674 



NATURE 



[February 17, 19 1() 



The book deserves the serious attention of 

 every student of chemistry. It will open his eyes 

 to the boundless possibilities of a field of inquiry 

 of which even the very fringes have only been 

 very imperfectly explored as yet, but which, there 

 is no doubt, is destined to yield fruit of the 

 greatest richness and value. 



THE STUDY OF VARIABLE STARS. 



An Introduction to the Study of Variable Stars. 

 By Dr. C. E. Furne -a. Pp. xx + 327. (Boston 

 and New York: Houghton Mifflin Co., 1915.) 

 Price 1.75 dollars net. 



TT has been said that it is more important to 

 measure the light than the place of a star. 

 Add the time factor and there is the observational 

 province of the student of variable stars, namely, 

 the measurement of the relationship between time 

 and lustre of particular stars. The present book 

 is largely given up to explaining methods by 

 which this can be accomplished The author is 

 one who has had almost unique opportunities 

 fitting her to undertake the task, which might have 

 been more successfully carried out had the aim 

 been more ambitious. As director of Vassar 

 College Observatory, Dr. Caroline Furness has 

 not only actively engaged in variable star observa- 

 tion, but has also conducted the regular courses 

 of study in this special subject in the astronomical 

 department of the College. These occupations 

 have ensured the necessary documentation and 

 provided valuable experience in the practice of 

 stellar observation, in the art of exposition, and 

 especially in the needs of novices in this important 

 branch of sidereal physics. The volume, it may 

 here be mentioned, finds a place in the "Semi- 

 centennial Series " of works by distinguished 

 alumni issued in commemoration of the fiftieth 

 anniversary of the foundation of Vassar, and at 

 present it stands alone in the English language. 



The intention of the work is primarily to make 

 observers, and the practical side of the subject 

 is kept prominently to the fore throughout. The 

 historical aspect, however, receives considerable 

 attention, and much interesting material has been 

 collected. With the first aim in view the author 

 attempts to supply the reader with concise in- 

 formation on a range of preliminary subjects such 

 as "Durchmusterung charts," "photometry in all 

 its branches," "spectroscopy," "star colours," etc. 

 These efforts lead to a tedious description of star 

 maps and charts, a summary of the rudiments 

 of spectrum analysis, a lengthy non-technical 

 account of Nichol's prism, taken, it would seem, 

 from a well-known English text-book of physics, 

 NO. 2416, VOL. 96] 



and, among other things, to the inclusion of 

 an abstract of a paper on the physiological 

 optics of the colours of double stars. This 

 paper is sufficiently interesting, but it would have 

 been better to describe the work of Hertz- 

 sprung, for example, or that of Tikoff ; and in- 

 stead of introducing the gentle gibe at the fanciful 

 colour scheme employed in such an ancient work 

 as Webb's "Celestial Objects," Espin's or Frank's 

 colour scales might have received mention. 



Although the title admittedly affords the author 

 considerable liberty in choice of material, yet, 

 since in these days the historical scale of star 

 magnitudes has been everywhere abandoned, 

 perhaps the sole important exception being the 

 catalogue of Boss, there might well have been 

 given some account of the absolute scale of mag- 

 nitude adopted by the astrographic conference in 

 1909, especially as this crowned the thirty years' 

 work of an American astronomer, Prof. E. C. 

 Pickering. 



So much attention is now being claimed by 

 photo-electric photometry that many who cannot 

 turn to the original memoirs will read the chapter 

 on this topic with interest. As no account is 

 given of work on, or with, selenium prior to that 

 of Stebbins, it may be permissible to recall some 

 facts not so widely known as they deserve to be. 

 Announced by Mr. Willoughby Smith early in 

 1873, a little later Lieut. Sale, R.E., investi- 

 gated quantitatively the effect of varied illumina- 

 tion on the conductivity of that element, the 

 property employed in the commercial selenium 

 bridges used in 1907 by Stebbins with such great 

 success. Three years after Sale's experiments. 

 Prof. Adams and Mr. R. E. Day detected the 

 potential difference set up under similar condi- 

 tions. The late Prof. G. M. Minchin applied this 

 fact nineteen years later, in 1895, in what would 

 appear to have been the first successful photo- 

 electric measures of stellar radiation ever made. i 



It is rather to be regretted that space was not 

 found for some discussion of the classification of | 

 variable stars instead of merely stating that the ( 

 Harvard scheme is best known and most widely [ 

 used. It may be, but it bears much the same j 

 relationship to present-day knowledge of stellar 

 variability that Secchi's classification does to the 

 Harvard classification of stellar spectra. 



The later history of Novae is even more inter- 

 esting than would appear from p. 255. It has 

 now been established that in their latest phases 

 several, at any rate, have assumed the Wolf- 

 Rayet features after passing through the nebular 

 stage. It may here be mentioned that the note 

 on p. 36 does not contain Prof. Fowler's latest 

 conclusions regarding the Pickering and the 



