XIX 



At Oxford, Stone applied himself to this work with such energy, 

 that in 1881 the Cape Catalogue of 12,441 stars for the equinox 

 1880 was passed through the press, and its publication was welcomed 

 by astronomers as one of the most important contributions ever made 

 to sidereal astronomy. 



His personal welcome amongst his colleagues was no less cordial. 

 He was at once elected a Vice-President of the Royal Astronomical 

 Society, and, on the vacation of the presidency by Mr. Hind, Stone 

 was elected to the chair. 



We must now briefly review Stone's other labours during his stay 

 at the Cape. In 1871 he published an experimental determination of 

 the velocity of sound, based on ckronographic determinations of the 

 interval which elapsed between the flash of the Cape Town time gun 

 and the instant when the noise of the report reached the Cape 

 Observatory. Various papers on the theory of probabilities, including 

 a criterion for the rejection of discordant observations, also appear 

 from Stone's hand during this period, and there are sundry papers 

 in the ' Monthly Notices ' on proper motions of stars, observations of 

 comets and variable stars, &c, which testify to his continued interest 

 in 'general astronomy, notwithstanding his preoccupation in the 

 great work of his catalogue. 



In 1874 he undertook an expedition to Klipfonteiu, in Namaqualand, 

 and successfully observed the solar eclipse there on the 16th April of 

 that year. He employed a slit spectroscope, with two dense flint 

 prisms of 60°, and was successful in observing the reversal of the 

 Fraunhofer lines at the instant of disappearance of the sun's limb. 

 On the same expedition he made a valuable series of magnetic 

 observations in Naniaqualand, the first series of its kind secured 

 in that region. 



In 1877 (Appendix to the Cape Observations for 1874) he pub- 

 lished a set of star constant tables for computing the apparent 

 places of stars from their mean places, or vice versa. These tables 

 have been largely used, first at the Cape, and subsequently at Green- 

 wich and other observatories. 



When the ' Parliamentary Report on the Telescopic Observations 

 of the Transit of Venus made in the expeditions of the British 

 Government ' reached the Cape, Stone immediately recast the phases, 

 recomputed the results, and by return mail communicated to the 

 Royal Astronomical Society* the results of his rediscussion, which 

 gave, instead of the official result (8*76"), the value 



8*89" 



for the solar parallax. He followed up this communication by a 

 further paper published in the next number of the 'Monthly Notices,' 



* March, 1878. 



