XXXVi REPORT — 1864. 



serviition having been omitted. The probable error + l'-5 ma}? be regarded 

 as including constant errors, considering the number of different circles and 

 needles which were emploj^ed, as well as the peculiarities of different ob- 

 servers, of whom there Averc seven." (The italics are General Sabine's.) 

 These are the probable en-ors which I cannot accept as accurate. 



It may not be superfluous to add that I have conversed -with several 

 foreign observers (one of whom has very lately quitted me), and that all 

 have found discordances comparable to those which I have myself observed. 

 I have therefore no novelty to claim, except the suggestion (made by mo 

 some years ago) of instabihty in the position of the magnetic axis, and the 

 construction (mthin little more than a year) of an instrument whose results 

 appear to support that suggestion. 



I should be much gratified if the powers of the Kcw Observatoiy could bo 

 devoted to the examination of this and analogous instrumental difficulties. 

 These experimental inquiries are not well suited to the system of the esta- 

 blishment over which 1 preside. And, speaking as a member of the British 

 Association, I think that the Xew Observatory would be better employed in 

 that way than in the course which now absorbs so ranch of its strength. It 

 was originally intended, and in my opinion wisely intended, for the verifica- 

 tion and improvement of instruments, and not for continuous observations. 

 If the examination which I propose should be taken up, I shall be happy to 

 cooperate, by repetition of observations (as my opportunities might serve), 

 and by communication of my results. 



I am, my dear Sir, 



Yours very truly, 

 J. P. Gassiot, Esq., (Signed) G. B, Amy. 



Chairman of the Kew Observatory Committee. 



III. 



Clapham Common, June 30, 1864. 



My dear Sib, — I have to acknowledge receipt of yours of 2Sth inst., 

 wherein you state that the paragraph in your recent report " was intended 

 to apply to the dip-observations made at Kew, and published in the publica- 

 tions of the Eoyal Society, inasmuch as the degree of accuracy, to which you 

 do not give your assent as real or well founded, is claimed for these ob- 

 servations." 



I have forwarded your letter to Mr. Stewart, the director of the Ob- 

 servatory, under whose immediate directions the observations were made, 

 and I hope yon will find that the explanation he will offer will satisfy you 

 as to the entire truthfulness of the results he obtained, and to the reliability 

 that should be placed thereon. 



I have always understood, that to the continued magnetical observations 

 which have been made at Kew Observatory has been mainly due the esta- 

 blishment of so many magnetical observatories abroad ; it woiild, however, 

 ill become me to offer to you any opinion as to their value, although I cannot 

 but regret that they do not appear to have met your approval. 



I am sure it would afford Mr. Stewart, as well as the Members of the 

 Committee, much pleasure to follow out any experimental iuquiiies which 

 you may at any time suggest. 



Believe me, my dear Sir, 



Yours most truly. 

 To G. B. Airy, Esq., (Signed) J. P. Gassiot, 



Astronomer lioyal, Greenwich. 



