Jl-NE, 1904.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



ASTRONOMICAL. 



Comet 1904. ' (Brooks). 



After an interval of seven months, during which no comet has 

 been under observation in the northern liomisjihcrc, a now 

 comet was discovered by Professor W. H. Brooks, director of 

 the Smith Observatory, Geneva, U.S.A. The new object, as 

 the following elements by Herr E. Striimgren will show, has 

 almost exactly the same perihelion distance as the comet dis- 

 covered by M. Giacobini, December 2, 1902. Only one other 

 comet is known with a perihelion distance greater than these, 

 namely, that of 1729. An examination of the Harvard photo- 

 graphs taken before the discovery of Brooks' comet furnished 

 six plates, showing objects which might possibly be identical 

 with it. These were taken on March 1 1 and 15, and April i, 5, 

 13, and 16. The first two places have not as yet been satisfac- 

 torily included in any orbit, and possibly the images shown on 

 these two plates do not in reality belong to the comet. The 

 nebula; N.G.C. 6555 and 6564 are in the innnediate neighbour- 

 hood of the place indicated by the plate of March 11. At the 

 present time the comet is receding both from the earth and 

 from the sun, and is slowly diminishing in brightness. This 

 makes the twenty-fourth comet discovered by Professor 

 Brooks. 



Elements. 



T = 1904, Feb. 28, 8130 M.T. Berlin 

 u = 50° 51' 30" 



a= 275° 17' 3^- 



i = 124° 59' 38" 

 logq = 0-42951 



1904-0 



Methods of Determining Jovian 

 Longitudes. 



In the " Monthly Notices " of the Royal .Astroiioniical Society 

 for March, 1904, Mr. Stanley Williams institutes a comparison 

 betv/een the method of determining tiie longitude of markings 

 on Jupiter by estimating the times when they appear to be 

 exactly in mid-transit with the method of measuring their dis- 

 tances from the two limbs of the planet Ijy a micrometer ; and 

 he gives good reason for thinking that the first and simpler 

 method is, in the hands of a practised observer, not at all 

 inferior in accuracy to the latter. The micrometric method 

 h.as been supposed the better from the comparison of measures 

 of the s.ame object made on the same night ; oljviously transits 

 of any object can only be compared ;is taken on difierent 

 nights. Mr. Williams has in this paper compared micru- 

 metric measures made of objects on different nights, and finds 

 that they show no superiority in accuracy over the method of 

 transits. 



* * * 



Change from Taurus to Aries as First 



Sign of the Zodiac. 



The same number of the " Monthly Notices " contains a paper 

 by Mr. and Mrs. Walter Maunder, in which they show that 

 there are clear indications in Assyrian records of two distinct 

 methods having been in use for the determination of the begin- 

 ning of the year. The earlier was that of the seleniacal setting 

 of Capella. This involved the recognition of Taurus as the 

 first constellation of the zodiac, and was no doubt in opera- 

 tion as early as 2000 B.C. The second was the direct deter- 

 mination of the equinox by some form of time-measurer. 

 Other advances io connection with this seem to be indicated ; 



the recognition of the ecliptic as distinct from the equator; of the 

 ascending node ; of the nature of the motions of some at le;ist 

 of the planets; and the division of the ecliptic was elTeeted 

 into twelve equal signs as distinct from the twelve irregular 

 constellations. The dale when tlu;se changes took place 

 cannot have been very different from tliat when tlie star 

 Hamal, the briglitcst of the constellation Aries, marked the 

 spring colurc, i.c'., about 700 B.C., and the remarkable out- 

 burst of scientific activity which is thus indicated was in ;ill 

 probability associated with the great literary activity of the 

 reign of Assurbanipal. 



The Astrographic Catalogue. 



It is now seventeen years since the delegates of seventeen 

 different nationalities met in Paris, under the presidentship of 

 Admiral Monche-z, to consider the question of a photographic 

 chart of the whole heavens, down to the stars of the fourteenth 

 magnitude, with a catalogue of stars to the eleventh magni- 

 tude. The latter portion of the programme is now beginning 

 to be realised ; the Potsdam observatory has already produced 

 three volumes of its catalogue; the observatories of I lelsingfors, 

 of P.aris, and of the l-'rench colonies have also begun to pul)- 

 lish ; and the Astronomer- Royal, at the meeting of the Royal 

 Astronomical Society, already alluded to, presented the first 

 volume of the Greenwich catalogue, covering one half the 

 Greenwich section. The introduction to the catalogue con- 

 tains a number of exceedingly interesting discussions ; of the 

 effect of personality on the measurement of the places of 

 stellar im;iges, of the probable error of the measures, and ol 

 the determinations of photographic magnitudes. The accuracy 

 of the measures of position are of the same order as of obser- 

 vations with the transit instrument ; the probable error of the 

 position of a star, in arc of a great circle, deduced from the 

 measures on one plate is + o'26" in R.A., and + o'ZiS" 

 in Declination. In the investigation of photographic magni- 

 tudes, it was found that in passing from one exposure to 

 another the law, exposure X brightness equals constant, held 

 almost exactly, except in the case of the shortest exposures, 

 which gave fainter stars than would be expected in accordance 

 with the law. 



Distribution of Stars of the Third and 

 Fourth Type. 



In a discussion of the distributiun ul'the coloured stars, Ilerr 

 Freidrich Kruger gives in the " Astronomischc Nachriehten," 

 No. 3947, a table dealing with 3>Soo stars of the third and 

 fourth types of spectra. These are distributed into eiglit 

 zones, each twenty degrees in breadtli, the galactic eijuator 

 running through the middle of the fifth zone. The table shows 

 that about 4 per cent, of the stars of the third type of spec- 

 trum are known to be variable, but 14 per cent, of the fonrth 

 type. Both cluster towards the galactic equator, but tliat 

 clustering is nuicli more evident with the fourth (ype stars. 

 These two relations were drawn attention to by Professor 

 Hale in his recent " Memoir on Stars of the h'ourth Tyi>e." 

 A curious point of difference between the two types is shown 

 by Herr Kruger's table, namely that whilst tlie numbers of the 

 third typi: show but very small increase with diminution of 

 magnitude, the faintest class of the fonrth type includes more 

 than all the other six classes combined. 



The Spectroscope Binary, Iota Pegasi. 



Professor W. \V. Campbell discovered in i'-ii)9 llial Iota 

 Pegasi was a spectroscopic binary, and Mr. Heber D. Curtis, 

 from a very thorough discussion of forty-three photographs of 

 the spectrum extending over six years, has obtained very 

 accurate final elements for it. The period found is 10-21312 

 d;iys, and the velocity — 4- r2 kilometres. The orbit is nearly 

 eiicular, the eccentricity being o-oo«5, so that the epoch of 

 periastron is not very certain. Dr. R. G. Aitken examined 

 the star in 1901 with the 36-inch refractor of the Lick 

 Observatory, but was not alile to detect any evidence of 

 duplicity. 



