May 4, 1893] 



NATURE 



15 



% 



The additions to the Zoological Society's Gardens during the 

 past week include a Crowned Gibbon {Hylobales pileatus,'}) 

 from Borneo, presented by Mr. Leicester P. Beaufort ; a 

 Bengalese Cat {Felis bengalensis] from India, presented by 

 Captain F. Whistler ; a White-bellied Hedgehog {Erinaceus 

 alHventris) from Somaliland, presented by Mr. H. W. Seton- 

 Karr, F.Z.S. ; five \Ne3.ie\s{Mustela vulgaris) British, presented 

 by Mr. George Long ; a Festive Amazon {Chrysotis fesliva) 

 from Guiana, presented by Mrs. Hills ; a Chinese Lark {Me- 

 lanocorypha mongolica) from China, presented by Mrs. Pollard ; 

 two Serin Finches {Serinus hortulanus) from south-west Spain, 

 presented by Mr. J. A. Crawford, F.Z.S. ; an Undulated Grass 

 Parrakeet (Melopsitlacus undulatus) from Australia, presented by 

 Mast.W. D. Savoiy;aGreater Sulphur-crested Cockatoo (Ca<ra/!<a 

 galeritd) from Australia, presented by Mr. E. P. Ramsay ; two 

 Hawfinches [Coccothraustes vulgaris) British, presented by Mr. 

 A. Klosz ; a Magpie Tanager (Cissopis Icveriana) from south- 

 east Brazil, presented by Mr. H. A. Astlett ; two Great 

 Cyclodus (Cyclodus gigas) from Australia, presented by Captain 

 Clarke ; a Common Viper ( Vipera bents) British, presented by 

 Mr. Briton Riviere, R.A., F.Z.S. ; a Poe Honey-Eater (Pros- 

 themadera novcc-zealandia:) from New Zealand, a Malabar Green 

 Bulbul (Phyllornis aurifrons), a Red-eared Bulbul (Pycnonotus 

 jocosus) from India, a Cape Coly {Colitis capensis), two Derbian 

 Zonures (Zonurus derbian'us) from South Africa, two American 

 Blue Birds (Sialia wilsoni) from North America, two Great 

 Eagle Owls {Bubo maximus) European, deposited ; two Black- 

 necked Swans ( Cygnus nigricollis, S 9 ) from Antarctic America, 

 two Madagascar Love-birds {Agapornis cana, i 9 ) from Mada- 

 gascar, a Red-sided Eclectus {Eclectus pectoralis, i ) from New 

 Guinea, purchased ; a Red Kangaroo {Macropus rufus, 6 ) a 

 Great Wallaroo {Macropus robustus, S ), seven Satin Bower 

 Birds {Ptilonorhynchus violaceus) from Australia, two Mauges 

 Dasyures \{Dasyurus maugsi, (J c5 ), a King Parrakeet {Apros- 

 mictus scapulalus), two Diamond Snakes {Morelia spilotes), a 

 Water Lizard {Physignathus lesuetiri) from New South Wales, 

 received in exchange. 



OUR ASTRONOMICAL COLUMN. 



South Polar Cap of Mars.— During the opposition of 

 Mars in 1S92 Prof. George Comstock made a series of deter- 

 minations of the position angles of the south polar cap of Mars, 

 of its angular extent, and of its polar and equatorial diameter. 

 In the first-mentioned measurements he placed the micrometer 

 thread tangent to the planet's disc, and so rotated it that it was 

 symmetrically situated about the point of tangency ; one ob- 

 servation included five settings of this kind, with a determina- 

 tion of the parallel from a neighbouring star, and for the 

 majority of the observations these measurements were made 

 both with telescope east and west. The angular dimensions of 

 the caps were measured by placing the thread tangential to the 

 disc of the planet at the extremities of the cap. The co- 

 ordinates of the centre of the spot, where 9 represents the 

 areographical longitude and A the south polar distance, together 

 with the diameter of the cap and the adopted corrections to the 

 position angle of the axis of Mars as given by Marth's ephemeris, 

 may be gathered from the following table : — 



July 26 

 Aug. 18 

 Sept. 19 



Diam. of 

 Cap. 



o 



.. 44 .. 



