360 



KNOWLEDGE. 



September. 1910. 



everv lover of astronom\- to join \\ith me in obser- 

 vations that must inevitahh' lead to new discoveries. 

 I took some pains to find out what Double Stars 

 had been recorded bv astronomers ; but my situation 

 permitted me not to consult e.xtensive libraries, nor, 

 indeed, was it \er\- material: for. as I intended to 

 view the heavens m\-self. Nature, that great volume, 

 appeared to me the best catalogue upon this 

 occasion."* 



Herschebs Double Star obser\ations failed to assist 

 him in the primar\' purpose for which he undertook 

 them, which he afterwards described as a desire to 

 ascertain "a scale wherebv the extent of the Universe, 

 so far as it is possible for us to penetrate into Space, 

 mav be fathomed." But, notwithstanding this primar\- 

 failure, there was unexpectedh' e\-oh-ed a discover\- 

 of a different sort and of the highest interest. This 

 was that many pairs of stars were not onl\-, as the\- 

 seemed to be. two stars side hv side, but were 

 physically connected, so that the smaller re\olved 



round the larger, verv much as 



irdinarx' planets 



revolve round the Sun. .\ccordingl\- he was able, 

 after watching certain of them for about twent\- 

 years, to inform the Ivoyal Society that he would 

 soon be in a position to communicate " a series of 

 observations [)ro\'ing that man\- of them ha\e alread\- 

 changed their situation in a jM-ogressive course, 

 denoting a periodical revolution round each other." 

 He fulfilled his pledge the following \-ear in a pai)er 

 presented to the Society on June 9th, 1S03. He 

 had taken specialh' in hand the following six stars : — 

 Castor (« Geminorum), y Leonis, e Bootis. ^ Herculis. 

 Serpentis, and y \'irginis : and he made it clear 

 that the facts \\-hich he had observed could <iiil\- be 

 accounted for by su[)posing that the six pairs in 

 question were " not merely double in appearance, but 

 must be allowed to be real binar\- combinations of 

 two stars, intimately held together by the bond of 

 mutual attraction." + He went on to assign periods 

 of revolution for each of the six Stars in question, 

 but. with one exception, it afterwards turned out 

 that this feature in his results failed to find subse- 

 quent confirmation, because his observations were 

 not sufficiently prolonged in time ; and he assumed 

 the orbits to be more or less circular, whereas all are 

 ellipses of great eccentricitw 



In the case of Castor he was able to base his 

 calculations on some observations of the star older 

 by far than his own, dating from 171S, 1719, 1722, 

 by Pound and Bradley, coupled with a similar old 

 record by Bradley and Maskelyne, dating from 1759. 

 These old materials + enabled Herschel to suggest a 

 period for Castor of about 342 years, which was, 

 however, eventually found to be altogether insufficient 

 by most computers, tliough one of the most recent 

 calculations b\- Doberck ;,.uts the period at 346 years. 



Other cominiters. however, put it at a period \'ar\-ing 

 from 300 to 900 years, and Burnham sa\s that the 

 matter must remain uncertain for another centurw 



The gnnmd having been broken b\' Sir \\'. Herschel, 

 who had been knighted for his eminent services to 

 science. Double Star work was taken up sluirth' before 

 his death by F. G. W. Struve. who in 1M22 published 

 his first catalogue of Double Stars compiled from 

 various sources, but follo\\ed hv a catalogue of 

 795 stars ()bser\-ed by himself at Dorpat, 1813-1<S20. 

 Several other Struve catalogues followed which will 

 be alluded to further on. 



In England the mantle of Herschel fell on his 

 son John, then starting his career. As regards 

 Double Stars he entered for a time into an alliance 

 w ith Mr. (afterwards Sir James) South w ho had an 

 observatory in Blackman Street, Southwark.ii Hence 

 it is that in the older records of Double Stars one sees 

 linked together the names of " Herschel and South." 



John Herschel, after doing various things, especially 

 after reviewing and cataloguing afresh his father's 

 nebulae and clusters, and discovering and measuring 

 a lart,'e number of pairs, thought that the labours of 

 his father and himself could only be properly cappeci 

 b\- an efficient and comprehensive survey of the 

 Southern Hemisphere. This led to his expedition 

 to the Cape, where he remained from 1835 to 1838, 

 the grand results of w hich were given to the world 

 in 1847. at the cost of the then Duke of Northumber- 

 land, a liberal patron of the science. V 



Further details respecting this interesting stage in 

 Herschelian \\ork would take me beyond the reason- 

 able limits of this paper. I must, therefore, briefly 

 sum up the modern situation as regards Double Star 

 Astrononn- by mentioning in the briefest possible 

 form the names of a few of the principal workers in 

 this field. The following seem to stand out in 

 advance of all others. In England : — W. R. Dawes, 

 W. Doberck, T. E. Espin, W. S. Jacob, G. Knott, 

 T. Lewis, W. H. Maw, G. M. Seabroke and J. M. 

 ^^'ilson. On the Continent : — G. Van Biesbroeck, 

 Baron H. Dembowski. N. C. Duner. S. De Glasenapp, 

 J. H. Miidler, J. Perrotin, H. C. F. C. Schjellerup 

 and A. Secchi : and in America, S. W. Burnham, 

 R. G. Aitken, G. C. Comstock. E. Dolittle, ]. M. 

 Gillis, A. Hall, G. W. Hough. W. J. Hussey and 

 O. Stone. 



It will be seen from the foregoing that a great deal 

 of Double Star work has been done during the last 

 fift\- \-ears, but as so many pairs of stars are in 

 motion the necessity for continuing observations of 

 this sort may be considered chronic : and it has been 

 alreadx* pointed out elsewhere that ver}- much 

 remains to be done in the Southern hemisphere, 

 which offers a limitless field for the labours of 

 competent Double Star observers. 



'■■ Phil. Tniits. Veil. LWII, p. 97, 1772. This extract appears in a \ery garbled form in Miss C 



I Phil. Trans. Vol. XCIII. p. .HO. 1803. 



I Discussed by J. Herschel in Mem. R.A.S., Vol. V, p. 23, 1833. 



§ South afterwards niitirated to I'.uis, but ended his Astronomical career at Canipden Hill, Kensington. 



*' Results of Astronuiincttl Obscrvtifioiis made at the Cape of Good Hope. 



's Hersclicls. p. 55. 



