Dec. 30, 1886] 



NA TURE 



207 



nK = 



la" VI - e- . sin (<^ - A) sin 7 _ 



/"rV 



I - e- cos'^ * 



■f, 



where ^ denotes the an^jle between the tangent and major axis, 

 \ denotes the angle between the line of nodes and major 



axis, 

 7 denotes the angle between the plane of orbit and tangent 



plane to sphere, 

 P denotes period in years, 

 / denotes mean motion of earth in miles. 



This equation therefore gives a relation between TI and V 

 depending only on the period and the angular elements of the 

 orbit, so that if either n or Kcan be measured the other may at 

 once be determined. If /■ be greater than unity, then either V 

 must exceed ten miles per second, or n one-tenth of a second of 

 arc. If, then, the spectroscope show the lines in the spectra of 

 both stars to be absolutely coincident, it follows that the parallax 

 must exceed o"'i, and the star will repay investigation. But if 

 a measurable displacement be noticed, V can be determined, 

 and the parallax will follow at once. So that " all double 

 stars for « hich k is at any time greater than unity may be said to 

 be within mea-urable distance either by the spectroscopic or 

 the trigonometrical method." If, however, k be less than unity, 

 the star may still chance to be within a mea urable distance, for 

 V may be small either from the small linear dimensions of the 

 orbit or the length of the period ; but if k be smaller than unity, 

 and Fbe large, then we shall at once know, "with a certainty 

 which the mere failure to measure its parallax trigonometrically 

 could never reach, that the star is at an inconceivable distance 

 from the solar system." Mr. Rambaut next proceeds to deter- 

 mine k for some 39 stars, the elements of whose orbits he takes 

 for the most part from Houzeau's " Vade Mecum." In the case of 

 five only does it exceed unity, viz., a Centauri 6023, Sirius 5'400, 

 70/Ophiuchi i"270, 17 Cassiopeije l'247, and 7 Coronje Australis 

 I '224. Of these the parallax has already been determined for all 

 but the last named. This star, the components of the pair being of 

 nearly equal magnitude, would be well adapted for examination by 

 the spectroscopic method if one of the new giant telescopes were 

 employed, and since k = i'224, had it been examined in 18S0 

 either the velocity in the line of sight would have been found to ex- 

 ceed 12 miles per second, or the parallax to exceed o"'i . Since a 

 star fainter than the fifth and a half magnitude would be beyond 

 the reach of even the most powerful instrument to successfully 

 measure its movement in the line of sight, the field of inquiry is 

 practically confined to o Centauri, and the following three stars 

 for all of which /• is fairly large though less than unity : | Ursaj 

 Majoris o 895, 7 Virginis o'624, and f Herculis o'6o5. The 

 result of Mr. Kambaut's inquiry is therefore to show that but 

 little practical use can be made of the suggested combination 

 of the two methods in the case of double stars. 



Names of Minor Planets. — The following minor planets 

 have recently received names : — No. 254, Augusta ; No. 255, 

 Oppavia ; No. 257, Silesia; No. 260, Huberta ; and No. 261, 

 Prymno. 



Comet Finlay (1S86 t-). — Dr. J. Holetschek gives {Ast. 

 Na(h., No. 2763) the following elements and ephemeris for this 

 object, which, though now diminishing somewhat in brightness, 



becoming well placed for observation in northern latitudes : — 



T = 18S6 November 22-4S4iS. 



6) =315 21 o'-'s 1 



a = 52 45 43-2 ■ Mean Eq. i8S6'o. 



i = 319-4) 

 log q = 9-997122 log a = 0-533468 



log e = 9-850744 Period = 6-31 years. 



18S7 

 Jan. c 



Ephemeris for Berlin Midiiiirht 

 V. .\ Decl. log r 



23 49 17 

 o 8 58 

 O 28 10 



o 46 52 



2-3 S. 

 237 N. 

 45 'o 

 59-9 N. 



0-0565 

 0-0670 

 0-0779 

 00889 



log i 



9'9245 

 9'9343 

 9-9461 

 9-9598 



Bright- 



2 '3 



1-9 



I 7 



The brightness at the time of discovery is taken as unity. 



Comet Barnard (1886/). — The following ephemeris for 

 Berlin midnight is in continuation of that given in Nature for 

 December 9 (p. 134) : — 



,.=187 



Jan. o 

 5 



ASTRONOMICAL PHENOMENA FOR THE 



WEEK 1887 JANUARY 2-8 



/"pOR the reckoning of time the civil day, commencing at 



^ Greenwich mean midnight, counting the hours on to 24, 



is here employed. ) 



At Greenwich ott January 2 



Sun rises, 8h. 8m. ; souths, I2h. 4m. 14-95. ; sets, l6h. im. ; 



decl. on meridian, 22° 55' S. : Sidereal Time at Sunset, 



22h. 49m. 

 Moon (at First Quarter) rises, lih. 56m.; souths, i8h. 12m.; 



sets, oh. 38m.* ; decl. on meridian, 2° 25' N. 



2 ... 20 ... Sun at least distance from the Earth. 



Saturn, January 2. — Outer major axis of outer ring = 46" -4; 

 outer minor axis of outer ring = lS"-5 ; southern surface visible. 



Variable Stars 



U Cephei . 



\ Tauri 

 S Cancri 

 U Hydrse . 

 R Crateris . 

 S Leonis 

 W Virginis . 

 5 Librze 



U Corona; ., 

 U Ophiuchi. 



W Cygni 

 5 Cephei 



R.A. 

 h. m. 

 • • o 52-3 



■ •• 3 54-4 - 



... 8 37-5 . 



... 10 32-0 



... 10 55-0 



... II 50, 



... 13 202 . 



... t4 54-9 . 



... 15 13-6. 

 ... 17 10-8 . 



... 21 31 S . 

 ... 22 25-0 



M signifies ma 



A/efeor-Showers 

 The principal shower of the week is that of the Quadrant ids, 

 maximum January 2, radiant R.A. 228', Decl. 53° N. Other 

 showers are as follows : — From the borders of Gemini and 

 Cancer, R.A. 119°, Decl. 16° N. ; near e Urs£e Majoris, R.A. 

 140°, Decl. 57° N. ; near f Bootis, R.A. 220°, Decl. 13° N. 