- 35 •• 

 22 



0-47 



295 



295 



341 

 311 



336 



Ephem. 



o 

 -2-26 



-3 06 

 -2-66 



Prof. Campbell finds the correction to the position angles, as 

 ■given by Marth's ephemeris as - o"-i6, while Prof. Hall's cor- 

 rection amounts to ■»- l°-24, both of which vary considerably 

 from the values given above. These differences, as Prof. Com- 

 stock points out, may arise from the systematic errors affecting 

 the three methods employed. 



N'O 1227, VOL. 48] 



The measures of the diameter as made at opposition were as 

 follows : — 



Date. Eq. diam. Polar diam. 



The Brightness OF THE Major and Minor Planets.— 

 The latest publication issued from the Astrophysical Observa- 

 tory at Potsdam (No. 30) contains all Dr. G. MilUer's deler 

 minations of the brightnesses of both the major and some of the 

 minor planets. These observations extend over a period of 

 about eight years, but the majority were made during the years 

 1883-85. The first chapter is devoted to a tabulation of the 

 diff'erent stars used throughout the work for purposes of com- 

 parison. In the second are brought together all the planetary 

 observations, while the third consists of a discussion of the 

 whole number of observations, each planet being independently 

 treated. To state briefly some of the results that these deter- 

 minations have brought to light we may say : {a) That with the 

 exception of the planets Jupiter, Uranus, and Neptune, the 

 variations in brightness are found to be directly dependent on 

 the phase differences, which can be plotted out in simple curves. 

 {b) That from the observations of each planet the " Licht- 

 schwankungen " accord with no theory, and that near opposition 

 the variations in brightness are found to be larger than those 

 which should be the case as regards the theoretical values. 

 (<-) The form of the light curves, when one expresses the bright- 

 nesses in stellar magnitudes, approaches very nearly, except in 

 the case of Venus, a straight line, and the variations in magni- 

 tude are also very nearly proportional to the corresponding 

 phase-differences, {d) Tlie observations give no indication of 

 the dependency of the " Lichtstiirke " on the rotation of the 

 planets. And lastly [e) that by taking series of observations 

 of the largest planets, obtaining the mean values from different 

 years, differences are found which, as Dr. Midler says, cannot be 

 due 10 the inaccuracy of the measures or to the fact that the 

 same instruments were not always used. The following table 

 shows clearly the relative brightnesses that result from the above 

 determinations : — 



Brightness. App. radius. Reduced Kelattve Zollner's 

 Distance i. Distance i. Brightness. Albedo. Albedo. 



Name of 

 Planet. 



Mercury .. 



Venus 



Mars 



Jupiter .. 



Saturn 



Uranus 



Neptune .. 



-0-003 

 -4004 . 

 -1-297 

 -8-932 . 

 -8-685 ■ 

 -6858 

 -7-053 ■ 



323 

 8-78 

 4-68 

 9423 

 77-63 

 36-67 

 43-15 



-0-808 

 -2-638 

 -1-297 



- 2-412 

 -2 586 

 -2-388 



- 2229 



064 



3-44 

 I -co 



2-79 

 3-28 

 273 

 236 



0-43 

 2-33 

 I 00 



2-34 

 187 

 2-40 



1-74 



Meti:or Showers. — Of the important meteor showers which 

 occur during the present monlh that which occurs on the sixth 

 exceeds all others in brilliancy. On the evening before and 

 after this date there are also two other showers, but they are 

 much fainter. The positions of the radiant points are, according 

 to Mr. Denning : — 



Date. 



R.A. 



Radiant. 



Decl. 



Meteors- 



Astronomy Popularised in America. — There seems to 

 be no diiubt that the interest taken in astronomy in America is 

 rapidly on the increase, and the demands for large telescopes 

 there have played no small pan in helping to stir up in many 

 minds the desire for enlightenment in this fascinating science. 

 Increase in the number of students and amateurs, and rapidly 

 growing demands for small telescopes are signs that cannot be 

 misconstrued, indicating as they do the vast interest that even 

 to-day is shown in the oldest of sciences. To satisfy and further 

 these favourable omens, or in other words to bring together 

 those who can instruct into close relations with those who are to 

 be instructed, the editors of Astronomy and Astrophysics pro- 

 pose, assuming tbey get a sufficient number of subscribers, to 

 issue a monthly publication entitled "Popular Astronomy." 

 The idea of this project is that it should serve as a guide for self- 

 instruction, and supply a medium for queries and answers for 

 methods of work, facts, books, &c. They propose to commence 



