NA TURE 



[January 30, 1908 



Messrs. Macmillan and Co., Ltd., have published a 

 third edition of " Comparative Anatomy of Vertebrates," 

 which has been adapted from the sixth German edition of 

 Prof. R. Wiedersheim's work by Prof. W. N. Parker. 

 The present edition has been almost entirely re-written, 

 and with Prof. Wiedersheim's permission, alterations 

 desirable in the interests of English students have been 

 made. The general plan of the original has been retained, 

 but some portions have been extended and others abridged. 

 The second English edition was reviewed in the issue of 

 Nature of September i, 1898 (vol. Iviii., p. 409), when the 

 characteristics of this widely known student's manual 

 were described. The price of the new edition is i6s. net. 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrences in February: — 

 Feb. 4. 4h. Iim. Moon in conjunction with $ and 3° 48' S. 

 5. 6h. 22m. to iih. 12m. Transit of Jupiter's Satellile 



IV. (Callisto). 

 „ I3h. 19m. to lyh. im. Transit of Jupiter's Satellite 

 III. (Ganymede). 



10. 7h. 50m. Venus and Saturn in conjunction. 



11. loh. 28m. Minimum of Algol (/3 Persei). 



,, I2h. 22m. to ijh. igm. Moon occults f Tauri 

 (Mag. 3). 



13. 2h. Mercury at greatest elongation (18° 9' E.). 



,, iih. 45m. to I3h. om. Moon occults 5 Gemtnorum 

 (Mag. 3-6). 



14. 7h. 17m. Minimum of Algol (3 Persei). 



15. 2h. 7m. Moon in conjunction with Jupiter and 



1" 12' N. 

 ,, Illuminated portion of the disc of Venus = 0797. 

 27. I2h. 48m. Moon in conjunction with Uranus and 

 0° 7' N. 



Photographic Observ.\tions of Encke's Comet 

 (igoSa). — Encke's comet was photographed at the Heidel- 

 berg Observatory on January 13, 14, 15, 18, and 19, and 

 in No. 4229 of the Aslronomische Nachrichtcn (p. 79, 

 January 21) Prof. Wolf records the positions and magni- 

 tudes derived from the plates. On the first three dates the 

 recorded magnitude was 12-0, on the last two 12-5. The 

 observed positions have been compared with those given 

 in the ephemeris, and corrections to the latter are 

 appended; those for R.A. are fairly constant at -t-3m., 

 but those for declination vary from — 24'.o (December 25, 

 1907) to + 1'-4 (January 19). 



Saturn, a New Ring Suspected. — Observing at an 

 elevation of 1550 metres, at the Revard, Puy-de-Dflme, 

 France, under exceptionally favourable conditions on 

 September 5, 1907, M. G. Fournier suspected a faint, 

 transparent, and luminous ring exterior to the principal 

 rings of Saturn. On September 7 the same observer con- 

 firmed the presence of a very pale luminous zone sharply 

 defined at its edges, but neither he nor M. Jarry-Desloges, 

 who communicates the discovery to the Bulletin de la 

 Sociiti astronomique de France (p. 36, January), was able 

 to find it on September 11. The latter observer suggests 

 the possibility that the ring is subject to periodical fluctua- 

 tions of brightness, and may, therefore, only become visible 

 at certain intervals ; he also suggests that observers 

 situated in high altitudes, such as the Arequipa and Flag- 

 staff stations, may, alone, be able to observe this difficult 

 detail of the Saturnian appendage. A drawing accompany- 

 ing the communication shows the nebulous ring, extend- 

 ing beyond the principal rings, as it appeared at 22h. 25™- 

 on September 7. 



Determination of the Moon's Light with a Selenium 

 Photometer. — In a recent note in these columns (p. 258, 

 January 16) reference was made to some results obtained 

 by Messrs. Stebbins and Brown in a determination of the 

 brightness of moonlight with a selenium photometer 

 {Astrophysical Journal, vol. xxvi., p. 326). The result was 

 given as 0-23 candle-power, but, as there seems to be 

 some misconception as to the meaning of this, an explana- 

 tion seems desirable. American observers state quantities 



NO 1996, VOL. 'jy'] 



of this kind in candle-metres, and thus interpreting the 

 above result it means that the light of the full moon 

 illuminates a white surface to the same extent as an 

 illuminating source of 023 candle-power, placed at a 

 distance of i metre, would illuminate it. 



