Xlll 



In two notes* Stone reverts to the determination of the moon's 

 mass, and, adopting 50377" for the luni-solar precession, and 9*223" 

 for the constant of nutation, he derives for the moon's mass the 

 value 



1 



81-36' 



Following the same general line of research, Stone then under- 

 takes a direct determination of the constant of nutation based on 

 Greenwich N.P.D. observations of Polaris, 51 H Cephei, and 8 Ursa? 

 Minoris, and the R.A. observations of Polaris made with the transit 

 circle 1851-65. The preliminary results of this work are published 

 in the £ Monthly Notices,' vol. 28, 1868, p. 229, and vol. 29, 1869, 

 p. 28. The complete discussion appears in the ' Memoirs of the 

 R.A.S.,' vol. 37 ; the resulting value of the constant of nutation is 



9-134". 



In the concluding portion of this memoir, Stone draws attention 

 to the strong evidence which his discussion gives of a periodic 

 change of latitude, a subject which, had he followed it up, might 

 have led to an earlier discovery of Chandler's now well-known law 

 of variation of latitude, but his thoughts were otherwise occupied. 



In the supplementary number of the ' Monthly Notices ' for 1868, 

 Stone communicated to the Royal Astronomical Society his " Re- 

 discussion of the Observations of the Transit of Venus of 1769," in 

 which, after reverting to the above-quoted evidence in favour of an 

 increase in the accepted value of the solar parallax, he proceeds to 

 rediscuss the observations made at five stations where internal con- 

 tacts of Venus with the sun's limb were observed both at ingress 

 and egress by ten observers. An independent interpretation was 

 put upon the language employed by each observer to describe the 

 phenomena which he noted at different instants of time, and the 

 assumption was made that such phenomena could be divided into 

 two distinct classes — viz., true and apparent contacts — separated by 

 a definite interval of time. This interval (assumed to be constant 

 for all observers) was introduced in symbolical form into all the 

 equations. The solution of the equations so formed led to the 

 value 



8-91" 



for the solar parallax, with the estimated probable error 



+ 0-02". 



The observations were there represented as follows : — 



* ' Monthly Notices R.A.S.,' vol. 28, pp. 21 and 42. 



