OCTOBEB 25, 1907] 



SCIENCE 



545 



inch Clark refractor, an instrument which he 

 used almost entirely in the observation of 

 double stars and which brought him a larger 

 number of discoveries than any other telescope 

 that he has used in his long and varied astro- 

 nomical career. At that time no complete list 

 of the known double stars existed, and there 

 were few books in Chicago relating to them. 

 The small refractor showed many pairs not 

 recorded in any of the books available, and 

 to make certain that these were new, he had 

 to search far and wide through nearly the 

 whole range of modern astronomical litera- 

 ture, to see what stars had previously been 

 recorded as double. Observatories were vis- 

 ited and their libraries consulted; books were 

 borrowed and what they contained relating to 

 this particular subject was laboriously copied 

 by hand; books and memoirs were also pur- 

 chased, making the beginning of a library 

 devoted to this special subject that has since 

 become practically complete. 



The manuscript catalogue which Professor 

 Burnham formed at the beginning has been 

 kept continuously posted to date, by adding 

 accounts of new discoveries whenever made, 

 and of new observations wherever published. 

 To make room for the new material, a second 

 manuscript edition eventually became neces- 

 sary, and later still a third, which finally 

 passed into the hands of the printer and now 

 appears in finished form. 



This great work divides into two parts. The 

 first contains a catalogue of 13,665 double 

 stars within 121° of the north celestial pole, 

 and the second, the notes to this catalogue. 

 Besides the catalogue. Part I. includes the 

 introduction, indexes, precession tables and 

 appendix, filling altogether 329 closely printed 

 quarto pages. Part II. makes a similar vol- 

 ume of 836 pages. 



To state the number of pages gives but a 

 faint notion of the magnitude of the labor it 

 has been to collect the information compressed 

 within these somewhat extended limits. The 

 labor would have been materially less had it 

 been a mere compilation. This, however, is 

 far from being the case. The predominant 

 virtue of this work is its trustworthiness, and 



this springs not so much from what has been 

 gathered from the published observations as 

 from the author's long hours at the telescope, 

 searching, verifying, measuring, and from his 

 continuous investigations from all the data 

 available. For many years he has been a 

 most industrious observer, and his energy, 

 devotion and sound judgment have had much 

 to do with placing double-star astronomy 

 in its present satisfactory condition. No 

 matter at how great a cost in time and labor, 

 he has made it his business to know the truth 

 concerning these distant systems, consistently 

 following stars in rapid motion during their 

 critical periods, measuring those suffering 

 from neglect, and in a larger degree than any 

 one else, comparing the double stars in the 

 sky with the record of them and bringing the 

 two into harmony. 



This work is arranged in a very convenient 

 and satisfactory form and is beautifully 

 printed. In both volumes the stars are ar- 

 ranged in the order of their right ascensions 

 for the epoch 1880, and are numbered con- 

 secutively. The usual double-star numbers, 

 star names, constellation letters and numbers 

 are also given, making identification easy by 

 whatever mode a pair may be designated. 



The catalogue in Part I. is in tabular form, 

 with eleven columns to the page. The data 

 there given, in addition to the numbers and 

 names just mentioned, are the position angle, 

 distance and epoch of the earliest reliable 

 measures; magnitudes; indication of the ob- 

 servers and the number of nights on which 

 measures were made; references and brief 

 notes, relating chiefly to notation and colors 

 of components. These are the data most use- 

 ful to the observer, and they are presented in 

 a form eminently suited to his needs. 



The notes in Part 11. are usually brief and 

 always to the point. They are generally re- 

 duced to a few lines to the star, giving in a 

 few words a synopsis of the history of each 

 pair, measures corresponding to selected 

 epochs, statements respecting relative and 

 proper motions, and complete references to 

 all published observations and to important 

 papers. The stars whose components have 



