852 



SCIENCE 



[N. S. Vol, XSVIII. No. 728 



nomical Papers " of the American Ephemeris as 

 well as the yearly volumes of the Ephemeris 

 during that time. During the past eleven years 

 the accuracy of the computations for the Ephem- 

 eris has been improved, a catalogue of zodiacal 

 stars published, and orbits and ephemerides of 

 certain new satellites of the planets computed. 

 The next volume to be issued is that for the year 

 1912. It is intended hereafter to leave out the 

 lunar distance tables, to insert the ephemerides 

 of about 300 additional fixed stars, and to sub- 

 stitute for the Struve-Peters constants the con- 

 stants adopted at the conference of directors of 

 national ephemerides held in Paris in May, 1896. 

 Among minor changes which are under consid- 

 eration may be mentioned: 



(o) Moon culminations given for lower as well 

 as for upper culmination. 



( 6 ) A more convenient arrangement of ephem- 

 erides of satellites of the planets. 



(c) Ephemerides of the brightness of the planets 

 in terms of stellar magnitudes. 



{d) Lphemerides for physical observations of 

 the sun, moon and planets. 



The second edition of the American Nautical 

 Almanac for 1909 will contain a star list and map 

 for the use of navigators, and it is hoped later on 

 to add certain tables and ephemerides for the 

 convenience of surveyors and engineers. 



Definite suggestions as to possible improvements 

 in the American Ephemeris and Nautical Almanac 

 from astronomers, navigators and others who 

 make practical use of that publication, are de- 

 sired, will be carefully considered and should be 

 addressed to " The Director, Nautical Almanac, 

 U. S. Naval Observatory, Washington, D. C." 



The American Nautical Almanac OfBee cooper- 

 ates with the British Nautical Almanac Office in 

 certain lines of work, and is also at present 

 cooperating with Professor Simon Newcomb, 

 U.S.N, (retired), in his lunar researches and in 

 a revision of the orbit of Mars. The present 

 superintendent of the Naval Observatory, Admiral 

 Wm. J. Barnette, is disposed to promote the 

 cooperation of the Department of Astronomical 

 Observations of the Naval Observatory with the 

 Nautical Almanac Office, especially as regards the 

 meridian work of the observatory and the places 

 of the fixed stars given in the American Ephemeris. 



The distributing list for the American Ephem- 

 eris and Nautical Almanac has recently been 

 enlarged by more than 50 per cent., and that for 

 the " Astronomical Papers " has been more than 

 doubled. The former publication is sent to 



libraries, though not, as a rule, to individuals, 

 while the " Astronomical Papers " are widely dis- 

 tributed to scientific men and institutions through- 

 out the world. 



A considerable number of sets of the "Astro- 

 nomical Papers," eight quarto volumes bound in 

 cloth, are now available for free distribution, as 

 also are a number of volumes and parts of vol- 

 umes for the completion of sets, carriage free 

 within the limits of the United States. There are 

 also several hundred copies bound in cloth of an 

 interesting and valuable book on " Astronomical 

 Constants," a supplement to the American Ephem- 

 eris for 1897, which will be mailed free to those 

 who apply for it. 



The publications of the Nautical Almanac 

 Office are no longer sold by the office. On October 

 1, 1906, the sale of these publications was trans- 

 ferred to the superintendent of documents, Gov- 

 ernment Printing Office, Washington, D. C. 



On an Infinite Universe: G. W. Hough. (Pub- 

 lished in Popular Astronomy.) 



The Luminosity of the Brighter Lucid Sta/rs:< 



Geoege C. Comstock. 



Parallaxes have been determined for about three 

 fourths of all stars brighter than magnitude 2.5. 

 These are here utilized to determine the intrinsic 

 brightness of each such star and to derive from 

 these a curve showing the relative frequency of 

 occurrence of the several degrees of luminosity 

 among the stars in question. A theoretical dis- 

 tribution curve for these luminosities, derived 

 from the hypotheses with regard to stellar dis- 

 tribution that are commonly made, is shown to 

 be widely divergent from the curve above found. 

 The cause of this divergence is sought in the 

 hypotheses upon which the theoretical curve is 

 based and it is shown that the theoretical and 

 observed distributions may be brought into agree- 

 ment by either of the following suppositions: 



{a) The intrinsically brightest stars are not 

 widely distributed through space, but manifest a 

 distinct tendency to cluster about the sun. 



(6) There is a sensible absorption of light in 

 its transmission through space, of such average 

 amount that a star having a parallax of a tenth 

 of a second appears one magnitude fainter than 

 it would appear in the absence of absorption. 



Photographic Determinations of Stellar Parallaw 

 until the Yerkes Refractor: Fbank Schies- 



INGEK. 



This paper is an informal report on work done 

 with the 40-inch Yerkes telescope under the 



