Archdeacon Pratt on the Figure of 



CO 





W 



S r- 



■^< 



« SS 





C3 O) CTi 



the three stations C or Damargida 

 (18° 3' 15"), B or Kalianpur (24° 

 7' 11"), and A or Kahana (29° SC 

 48"), and cutting the Himalayas 

 in H. (N.B. The heights in this 

 diagram are enormously exaggera- 

 ted in order to make them visible.) 



Suppose a canal is cut from the 

 ocean at P up to the Himalayas, 

 so that the sea-water may flow up 

 it. When it is at rest the surface 

 will mark the actual level. Let 

 c 6 fl be this level. Draw through 

 C, B, AthelinesmCc, nBi, rAa, 

 in which the plumb-line hangs at 

 the three stations. The Survey 

 makes Cc = 2090-5, B6 = 1878-2, 

 Aa = 942-3 feet (see Colonel Eve- 

 rest's volume of 1847). The por- 

 tion cb a oi the sea-level is the 

 Arc of the Meridian which the Sur- 

 vey measures. It is assumed in 

 Colonel Everest's volume to be 

 part of an ellipse of which the 

 ellipticity is ^~, the centre being 

 at the centre of the earth, and the 

 minor axis in a line with the earth's 

 axis. Proceeding upon this hypo- 

 thesis, he finds that the computed 

 length of ei is 63-73 fathoms longer 

 than the length as measured hy the 

 Survey; and that of ba 88-15 fa- 

 thoms shorter. But the fact is, it 

 is perfectly gratuitous to assume 

 that cb a is part of such ellipse, or 

 of any ellipse. An ellipse of the 

 kin d described is, we know, the form 

 which the ocean would assume if H 

 (and every similar disturbing cause) 

 did not exist and modify, as it does, 

 the effect of gravity ; and therefore 

 there is an a priori argument 

 against cba being elliptic. I can, 

 however, prove it to be a fact. 



In my paper in the Phil. Trans, 

 of 1855, I show that the deflec- 



