March i6, 1893] 



NATURE 



47: 



gaUritd) from Australia, presented by Miss Amy M. Dundas ; 

 three white-tailed Gnus {ConnochaUs ,^mi, 6 ? 9 ) from South 

 Africa, deposited ; a Burchell's Zebra {Equus burchelli, 9 ), two 

 Silver-backed Foxes {Cam's chama), a Cape Bucephalus 

 (Bucephalus capensis) from South Africa, a Salvin's Amazon 

 (Chrj'sotis salvini) from South America, purchased; four Up- 

 land Geese {Bernicla magellanica) from the Falkland Islands, 

 received in exchange ; four Coypus (^Myopotamus coypus) born 

 in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Comet Holmes (1892 IH.). — This comet has now become 

 rather a difficult object, but the following ephemeris may be 

 useful for those employing large instruments :— 



12A. Paris Mean Time. 

 1803. R.A. (app.) Decl. (app.) 



h. m. s o , // 



March 16 2 55 29*0 -t- 35 27 53 



17 57 i6'i 30 43 



18 2 59 3-5 33 33 



19 3 o si-i 36 23 



20 2 38-9 39 13 



21 4 27-0 42 2 



22 6 15-3 44 51 



23 3 8 38 35 47 40 



The Sizes of Jupiter's Satellites. — M. J. J. Landerer 

 describes in the Comptes Rendus some experiments made to test 

 the accuracy attainable in measuring the diameters of satellites 

 by their shadows ca<t on the primary. He took a finely-ground 

 glass plate and blackened it, leaving a space in the middle repre- 

 senting the appearance of Jupiter with its bands and small black 

 spots representing shadows. He then placed it at a distance of 

 314 m., illuminated it by a suitable light from behind, and 

 sketched the disc through the telescope used for the actual 

 observations. With some practice it was found possible to draw 

 such spots correctly to within one-tenth per cent. M. Landerer 

 then applied his method to the satellites themselves, and found 

 the following numbers for their radii :— o'Oi99, 00184, o 043S> 

 and o*04i9. The number of observations was twenty-six for the 

 first satellite, seventeen for the second, thirty for the third, and 

 twenty-two for the fourth. The commonly accepted numbers, 

 obtained by micrometric measurements of the bright satellites, 

 are 00291, 00259, 0-0431, and 00367. 



Observations of the Zodiacal Light. — In No. 3155 

 of the Astronomischen Nachrichten Mr. Arthur Searle gives an 

 account of the experimental work he and Prof. Bailey have 

 been carrying on with respect to the best methods of making 

 and recording observations of the zodiacal light. Owing to the 

 prevalent use of electric light in the neighbourhood of Harvard 

 College Observatory, the observations were made at some dis- 

 tance away. The general mode of defining the position of the 

 zodiacal light up to the present has been by drawing its outline 

 on a star atlas exactly as it appeared in the sky at the time of 

 observation. The great drawback about this method is that 

 in the majority of cases the zodiacal light has no definite out- j 

 line, but gradually decreases in brightness as one recedes from 

 the axis of the figure, eventually lading imperceptibly away. 

 That this is so is the general idea and is backed up by observa- 

 tions, but it is also true that the contour, so to speak, of the 

 luminous figure is sometimes sharper at some places than 

 at others. Instead of outline drawings these observers have sub- 

 stituted contour lines in which the degree of light represented 

 by each contour is stated ; the latter is accomplished by select- 

 ing a portion of the sky '* unaffected by the zodiacal light, but 

 of equal brightness with those portions traversed by the contour 

 line." This region would naturally lie near the Milky Way and 

 its situation is defined by the stars in the vicinity. To com- 

 plete the record the geographical position of the observer's 

 station and the time of observation should be included in the 

 statement. In addition to the contour lines two other sugges- 

 tions are put forward, (i) that the axis of brightness should be 

 indicated by a line, and (2) that should there be distinctly ob- 

 served by any chance two cones of light, an outer and an inner, 

 such a distinction should be shown in the record by drawing a 

 boundary between them. 



