20 Reply to Mr. Pratt's letter to the Asiatic Journal. [No. 1. 



10. From what I have said ifc immediately follows that the coin- 

 cidence of the deduced, form of an arc with the fundamental one is 

 evidence of the absence of local disturbance or compensation for its 

 effects, while deviation from the fundamental form shows in itself 

 that the local disturbance has been either wrongly estimated or 

 entirely neglected. If this be not so, we have to add to a sufficient 

 and actually existent though numerically unassignable cause for the 

 difference, one whose existence is uncertain, if not, as I believe, 

 impossible. 



11. Mr. Pratt appears to rest his opinion that I have misunder- 

 stood the subject, on the fact that I have not gone through his 

 voluminous computations and produced a new result. I have not 

 been guilty of this presumption. Our knowledge of the forms of 

 the disturbing masses is very imperfect, and their internal constitu- 

 tion is almost unknown, so that I cannot natter myself that I should 

 attain a result in which I. had more confidence than in Mr. Pratt's; 

 and the research required would be very great. I have therefore 

 preferred showing that the result at which he arrives has no claim 

 to be considered a satisfactory representation of the form of India 

 either practically or theoretically ; and, if I have succeeded (as I 

 believe I have) my answer must be considered conclusive as to the 

 existeuce of some flaw in Mr. Pratt's data or processes without my 

 actually pointing out where it occurs. As, however, my avoidance of 

 the subject has been misunderstood, I may say that there is some 

 reason to believe that the masses of the Himmalehs have been 

 considerably overstated in Mr. Pratt's paper, while no notice has been 

 taken of the mountains of Central and Southern India. 



12. h\ Article 7, Mr. Pratt remarks on the indefiniteness of my 

 estimate of the attraction at Banog. With my opinions I could 

 evidently have no such confidence in the best attainable estimate as 

 would have justified the time and labour requisite for its production. 

 The most cursory consideration of Mr. Pratt's estimated attractions 

 at the stations mentioned in his paper with a knowledge of the 

 position of Banog will show that I am justified in calling it enormous 

 on Mr. Pratt's hypothesis. That such was the view I took, and that 

 I did not extend Mr. Pratt's law as he appears to imagine, is evident 

 since by it, the attraction would, in longitude, much exceed the 20 

 at which I took it. 



