318 POPULAR SCIENCE MONTHLY. 



bright star with the Mills spectrograph. The method promises to be 

 of great utility, capable of application to several thousand stars be- 

 tween the fifth and eighth magnitudes. 



On account of the large proportion of spectroscopic binaries, stars 

 should not be used statistically until observations covering several years 

 have established the constancy of their motions. To determine the orbits 

 and the speeds of the centers of mass of the binary systems, from twenty- 

 five or more spectrograms each, is a task several fold more extensive 

 than that of measuring the constant speeds of the non-binary stars. 



There remains the question of cooperation, on the part of radial- 

 velocity observers, to avoid useless duplication, and to increase the out- 

 put of results. Seven leading observatories in the northern hemisphere, 

 and one in the southern, are in this field, presumably with the intention 

 of remaining indefinitely. A second observatory in the southern 

 hemisphere, devoted exclusively to this work, is pf an expeditionary 

 character, and its long continuance is problematical. It is fair to the 

 participating observatories to say, judging by results thus far pub- 

 lished, that some are still in the period of experiment and development ; 

 and, in fact, that all observers are introducing frequent improvements, 

 which lead to greater accuracy. As long as the development of instru- 

 ments and methods is in rapid progress, formal cooperation is unwise. 

 Premature cooperation leads to confusion. Duplication of observa- 

 tions for the principal stars is as valuable and desirable in radial- 

 velocity measurements as in meridian determinations of stellar posi- 

 tions. But just as soon as the methods assume a reasonably stable 

 form, the entire sky should be apportioned amongst the interested ob- 

 servatories, in accordance with carefully considered plans which shall 

 permit and encourage individual initiative. I have little doubt that 

 this point will be reached, by a sufficient number of observatories, 

 within two years, and that it would be well to conclude the preliminary 

 organization of cooperative plans within the coming year. Such 

 plans should be formed with severe deliberation, as the labor involved 

 would be commensurate with that devoted to the construction of the 

 Astronomische Gesellschaft Zones for the entire sky. 



The problems immediately confronting the astrophysicists of the 

 twentieth century are serious ones. They call for our best efforts. 

 The volume of work demanded is stupendous, and the difficulties to be 

 overcome are correspondingly great. Nevertheless, the men and the 

 means will be forthcoming. The mass of solid fact brought within 

 the realm of knowledge by astronomers now living, many of whom 

 are happily with us this week, is sufficient indication that the general 

 solution of the problems of to-day is but a question of time. And 

 we should be equally hopeful as to the problems of the future, for the 

 desire to know the truth about the universe which surrounds us is an 

 enduring element in human nature. 



