I40 



NATURE 



[December 2 1909 



M. Poincar^'s works in mathematical analysis, analytical 

 and celestial mechanics, mathematical physics, and scien- 

 tific philosophy ; his obituary notices of numerous men of 

 science, including the late Lord Kelvin ; and his more 

 various writings. Each of the sections dealing with M. 

 Poincar^'s scientific work is prefaced by an appreciation 

 by some great authority ; thus, that on celestial mechanics 

 is preceded by a translation of Sir George Darwin's address 

 in presenting the gold medal of our Royal Astronomical 

 Society last February. The price of this interesting volume 

 is 7 francs. 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrences in December: — 

 Dec. 2. 6h. Venus at greatest elongation, 47° 18' E. 



,, iSh. Mercury in superior conjunction with the Sun. 

 6. loh. 35m. lupiter in conjunction with the Moon 



(Jupiter 3° 35' S.). 

 12. 7h. 45m. Sun eclipsed, invisible at Greenwich. 

 ,, igh. 27m. Mercury in conjunction with the Moon 



(Mercury 0° 3' S.). 

 14. Ijh. 51m. Uranus in conjunction with the Moon 



(Uranus 3° s' N.). 

 16. 3h. lom. Venus in conjunction with the Moon 



(Venus 2° 50' N.). 

 iS. gh. Mercury in conjunction with \ Sagittarii (Mer- 

 cury 0° 3' N.). 

 20. loh. Saturn stationary. 

 ,, llh. 56m. Mars in conjunction with the Moon 



(Mars 5° o' N.). 

 ,, 2ih. 2m. Saturn in conjunction with the Moon 



(Saturn 1° 40' N.). 

 27. 8h. 30m. Neptune in conjunction with the Moon 



(Neptune 4° 9' S.). 

 ,, 20h. Im. Mercury in conjunction with Uranus 

 (Mercury 1° 43' S.). 

 Halley's Comet, igogc — The following is a further 

 <?xtract from Mr. Crommclin's revised ephenieris for 

 Halley's comet as given in No. 4359 of the Astronomische 

 Nachrichten : — 



Ephemeris. 



Magni- 



log ) 



log A 



1Q09 R.A.'(iQio-o) Decl.(igioo) 

 <BetlinM.T.) h. m. , , 



Dec. I '4 ... 4 26-9 ... +15 52 



6-4 ... 4 6-2 ... +15 23 ... 03775 ... 0-1505 ... 124 

 11-4 ... 3 44'4 -•• +14 45 



16-4 ... 3 22-3 ... +14 4 ... 0-3527 ... 0-1340 ... 12-0 

 21*4 ... 3 0-6 ... + 13 18 

 26-4 ... 2 40-2 ... -t-12 28 ... 0-3259 ... OT381 ... iiS 



From this we see that the comet is now a little to the 

 west, and south of, Aldebaran, and on December 4 will 

 pass very near to 7 Tauri. 



According to a note by Mrs. Maunder in the Dat7y 

 Chronicle. Mr. Hollis found the comet a conspicuous object 

 ill a lo-inch telescope on November 22, and the Rev. 

 T. E. R. Phillips observed it the same evening, and was 

 still able to see it when the aperture was reduced to 

 3 inches. Photographs taken at Greenwich on that date 

 showed the comet to be somewhat brighter than the tenth 

 magnitude, i.e. about eight times as bright as computed. 



Observations of Mars. — Seven new canals, bringing the 

 total found at the Hem Observatory up to twenty-three, 

 are announced by Mr. Jonckheere in No. 4371 of the Astro- 

 ■nomische Nachrichten. For two of them, leaving the 

 •Cyclopum Lucus and going to Hephaestus and .-\menthes 

 respectively, _Mr. Jonckheere proposes the names Cepheus 

 and Cassiopeia. 



The Cotnptes rendus for November 15 (No. 20) contains 

 three notes dealing with the planet. In the first M. Idrac 

 describes the visual and photographic observations made by 

 Tiim at Meudon during the recent opposition. The photo- 

 graphs were taken in the focus of the 24-inch photographic 

 equatorial, and show a fair number of details, some of which 

 were not visible, or very faint, to the naked eve ; the plates 

 iised were sensitive to the blue and ultra-violet radiations. 

 On September 20 the edge of the north polar cap was 

 NO. 2092, VOL. 82] 



shown clearly on the photograph, and on September 25 

 extended down to about latitude 55°. 



