1858.] and the Figure of tie Earth. 205 



method ; but to compare it with other arcs, and to see whether they 

 are curved so as to belong to oue and the same spheroid with mine. 

 One arc he compares it with, runs westward from Kulianpur to 

 Kurachi; the other is a prolongation of the great arc southward 

 from Damargida to Punnce (latitude 8° 9' 32'') . The only question, 

 therefore, which he can solve is, whether his arcs and mine belong 

 or not to one spheroid; not, whether my calculation is right or not. 

 In fact, his process goes wholly upon the gratuitous hypothesis, 

 that all arcs wherever measured belong to one and the same spheroid ; 

 that is, that every meridian is an ellipse, and all meridiaus the same 

 ellipse, and that every arc of longitude is circular. It is a notice- 

 able coincidence, and by no means unfavorable to my calculation, 

 that he finds that the curvature of the arc from Damargida to 

 Punnce (the prolongation of my arc) coincides more nearly with 

 my ellipse than with the average one. Further on, in his first paper, 

 Mr. Tennant applies a third test, viz. the comparison of the com- 

 puted and observed azimuth of Kalianpur and Kurachi. But the 

 same objection applies to this also. In fact Mr. Tennant's calcu- 

 lations do not affect my arc ; and simply because he has not 

 examined that arc, nor gone through my calculations. 



7. There are other indications that Mr. Tennant has mistaken 

 the subject. Por example (art. 13) " the attraction is so enormous, 



if Mr. Pratt's values hold good, near the mountains " But 



I particularly specify, and the whole line of reasoning shows, that 

 my calculation does not apply to such places (see p. 66, note, of my 

 paper) : and in the continuation of the note in the next three pages 

 I point out a method for such* places in and near the mountains : 

 so that the wish expressed by Mr. Tennant in par. 17 was met in 



occur at the close, and not in any important place, at least important for my 

 results, but in a kind of corollary. 



With reference to paragraph 3 of Mr. Tennant's second paper, I would here 

 observe, that, in the application of the above formula, the three arcs are brought 

 to chords in the same line and the sagittae compared, merely as a piece of geometry, 

 without any reference to the manner in which they lie and cut each other in the 

 Problem of the Figure of the Earth. The object is simply to compare the degrees 

 of bending between the two extremities, in the three cases, as indeed I state iu the 

 paper ; and the result is given above. 



