XV 



Throughout his wliole life, one of Stone's most characteristic 

 qualities was his high sense of responsibility and strict regard to 

 official duty. However absorbing may have been the independent 

 researches in which he was engaged, his official duties were at all 

 times his first consideration. These occupied not only his official 

 hours at the Observatory, but he gave to them and to strictly allied 

 work much of the labour of his private time. 



In the Greenwich catalogue for 1850, Airy employed the very 

 unsatisfactory proper motions of the British Association Catalogue 

 of Stars. For the formation of the 1860 catalogue the proper 

 motions determined by Main* were available. Recognising the 

 importance of Main's work, Stone continued it, and, in the ' Memoirs 

 of the R.A.S.,' 1864, vol. 33, gave, for 460 stars of the seven-year 

 catalogue, proper motions computed by reducing Bradley's observa- 

 tions (as derived in Bessel's Fundamenta) to the equinox of I860, 

 and comparing the results with the corresponding places of the 1860 

 catalogue. 



A further proof of his deep interest in his official duties is given 

 in his paper 44 On the Accuracy of the Fundamental Right Ascen- 

 sions of the Greenwich Seven-year Catalogue for 1860," published 

 in vol. 34 of the ' Memoirs of the R.A.S.,' where he specially dis- 

 cusses the accuracy of the fundamental right ascensions of 7 Pegasi, 

 y3 Geminorum, a Virginis, and a Aquilee. 



In November, 1867, Stone communicated to the Royal Astronomi- 

 cal Society a paper " On Bessel's Mean Refractions," in which he 

 showed that the tabular refractions of Bessel's Fundamenta were 

 too great, and required to be diminished by one five-hundredth part, 

 in order to represent the Greenwich observations of circumpolar 

 stars made in the years 1857-65. This important conclusion has 

 since been fully corroborated at the Washburn Observatory, in the 

 United States, by Comstock in his determination of the constant of 

 aberration, and also by a discussion of the Cape and Greenwich 

 observations.f Nyren's discussion of the Pulkowa refractions also 

 points to the same conclusion. 



Besides the already mentioned important papers connected with 

 well-marked lines of continuous research, we find no less than 

 twenty notes of a more miscellaneous character, communicated by 

 Stone to the Royal Astronomical Society. These papers testify to 

 the wide interest which he took in all contemporary astronomical 

 research during the ten years he remained Chief Assistant at Green- 

 wich. 



In the early part of 1870 Sir Thomas Maclear resigned his post 

 as Her Majesty's Astronomer at the Cape, and in June of the same 



* ' Memoirs R.A.S.,' vols. 19 and 28. 



f Introduction to the e Cape Catalogue ' for 1885. 



