NATURE 



53 



THURSDAY, NOVEMBER 20, 1S79 



THE DOUBLE STARS 

 A Handbook of Double Stars. By Edward Crossley, 

 F.R.A.S., Joseph Gledhill, F.R.A.S., and James M. 

 Wilson, M.A., F.R.A.S. (London: Macmillan and 

 Co., 1879.) 

 Double Star Observations made in 1S77-78 at Chicago 

 ■with the \Z\-inch Refractor of the Dearborn Observa- 

 tory, &>c. By Sherburne Wesley Burnham, M.A. 

 (From Memoirs of the Royal Astronomical Society, 

 vol. xliv.) 



IT cannot be said that a special work upon the double 

 and compound stars has hot been long a desideratum. 

 Of the various branches of astronomical science the study 

 of the double stars appears to have formed one of the 

 most attractive to amateurs generally ; so far as the 

 reduction of the observations is concerned it involves 

 little calculation, and the observations themselves are not 

 laborious but admit of being proceeded with at intervals 

 of leisure, with comparatively moderate appliances, at least 

 in a large number of cases. Many of our amateurs have 

 their daily duties and occupations in other lines, and seek 

 relief in their evenings from the monotony of routine ; 

 the observation of the double stars upon a well-arranged 

 list perhaps offers as favourable opportunities for render- 

 ing themselves really useful and for doing really good 

 work in astronomy without the labour of one kind or 

 another involved in several other classes of observation 

 as it is possible to find. 



The branch of astronomy to which we are referring has 

 progressed as rapidly as others, and the observations of 

 double stars and particulars relating to them have been 

 scattered through a large number of astronomical publi- 

 cations, to consult which involves a great outlay of time 

 and trouble, even if they are accessible without difficulty. 

 The main purpose of the volume before us has been to 

 present the great majority of measures of some twelve 

 hundred double stars in a convenient form, with notes 

 bearing upon binary character or other peculiarity, or. 

 speaking generally, to furnish a history of each star. 

 Part I. is introductory or explanatory, containing a brief 

 historical notice and reference to those astronomers who 

 have been most occupied upon the double stars, with 

 particulars of the instruments employed, the adjustments 

 of the equatorial, the micrometer and methods of observ- 

 ing with it, forms for registering measures and similar 

 details. Part II., which possesses considerable value, 

 treats of the calculation of the orbits of the revolving 

 double stars, and in this division of the work the authors 

 have been fortunate in being assisted by Dr. Doberck 

 who has a greater experience in this direction than any 

 other astronomer of the day, and who has contributed in 

 so important a degree to advance our knowledge of the 

 elements of these revolving suns. Sir John Herschel's 

 graphical process for determining the apparent orbit 

 which is still of such material assistance towards more 

 refined investigation is explained and illustrated (which is 

 better still) by an application to Castor. This is followed 

 by the calculation of an orbit by analytical methods, 

 applied to a- Corona;, the different steps being clearly 

 Vol. xxi. — No. 525 



defined, but these methods are necessarily much more 

 laborious, and at present we do not seem to get the full 

 advantage in many cases that might be expected from 

 them. It will be no fault of Dr. Doberck's if the com- 

 puter does not succeed in obtaining elements upon the 

 principles he so well explains, which will continue to 

 represent the motion of the star. Other causes frequently 

 operate, however, which appear to render elements less 

 satisfactory for prediction than might be expected, con- 

 sidering the refinement used in their calculation. The 

 comparison of Dr. Doberck's orbit of <r Corona; with 

 observation affords a very close agreement. In the next 

 three chapters Mr. Wilson enters upon relative rectilinear 

 motion, the effect of proper motion and parallax on the 

 observed angles and distances of a star optically double, 

 and the errors and combination of observations. 



Part III., "the Catalogue and Measures," prepared by 

 Mr. Gledhill, is that which will be most frequently con- 

 sulted. Considerable care appears to have been taken in 

 the selection of the objects, and in the collection of the 

 measures by various observers. A great amount of 

 trouble must have been expended upon this portion of 

 the volume, which is well brought up to date, and few 

 facts of importance bearing upon the history of any 

 object appear to have been overlooked, though such 

 omissions must almost necessarily occur sometimes in a 

 work of this character. There has evidently been the 

 wish to make this part of the work as useful as possible 

 to the amateur. Perhaps in a short supplement to another 

 edition it may be desirable to reproduce the double star 

 measures with the Konigsberg heliometer, collected in 

 vol. xxxv. of the Observations at that Observatory, the 

 more especially as these volumes of observations have 

 but a small circulation in this country ; we miss most of 

 these measures in the " Handbook." 



An appendix contains the positions and measures of 

 two hundred of Mr. Burnham's new double stars, placed 

 at the service of the authors by the discoverer. Part IV. 

 is bibliographical, and supplies a list of the principal 

 works and papers relating to double stars and upon 

 various forms of micrometer. 



The volume is one which may be expected to find its 

 way to the shelves of most amateurs and students of 

 astronomy. 



Mr. Burnham's important contribution to vol. xliv. of the 

 Memoirs of the Royal Astronomical Society, contains (1) 

 a catalogue of 25 1 new double stars with measures, and 

 (2) micrometrical measures of 500 objects, amongst them 

 some very' difficult ones and a number of evident 

 binaries. 



At the time the Chicago Astronomical Society was 

 organised in 1862, Messrs. Alvan Clark and Sons had 

 still in their possession an object-glass of i8i inches 

 aperture, which was then the largest in the world. Steps 

 were taken to secure it, and, thanks to the energy of the 

 Hons. Thomas Hoyne and J. Young Scammon, the 

 latter of whom has been president of the Society from its 

 organisation, the glass was secured for Chicago, and by 

 means of a public subscription 18,000 dollars were raised 

 for its complete mounting, and Mr. Scammon contributed 

 30,000 in addition for the building. Fortunately an ob- 

 server equal to the use of so fine an instrument was at 

 hand, and latterly Mr. Burnham has devoted it to the 



