[anuary 2iO, 19 1 3] 



NATURE 



60 [ 



scheme is in its essential idea similar to Sommerfeld's 

 four-dimensional vector-alg:ebra and analysis {Annalen 

 d. Physik, vol. xxxii.-xxxiii., 1910), but is more radic- 

 ally vectorial, introducing, instead of a mere juxta- 

 position of four scalars, a formal sum of four vectors 

 corresponding to as many mutually perpendicular unit 

 vectors, with six " 2-vectors " and four "3-vectors" 

 to match. Another chief characteristic is that, while 

 Sommerfeld has developed a vector algebra and 

 analysis of essentially Euclidean four-dimensional 

 space, Wilson and Lewis give us from the outset a 

 non-Euclidean system, which suits better the require- 

 ments of relativity. Especially interesting as regards 

 novelty of ideas is a discussion, given as a preliminary 

 to "Electromagnetics and Mechanics" (art. 45-47), of 

 the possibility of replacing conceptually continuous and 

 discontinuous distributions by one another, and of a 

 case in which such a substitution is impossible. To 

 make the whole system more accessible to a wide 

 circle of non-specialists, the authors proceed by de- 

 veloping their new geometry first in two, then in 

 three, and, finally, in four dimensions. Another 

 feature of the paper is an uncommon brilliancy of 

 exposition. With but one caution regarding a certain 

 statement about the "extended momentum" (p. 479), 

 which possibly is erroneous, we can recommend the 

 paper warmly, both to freshmen in relativity and to 

 specialists. 



The Clarendon Press has published a translation 

 by Mr. A. S. L. Farquharson of Aristotle's " De 

 Motu Animalium de Incessu Animalium," at the price 

 of 2S. net. This booklet completes the fifth volume 

 of the English translation of the works of Aristotle 

 which is being issued under the editorship of Messrs. 

 J. A. Smith and W. D. Ross. It was the desire of 

 the late Dr. Jowett, as formulated by his will, that 

 the proceeds from the sale of his works, the copy- 

 right in which he bequeathed to Balliol College, 

 should be used to promote the study of Greek litera- 

 ture. In a codicil to his will he expressed the hope 

 that the translation of Aristotle's works begun by his 

 own translation of the "Politics" should be pro- 

 ceeded with. The volumes to which the present part 

 is a contribution represent the result of the coopera- 

 tion of Balliol College and the delegates of the 

 Clarendon Press to carry out Jowett's wishes. 



OUR ASTRONOMICAL COLUMN. 



.'\STRONOMICAL OCCURRENCES FOR FeURUARY : 



Feb. 2 Sh. 43m. Jupiter in conjunction with the 

 Moon (Jupiter 5° 17' N.). 



3. 6h. 38m. Mars in conjunction with the 



Moon (Mars 4° 13' N.). 



4. i3h. 56m. Uranus in conjunction with the 



Moon (L'ranus 4° i' N.). 



5. 4h. 14m. Mercury in conjunction with the 



Moon (Mercury 2° 9' N.). 

 10. oh. 13m. Venus in conjunction with the 



Moon (Venus 0° 51' N.). 

 12. 2h. om. Venus at greatest elongation E. 



of the Sun. 

 ,, iih. om. Mercury in superior conjunction 



with the Sun. " 

 I4- 3^- 33m- Saturn in conjunction with the 



•Moon (Saturn 6° 20' S.). 



NO. 2257, VOL. 90] 



Feb. 16. 6h. om. Saturn at quadrature to the Sun. 

 16. oh. iim. Neptune in conjunction with the 



Moon (Neptune 5"^ 30' b.J. 

 25. i6h. 44m. Mars m conjunction with 

 L'ranus (Mars o'-' 2b' S.). 



The Reported Bright Meteor of December iS. — 

 From notes published by Mr. J. H. Elgie in The 

 Yorkshire Weekly Post we learn that the bright 

 object, mentioned in these columns on January 2 as 

 having been seen near Manchester on December 

 18, was also seen by several observers in Yorkshire. 

 Mr. Platts describes it as being spherical, the 

 diameter being about half that of the moon, and as 

 leaving a bluish trail. After travelling some distance 

 the meteor divided into two portions, the smaller 

 appearing to fall earthwards, while the larger con- 

 tinued in the original path ; other observers describe 

 the object as being of exceptional brilliance. Several 

 further letters appeared in the Manchester Daily Dis- 

 patch, but contain no mor« precise data than that 

 already given here. Mr. Elgie suggests an atmo- 

 spheric, rather than a cosmic, origin, and the more 

 precise details necessary to determine the true nature 

 and path of this object would be of scientific interest 

 and value. 



Catalogue of Celestial Objects. — We have re- 

 ceived the second part of M. G. Raymond's catalogue, 

 "Les Merveilles du Monde Sid(^ral" (Paris: G. 

 Thomas), which gives brief descriptions, positions, 

 &x., for all peculiar objects between vih. and xiih. 

 right-ascension. This catalogue will be found ex- 

 tremelv useful by amateur observers, the objects being 

 arranged in right-ascension, and a brief description 

 given for each ; thus one constellation may appear in 

 several different sections, but the different units may 

 be successively examined in the order given. A large 

 number of the descriptions are those of the author 

 himself, others are quoted from different authorities, 

 and in regard to those for double and coloured stars 

 it is possible that some of the hues given are sub- 

 jective, due to contrast, retinal fatigue, and "dazzle 

 tints," as suggested by Prof. Louis Bell. 



The Vagaries of Enxke's Comet. — An interesting 

 article discussing the peculiar variation of the period 

 of Encke's comet is contributed by Mr. E. V. Reward 

 to the December number of The Oxford and Cam- 

 hridi^e Review. Mr. Reward recounts the results 

 obtained from the various calculations of Encke 

 which led him to the idea of a resisting medium in 

 interplanetary space, and briefly discusses the argu- 

 ments for and against the existence of such a medium. 

 Until the 1867-71 return the acceleration of the 

 comet's motion was fairly constant, but it then sud- 

 denly diminished by nearly one-half, only to return 

 to its earlier value at subsequent revolutions. Mr. 

 Reward points out that the theory promulgated by 

 Dr. Backlund, viz. that the comet encountered a 

 stream of meteors of varying density when near peri- 

 helion, satisfactorily e.xplains the vagaries of period 

 and is not a negation of the resisting medium idea. 



Relati\e Proper Motions of 162 Stars near the 

 Orion Nebula. — While spending the year 1911-12 at 

 the Yerkes Observatory Dr. A. van Maanen 

 measured a number of plates of the neighbourhood 

 surroundinff the Orion nebula, which were taken on 

 different dates between igoi and 1912, with the 

 40-in. refractor. The results show the advantage of 

 using a long-focus instrument, the mean probable 

 errors of the final proper motions being onlv o'oo6o" 

 in a and 00047" ■" ^- One hundred and sixty-two stars 

 were discussed, and the proper motions are nearly 

 all very small, only three exceeding o'loo' per annum. 

 (A<:troiwmical Journal, No. 642.) 



