199 



the author, with the additional correction for ocean attraction 

 introduced. 



a. 6. b i a b. 



I. ... 20926500 20855400 294 

 II. ... 20920328 20846522 2837 

 III. . . . 20919988 20846981 286-55 



The residual errors of latitude at Damargida, Kaliana, and Kali- 

 anpur, which in Captain Clarke's ellipse were +1"'05, 0"'95, 

 + 1"-20, are now reduced to + 0"'93, _0"-37, +0"74. 



In conclusion, the author calculates the distance of a point in the 

 latitude of Kaliana from the centre of the earth in the three ellipses, 

 and finds it to be near 7000 feet greater in the ellipses II. and III. 

 than in the mean ellipse I. That deviations to such an extent as 

 this from the mean ellipse should actually occur he thinks likely 

 enough, and he is not disposed to have recourse to some yet un- 

 discovered cause to reconcile the Indian Arc with the mean ellipse. 

 The occurrence of marine fossils in mountains and elevated regions, 

 shows that great changes of level of the land relatively to the water 

 have actually taken place ; and it seems unlikely that an extensive 

 internal change in the state of the earth would cause an upheaval or 

 depression of the land or the water alone ; it might rather be expected 

 that both would be affected, though unequally. Hence the absolute 

 change of distance of the land from the centre of the earth may have 

 been much greater than the elevation relatively to the water, while 

 the phenomena adduced indicate that even the latter must have been 

 very great. 



IV. " Comparison of some recently determined Refractive Indices 

 with Theory." By the Rev. BADEN POWELL, M.A., F.R.S., 

 F.G.S., F.R.A.S., Savilian Professor of Geometry in the 

 University of Oxford. Received November 17, 1859. 



In a series of papers inserted in the Philosophical Transactions 

 (1835, 1836, 1837), and afterwards, in a more correct and complete 

 form, in my Treatise ' On the Undulatory Theory applied to the Di- 

 spersion of Light' (1841), I endeavoured to investigate the great 

 problem of the explanation of the unequal refrangibility of light on 



