January i6, 1908 J 



NA TURE 



259 



SIMULTANEOUS OBSERVATIONS OF 

 JUPITER.' 



T N the December BiiUctin de la Societe astroiw)iiique 

 -*■ dc France for 1905 (p. 55(1), readers who possessed 

 telescopes were invited to collaborate in a scheme for the 

 simultaneous observation of Jupiter on prearranged dates, 

 and to make drawings and notes of what they saw, which 

 were to be forwarded to a central authority for correlation 

 and discussion. 



The valuable results likely to accrue from such a com- 

 bined attack are too obvious to need recapitulation, and 

 when iM. N'icolas Poutiata suggested the idea to M. 

 Camille Flammarion, that indefatigable organiser trans- 

 mitted it immediately to the French Astronomical Society, 

 and asked for its cooperation. A scheme was drawn up, 

 thirty-six observers in various parts of Europe responded 

 to tile invitation in the December Bulletin, and Dr. Je.in 

 Mascart undertook to discuss all the drawings and notes 

 sent in. The present brochure collects his discussions, 

 which have been appearing month by month in the 

 Bulletin, and gives some valuable hints 

 for any similar undertaking in the future. 



Briefly, the programme arranged was as 

 follows : — (i) Observers were to draw on 

 prepared discs all the markings they wen- 

 able to see on the planet's surface, at 

 2oh. om. (8 p.m.) precisely (G.M.T. Paris), 

 on every clear night from January 2-20, 

 inclusive, 1906. (2) Arrangements were 

 made so that observers residing rn other 

 longitudes than Paris should know the 

 exact local tirtie at which the observations 

 were to be made, thus preventing any 

 ambiguity as to the precise ^hour of 

 observation. (3) Drawings w-ere to be 

 made on previously prepared white discs 

 identical in size and shape, the scale being 

 such that I mm. on the disc corresponds 

 to about 2000 km. on the planet. (4) De- 

 tailed instructions were also given as to the 

 preparation of fair copies of the drawings, 

 their orientation, &c., and also as to the 

 noting of any written details which would 

 assist the general discussion. 



The instruments employed varied in 

 aperture from 75 mm. to 380 mm., and 

 eye-pieces of various powers were used. 

 The number of obser\'ations varied from 

 five, on January 15, to seventeen, on 

 January 14, and, altogether, 172 individual 

 observations were made. 



To illustrate the general character and 

 variety of the drawings, we reproduce the 

 set made on January 2, 1906. It is 

 interesting to note that the personality of 

 many of the individual observers appears 

 throughout the entire series. Thus, for 

 example, \o. 4 here reproduced was made 

 by Herr Phil. Fauth, who for twenty years 

 has been training his eye to see finer and 

 finer details on the moon's surface, and 

 characteristic of all the drawings made by him in this 

 series. The similarity of the drawings of this observer 

 and those of Dom .\mann, of Aosta, Italy, is a feature 

 of each of the series where both occur, and the apertures 

 and powers employed were practically the same in each 

 case. No. 5 was tlrawn by the latter observer. 



Dr. Mascart gives the notes made each day by each 

 observer, and reproduces the drawings with numbers so 

 that each may be identified, the latter being arranged, so 

 far as possible, in the order of the instrumental aperture 

 employed. Thus No. i in the above series was made by 

 an observer using a telescope of 75 mm. aperture. No. 5 

 with a refractor of 170 mm., and No. 7 with a reflector 

 of 105 mm. aperture made by the observer himself, M. 

 Paul Vincart, of .Antwerp, who thus demonstrates to his 

 co-workers that, lacking the necessary wherewithal to 



1 *' Ob ervationi simulranee'; d*» la Surface de Jupiler rtfunie^." Bv M. 

 lean Mascarl. Exirail du Eullelin de la SocIiSti astrcnom que de Fr3n:e. 

 (■507-) 



NO. 1994. VOL. 77] 



purchase an instrument of serious size, a «cry good sub- 

 stitute may be made " par tin peu de volonte et beaucoup 

 d'huilc de . . . biceps." Following the seriatim dis- 

 play of each day's notes, the author points out briefly 

 the similarities and differences of the various drawings, 

 directing particular attention to any striking peculiarity 

 of any one of thein. 



These notes are too numerous to give in detail here, 

 but it is safe to predict that they will amply repay the 

 close study of every Jovian observer. The various undula- 

 tions of the great southern equatorial band, the various^ 

 tints of the polar regions, the fine rifts in the several 

 bands, and many other features of interest, and of possible 

 variation, are all recorded and commented upon. One 

 item of more practical interest perhaps, illustrated, for 

 example, in the drawings of January 5, is that the smaller 

 apertures appear to give a greater relative intensity to the 

 tints of the polar regions. Several curious globular struc- 

 tures, attached to the northern edge of the south equatoriat 

 band, and some striae in the north polar regions were 

 recorded bv Senor J. Comas Sola, using the 3S0 mm. 



The Planet Jupile 



ng made by different obser\er^ January 2, 1906. 



idedlv 



Mailhat equatorial, on January 12. The seventeen draw- 

 ings of January 14 form the most extensive and most 

 valuable series, of which the various features provide- 

 plenty of material for a detailed study ; one unique feature 

 is the delineation of the south tropical band by it. Crouzel, 

 who used the 380 mm. equatorial of the Toulouse Observa- 

 tory, and shows this band as a chain-like series of loops. 



When the January campaign was ended, several 

 observers expressed the desire to continue, but it was 

 found that the notice was too brief to organise the matter 

 effectively. Nevertheless, some of the observers did con- 

 tinue, and valuable results, which Dr. Mascart discusses, 

 were obtained. 



An attempt was made by M. Blum, at Dr. Mascart's. 

 request, to obtain photographs showing the combined!' 

 results of each day's work. The methods employed are 

 fully described in the paper, and some reproductions of 

 the combined photograph for January 8, obtained by 

 different methods of exposure, &-c., are shown, and seem 

 to give excellent promise. 



