October 15, 1896] 



NA TURE 



579 



The additions to the Zoological Society's Gardens during the 

 past week include two Lions (Fclis ko, <J 9 ) from North-east 

 Africa, presented by Mr. C. A. Osborne ; two Globose Curassows 

 (Crax globicera, <J 9) from Central America, presented by Mrs. 

 Sedgwick ; a Whinchat (/'/•<;//;/(Y>/(j riibctra), a Redstart {Kii/ici/la 

 phanutiriis), a Blackcap (Sylvia atricapilla), a Swallow 

 (Hirundo riis/ica), British, presented by Mr. John 'Soung ; a 

 Cape \'iper {Catisiis r/ioniiea/iis) (lom South Africa, a Rufcscent 

 Snake (Leplodira ni/escens) from East Central Africa, pre- 

 sented by Mr. F. V. Kirby ; a Smooth Snake {Coronella /,n'is), 

 European, presented by Mr. A. E. T. Jourdain ; two Mairy 

 Armadillos (Dasypiis villosiis) from La Plata, a Peba Armadillo 

 { Tatusia peba) from South America, deposited ; two Maguari 

 Storks (Dissiira /iiaguari) from Chili, three Laughing Gulls 

 \Larus alriceila) from North America, purchased ; two Collared 

 Fruit Bats {CynonycUris collaris), born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Astronomical Society ok Wales. — We have received the 

 /oitri:a/ of this Society for September, and find it contains some 

 useful information for amateurs. Besides current notes .ind 

 some short contributions from various members, a brief de- 

 scription is given of the conditions under which Mars is now 

 visible. This is accompanied by some illustrations, among which 

 is an excellent map of Mars, by Schiaparelli. We notice in the 

 table given at the end, describing " The Heavens" for October, 

 that the period of the variable star 77 .^quila is given as two days 

 nine hours ; this is evidently incorrect, being the time from 

 a minimum to a ma.ximum. .-V variable star period is generally 

 reckoned either from minimum to minimum, or from maximum 

 to maximum, and its length in the case of this star is, roughly, 

 seven days four hours. 



The Elements ok Comet 1885 IIL— Both Messrs. W. 

 W. Campbell and Gallen MiiUcr have calculated the elements 

 of the orbit of this comet, discovered by Mr. W. R. Brooks at 

 Phelps, New York, on August 31, 1885. These computations were 

 made independently of one another. Mr. Campbell's w-ork led 

 us to believe the orbit of this comet to be an ellipse, with a 

 period of revolution of 4957 years ; while Mr. Miillergave us two 

 orbits, one elliptical with a period of 403 '2 years, the other a 

 parabolic orbit. It seems that the observations used as a basis 

 for the calculation, both include one made at Dun Echt by Dr. 

 Copeland on October 5. This observation forms the last placed 

 position in both calculations. On this the value of the eccentri- 

 city obtained entirely depends. • (^wing to this uncertainty, the 

 observation has been replaced by three observations by M. 

 Bigourdan, which had not been published when the calculations 

 were commenced. These latter observations get rid of this 

 difficulty, and give us the means of ascertaining whether the 

 eccentricity is real or not. The computation has been under- 

 taken by Mademoiselle Klumpke, at the request of Prof. 

 Schulhof, and is published in the Biilktin Aslronoinique for 

 September. The investigation shows that the new elements 

 deduced give a period of revolution of 247 "5 years. This period 

 is, as Mademoiselle Klumpke says, with certainty relatively 

 short. It takes a fifth place among those comets, the time 

 of revolution of which is greater than a hundred years. 

 Mademoiselle Klumpke further suggests that the theory of the 

 capture of comets would attribute the elliptical character of 

 this orbit to the action of Jupiter, the minimum distance 

 between the two orbits being 022. The following are the 

 elements finally deduced : — 



Final Elements. 



T = 247 36 57"6S 



Q, = 204 45 24-52 



i = 59 6 35-43 



log i] = 9-8745682 



e = 0-9822627. 



The Leander McCormick Observatory. — The Alumni 

 Bulletin of the University of Virginia contains an account of the 

 principal work in hand at the Leander McCormick Observatory. 

