March 



1898J 



NATURE 



519 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrences in April 1898 : — 

 April 3. Pallas 15' south of o Eridani (mag. 4"l). 



5-15. Mercury well visible in the evenings near Venus. 

 9. Juno (mag. 87) in opposition to the sun. 



I3h. Mercury at greatest elongation (19° 23' E.). 



I4h. 38m. to I5h. 8m. A Ophiuchi (mag. 47) oc- 

 culted by the moon. 



Saturn. Outer minor axis of outer ring = i8"'i4. 



5h. 51m. to 8h. 26m. Transit of Jupiter's Sat. III. 



Venus. Illuminated portion of disc = o"968. 



Mars „ ,, „ =0-953. 



9h. 4m. Minimum of i3 Persei (Algol). 



Mercury and Venus in conjunction (Mercury 3° 20' N. ). 

 Meteoric shower from near a Lyra (radiant 

 270° + 32°). 



9h. iim. to iih. 49m. Transit of Jupiter's Sat. III. 



I5h. Mercury in conjunction with moon (Mercury 

 2^2'S.). 



6h. 41m. to 7h. 44m. 79 Geminorum (mag. 65) 

 occulted by moon. 



I2h. 34m. to I5h. 15m. Transit of Jupiter's Sat. III. 



I3h. im. to I3h. I5h. I Leonis (mag. 5-2) occulted 

 by moon. 



Favourable Apparition of Mercury. — The most con- 

 venient period in 1898 for observing Mercury will be during the 

 fortnight from April 5 to 18, when the planet will become 

 visible about an hour after sunset above the W. by N. horizon. 

 He will reach his greatest eastern elongation on the morning of 

 April II, and will set on several evenings at about this time, a 

 little more than two hours after the sun. Fortunately, at this 

 special period, the planet will be situated within a few degrees 

 of Venus, and the latter will form a brilliant guide to the position 

 of Mercury. On April 5 Mercury will be apparently 6 degrees 

 above Venus, and on ensuing nights the interval decreases until 

 on April 18 the two objects will be in conjunction, Mercury 

 being about 3° 20' N. of Venus. Mercury will then appear on 

 the north-west side of Venus, but is likely to be much fainter 

 than be/ore elongation, as he rapidly loses brightness owing to 

 the crescent-phase which his disc assumes. The following are 

 the times of setting 'of the sun. Mercury and Venus, and the 

 intervals at which Mercury sets after the sun : — 



lo. 



ID. 



10. 

 14. 

 IS- 

 IS- 

 16. 

 18. 

 19-20. 



21. 

 21. 



27. 



28. 

 29. 



The conjunction of Mercury and Venus on April 18, at about 

 5h. , does not appear to be mentioned in the Nautical Almanac. 



Comet Perrine. — Dr. F. Ristenpart has calculated the 

 elements and ephemeris of this comet from the observations 

 made on March 19, 21 and 22. These, as given in Circular 

 No. 3 from Kiel, are as follows : — 



Elements, 

 T = 1S98 .March 18*501. Berlin Mean Time. 



w = 48 47-1 1 



Ci = 263 164 1 1898 o 



/■ = 72 447 \ 



log^ = 0-04316 



NO. 1483. VOL. 57] 



Ephemeris for 12//. Berlin Mean Time. 



We may mention that the elements calculated by Me.ssrs. 

 Hussey and Perrine are almost identical with those given above. 



At the time of this comet's discovery its diameter was 2', with 

 a strong condensation, and a tail of length equal to 1°. It was 

 then of the 7th magnitude. 



Two New Variable Stars of Short Period.— Herren 

 G. Miiller and P. Kempf contribute some interesting data to the 

 current number (No. 3483) of the Astronomische Nachrichten, 

 relative to the two new variables of short period which were 

 originally discovered during the series of zone observations for 

 the second part of the Potsdam Photometric Durchmusterung. 

 These two stars are BD + 20° -4200 and BD + 28" -3460, or, 

 as they have been named, U Vulpeculae and ST Cygni 

 respectively. 



The first of these stars, whose position for 1900 is R.A. igh. 

 32m. 15s., declination + 20° 6' -6, has a period of nearly eight 

 days, the light curve varying from mag. 69 or 7 -o at maximum 

 to 7 -6 at minimum ; the epoch for the calculation of the maxima 

 being 1897 October 2-47 Greenwich mean time. The light curve 

 shows small secondary variations both in the ascending and 

 descending portions, the rise to maximum and fall to minimum 

 occupying equal intervals of time. 



The second variable, whose position for 1900 is R.A. I9h. 40m. 

 49s. , declination -f- 29° i' 2, has a period of 3844 days, the 

 magnitudes at maximum and minimum being 6-6 and 7-4 re- 

 spectively. The dates of maxima can be calculated from the 

 epoch (maximum) 1897 October 4*66 Greenwich mean time -I- 

 3*844 E. In the case of this star the curves on either side 

 maximum are not equal, but the rise to maximum com- 

 prises less time than the fall to minimum. The former occupies 

 only 0-9 days, while the latter takes 29 day.?. The 

 curve is described as similar to 5 Cephei. The observations 

 suggest that on the downward side of the curve, 1*75 days after 

 the maximum, the light becomes stationary for a short period of 

 time, afterwards decreasing to the next minimum. 



Variables and their Comparison Stars. — Variable star 

 observers may be glad to know that Prof. E. C. Pickering is 

 able to furnish the photometric magnitudes of a great many 

 comparison stars for long-period variables, and that he will 

 communicate the information in advance of publication should 

 any one require it {Harvard College Observatory Circular, 

 No. 27). Sequences of comparison stars have been selected for 

 about one hundred variables, stars brighter than the tenth 

 magnitude having been measured on at least three nights with 

 the meridian photometer, and those from the eleventh to the 

 thirteenth magnitude on two nights with the photometer having 

 achromatic prisms. Observations are already completed for the 

 following stars :— T Andromedse, T Cassiopeise, R Andromedss, 

 S Ceti, S Cassiopeise, R Piscium, R Arietis, T Persei, o Ceti, 

 S Persei, R Ceti, U Ceti, R Tauri, S Tauri, R Aurigae, 

 U Orionis, R Lyncis, R Geminorum, S Canis Minoris, R Cancri, 

 S Hydrae, T Hydrae, R Ursse Majoris, X Virginis, R Comae, 

 T Virginis, V Virginis, T Ursse Majoris, R Virginis, S Ursse 

 Majoris, U Virginis, R Hydrse, S Bootis, R Camelopardali, 

 U Ilerculis, W Herculis, R Ursse Minoris, R Draconis, x Cygni, 

 S Cygni, R Delphini, U Cygni, V Cygni, T Aquarii, T Cephei, 

 S Cephei, SS Cygni, S Aquarii, R Pegasi, S Pegasi, R Aquarii, 

 and R Cassiopeise. 



Prof. Pickering adds that the brightness of each of these 

 variables is being determined monthly by Argelander's method, 

 and it would be a good thing if other observers would reduce 

 their observations to the same scale of magnitudes, as then the 

 desired uniformity in results would be obtained. 



The variability of the star in Aquila, R.A. igh. 33 ■3m., 

 Decl. -h 11' 29' (1900), announced recently by the Rev. T. D. 

 Anderson, has been corroborated by an examination of the 

 Harvard photographs. Measures of fifty-seven negatives gave 

 the maximum brightness 9*2, and minimum less than 12 9. 

 The variations can be closely represented by the formula J. D. 

 2411550 + 330 E. 



