206 The Or eat Indian Arc of Meridian, [No. 3 



the paper before hira — " If an estimate of tbe attraction at Benog 



[in tbe mountains] could be made " Then in Mr. Tennaut's 



second paper there are other expressions which show the same bias. 

 He says "He [Mr. Pratt] has failed in satisfying the geodesical 

 data of the great Longitudinal Series." But I did not make the 

 attempt. Mr. Tennant must mean that on applying my results to 

 the great longitudinal series, he failed to show that they tally, on 

 the supposition that the earth's figure is a perfect spheroid. This 

 is what I should have expected : and quite confirms my general 

 view. He says further on, "It [the ellipticity I deduce for the great 

 arc of 800 miles long] is useless for geodesical purposes." Of 

 course it is, if the geodesical operations are carried on with an 

 assumed, and most probably wrong, ellipticity. If the mean 

 ellipticity be not the right one, then not that ellipticity, but some 

 other, ought to be used in computing the latitudes of places 

 in the neighbourhood of the arc, otherwise the geodesical oper- 

 ations of the Great Survey will be "useless" for the purpose of 

 attaining to that accuracy which the survey is expected to attain. 

 I need not quote other passages. I have read through both Mr. 

 Teunant's papers and his interesting calculations with great care. 

 They cannot disprove the results of my paper for the reason I have 

 mentioned. The only way will be to point out where my calcu- 

 lations are wrong, or to show that some other cause is in operation 

 which nullifies the mountain attraction. One other expression only 

 I will notice, as it convinces me, that Mr. Tennant will never clear 

 up the discrepancies while he takes his present view. He speaks of 

 my " hypothetical attractions." Now the only hypotheses my cal- 

 culation of the attraction goes upon are, (1) that the Himalaya 

 Mountains exist, and (2) that each particle of them attracts accord- 

 ing to the law of universal gravitation. The amount of this attrac- 

 tion is a matter of calculation ; and to determine this was the 

 primary object of my paper in the Philosophical Transactions. The 

 calculation is there printed, and has been before the public for three 

 years. It is impossible to ignore either the existence or the attrac- 

 tion of this enormous mass. It is possible to show that some other 

 cause exists, to counteract this disturbing cause. It is also possible 

 to show that the amount I have deduced is wrong ; because I may 





