18 



GEOGRAPHICAL POSITIONS. 



WEST COAST OF IBELAND. 



LAT. N. 



LONG. W. 



VAR. 



WEST. 



1895. 



AUTHORITIES. 



Ckre Island, Lighthouse... 



Achil Head 



Slieve More, Achil Island 

 Eagle Island, Lighthouse ... 

 Tawnaghmore, Station ... 

 Telling or Teelin Head ... 

 Rathlin O'Birne Lightho. 

 St. John's Point, Lightho. 



Ballyshannon Church 



Sheve League (1,977 feet) 

 Rinrawros Point, Lightho. 

 Bloody Foreland (1,024 ft.) 

 Muckish HiU (2,186 ft.) ... 

 Rockall 



53 

 53 

 54 

 54 

 54 

 54 

 54 

 54 

 54 

 54 

 54 

 55 

 55 

 57 



49 



58 







16 



17 



42 



39 



34 



30 



39 



50 



8 



6 



36 



38 

 20 

 35 





 40 





 47 



8 

 11 



5 





 14 





 20 



9 



10 



10 



10 



9 



8 



8 



8 



8 



8 



8 



8 



7 



13 



58 

 16 

 3 

 5 

 35 

 48 

 49 

 27 

 11 

 42 

 33 

 15 

 59 

 41 



58 

 

 26 

 32 

 47 

 10 

 52 

 33 

 47 

 19 

 30 

 41 

 49 

 32 



The Grand Trigonometei. 

 CAL Survey, &c. 



Capt. Vidal, &c. 



NOTES. 



1. The positions of places on the Irish coasts depend upon the observations made in 

 the Trigonometrical or Ordnance Survey. The principal triangles, commencing with the 

 measurement of the base on the East side of Lough Foyle, in 1826-8, were extended over 

 the whole area, between that period and 1852, and gave results which may be practically 

 taken as absolutely correct. 



Suace that period, the minute surveys of the land, on a very large scale, have also been 

 completed ; and upon this basis our xldmiralty surveyors have constructed om* present 

 charts, by adding the soundings and maritime features outside the low-water line. The 

 names of Mudge, Bedford, Wolfe, Beechey, Frazer, and Chvirch, should be mentioned 

 among the officers connected with those operations. 



2. Dublin. — The Astronomical Observatory at Dimsuak, 3 miles N.W. of Dublin, in 

 lat. 53° 23' 13" N., long. 6° 20' 30" W., is a pomt verified by triangvdation as well as by 

 observation. 



3. Valentia. — One of the most important geodetical operations in connection with the 

 Ordnance Survey, was the clironometric determination of the difierence of longitude 

 between Valentia and Greenwich, in December, 1845. This arc, one of the largest which 

 could be measured in the British Isles, has been of very great importance, as well in 

 verifying the accuracy of the Trigonometrical Survey, as in determining the true figure 

 o£ the earth. It was carried on by Professor Airy, the Astronomer Royal, assisted by 

 Mr. Sheepshanks, Mr, Hartnup, Mr. Hind, and several other observers, by means of thirty 

 pocket chronometers. The stations were Greenwich, Liverpool Observatory, a temporary 

 Observatory at Kingstown, and Feaghmaan at Valentia. The final determination of the 

 longitudes, chronometrically, were — Liverpool, 12'" 0'05' ; Kingstown, 24^" 31-20^ ; and 

 Valentia, 41*" 23-23". By the Ordnance Siu'vey, these longitudes were made — Liverpool, 

 12'" 0-35^ "lingstown, 24"" 31-48* ; and Valentia, 41™ 23-07^ 



The Variation of the Compass is now decreasing on the Coast of Ireland at the rate of 

 from 6^' to 8' per annmn. 



