2IO 



NA TURE 



[June 30, 1898 



{Psophia viridis) from the Amazons, two White-necked Storks 

 (Dissura episcopus) from Africa, two Dusky Francolins 

 (Pternistes infuscatus) from British East Africa, a Madagascar 

 Tree Boa {Corallus madagascariensis) from Madagascar, pur- 

 chased ; two Red and Yellow Macaws {Ara chloroptera) from 

 South America, received in exchange ; a Hybrid Zebra (between 

 Equiis cabalhis, $ , and Eqiius burchelH, 9 ), a White-tailed Gnu 

 [Connochcetes gnu, <J ), two Thars {Hemitragus jemlaica, d 9 ), 

 born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 

 Astronomical Occurrences in Tuly : — 

 July 3. 8h, 57m. Partial eclipse of the moon. Magnitude 

 0-934- 

 4. Wolf's comet due at perihelion. 

 13. Venus 1° north of o Leonis (Regulus). 

 15. Venus. Illuminated portion of disc 0765. 

 15. Mars. ,, ,, ,, 0'904. 



15. Jupiter. Polar diameter, 3l"'9. 



15. Saturn. „ ,, 16" 6. 



16. 6h. 31m. to 9h. 25m. Transit of Jupiter's Sat. III. 

 18. 8h. 7m. Annular eclipse of the sun invisible at 



Greenwich. 



18. Wolf's comet 27' distant from Mars. 



19. Saturn. Outer minor axis of outer ring, 1 7" "89. 



26. 22h. om. Mercury nearly occults o Leonis (Regulus). 

 28. I2h. 49m. Moon in conjunction with a Scorpii 



(Antares). 

 28. Many meteors from Aquarius and Perseus. 

 30. 7h. 31m. to 8h. 41m. Occultation of \ Sagittarii 



(mag. 3'i) by the moon. 



Comets that are now Visible. — There is plenty of 

 cometary news in the three most recent numbers of the Astrono- 

 mische Nachrichten (3498-3500). As regards comet Coddington- 

 Pauly, which has a declination too southern for the ephemeris to 

 be of any use in this column. Prof. Berberich publishes some new 

 elements {Astr. Nach., No. 3500) based on other observations 

 than those previously used by him, which differ somewhat from 

 the values given in his first computation. The comet has a 

 southerly movement, so that it will not be visible in our 

 latitude. 



Comet Perrine (June 14), on the other hand, has a great 

 northerly declination, and is increasing in brightness very 

 rapidly. The elements and ephemeris of this comet have been 

 computed by Perrine and Aitken, and also by Berberich. The 

 elements obtained by the former we published last week, but 

 they differ slightly from those calculated by Berberich, these 

 being as follows : — 



August 47473 Berlin M.T. 



CO = 235 1677) 



Si = 252 2-34 V- 1898-0 



i = 72 II 43 j 



log 5' = 9 "44405 



The ephemeris for the current week, according to these values, 

 is : — 



Ephenie7-is for i2h. Berlin M.T. 

 1898. R.A. (app.) Decl. (app.) log r. log A. Br. 



h. m. s. o / 



June 30 5 4 3 +52 57-9 



July I 9 56 52 23-3 9-9817 0-2061 234 



2 15 46 51 46-9 



3 21 34 51 8-7 



4 27 19 50 28-7 



5 33 I 49467 9'94iS 0-1904 303 



6 38 40 49 2-7 

 July 7 5 44 15 +48 167 



The new comet discovered by Giacobini is gradually decreasing 

 its southern declination, but the elements at present calculated 

 are described as uncertain. With a diameter of 2', an excentric 

 condensation, and of about the loth magnitude (June 21), the 

 comet is not an easy object. Those wishing to observe it will 

 find the following positions useful. 



Ephemeris for \2h. Berlin M.T. 

 Decl. (app.) 



June 29 



July 3 



7 



II 



R.A. (app.) 



h. m. s. 



18 5 48 



17 8 I 



16 20 13 



15 43 37 



-21 362 

 19 28-6 

 16 47-2 



-14 II-4 



Br. 