NO. 1220. VOL. 47I 



Weinek's Lunar Enlargements. — Since the appearance 

 of the magnificent enlargements obtained by Dr. Weinek from 

 the Lick Observatory negatives, many details of surface struc- 

 ture have been brought to light which have up till now evaded 

 even the aided eye. These details, consisting as they do of 

 winding rills, valleys, and hair-like markings, appear quite 

 sharp and distinct in contrast with the larger surface features, 

 and it is this fact that has caused some uncertainty about their 

 being actual features on the lunar surface. Every one acquainted 

 a little with photography knows that a photograph loses in 

 sharpness the more it is enlarged, and it is here very curious to 

 find a picture after being twenty times enlarged with minute 

 details quite crisp and sharp, and the larger portions quite fluffy, 

 as is the case in the enlargement of Vendelinus, taken on 

 August 31, 1890. As Mr. YAg(ix\tmz.xV$, (Observatory, March), 

 ** if these curious markings represent actual features on the moon's 

 surface, ought they not to be easily seen in any good telescope 

 that shows the formation and its principal details with far greater 

 sharpness than the twenty-times enlarged negative, and many 

 small craters, &c., in addition which are scarcely traceable upon 

 it? One does not understand why this should not be so, unless 

 these objects make an impression on the sensitive plate that they 

 fail to do on the retina, which is hardly likely to be the case." 

 M. Faye, in Comptes Rendus (No. 9) for March, when referring 

 to these enlargements, says that several members, MM. 

 Fizeau, Mascart, and Cornu included, reserved their opinions 

 on the interpretation of these markings, which seemed to be the 

 results of retouching. " Certain vermiculees appearances," says 

 he, "show a clearness which is strictly in contradiction with 

 the very general ' estompee ' appearance of the lunar cliche." 



" L'Astronomie" for March — The March number of this 

 magazine commences with some observations of Jupiter made at 

 the observatories in Juvisy, Bruxelles, and in Spain during the 

 past year. The numerous drawings which accompany the ob- 

 servations impress one with the incessant change that is 

 taking place in the dense atmosphere, while the large red spot 

 was as usual seen ploughing its way apparently through one of 

 the dark belts. The period of rotation of this spot seems to 

 have suffered a retardation during the last twelve months, as 

 will be seen from the following table, which we take the liberty 

 of producing here : — 



M. Guillaume, of the Lyons Observatory, contributes some in- 

 teresting notes on the appearances of Saturn's rings during the 

 same year, at which time it will be remembered we were lying 

 nearly in its plane. Besides the drawings showing the general 

 features of the planet, there are some illustrating the different 

 degrees of luminosity observed at various parts of the ring itself. 

 "The Circulation of Winds at the Surface of the Globe " is 

 the title of an article by M. A. Duponchel, in which he gives as 

 an introduction a brief historical account of the early hypotheses ; 

 while M. Flammarion gives us the fifth chapter on " Comment 

 Arrivera la fin du Monde," dwelling for the most part on the 

 destructive forces at work on the earth's surface. 



Bermerside Observatory. — In the advertising sheets of the 

 Observatory for March we are sorry to see the following notice : — 

 " On sale (the owner giving up astronomical work) the 3-foot 

 Common reflector, with or without dome, complete, in perfect 

 order. Mirror by Sir H. Grubb. Full particulars on applica- 

 cation to J. Gledhill, Bermerside Observatory, Halifax." 



GEOGRAPHICAL NOTES. 



A TELEGRAM from Port Stanley announces the return of the 

 Dundee whaling ships to the Falkland Islands (see Nature, 

 p. 282) on their way home. In the two months during which 

 they were absent it is improbable that high latitudes were 

 reached, but it is evident that a cargo was rapidly obtained, 

 although it is not reported whether the species of whale hoped 

 for was found. 



The Geographical Studentship at Oxford lately held by Mr. 

 Grundy has been awarded to Mr. W. H. Cozens- Hardy, New 