 At present the chief w ork is the observation of the relative posi- 



NO. 1407, VOL. 54I 



tionsof the satellites of .Saturn, and the discussion of the measures 

 for the purpose of improving our knowledge of their motions. 



The orbits of Titan and Japetus are fairly well known, so 

 special attention is given to the remaining satellites. All of these 

 are faint, and a powerful telescope is needed to observe them 

 accurately. The most easily observed are Rhea, Dione, and 

 Tethys, and a fine series of relative positions of these has already 

 been secured, from which it is hoped to obtain greatly improved 

 orbits of those bodies. Mimas, the satellite nearest to the ring, 

 is very faint, so that it can be observed only under favourable 

 atmospheric conditions, and only when near the points in its 

 orbit where its apparent distance from Saturn is greatest. As a 

 result the inequalities in its motion are not at all well known, 

 and further observation is desirable. The same is true to a less 

 extent of Enceladus, the next satellite beyond Mimas. The 

 orbits of both these satellites are useful in determining the mass 

 of Saturn's ring. Hyperion is also extremely faint. The motion 

 of this satellite is greatly aflected by the attraction of Titan, and 

 the determination of its orbit involves difficulties that render it 

 one of the most interesting problems of the solar system. 



The observations of these satellites are being published from 

 time to time in the .4stronomi<al Journal. Their discussion has 

 occupied the attention of the Director during a large portion, 

 of the past year. The investigation is of great importance, and 

 the results obtained will lead to the gradual solution of the 

 mechanical problems involved in the motions of the Saturnian 

 system. 



The Solar Rotation. — The great amount of material that 

 we now possess with regard to solar phenomena has led many 

 to form theories of the rotation of the sun, which differ among 

 themselves both in the method of treatment employed and in. 

 their value. Of those more recent, that which we owe to E. J 

 Welczynski, is published in the current number of the Asti-o- 

 physical Journal (.August 1S96). The author commences by 

 forming the hydrodynamic equations of Lagrange, by assuming 

 the coordinates of any point of a fluid, and the position of this 

 point at a certain time {t = o). A fourth equation is obtained 

 further by differentiating with regard to the time, the product of 

 the density of the fluid at the initial position, and a determinant 

 containing (in rows) the differential of the coordinates of the 

 first point to those of the second. He then proceeds to rotate 

 the whole mass round the axis of 0, where a is the angular 

 velocity of rotation depending on the coordinates of the point 

 / = o. The equations then become simplified, and it is found 

 that the square of the angular velocity is a function of the 

 distance of the moving point from the axis of rotation, or, in 

 other words, a depends only on the value of r. The equations 

 of Lagrange thus become further simplified, and conditions are 

 inserted for the case in which the fluid is a gas, and the absolute 

 temperature not constant throughout. The equation arrived at 

 finally is 



4Trp + iAT -I- <A log p = 2ui- 4- ; i^ - 



Welczynski then identifies this rotating mass with the sun, which 

 he assumes spherical. Since a depends on /', he imagines the 

 sun's axis the common axis of a series of cylinders, so that the 

 velocities of points on the surfaces of each of these would be 

 constant for each cylinder, the surfaces rotating as if they were 

 solid. " But from one cylinder to another tu changes according 

 to a certain law, 10 =J{r), which, according to (10) [equation 

 given above] depends upon the distribution of temperature and 

 pressure in the sun's interior. Since we know nothing of these 

 qualities it is impossible to deduce theoretically a formula for the 

 solar rotation.'' He remarks further that it is important to note 

 that " if a =J{r) is known from observation, equation (10) 

 gives a condition which the temperature and density of the solar 

 interior must satisfy. If it were possible to find a second con- 

 dition of this kind, it would be possible to find the laws accord- 

 ing to which these quantities vary from point to point." He 

 suggests that such an equation would follow if the periodicity of 

 the sun-spots be a hydrodynamic phenomenon. The paper 

 concludes with a reference to the position of the facukx- with 

 reference to these spots. The facuUe being further from the 

 centre of the sun than the spots, the former, even on the same 

 heliographic latitude, would move faster, as the velocity of 

 rotation increases the greater the distance from the sun. In fact 

 a means is afforded here of determining the difference in the 

 altitude of spots and faculie, this difference being stated to be 

 "considerable, almost 1/60 of the solar radius." 



