88 Colonel A. R. Clarke on the Figure of the Earth. 



curve is simply that elliptic curve which best represents the 

 observations. 



Indian. 



Anglo 



-French. 



Russian. 



Lat. 



I. 



Lat. 



& 



Lat. 



& 



o 



ft, 



o 



ft. 



o 



ft. 



10 



-11-8 



40 



4- 81 



48 



-2-7 



12 



-18-5 



42 



+ 15-7 



50 



-37 



14 



-19-6 



44 



+ 18-9 



52 



-4-0 



16 



-16-7 



46 



+18-8 



54 



-37 



18 



-111 



48 



4-161 



56 



-2-9 



20 



- 4-3 



50 



4-11-8 



58 



-1-8 



22 



4- 2-1 



52 



4- 6-8 



60 



-05 



24 



4- 6-9 



54 



4- 1-9 



62 



4-0-8 



26 



4- 9-3 



56 



- 1-8 



64 



4-2-0 



28 



4- 8-3 



58 



- 3-6 



66 



4-3-1 



30 



4- 3-8 



60 



- 2-7 



68 



4-3-8 



32 



- 4-2 







70 



4-4-1 



Here we see the local form of the meridian sea-level in 

 India with reference to the mean figure of the earth. Sup- 

 posing that there is no disturbance of the sea-level at Cape 

 Comorin, then from that point northwards a depression sets in, 

 attaining a maximum of nearly 20 feet at about 14° latitude ; 

 thence it diminishes, disappearing at about 21°. An elevation 

 then commences, attaining at 26° about nine feet; then this 

 elevation diminishes, and becomes a small depression at 32°. 

 This deformation may or may not be due to Himalayan attrac- 

 tion; at any rate we have here an indication that that vast 

 tableland does not produce the disturbance that might a priori 

 have been anticipated. This is in accordance with the fact 

 that there is an attraction seaward at Mangalore and Madras, 

 and slightly also at Bombay : and I think we have here a cor- 

 roboration of Archdeacon Pratt's theory, that where the crust 

 of the earth is thickest there it is least dense ; and where thin- 

 nest, as in ocean-beds, there it is most dense. 



The Anglo-French arc shows a deformation nearly as great 

 as the Indian — though, after all, the linear magnitude in either 

 case is certainly as small as could be expected. One cannot 

 help remarking here, that the remeasurement of the French 

 meridian-arc, with all modern refinements of observation and 

 calculation, with a considerable increase in the number of lati- 

 tude stations, would be a vast service to science. 



With .the elements of the earth's spheroidal figure at which 

 we have arrived above (E) the following results are obtained. 

 The radii of curvature in and perpendicular to the meridian in 

 latitude <f> being p, p r , their values in standard feet are ; 

 p = 20890564 - 106960 cos 20 + 228 cos 40, 

 p' = 20961932- 35775cos204- 46cos40. 



