I50 



NATURE 



[November 30, 191 1 



boxes at the theatre and Op^ra were placed at the 

 disposal of members of the congress. 



The results of the congress promise to be of great 

 interest and value, not merely by extending the scope 

 and utility of the national ephemerides for the pur- 

 poses of practical astronomy, but by the facilities 

 which the universal adoption of Greenwich time offers 

 for the comparison of the different lunar and planetary 

 tables. 



A probable sequence to these resolutions will be the 

 universal adoption of Greenwich as the origin of 

 longitudes in all future maps and hydrographic charts. 

 The gain in simplicity and convenience will he 

 immense. 



Let us hope that England will respond to the inter- 

 national compliment thus paid to her by the adoption 

 of the metric system of weights and measures. 



Resolutions and Recommendations adopted by the 

 Conference. 



The conference strongly recommends that : — 

 (i) In all ephemerides the ecliptic coordinates of the 

 sun should be given for Greenwich mean noon, and that 

 the equatorial rectangular coordinates should be given for 

 midday and midnight of Greenwich mean time. 



(2) The ecliptic coordinates of the moon should be given 

 at least for oh. and i2h. of Greenwich mean time. 



(3) The ecliptic heliocentric and geocentric coordinates 

 of the planets should be given for oh. or i2h. of Greenwich 

 mean time. 



(4) The ephemerides of the stars, that is to say, their 

 correction from mean to apparent place, should be calcu- 

 lated for upper transit at the meridian of Greenwich. 



The conference is of opinion that the adoption of the 

 meridian of Greenwich for all ephemerides should be 

 realised as soon as possible. 



The conference is of opinion that in all catalogues and 

 all collections of observations d<>clinations instead of polar 

 distances should be adopted. 



The conference decides that those portions of the 

 ephemerides which deal with the data necessary for the 

 calculation of the perturbations of the small planets and 

 comets shall be based on the masses of the planets adopted 

 by Newcomb. 



The conference decides that the names of stars shall be 

 accompanied by a letter indicating their spectral type in 

 terms of Pickering's notation. It is of opinion that these 

 indications (so far as they have been determined) should 

 in future be given in the list of 3064 stars to be published 

 by the Bureau des Longitudes. 



The conference decides that in future the stars in the 

 fundamental and standard lists of Auwers, Boss, and New- 

 comb shall be designated by the letters A, B, N, and the 

 Backlund-Hough stars by the letters BH. 



For the prediction of occultations of stars the list of the 

 Nautical Almanac shall be adopted. 



The commission adopts the following resolutions : — 



For the sake of uniformity in the calculation of 

 parallaxes, eclipses, and occultations, the ephemerides shall 

 adopt for the value of the compression of the earth the 

 number 1/2970, resulting from the final researches of 

 Messrs. Tittmann, Hayford, and Helmert. 



For like reasons, in the calculation of eclipses, the semi- 

 diameter of the sun (Auwers) shall be retained, as already 

 employed in all ephemerides. 



The bureaux charged with the calculation of eclipses of 

 the sun and moon and the occultations of stars shall choose 

 in common agreement the tables and apparent diameters 

 which they find most desirable, taking care to communicate 

 in the most precise and complete fashion the data which 

 they employ and the origin whence the adopted data have 

 been derived. 



The conference decides that the Connaissance des Temps 

 shall continue to calculate the positions of the sun and 

 of the planets from the Leverrier-Gaillot tables, but that 

 bureau will in future compute the positions of the moon 

 from the new tables of M. Radau, which are based upon 

 Delaunay's theory. In the other ephemerides these calcula- 

 tions shall be based on the tables of Newcomb and of Hill 



NO. 2196, VOL. 88] 



for the sun and planets, and on Hans<-> 



Newcomb 's corrections, for the moon uri 



the latter tablet) shall be replaced by the n-w iarji»-b 



Brown. 



This fcrond !»eric-s of solar, planetary, and lunar r^hi, 

 tions shall be undertaken by the Nautical Almanac < 

 with the exception of the ephemcris of Mercury, for 

 the office of the " Berliner Jahrbuch " shall be responkiLi 



Relative to the Start. 

 (i) The corrections from mean to apparent place 

 stars BH shall be computed at the National A! 

 Office, and be printed by the Observatory of Pulkov. , 

 same will apply to the daily corrections of the pri.,,..i, 

 fundamental clock-stars, which latter shall include tl 

 lunar terms of short period. 



(2) The ephemerides of such of the stars A, B, N 

 not occur in the list of Auwers stars, which is pui 

 annually in the "Berliner Jahrbuch," shall be calculat; 

 and printed in the observatory at. Ti^r>. 



(3) The ephemerides of the .Auwers stars shall be calcu- 

 lated and printed by the " Berliner Jahrbuch," with the 

 exception of the 343 stars printed within brackets; the 

 calculation of the ephemerides of these latter shall be 

 undertaken by L'.Almanaque Nautico. 



(4) The ephemerides of the pole-stars, that is to say, of 

 all the stars situated within 10 degrees of north or south 

 polar distance which are to be found in the provisional 

 list of 3064 stars published by the Bureau des Longitudes, 

 and of the other polar stars hitherto given in the 

 ephemerides, shall be calculated from day to day by the 

 Bureau des Longitudes, and shall contain the terms of 

 short period, the values of which shall be separately 

 indicated, however ; for polar stars situated between 80' 

 and 83° declination it will be sufficient to give the 

 ephemerides for each alternate day. 



The Coiinaissance des Temps undertakes to print 

 all the ephemerides of the above-mentioned stars which 

 are not given in other similar works. 



The ordinary ephemerides of the stars shall be calcu- 

 lated to ooois. in R.A. so far as 60° of declination and 

 o-oi* in declination, not for each tenth day, but for each 

 tenth successive culmination at the meridian of Greenwich 

 in order to facilitate interpolation ; they will be accom- 

 panied with the data necessary for the computation of th' 

 terms of short period. 



The calculation of the constants of reduction shall b- 

 carried out by each bureau in their usual wav with four 

 or five decimals. 



Relative to Eclipses and Occultations. _™ 



The calculation of eclipses of the sun and moon shall fl 

 be made (in conformity with the rules established by the 

 preceding resolutions) once by the -American ephemeris and 

 once by the Connaissance des Temps. 



The computation of occultations shall be made in dupli- 

 cate by the American ephemeris. 



The predictions of eclipses and the elements of occulta- 

 tions shall be calculated with all possible precision. 



Relative to Satellites. 



(1) The calculation of new ephemerides of the four prin- 

 cipal satellites of Jupiter and their phenomena shall be 

 made by the Bureau des Longitudes, and be based on 

 Sampson's new tables. 



(2) The ephemerides relative to the ring and to the 

 satellites of Saturn (with the exception of Phcebe) shall be 

 calculated by the " Berliner Jahrbuch." 



(3) The calculations of the ephemerides of the satellites 

 of Mars, of the new satellites of Jupiter, of Phoebe, and 

 of the satellites of Uranus and Neptune shall be made by 

 the American ephemeris. 



The ephemerides relative to physical observations of the 

 sun, moon, planets, &c., shall be calculated by the 

 American ephemeris, except the ephemeris of the crater 

 Mosting A, which will continue to be published bv the 

 " Berliner Jahrbuch." 



The computation and printing of the ephemerides of the 

 small planets and variable stars shall be undertaken bv the 

 " Berliner Jahrbuch." 



