XXlll 



Astronomical Observations at Capetown 

 Observatory. 



Mr. Kingsmill began by referring to the 

 kindness of Sir David Gill, the Govern- 

 ment Astronomer at Capetown, who gave 

 him opportunities of seeing the work of 

 his observatory, and made him a present 

 of some beautiful photographic slides, 

 showing some of the most remarkable re- 

 sults. These slides were supplemented 

 by others obtained from the Eoyal As- 

 tronomical Society. The lecturer first 

 gave a description of the Capetown Obser- 

 vatory. It is an Imperial institution, pro- 

 vided for and controlled by the Admir- 

 alty, and it is liberally endowed for as- 

 tronomical research, having la staff of 30 

 observers. It resembles a village, having 

 a number of buiklinges for the instru- 

 ments, and for the observers" residences. 

 The site chosen was as near the bay as 

 possible, for the sake of the shipping. 

 Formerly, a gigantic time - ball 

 was dropped at the observatory, 

 which was visible to the ships 

 four miles off in Tab'e Bay; now a 

 sm.aller time-ball is dropped electrically 

 close to the docks by means of a wire 

 from the Observatory. 



The accurate determination of time is 

 a very small part of the Observatorj^ 

 work; the position of stars is deter- 

 mined for the use of mariners; in fact, 

 most of the Southern stars whose posi- 

 tion is given in the "Nautical Almanac" 

 ar© recorded there from observations tak- 

 en at tlie Capetown Observatory. The 

 most interesting work, however, to tie 

 general public is that which simply sat- 

 isfies the thirst of the human mdnd for 

 knowledge of what is observed in the 

 heavens without any reference to commer- 

 cial utility. 



The lantevn slides shown illustrated in 

 a most interesting manner the methods 

 by which the actual materials of the 

 stars were ascertained. It was shown how 

 irO'U was proved to exist in form of va- 

 pour in the sun's atmosphere, in the 

 atmosphere of the bright star Canopas, 

 and in that of Alpha Centauri. Hydro- 

 gen was also shown to be an element as 

 abundant in the stars as it is on the 

 earth. These wonderful revelations are 

 due to the spectroscope. That instru- 

 ment not only enables us to ascertain the 

 materials of which a star is composed, 

 but it actually can be made to reveal the 

 motion of a star along the line of sight, 

 to show whether it is aproaching to or 

 receding from the earth, and the rate at 

 which this takes place. 



Three beautiful photographs were 

 shown on the screen of the star Argus, 

 and the portion of sky around it. This, 

 the lecturer said, womld, no doubt, be 



specially interesting to members of the 

 Royal Society here from the fact that its 

 records contain several papers read on 

 the nebula of Argus by the late Mr. 

 Francis Abbott, whose observations of 

 the star and of its nebula extended from 

 the years 1867 to 1872. This star has gone 

 through the most extraordinary varia- 

 tions in brightness during the last 200 

 years. It was first observed at St. Helena 

 by Halley ; then at the Cape of Good 

 Hope by Sir John Herschel. It increased 

 in brightness, until it became the s'^cond 

 star in the sky in 1843. During the 25 

 years following it steadily but slowly di- 

 minished. In 1867 it was barely visible 

 to the naked eye, and the year following 

 it vanished entirely from the unassisted 

 view, and has not yet begun to renew its 

 brightness. The time it was observed by 

 Mr. Abbott it was a faint telescopic ob- 

 ject, surrounded, however, b,y a if mark- 

 able nebula. A photograph of this was 

 shown hj the lantern, taken during an 

 expoi?xire of 45 minutes. A second photo- 

 graph was shown of the same object from 

 exposure of over three hours, and a third 

 photograph from a 25 hours' exposure. In 

 rhe first of these a considerable number 

 of stars appeared in th field of view; ire 

 the second the number of stars was 

 greatly increased; in the third (the 25 

 hours' exposure) revealed an absolutely 

 countless multitude of stars surrounding 

 the nebula. Many of these are too faint 

 to be detected by the human eye. 

 even when aided by the most powerful 

 telescope. 



Some groups of star clusters in other 

 parts of the sky were shown, and it seem- 

 ed as if there was no limit to the number 

 of stars that could be revealed in a single 

 telescopic field by photography. The star 

 clusters were, in some cases, so dense as 

 to appear like a continuoits mass of light. 

 Slides of nebulae were next shown, and 

 it was pointed out hj the lecturer that 

 at first nebulae were supposed to be sim- 

 ply star clusters, the diffused light of 

 which could be resolved into separate 

 stars if Ave had a sufficient magnifying 

 power; but modern observations, with 

 the aid of the spectroscope and photogra- 

 phy, show that this hypothesis is incor- 

 rect. The nebulae have been proved to 

 consist of vast spaces filled with glowing 

 gas, which sometimes envelopes stars. 

 These masses of gas generally have defi- 

 nite forms, the spiral being the most 

 common. 



The systematic study of nebulae may be 

 said to have commenced through the la- 

 bours of Sir William Herschel at Slough. 

 The discoveries that Herschel made were 

 reckoned not by tens, nor by hundrede, 

 nor by thousands. It was left to Sir John 



