Local Attraction on Geodetic Operations. 271 



From the Anglo-Gallic Arc, 







Deflec- 

 tions. 



Calculated 

 attractions. 



Deflections 

 to be ac- 

 counted for. 



(1) Barcelona 



(X\ HiVh Pnrf Cliff 

 \0 J ni^Li lUit v<'iixi« 



(4) Week Down ... 



(5) Boniface Down 



(7) Blackdown ... 



(8) Burleigh Moor. 



(10) Ben Hutig 



+ 1-440-3-0644 U+0-0553 V-l-37 = 

 + 0-767+0-4115 U-0 0765 V-1-37- 

 -4- 1-778 -1-0-25'i2 IT — 0-0450 V— 1 -37 — 

 + 1-747+0-2539 U-0-0452V-l-37 = 

 + 1-967+0-2559 U-0-0455 V-l-37 = 

 -0-499 + 0-2613 U-0-0466V-l-37 = 

 + 4-279+ 0-2859 U-0-0513V-l-37 = 

 -1-814 + 1-6845 U-0-4137V-l-37 = 

 -6-915+2-8048 U-0-8340 V-l-37 = 

 +0-095+3-1173 U-0-9708V-l-37 = 

 +4-403+3-9370 U- 1-3699 V- 1-37 = 



+ 2-22 

 -0-84 

 + 1-28 

 +0-25 

 +0-46 

 -200 

 + 2-76 

 -4-15 

 -9-31 

 -3-25 

 + 0-41 



+3-29 

 + 1-98 

 +2-42 

 -0-54 



-4-55 



-5-50? 



-2-01 



— 2-01 

 -1-73 

 -1-96 

 -1-46 



+0-40 

 -3-81 

 -1-24 



From the Russian Ai^c. 





+ 11-826 + 7-3799 U-2-5821 V-2-22 = 

 + 10-008 + 9-1231 U-3-8418 V-2-22 = 



+ 4-69 

 + 1-13 







From the Indian Arc. 





+ 0-625-3-5622U-3-1853V-0-033 = 

 + 0-403+4-1251U+2-7756V-0-083 = 

 +53-796+4-4215U-0-1010V-0-033 = 



-0-94 

 + 1-34 

 +52-0i 



+22-71 

 +34-16 



) 



-23-65 

 -32-82 



I have inserted the formula of Cowhythe from p. 771 of the Ordnance 

 Survey Volume. I have also added two columns, in one of which are given 

 the deflections of the plumb-line arising from attraction at those of the 

 stations for which it has been calculated. For those of the Anglo-Galhc 

 Arc, I refer to the Ordnance Survey Volume, sect. xi. p. 625 ; and for 

 those of the Indian Arc to my paper in the Philosophical Transactions for 

 1861, p. 593. I would observe that not only in the two stations of the 

 Indian Arc, but in those I have selected from the Anglo-Gallic Arc (all of 

 which are near the sea-shore), allowance is made for deficiency of density and 

 attraction of sea-water. In the stations (3), (4), (5), (6) the effect of the 

 sea for about 9 miles south of the coast is taken and estimated at +0"'27 

 (see Ordnance Survey Volume, p. 631) ; in station (8) for 36 miles north, 

 and estimated at --0"'39 (p. 642) ; in station (9) for 50 miles north, and 

 estimated at — 0"*70 (p. 664) ; in station (10) for 50 miles north, and esti- 

 mated at — 0"*64 (p. 662). It is of importance to bear this in mind. For 

 stations (14) and (15) the effect of the sea the whole way to the south pole 



* This is calculated by the formulae at p. 737 of the Ordnance Survey Volume, from the 

 following data obligingly furnished me by Major Walker, Superintendent of the Govern- 

 ment Trigonometrical Survey of India, viz. 



Astronomical latitude of Dehra 30° 19' 19". 



Distance of parallels of Dehra and Damargida 4463510-7 feet. 



The latitude of Damargida is 18" 3' 15". 