In the second note M. Antoniadi describes the results of 

 thirteen nights' observations made between September 20 

 and November 9. The most remarkable changes, since the 

 opposition of 1907, appear to be the return of Syrtis Major 

 to the form it had in 1864 and 1877, the re-apparition of 

 Lac Moeris, and the formation of a multiple " island " in 

 the eastern part of the Mare Cimmerium. About fifty 

 " canals " were seen, but M. Antoniadi discusses the 

 meaning of this term before applying it definitely to the 

 features seen. He defines eight types of markings which 

 may be called "canals," and finds that there is no geo- 

 metrical rdseau of straight lines intercrossing on the surface 

 of Mars ; but across the continental areas there is a struc- 

 ture like a grey marbling, which is too evanescent and 

 intricate to be drawn. A useful chart (Mercator) accom- 

 panying the note embodies the features seen at Meudon. 



M.M. de la Baume Pluvinel and F. Baldet contribute the 

 third note, which describes the photographic researches 

 carried out on the Pic du Midi during September and 

 October. Ordinary plates were used at first, with exposures 

 of o-is., but these showed only the polar caps. Later 

 exposures, with Lumi^re colour filters and various bathed 

 plates, took 6s. to 12s., and show nearly all the details 

 observed visually ; the geometrical rcsemix of fine canals 

 are not, however, to be found on the photographs. 



During the recent opposition, M. Kostinsky, using the 

 Pulkowa astrographic telescope, succeeded in obtaining 

 photographs of the two satellites Phobos and Deimos, and 

 now publishes the measures in No. 4369 of the Astro- 

 nomische Nachrichten. The accordance with the ephemeris 

 (based on Struve's elements) is satisfactory, and the photo- 

 graphic magnitudes of the satellites are ii-6 and 12-3 

 respectively. 



Perrine's Comet, 1909b. — An observation of Perrine's 

 comet, made at Heidelberg on November 20, gave the posi- 

 tion at I3h. o-2m. (Konigstuhl M.T.) as 7h. 6m. 20-335., 

 -(-15° 31' 28" (iqog.o), and the magnitude as 14-0 (Astro- 

 nomische Nachrichten, No. 4371). 



In No. 4369 of the Astronomische Nachrichten Prof. 

 Wolf directs attention to an abnormal decline of the bright- 

 ness of this object .about November 9. On October 11 it 

 was seen with difficulty in the reflector, and on November 6 

 could not be found visually, although since September 5 it 

 has been observed visually with a 6-inch telescope. ■\ 

 photograph taken with tlie Bruce telescope on Noveinber q 

 failed to show any trace of the comet, which must there- 

 fore have become enormously fainter. 



The Design of Spectrographs. — .^11 those who are 

 interested in the design and performance of spectrographs, 

 more especially such as are used for radial-velocity deter- 

 minations, will welcome a paper by Mr. J. Plaskett which 

 appears in No. 4, vol. iii., of the Journal of the Royal 

 Astronomical Society of Canada. As is now generally 

 known, Mr. Plaskett has, since 1905, devoted a great deal 

 of labour to the design of a generally effective instrument, 

 and he has now succeeded in producing a single-prism 

 spectrograph which has proved beautifully effective 

 Rigiditv, temperature control, and optical efficiency have 

 all been provided for, and the instrument can be changed 

 from a one- to a three-prism spectrogr.aph in two minutes 

 without affecting the temperature conditions. Mr. Plaskett 

 gives illustrations and full details of the numerous minor 

 devices and accessories, which it is impossible to reproduce 

 here. 



The Astronomical Society of Wales. — No. 3, vol. xi., 

 of the Canilirion Natural Observer, the quarterly record of 

 the Astronomical Society of Wales, contains several useful 

 notes for amateur observers. Miss Hagerty contributes an 

 interesting article on solar energy, and Mr. Mee asks all 

 Welsh observers to forward to him accounts of any astro- 

 nomical phenomena they may observe ; he gives some useful 

 hints as to what the naked-eye observer may see and should 

 record. 



British Astronomical Associ.ation. — Messrs. Neill and 

 Co., Edinburgh, have just published, for the British Astro- 

 nomical .Association, a general index of the Journal from 

 vol. i. to vol. xviii. The index has been compiled by Mr. 

 F. ^^^ Levander. 



