#' 



rxl PQ^esidenf s Address. \_Awg. 29, 



that it was not a solid globe of this size but only an aggregation of 

 small bodies, which were sufficiently small and sufficiently far apart 

 not to be visible on the sun. This comet and the one discovered by 

 Wells earlier in the year revealed a new fact in the chemical con- 

 stitution of these bodies ; when they were near the sun the usual 

 hydro-carbon bands seen in the spectroscope Avere entirely replaced 

 by the bright sodium lines, and these again disappeared and gave 

 way to hydro-carbon bands as the comets receded from perihelion. I 

 have already mentioned that there is a group of comets connected in 

 some way apparently with the planet Neptune and which have a 

 period of about 70 years, one of which is Halley's famous comet. 

 A second was discovered in 1812 by Pons, and a third in 1815 by 

 Gibers ; these have both presented themselves to view again, the 

 former in 1883 the latter in 1887 ; the other members of the group 

 are not yet due. The connection between meteor-swarms and comets 

 as now well established, viz. that these swarms result from the 

 disintegration of a comet ; and each return to perihelion of what was 

 once Biela's comet gives us a brilliant shower of these small bodies. 

 The last was in November 1885, 



STARS. 



We are at least beginning to feel our way, with no uncertain steps, 

 to the determination of the distances of the stars from our system. 

 In 1884 Gill and Elkin published the results of their heliometer 

 observations of the parallax of Southern Stars — a classical investi- 

 gation far surpassing all previous attempts in accuracy and extent. 

 It is a pleasing fact for Cape astronomers that they confirmed the 

 substantial accuracy of Henderson's value for the parallax of a 

 Centauri, deduced 50 years ago from his own observations with the 

 Cape mural circle. This star still remains, with our present know- 

 ledge, the nearest star to us ; while /3 Centauri refuses to yield any 

 ;sensible parallax. Asaph Hall and Ball have also contributed very 

 valuable work on this question ; and the new Cape heliometer is now 

 actively at work on it. Several important catalogues t)f star-places 

 have been published in the last few years, notably Stone's Cape 

 Catalogue of 12,441 stars, and G-ould's Cordoba Catalogue of 32,448 

 stars. Each of these gigantic pieces of work was carried through 

 in a few years, Stone's in 10 years, Gould's in 15. Up to the year 

 1870 our knowledge of the accurate positions of stars in the Southern 



