Jan. 17, 1878] 



NATURE 



231 



OUR ASTRONOMICAL COLUMN . ;. ^ 



The Variable Star R Aquarii. — Harding nolTfied 

 his discovery of variability in this star in 181 1, in 

 the first volume of the Zeilschrift fiir Astronomie. 

 The earliest attempt to determine the period appears to 

 be that of Westphal, in the Zeitschri/l fiir Astronoinie, 

 vol. iv. p, 218 ; he used Harding's observations between 

 October 20, 1811, and January 19, 181 7, which, though 

 not numerous, sufficed to give an approximate value, 

 while they also indicated that the star at times was as 

 bright as 67 m., and at others was invisible in Harding's 

 telescope. Westphal's period is 382-5 days. Although 

 the variability of the star has thus been long known, it 

 would seem that few of these objects have been less ob- 

 served, and it may be recommended to the attention of 

 those who are interested in this branch of astronomy, 

 and whose positions enable them best to command a star 

 at 16° south declination. In vol. vii, of the Bonn obser- 

 vations, Argelandcr deduces the following formula for the 

 maxima ; — 



1S43, Scp.e.iibcr 4 7 + 388^011 E., 



which is adopted in Prof. Schonfeld's second catalogue 

 (Manheim, 1875) ; the maximum of the present year 

 would therefore fall on September 25, and may be well 

 observed. In the same catalogue the degree of bright- 

 ness at minimum is set down as " 1 1 m (?)." Harding 

 estimated ti.e star 67 m. on October 20, 181 1, and on 

 January 24, 1 81 2, it was not visible in his telescope, being 

 then beioiv what be called a tenth magnitude, so that 

 obseivations for determination of the minima should pro- 

 bably be commenced not later than seventy days after 

 the maxima, but it is hardly necessary to remark that in 

 the actual state of our knowledge of the variations of this 

 star, continuous obseivations through as long a period 

 as its position allows, will possess much interest. The 

 best determination of the place of R Aquarii will be that 

 of the Greenwich Catalogue of 1864, giving for the begin- 

 ning of the present year^ — 



R.A. 23h. 37m. 30i-35, N.P.D. 105° 57' 37"-3. 



e iNDi. — When may we hope that some southern 

 observer will find opportunity of attacking the parallax 

 of this remarkable star, the large proper motion of which 

 was first pointed out by the late Prof. D'Arrest, and con- 

 firmed by Moesta from the Santiago observations of 1856? 

 Mr. Giil, who allows nothing to escape him, during his 

 brief visit to the other hemisphere, wherein Lord Lindsay's 

 heliometer enables him to do an astronomical service, 

 slates that he has measured the distance and position- 

 angle of f Indi relative to five surrounding stars, and 

 hopes " that this may serve as the foundation at some 

 future day of a determination of its parallax and proper 

 motion," but it is obvious that the shortness of his stay at 

 Ascension does not permit of an attempt to measure the 

 amount of parallax— a very interesting undertaking in the 

 case of this star, which, had time allowed, we do not think 

 that Mr. Gill would have hesitated to attempt. And 

 e Indi is not the only star which holds out prospect of 

 success in parallax investigations in the southern hemi- 

 sphere. 



The Satellites of Mars.— In the last number of the 

 '' Monthly Notices of the Royal Astronomical Society " 

 is a communication from the director of the Observatory 

 at Melbourne, giving the results of a search made for the 

 sateUites of Mars, in consequence of a telegram notifying 

 their discovery, and received from Sir George Airy on 

 August 22. At that time, from an accident to the declin- 

 ation movement, the large reflector was not available, but 

 observations with it were commenced on September 26. 

 Mr. Ellery states his search to have been fruitless, except 

 that on one occasion it was believed that one of the satel- 

 lites was seen. This was on the night of October 16, 

 >vhen Mars having occulted a star of the thirteenth mag- 



nitude at 22h. 15m. sidereal time, after its emergence a 

 very faint point was seen tialf a diimeter from Mars s.d. ; 

 "this was watched for nea'ly an hour, when its position 

 indicated a motion with Mars," but the sky bee iming 

 cloudy, no measures could be made, and, it is added, "no 

 other signs of satellites have been observed since." 



If we use the elements of the exterior satellire employed 

 for the ephemerides which have appeared in this column, 

 and which agree precisely with measures of position-angle 

 made by Mr. A. Common, of Ealing, with his eighteen- 

 inch silver-on glass reflector on the date in question 

 (October 16}, we have the following angles and dis- 

 tances : — 



Melbourne 



Sidereal Time. 



h. m. 



22 15 



o 15 



Position. 



Distance. 



Distance 

 from Limb. 



2160 ... 346 ... 25*2 



1967 ... 27*1 ... 177 



167-6 ... 23s ... 14-1 



Therefore, although the satellite v/ould be in the south- 

 preceding quadrant up to about 23 h. 45m. sidereal, its 

 distance would be greater than that estimated at Mel- 

 bourne, and it is doubtful if this satellite was seen. 



As regards the inner satellite, it is not practicable from 

 the measures hitherto published to form so close an esti- 

 mate of the positions as late as October 16, but on calcu- 

 lation from elements which represent sufficiently well the 

 measures to September 20, it would appear that the satel- 

 lite was in the south-preceding quadrant after about 23h. 

 30m. sidereal time, and its distance from the limb at that 

 time would be approximately a semi-diameter of the 

 planet. Thus if either satellite were really observed, it 

 was most probably the interior one — which, indeed, we 

 are assured, is intrinsically the brightest. But the want 

 of better success with the great Melbourne reflector would 

 rather imply that however well adapted for delineation of 

 nebulae and similar purposes, the instrument fails with 

 observations of such objects as the satellites of Mars. 



NOTES 



We understand that on the representation of the Professors 

 of the Royal School of Mines and of the Director-General of the 

 Geological Survey as to the want of proper accommodation for 

 geological teaching in the School of Mines in Jermyn Street, the 

 Lords of the Committee of Council on Education have trans- 

 ferred the instructioa in that subject to the Science Schools at 

 South Kensington. As Prof. Judd is supplied with a complete 

 collection of specimens for teaching purposes, and as a labo- 

 ratory is now provided for him, he will be in a position to 

 give that practical instruction which it is so desirable should be 

 within the reach of geological students. 



Students of pleistocene geology will be gratified to learn 

 that the well-known very fine collection of Ilford fossils, formed 

 by the late Dr. Richard Payne Cotton, F.G.S., has been 

 bequeathed to the Museum of Practical Geology, Jermyn Street. 

 The collection contains 246 'specimens of veitebrate remains, 

 consisting of boues belonging to species of mammoth, rhinoceros, 

 ox, aurochs, hippopotamus, horse, deer, Irish elk, lion, bear, 

 beaver, water-rat, wolf, and several kinds of birds. A very per- 

 fect lower jaw of the beaver {Casiof europaus), with fome well- 

 preserved bones ol i\ie Elephas primii^enius, the Rhinoceros leptor^ 

 kinus, and \.h.fi Bos priinigenius, are among the gems of this private 

 collection, which will form a welcome and most valuable addition 

 to the contents of the National Museum of British Fossils — the 

 more so as the series of late tertiary vertebrates in that collection is 

 by no means so large and complete as could be desired. Every 

 one interested in the geo'ogy of the metropolitan area is aware 

 that the Cotton collection, together with that made by Sir Antonio 

 Brady, which has lately been acquired by the British Museum, 



