June 23. 1898J 



NA TURE 



181 



The additions to the Zoological Society's Gardens during the 

 past week include a Guinea Baboon (Cynocephaltis sphinx) from 

 West Africa, presented by Captain C. C. Wyatt ; three Common 

 Marmosets (Hapale jacchus) from South-east Brazil, presented 

 by Colonel A. H. Maclean ; two White-tailed Gnus {Conno- 

 chcetes gnu, <J ? ) from South Africa, presented by Mr. C. D. 

 Rudd ; a Cape Zorilla {Ictonyx zorilla), a Little Ichneumon 

 {Helogale parvula), a Spotted Eagle Owl {Btibo maculosus) from 

 South Africa, presented by Mr. J. E. Matcham ; two South 

 African Kestrels (Ttmiunculiis rupicolus) from South Africa, 

 presented by Mr. C. Southy ; a Naked-footed Owlet {Athene 

 noctua), European, presented by the Hon. Mrs. Barrington ; 

 two Senegal Parrots {Pceocephaltts seneqalus) from West Africa, 

 presented by Miss E. L. Barford ; four Fieldfares ( Turdus 

 pilaris), a Black Guillemot ( C/r/a ^y/^) from Christiansund, 

 North Norway, presented by Dr. R. B. Sharp ; an Indian 

 Python (Python molurus) from India, presented by Mr. 

 Percival F. Tuckett ; a Four-lined Snake (Coluber quator- 

 lineatus), European, presented by Mr. J. W. Temple ; twelve 

 Algerian Skinks (Eumeces algeriensis) from Algeria, presented 

 by Mr. Robert S. Hunter ; a Malabar Squirrel (Sciurus 

 maximus, var. dealbatus) from India, two Forster's Ceratodus 

 ( Ceratodus forsteri) from Australia, deposited ; a Crowned 

 Partridge [Rollohis cristattis) from Malacca, four Common 

 Cormorants (Phalacrocorax carbo) from Holland, two Cereopsis 

 Geese {Cereopsis novte-hollandiie), two Forster's Ceratodus 

 {Ceratodus forsteri) from Australia, purchased ; three Tri- 

 angular-spotted Pigeons {Columba maculosa), bred in the 

 Gardens. 



OUR ASTRONOMICAL COLUMN. 

 Come IS now Visible. — Last week it was noted in these 

 columns that Mr. Coddington had discovered a comet in the 

 position R.A. i6h. 24m. 45'9s., and Declination (South) 25° 

 14' 20". Circular (No. 7) of the Centralstelle gives the 

 elements and ephemeris of the comet, based on the positions 

 observed on June 11, 13 and 15, and calculated by Prof. A. 

 Berberich. The former are as follows : — 



T = 1898 August 4-478 Berlin M.T. 



CO = 206° 8-5 ^ 



^ =-- 73 587 V 1898-0 



i= 76483) 



log q = 0-31850 



As the comet is moving rapidly south, and has now a Declin- 

 ation (South) of about 32°, we do not give the ephemeris. This 

 comet was independently discovered by Dr. W. Pauly in 

 Bucharest on June 14. 



We have received two telegrams from Kiel concerning another 

 comet, Perrine (June 14). The former gives the observation 

 made on June I4 at Lick mean time I5h. 1 60m., giving the 

 position Right Ascension 3h. 29m. and Declination + 58° 36', 

 the latter showing the position to be Right Ascension 

 3h. 34m. 58s. and Declination + 58" 24' 2" at Lick mean time 

 I4h. 12m. on June 15. A Circular (No. 5) from the Central- 

 stelle gives us the elements and ephemeris calculated by Perrine 

 and Aitken from the observations made on June 14, 15 and 16. 

 These are :— 



Elements. 

 T = 1898 August 17-40 Greenwich M.T. 



« = 196 46 \ 

 r. = 260 6 M898-0 

 t = 69 42 j 

 q = 0-7418 

 Ephemeris for iih. 

 R.A. 



June 20 

 24 

 28 



July 2 



h. 



4 2 52 



4 25 24 



4 48 48 



5 10 o 



Greeenwich M. T. 

 Decl. 



+ 57 15 



55 56 



54 20 

 + 52 27 



1-18 



1-72 



The comet will thus gradually brighten as July is approached, 

 but takes a somewhat southerly course. 



