634 



NA TURE 



[October 27, 1904 



character given to the part on voltaic electricity. Under 

 magnetism a brief account has been included of tubes of 

 force, magnetic flux, permeability, and reluctance. 



New editions of three standard works on botany have 

 just reached us from Germany. One volume is the third 

 edition of Prof. G. Haberlandt's " Physiologische Pflanzen- 

 anatomie " (Leipzig : W. Engelmann), the second edition 

 of which was reviewed in Nature of March i8, 1897 (vol. 

 Iv. p. 457). About sixty pages have been added to the 

 work, and the number of figures has been increased from 

 235 to 264. Mr. Engelmann has also published the twelfth 

 edition of Prantl's " Lehrbuch der Botanik, " revised by 

 Prof. F. Pax. The additional matter has enlarged the book 

 by twenty-two pages, and twenty-five new figures have been 

 included. The fourth revised edition of Prof. A. Engler's 



Syllabus der Pflanzenfamilien " has been issued by the 

 firm of Borntraeger Bros., Berlin. The work is a summary 

 of systematic botany, with special reference to medicinal and 

 useful plants, and a survey of kingdoms and regions of 

 flowering plants ; it is of particular value to students of 

 special and pharmaceutical botany. 



OVR ASTRONOMICAL COLUMN. 



A New Variable Star. — A telegram received at the Kiel 

 Centralstelle from Prof. E. C. Pickering, on October 7, 

 states that the object discovered by Mr. Stanley Williams 

 on September 20 is, according to its 'spectrum, a long 

 period variable star. 



On a plate obtained by Herr P. Gotz at Heidelberg on 

 .\ugust 84 the star was fainter than B.D.-|-29°4653, which 

 has a magnitude of qi ( Astronoinisclie Xachrichtcn, No. 

 3971)- 



Ephemeris for Tempel's Second Comet. — In No. 3971 

 of the Astronomischc Nachrichten M. J. Coniel publishes a 

 continuation of his daily ephemeris for Tempel's second 

 comet, extending from October 25 to January i. 



Abstracts of the previous portions have already appeared 

 in these columns, and the following is from the present 

 publication : — 



Ephemeris izh. (M.T. Paris). 



1904 a app. 5 app. log. Ji I : r^A' 



.Although the comet was unsuccessfully sought during 

 .August and September, and, theoretically] its light should 

 commence to diminish towards the end of the present month, 

 the fact that at previous apparitions the light has been 

 sensibly stronger after perihelion than before leads M. 

 Coniel to hope that the object may yet be observed during 

 its present return. As before mentioned in these columns, 

 the feeble light of the comet, combined with its southerly 

 declination, will render it a difficult object for observers in 

 the northern hemisphere. 



PiicEBE : Saturn's Ninth Satellite. — The promised 

 extended discussion of the observations of Phoebe by Prof. 

 \y. H. Pickering appears in No. 3, vol. liii., of the Harvard 

 College Observatory Annals. 



The discoverer of the satellite therein describes the first 

 discovery of, and the subsequent searchings for, the object, 

 explaining in detail the examination of the plates and the 

 difficulties experienced in recognising the satellite's image. 



Sixty photographs of Saturn have, so far, been obtained 

 with the Bruce telescope, and of these twelve were taken 

 when the planet was moving rapidly, and were therefore 

 useless in locating the satellite's position. Several others 

 were, for various reasons, useless, but the object sought is 

 to be seen on forty-two plates, which are used in the 

 discussion. 



NO 1826 VOL. 70] 



.After preparing the description of the observations and 

 results for the press, Prof. Pickering received information 

 from Arequipa which considerably modified his ideas of the 

 satellite's orbit. An approximate ephemeris had been sent 

 to Prof. Bailey, at Arequipa, in March of this year, but he 

 was unable to find the image of the satellite in the computed 

 positions. Subsequent research has shown that the motion 

 of this body in its orbit is probablv retrograde, an unlooked- 

 for possibility, since the other eight of Saturn's satellites 

 all have direct motions. Consequently Prof. Pickering 

 gives the details of the reductions for both retrograde and 

 direct motion. 



The elements, as determined for the case of retrograde 

 motion, are as follow : — 



.Semi-major axis at a distance of 10 units measures 29'-62. 

 This corresponds to a distance of 00862 astronomical unit, 

 or 7,096,000 miles. 



Eccentricity =o'22 



Inclination to ecliptic =5°'i 



Longitude of ascending node =220° 

 ,, ,, perisaturnium.. -289°-7 



Epoch of perisaturnium ... =1900 Mar. 28-0 (Ci. M.T.) 



Period =546"5 days. 



The inclination of the orbit of Phu'be to that of Saturn 

 is, therefore, 6°o, and the longitude of the ascending node 

 is i7o°o. 



The eccentricity is remarkable as being greater than 

 that of any other satellite or major planet in the solar 

 system. 



The brightness of Phoebe is judged as two magnitudes 

 fainter than that of Hyperion, which is assumed to be of 

 the fourteenth magnitude. From photometric considerations 

 the diameter of the satellite is thought to be about 200 miles. 



In conclusion. Prof. Pickering gives a table showing the 

 differences between the computed and the observed places 

 of the satellite, and then discusses the deviations and gives 

 an ephemeris for 1904. 



Faint Stars Near the Trapezium in the Orion Nebula. 

 — The lists of stars in the Orion nebula recently published 

 by Profs. Wolf and Pickering included none of the stars 

 near the Trapezium, because, with the short-focus cameras 

 used in obtaining their plates, the images of the stars in 

 that region were blotted out by the bright nebula. 



On the plates obtained by Prof. Ritchey in 1900 and 1901, 

 using the Verkes 40-inch telescope with a yellow screen 

 placed immediately in front of the plate, these fainter stars 

 are easily seen, therefore Mr. J. A. Parkhurst has measured 

 their coordinates from 8' Orionis, and gives these, together 

 with the magnitudes of the stars, in a list published in the 

 September number of the .istrophysical Journal. The list 

 contains forty-two stars, all within two minutes of arc of 

 the trapezium star 6' Orionis, of which twenty-three were 

 observed visually by Bond — these include ten ob.servecf 

 photographically by Prof. Pickering — whilst nineteen are 

 presumably catalogued for the first time. 



Photographic Determination of Parallax. — Encouraged 

 by the successful photographs obtained by Prof. Ritchey 

 with the Yerkes 40-inch telescope, Mr. Frank Schlesinger 

 tried several exposures with the same instrument for the 

 determination of several stellar parallaxes. The yellow 

 screen used in the former work was found to be unnecessary, 

 and, as it introduced several troublesome errors, it was 

 dispensed with. 



The great focal length of (he instrument renders errors 

 in measuring the plates much less important than when 

 smaller instruments, such as those used in the production of 

 the astrographic chart, are used, and Mr. Schlesinger com- 

 putes the probable error for one exposure to be only 

 ± o"-o3o. 



Among the results obtained there occurs the parallax of 

 the star Krucgcr 60 (R.A.=22h. 24m., dec. = -fS7° 10'), 

 which was placed on the working list because Prof. Barnard 

 suggested that it has a large parallax. The result 

 shows that the suggestion is probably correct, and, if con- 

 firmed by other measures, it places the star as one of our 

 nearest neighbours, its parallax being -)-o"-278. This value 

 was obtained as the result of measuring eight plates, con- 

 taining twenty exposures, and using five comparison stars 

 (Astrophysical journal, No. 2, vol. xx.). 



