794 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1800. 



Stations. 



Ground above low- 

 water mark. 



Bradley Knoll Feet 973 



Mendip 999 



Westbury Down 775 



Dundry 790 



Lansdown 813 



Farley Down 700 



Moor Lynch 330 



Dnndon Beacon 360 



Lugshorn Corner 49 



Greylock's Foss-way 42 



Ash Beacon 655 



Cadon Barrow 1011 



Brown Willy 1368 



Inkpin 1011 



Stations. Ground abore low- 



T.-T rn i t water mark. 



Nuffield jr eet j^j 



White Horse Hill .* ." 8 g 3 



Shotover Hill .- 50,9 



Muzzle Hill, (Brill station) 744 



Whiteham Hill ,'] 576 



Wendover, ground above. ... 905 



Bow Brickhill 6'83 



Kinsworth 904 



Lillyhoe . 664 



Stow on the Wold 883 



Epwell Hill 836 



Broadway Beacon ] 086" 



Arbury Hill 804 



Between 



Bodmin Down and Cadon Barrrow ± 



Bradley Knoll and Westbury Down ■$■ 



Maker Heights and Black Down ■£■ 



Highclere and Inkpin £ 



St. Agnes Beacon and Trevose Head ^ 



Moor Lynch and Lugshorn Corner -jV 



Hensbarrow and Trevose Head -fa 



Wingreen and Bradley Knoll T l 7 



Bodmin Down and Trevose Head -y'-g- 



Carraton Hill and Black Down. ^ 



Westbury Down and Mendip -fa 



Carraton Hill and St. Stephen's Down -^ 



Farley Down and Mendip -r'-g- 



Beacon Hill and Westbury Down -^ 



Dundry and Farley Down T ' T 



Dundon Beacon and Mendip x'-y 



Bradley Knoll and Mendip -fa 



Lansdown and Mendip -fa 



Moor Lynch and Dundon Beacon ^ 



Dundry and Mendip -fa 



Westbury Down and Farley Down -Jp 



Mean Terrestrial Refractions. 

 Between 



Mean. 

 Retractions. 



Mean 

 Refractions. 



St. Stephen's Down and Black Down. . . , 



Moor Lynch and Dundon Beacon > 



Dundon and Lugshorn Corner ' 



Moor Lynch and Greylock's Foss-way 4. 



Lugshorn Corner and Greylock's Foss-way . . 

 Cadon Barrow and horizon of the sea in the 



direction of Trevose Head 



Ditto in a northern direction 



Brill and Nuffield '.'"'* 



Broadway and Stow 



Epwell and Broadway 



Highclere and White Horse Hill JL 



Nuffield and White Horse Hill {jI 



Nuffield and Bagshot ^l 



Epwell and Stow j 



Brill and Stow on the Wold 



Wendover and Bow Brickhill 



Kinsworth and Bow Brickhill 



Shotover and White Horse Hill 



Epwell and Brill 



Bow Brickhill and Brill 







T 



TV 



tV 



T7 

 _i 



TV 



1 



The height of the station on Trevose Head, above the surface of the sea at 

 low-water, was determined in 1797, by levelling. The transit instrument was 

 used for the purpose ; and there is reason to believe the result, 274^- feet, is 

 within a very few inches of the truth. In the Philos. Trans, for 1797, the height 

 of the station on Maker Heights is said to be 402 feet ; this was also found by 

 levelling. The altitude of St. Agnes Beacon, determined from that station, is 5QQ 

 feet ; but if the calculation be made from the base of altitude at Trevose Head, 

 the height of that station, above the level of the sea, will be 62 1 feet, which 

 gives a difference of 22 feet. It must be recollected however, that in the first 

 result, the computation was carried through 2 intermediate stations, which gave 3 

 arcs, and as many mean refractions ; and, considering the extreme variableness to 

 which refractions are liable, we are assuredly not to consider 22 feet deviation from 

 the truth as a large quantity. 



Besides St. Agnes Beacon, the altitudes of Cadon Barrow, Brown Willy, Hens- 



