carraton Hill = l6° 22' l", we get 49435 

 feet for the distance of the Eddystone Light-house from the building on Rame- 

 head. It may be proper to observe, that the Eddystone Light-house is nearer to 

 the Rame-head than to any other point on the coast. Next follow triangles for 

 ascertaining the situations of the Lizard Light-houses ; and the Lizard Point. 

 Hence is inferred, that the distance from Karnbonellis to Pertinney 101474 feet. 



From the last 2 triangles we obtain 79640 feet for the mean distance between the 

 Lizard Signal-staff and the station on Karnbonellis. Computing with this distance, 

 and also that from the Western Light-house to the same station, with the observed 

 angle 0° 31' 8", we get 1857 feet for the distance between those objects. 



For the purpose of ascertaining the situation of the Lizard point, 2 angles in the 

 following triangle were observed with a sextant, viz. 



Naval Signal-staff jf 4' 



Western Light-house 60 50 



Lizard Point 



These, with the computed distance from the Signal-staff to the Light-house, give 

 the distance of the Lizard Point from the Signal-staff 24 1 9, Light-house 2700 feet. 

 Hence the distance of the point from the station on Karnbonellis is 81085 feet, the 

 angle at that station, between the Lizard Point and Western Light-house, being 

 1° 53' 47' / . 



Then follow triangles for finding the distances of the Day-mark, St. Agnes' 

 Light-house, and other objects in the Scilly Isles, from particular stations in the 



therefore, as 47337 : radius : : 5\ feet : tang. 24" the angle subtended by 5^ feet at that distance , which, 

 taken from 31' 27", gives 31' 3" for the depression of the place of the axis, instead of the ground. 

 Again, at Bodmin Down, the ground at Hensbarrow was elevated 23' 57", to which adding 24", we 

 have 24' 21" for the elevation of the place of the axis. — Orig. 



* On referring to the late Mr. Smeaton's Narrative of the Building of the Eddystone Light-house, it 

 will be found, that, from a trigonometrical process, founded on two bases measured on the Hoe, among 

 other deductions, he concluded the distance between the above objects was 73464 feet } being 403 

 greater than the distance found by the above computation.— Orig. 



