550 



NATURE 



{Oct. 3, 1889 



OUR ASTRONOMICAL COLUMN. 



Mr. Tebbutt's Ohservatory, Windsor, New South 

 Wales. — Mr. Tebbu't, who, it will be remembered, published 

 a short account of his observatory about a year and a half ago 

 (Nature, vol. xxxvii. p. 400), has resolved to supplement it by 

 a brief annual report, the first of which reports, that for 1888, 

 he has now just issued. The record of his work during the 

 year shows him to have been fully as active as formerly ; the 

 list of observations, including, in addition to routine meridian 

 and meteorological work, 56 occultations of stars, besides those 

 of Venus and Saturn, the occultation of 47 Librae by Jupiter, 

 75 phenomena of Jupiter's satellites, 230 comparisons of 

 Jupiter and ;8^ Scorpii at their conjunction ; 164 observations 

 of Pallas on 17 nights, 215 of Comet Sawerthal on 23 nights, 63 

 of Encke's comet on 10 nights, and 187 of Comet Barnard (1888, 

 September 2) on ?.o nights, besides measures of 24 double stars. 

 Faye's comet was seen on December 3, but no determination 

 of place was obtained. The whole of the observations were 

 made by Mr. Tebbutt himself, who has a well-earned reputa- 

 tion for accuracy, and it is with a just and natural satisfaction 

 that he alludes to the use made of his observations by Dr. 

 Kreutz in his discussion of the orbits of the comets of 1880 and 

 1882, and by Von Ilaerdtl of that of Winnecke's comet. 

 During the present year, 1889, Mr. Tebbutt proposed to 

 continue observations of the same nature as in 1888, with 

 especial attention to lunar occultations. 



The Variable 77 Argis. — Mr. Tebbutt mentions in his 

 report the recent increase in light which has been shown by 

 Tj Argus, and to which he had already called attention in the 

 Astronomische Naclwichten. Dr. Thome now supplements this 

 statement in the same publication. No. 2922, in which he gives 

 the Cordoba observations of the star. From these it appears 

 that the star ran steadily down in brightness from 1871 to 1887, 

 and that since then there has been a fairly rapid recovery, also 

 steady in character. The star has at the same time shown a 

 remarkable change as to colour : before minimum it was a dull 

 s:arlet, now it is bright orange ; indeed it was the change in 

 colour rather than any increase in brightness which first attracted 

 Dr. Thome's attention. This change he first noticed on March 

 20, 1887 ; the last observation previous having been made in 

 July 1886, from whence he infers that minimum fell about 

 October or November 1886. "But if," he adds, "we have 

 here, as seems probable, a type of Mr. Lockyer's binary meteor 

 swarms, March 20 would correspond nearly with the beginning 

 of collisions, and opposition may have occurred years earlier." 

 Dr. Thome estimates the minimum brightness as 7"65 ; taking 

 the maxiaium brightness in 1843 ^^ - I 'o mag. (between Sirius 

 and Canopus), the total range will be 8^ magnitudes in a period 

 of forty-three or forty-four years. 



Dr. Thome conside's that the observations since 1811, if 

 reduced to the same scale, might no longer show secondary 

 maxima. , 



The Rotation Period of the Sun. — Mr. Henry Crew, 

 who published about eighteen months ago (Nature, vol. xxxvii. 

 p. 495) a determination of the rotation period of the sun by means 

 of the relative displacement of lines in the solar spectrum when 

 observed at the east and west limbs, has recently undertaken a 

 fresh series of observations for the correction or confirmation of 

 those made last year. It will be remembered that Mr. Crew 

 found that his earlier observations give an increase in the angular 

 velocity with increase of latitude, in opposition to the results 

 obtained by Carrington and others from the observation of sun- 

 spots, and which showed the greatest angular velocity for the 

 equator and its neighbourhood. Mr. Crew now finds that his 

 earlier result needs revision, for there was apparently a systematic 

 error connected in some way with the date of observation. The 

 new series, however, still points ti a shorter rotation period for 

 the higher latitudes, the mean value for the rotation period at 

 lat, 45° being 18 hours shorter than at the equator. Having 

 regard to the smallness of this amount and the uncertainty of the 

 observations, Mr. Crew concludes that "no certain variation of 

 period with latitude has been detected by the spectroscope." He 

 calls attention, however, to the wide difference in the values of 

 the equatorial period as obtained by different msthods. Horn- 

 steia and others, from the variations in the daily range in the 

 barometer, fixed the sidereal rotation period as 24' 12 days ; 

 Braun and Hornstein, from the variation of the magnetic ele- 

 ments, deduced the values 24"i8 and 24'5t respectively; 

 Carrington obtained from sun-spots 24*97 days ; Wilsing, from 



faculte, 25*23 ; whilst Crew's value from the spectroscopic 

 method is the longest of all — 26*23 days. Mr. Crew makes the 

 suggestion that the different methods really deal with different 

 strata of the sun, and that those portions of the sun which affect 

 the variations of the barometer and of terrestrial magnetism are 

 more deeply seated than the sun-spots, which, again, lie lower 

 than the faculre, the angular velocity of rotation diminishing on 

 this view from the more central portions of the sun outwards. 