Owing to the colour-sensitiveness of the selenium cells 

 being as yet unknown, this result must be accepted as 

 purely preliminary ; different cells gave results varying 

 from 007 to 037, the mean being 022 candle-power, and 

 very near to the 023 adopted by Miiller (" Die Photo- 

 metrie der Gestirne," Leipzig, 1897, p. 344) as the mean 

 of several visual observations by different observers. 



The method of observation adopted by Messrs. Stebbins 

 and Brown was to determine at what distance from the 

 selenium cell the standard candle would produce the same 

 deflection as the light from the moon, and then to reduce 

 this distance to terms of the standard candle-metre, after- 

 wards applying the corrections for atmospheric absorption. 

 The determinations of the variation of moonlight with the 

 moon's phase gave consistent results for each cell, and 

 forms the most valuable part of the work. The standard 

 candle employed is by Max Kohl, and burns amyl acetate ; 

 the diameter of the round wick is 8 mm., and the height 

 of tile flame was regulated to 40 mm. 



A Useful Sun and Planet Chart. — From the firm of 

 Carl Zeiss we have received a copy of their chart for 

 showing the position of the sun, or of any of the planets, 

 at any epoch during the present year. The chart is con- 

 structed on a principle employed by Mr. R. H. Bow, of 

 Edinburgh, and consists of two sets of curves and a star 

 map. On the one set of curves, which is placed to the 

 right of the star map, the declinations of the various 

 bodies during the twelve months are shown, whilst the 

 second set, placed directly below the star map, shows the 

 right ascensions. To find the position of a planet on any 

 date, the declination of the planet on that date is found 

 on the former set of curves, and from the point thus 

 determined a horizontal line is drawn across the star map. 

 A vertical line is then drawn from the corresponding point 

 on the right-ascension curve, and where these two lines 

 intersect on the star map is the position occupied by the 

 planet. A calendar of oppositions, quadratures, and con- 

 junctions is also shown on the chart. 



1 



CHICAGO MEETING OF THE AMERICAN 

 ASSOCIATION. 

 'X'HE fifty-eighth meeting of the American Association 

 for the Advancement of Science and of its affiliated 

 scientific societies was held at Chicago from December 30, 

 1907, to January 4, 1908, under the presidency of Prof. 

 E. L. Nichols, professor of chemistry at Cornell University. 

 The attendance was estimated at about 1400, the accurate 

 registration of the affiliated societies having not been 

 handed in at the time of writing. The programme was 

 one of unusual interest, and a number of important 

 measures were adopted. 



The opening meeting of the association was held on the 

 morning of Monday, December 30. Addresses of welcome 

 were made by Dean G. E. Vincent, of the University of 

 Cliicago, in the enforced absence of the president. Dr. 

 H. P. Judson, and by Mr. G. E. Adams, vice-chairman 

 of the local committee for the meeting. The retiring 

 president. Dr. W. H. Welch, of Johns Hopkins University, 

 introduced the president of the meeting. Prof. Nichols, 

 who replied to the addresses of welcome. The address of 

 the retiring president. Dr. W. H. Welch, was given on 

 December 30 before a large audience, and consisted of a 

 masterly treatment of the subject of the interdependence 

 of medicine and other sciences of nature (see Nature, 

 January 23). At the conclusion of the address a reception 

 was given to the members of the association and affiliated 

 societies. 



The vice-presidential addresses, that is, addresses of 

 presidents of sections, were distributed through the week 

 at afternoon sessions. That before Section A (mathematics 

 and astronomy) was delivered by the retiring vice-presi- 

 dent, Edward Kasner, of Columbia University. Its title was 

 " Geometry and Mechanics." The address of the retiring 

 vice-president of Section B (physics) was given by Prof. 