1-35 

 1-22 

 I-OI 

 0-79 



NO. 1496, VOL. 58] 



The First Satellite of Jupiter. — In two early numbers 

 of Astronomy and Astrophysics (November 1894 and May 1893) 

 our readers may remember that Prof. W. H. Pickering con- 

 tributed an account of a very interesting series of observations 

 on the shapes of the satellites of Jupiter, and the conclusions he 

 arrived at were that the discs were by no means round, but 

 assumed very decided irregularities as they performed their 

 rotations. These satellites have been further minutely examined 

 by Mr. A. E. Douglass during last year, and in the Astronomische 

 Nachrichten (No. 3500) he describes what knowledge has been 

 gained by the observations of the first satellite. These were 

 made in Mexico, from February 18 to March 28, with the Clark 

 24-inch, and in Flagstaff from May 16 to June 9. We must 

 confine ourselves to a very brief summary of this paper, and 

 refer our readers to the original for the minute details given both 

 in the text and accompanying plate. 



Although the markings on the satellite were sometimes well 

 seen, the observations were not numerous enough over a long 

 period of time to effectively map and determine the period of 

 rotation by tracing the succession of detail. Mr, Douglass 

 adopted Prof. Pickering's method of observing the changes in 

 the elliptical form of the satellite's disc. After an elaborate trial 

 of several periods he was led todeducea period of I2h. 25*8m. 

 for the year 1897, a value not very different from that found 

 by Pickering in 1892, namely 13 hours. Most peculiar are the 

 markings on this satellite. Assuming the axis of the satellite 

 to be perpendicular to the plane of its orbit, they appear to 

 extend from about -t- 60° to -60° in latitude, and they take 

 roughly the form of lines directed either to the north or south 

 pole. Their general distribution can be bast described and 

 their symmetry best illustrated, as Mr. Douglass says, " by say- 

 ing that they nearly form portions of five great circles passing 

 round the satellite." 



The micrometer measures for determining the elliptical form 

 of the disc gave indications of a large ellipticity. Mr. Douglass 

 thinks that this flattening is real, and not due to the presence of 

 surface markings near the limb. The following brief table sho ws 

 the values of the ellipticity and period of rotation for the periods 

 observed since 1892 : — 



Date. Ellipticity. Period. Obs. Telescope 



h. m. 

 Dec. 1892 ... loo-iio ... 13 3 ... Pickering ... 13 inch 

 Oct. 1894 ... 108-120 ... 13 3 ... ,, ... 18 inch 

 March 1895 ••• 104-120 ... (?) ... Douglass ... „ 

 March 1897 ... I15-130 ... 12 25-8... ,, ... 24 inch 



The indications of an increase in the ellipticity and decrease in 

 the period of rotation led Mr. Douglass to investigate the 

 question of whether a decrease in the size of the disc had been 

 observed. An examination of the existing measures showed 

 that such a change has probably taken place, but the values 

 cannot be relied on for certain. If this decrease in size be an 

 actual fact, then the increase in rotational velocity and increase 

 in mean polar compression would naturally follow. 



The Meteor Shower of November 13, 1897. — Those who 

 intend to systematically observe or photograph the meteor 

 shower next November, will find in the account of the arrange- 

 ments made last year at the Harvard College Observatory 

 {Annals, vol. xli. No. 5) many interesting suggestions. Prof. 

 W. H. Pickering, as will be gathered from his description in 

 the above-mentioned Annals, made arrangements for a combined 

 attack on the night of the 13th at various stations connected 

 with the observatory. To present an idea of the scale in which 

 such work is undertaken in America, in addition to visual observ- 

 ations, we give the number of plates exposed and instruments used. 

 Three plates were taken with the Draper 1 1 -inch telescope, with 

 two objective prisms of 15°. Fourteen plates with the 8-inch, 

 with two objective prisms of 6° each. Twelve plates with the 

 6-inch, with objective prism of 6°. Eight plates with a 

 Voigtlander 5inch, with an objective prism of 6°. Three plates 

 with a Ross rapid rectilinear lens of 1*5 inch, angle of prism 

 15°. With such a collection of fine instruments at work, it was 

 only too disappointing that the meteors were so few and faint ; 