Another Kiel telegram, dated June 18, tells us that Perrine 

 found Wolf's comet on June 16, at I5h. S'Sm. Lick mean time, 

 in position — 



R.A. 2h. 16m. 19s., and Declination + 19° 42' 44". 



Still another and last" telegram from Kiel, dated June 19, 

 informs that comet Giacobini was seen on June 18 at I3h. Nice 

 mean time in the position of Right Ascension 2oh. 36m. 30s. and 

 Declination - 21° 14' o". 



The 40-INCH Yerkes:Refragtor. — Prof Barnard,, writing 

 in the Astronomical Journal (No. 436) with respect to a series 

 of measures of the satellite of Neptune, gives an interesting 

 account of the behaviour of the Yerkes telescope. Actual observ- 

 ation was not possible until the best season was essentially over, 

 but it was found that even a part of this unfavourable weather 

 permitted the power of the telescope to be tested. On one or two 

 occasions, when observing double stars, he was able to use 

 powers of several thousand diameters, and on one date he em- 

 ployed a power of 3750 with good success. The object-glass he 

 finds entirely free from any form of ghost, and the definition is 

 at times very good, showing, as he says, that " this last great 

 work of Alvan Clark is one of his noblest monuments." The 

 driving clock moves the great tube with such perfect steadiness 

 that he was astonished at the result, and so stable is the mount- 

 ing of the instrument that the effect of the clock, rewinding itself 

 automatically at periods of ih. 48m., does not in the least inter- 

 fere with micrometer work. Very satisfactory also are the 

 electrical contrivances at the eye end for clamping and slow 

 motion ; the clock takes up the tube upon the application of the 

 electric clamp in Right Ascension perfectly instantaneously, and 

 the slow movement is so exact that a star can be brought from 

 the edge of the field and stopped instantly behind the micro- 

 meter-wire, the motion being about i' in 8 seconds. Prof. 

 Barnard further mentions the ease with which the instrument can 

 be handled ; as an instance, he says that he placed the telescope 

 on the west side of the pier in position of -I- 50° declination, 

 and by means of the electric motors he moved it on the other 

 side of the pier to the same Declination in im. 50s. An im- 

 portant addition to the dome is the wind-break. This consists 

 of two curtains working on endless chains, onfe rising from the 

 i base of the slit, and the other passing through the zenith from 

 the rear. With these, excepting at low altitudes and right in 

 the face of the wind, the tube is always perfectly protected even 

 on the windiest nights. 



Variable Stars of Short Period.— Prof. E. C. Picker- 

 ing describes in a Harvard College Observatory Circular (No. 

 29) a very simple means of detecting variables whose periods 

 are short if the observer is provided with a telescope mounted 

 equatorially and a fairly good driving clock. The method is so 

 simple and complete that it has probably been tried before, 

 although, so far as we know, no mention of it has come under 

 our notice. The idea is to expose a photographic plate in a 

 telescope, the clock of which is working somewhat fast, and at 

 intervals of ten and fifty minutes to alternately expose and 

 cover the lens by an electrical attachment. Prof. Pickering de- 

 scribes one of the plates so exposed. An 8x10 plate was ex- 

 posed in a telescope with a Cooke anastigmatic lens, aperture 

 2-6 cm. and focal length 33-3 cm. and eight successive images 

 of each star were obtained in the period of about eight hours, 

 The plate covered a region of about 33° square, and a portion 

 of it, shown in the Circular, indicates the variable intensity of 

 the images of the star U Cephei, while those of the neighbour- 

 ing stars show no such variations. 



On this scale forty plates would cover the whole sky from 

 north to south pole, and Prof. Pickering proposes to undertake 

 this work as soon as the best method of taking the plates has 

 been determined. By the above plan it is hoped to secure a 

 complete list of all variable stars of short period brighter than 

 the ninth magnitude at maximum, whose variation exceeds half a 

 magnitude, and whose period is less than a day. In such a 

 sweep, probably, many other variable stars of longer period, and 

 stars of the Algol type will be discovered. 



The beauty of the above method lies in the simple equipment 

 that is necessary to obtain results of considerable value. It will 

 be noticed that the method is a differential one, clouds passing 

 across the field of view during an exposure affecting all the 

 photographic images alike. 



NO. 1495, VOL. 58] 