Comet 1889 d (Brooks, July 6). — The following elements 

 for this comet have been derived by Dr. Otto Knopf from 

 observations made at Mount Hamilton on July 8, Dresden July 

 30, and Vienna August 19 : — 



T = 1889 September 26*9997 Berlin M.T. 



«■ - ft = 341 56 26"*6 \ 



a = .18 14 21*2 / Mean Eq. 1889*0. 

 ( = 63 24*0 ) 



6 3 24*0 

 i^ - 28 33 52*4 

 log (7 - 0*292550 

 /i = 486"*969 



logrt = 0-575004. 

 Period = 7 '286 years. 



Ephemei'is for Berlin Midnight. 



1889. R.A. Decl. Log A. Log r. Bright- 



h. m. s. - "^*^- 



Oct. 4 •• 234557 ... 4 53*6 S.... 9'9937 ••• 0*2928 ... 2*5 



8 ... 2344 5 ... 4 39 9 ••• 0*0003 ... 0*2931 ... 2*4 



12 ... 234235 ... 424*0 ... 00081 ... 0*2935 ... 2*3 



16 ... 2341 28 ... 4 6*1 ... 0*0172 .. 0*2941 ... 2*2 



20 ... 234048 ... 3 45*9 S.... 0*0273 ... 0*2948 ... 2*1 



The brightness at discovery has been taken as unity. 



ASTRONOMICAL PHENOMENA FOR THE 

 WEEK 1889 OCTOBER 6-12. 



/"T7OR the reckoning of time the civil day, commencing at 

 ^ ■'- Greenwich mean midnight, counting the hours on to 24, 

 is here employed.) 



At Greenwich on October 6 

 Sun rises, 6h. 12m. ; souths, iih. 48m. 2*is. ; daily decrease 

 of southing, 17*33. ; sets, I7h. 25m.: right asc. on meridian, 

 I2h. 49*3m. ; decl. 5° 18' S. Sidereal Time at Sunset, 

 i8h. 27m. 

 Moon (Full on October 9, ih,1 rises, I7h. 5na. ; souths, 

 22h. 17m.; sets, 3h. 42m.*: right asc. on meridian, 

 23h. 20 om. ; decl. 9° 26' S. 



Right asc. and declination 

 Planet. Rises. Souths. Sets. on meridian. 



h. D). h. m. h. m. h. m. • / 



Mercury.. 8 6 ... 12 50 ... 17 34 ... 13 51*8 ... 15 10 S. 

 Venus ... 3 5 ... 9 5^ •• 16 37 ... 10 52*3 ... 8 25 N. 

 Mars ... 2 46 ... 9 40 ... 16 34 ... 10 41*3 ... 9 42 N. 

 Jupiter... 13 It ... 17 3 ... 20 55 ... 18 5*0 ... 23 30 S. 

 Satum ... 20... 99 ... 16 18 ... 10 99 ... 12 41 N. 

 Uranus... 6 57 ... 12 20 ... 17 43 ... 13 21*5 ... 7 58 S. 

 Neptune.. 19 22*.. 3 11 ... 11 o ... 4 10*8 ... 19 22 N. 

 * Indicates that the rising is that of the preceding evening and the setting 

 that of the following morning. 



Saturn, October 6. — Outer major axis of outer ring = 37"*9 ; 

 outer minor axis of outer ring = 6"*3 : southern surface visible. 



Variable Stars. 



Star. 



R.A. 



Decl. 



U Cephei 

 Algol ... 



o 52*5 ... 81 17 N. 

 3 I'D ... 40 32 N. 



h. m. 



Oct. 10, 3 6 W 



„ 7. o 33 »« 



,, 9, 21 22 m 



„ 8, 23 51 m 



„ 8, 23 o m 



„ 8, m 



„ 9, »' 



,, 9, 22 24 m 



„ 6, m 



„ II, Af 



9. *n 



,, 10, 2 o yl/ 



,, 9, 20 o m 



,, 10, 22 o Af 



... 21 31*8 ... 44 53 N. ... „ 12, M 



... 22 25*1 ... 57 51 N. ... ,, 6, 3 o w 

 M signifies Biaximuni : tn niiiiimuin. 



\Tauri 3 54*5 ... 12 11 N. ... 



CGeminorum ... 6 57*5 ... 20 44 N. ... 



R Ursae Minoris ... 16 31*5 ... 72 30 N. ... 



R Draconis 16 32*4 ... 66 59 N. ... 



U Ophiuchi 17 10*9 ... i 20 N. ... 



R Lyrse 18 52*0 ... 43 48 N. ... 



S Vulpeculae ... 19 43*8 ... 27 i N. ... 



U Cygni 20 i6*2 ... 47 33 N. ... 



X Cygni 20 390 ... 35 11 N. ... 



T Vulpeculae ... 20 46*8 ... 27 50 N. ... 



W Cygni 

 5 Cephei 



