March 3, 1887] 



NA TURE 



425 



ant researches in stellar photography which have recently been 

 carried out at the Harvard College Observatory, see Nature, 

 vol. XXXV. p. 37. 



New Minor Pl.^xet. — A new minor planet. No. 265, was 

 discovered on February 27, by Herr P.ilisa, at Vienna. This is 

 the fifty-eighth that Ilerr Palisa has discovered. 



ASTRONOMICAL PHENOMENA FOR THE 



WEEK 18S7 MARCH 6-12 



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



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



is here employed.) 



At Greenwich on March 6 

 Sun rises, 6h. 37m. ; souths, I2h. iim. aS'is. ; sets, I7h. 46m. ; 

 decl. on meridian, 5° 40' S. : Sidereal Time at Sunset, 

 4h. 43m. 

 Moon (Full on March 9) rises, I3h. 39m. ; souths, 2ih. 29m. ; 

 sets, 5h. lom.* ; decl. on meridian, 17° 4' N. 

 Planet Rises Souths Sets Decl. on meridian 



h. m. h. m. h. m. „ , 



Mercury ... 6 54 ... 13 15 ... 19 36 ... 3 22 N. 



Venus 7 20 ... 13 35 ... 19 50 ... 2 16 N. 



Mars 7 o ... 12 54 ... 18 48 ... i 58 S. 



Jupiter 22 I9» ... 3 21 ... 8 23 ... 12 2 S. 



Saturn 12 2 ... 20 11 ... 4 20* ... 22 28 N. 



* Indicates that the rising is that of the preceding evening and the setting 

 that of the following morning, 



Occultations of Stars by the Moon (visible at Greenwich) 



Corresponding 

 March Star Mag. Disap. Reap. '■'^i^^^'^^^;'i^^, 



inverted image 



O 41 

 4 I 

 18 24 

 20 50 



I 40 ... 131 289 



4 39 ••• 67 337 



19 14 ... 68 1S5 



21 54 ... 61 HI 



6 ... /Geminorum ... 6 



8 ... 18 Leonis 6 



8 ... 45 Leonis 6 



8 ... p Leonis 4 



8 ... 49 Leonis 6 ... 22 53 near approach 332 



II ... 7Virginis 2J ... 3 7 ... 3 40 ... 145 210 



II ... 15. A. C. 4277 ... 6 ... 4 22 near approach 186 — 

 March h 



12 ... 3 ... Mercury stationary. 



12 ... 20 ... Jupiter in conjunction with and 3" 34' south 

 of the Moon. 

 Saturn, March 6. — Outer major axis of outer ring = 44""0 ; 

 outer minor axis of outer ring = l8"'3 ; southern surface visible. 

 Variable Stars 

 Star R.A. Decl. 



h. m. . , h. m. 



U Cephei o 523 ... 81 16 N. ... Mar. 7, 19 36 m 



S Arietis i 58-6... 11 59 N. ... ,, 6, M 



T Cancri 8 so'2 ... 20 17 N. ... ,, 9, ?« 



R Ursa; Majoris... 10 367 ... 69 22 N , 11, M 



TVirginis 12 8-8... 5 24 S. ... ,, 7, M 



S Ursse Majoris ... 12 390 ... 61 43 N. .. ,, 10, M 



\V Virginis 13 202 ... 2 48 S. ... ,, 12, S oM 



S-Librae 14 54-9 ... 8 4 S. ... ,, 9, 23 39 ni 



U Coronce 15 136 ... 32 4 N. ... ,, 6, 18 46 m 



R Scorpii 16 I0'9 ... 22 40 S. ... ,, H, M 



U Ophiuchi 17 io'8 ... i 20 N. ... ,, 7, 5 46 tn 



and at intervals of 20 8 



U Sagittarii iS 252 ... 19 12 S. ... Mar. 9, 3 o m 



fl I-yiC 18 459 ... 33 14 N. ... ,, 9, I ow 



S Vulpecula; ... 19 43-8 ... 27 o N. ... ,, 12, A/ 



71 Aquilte 19 467 ... o 43 N. ... ,, 9, 5 o m 



! Cephei 22 250 ... 57 50 N , 12, o o m 



M signifies 1 



ON RADIANT-MATTER SPECTROSCOPY:— 

 EXAMINATION OF THE RESIDUAL GLOW^ 



I. 



T 



HE duration of phosphorescence after cessation of the ex- 

 citing cause is known to vary within wide limits of lime, 

 froin several hours in the case of the phosphorescent sulphides to 

 a minute fr.iction of a second with uranium glass and sulphate of 

 quinine. In my examinations of the phosphorescent earths glow- 

 ' Paper read before the Royal Society by Mr. Williair Crookes, F.R.S., 



ing under the excitement of the induction discharge in vactio, I 

 have found very great differences in the duration of the residual 

 glow. Some earths continue to phosphoresce for an hour or 

 more after the current is turned off, while others cease to give 

 out the light the moment the current stops. Having succeeded 

 in .splitting up yttria into several simpler forms of matter differ- 

 ing in basic power (Roy. Soc. Proc. vol. xl. pp. 502-509, 

 June 10, i885), and always seeking for further evidence of the 

 separate identily of these bodies, I noticed occasionally that the 

 residual glow was of a somewhat different colour to that it ex- 

 hibited while the current was passing, and also that the spectrum 

 of this residual glow seemed to show, as far as the faint light 

 enabled me to make out, that some of the lines were missing. 

 This pointed to another difference between the yttrium com- 

 ponents, and with a view to examine the question more closely 

 I devised an instrument similar to Becquerel's phosphoroscope, 

 but acting electrically instead of by means of direct light. 



The instrument, shown in Fig. i, A and B, consists of an 

 opaque disk, a b c, 20 inches in diameter, and pierced with 

 twelve openings near the edge as shown. By means of a multi- 

 plying wheel, (/, and band, ef, the disk can be set in rapid rota- 

 tion. At each revolution a stationary object behind one of the 

 apertures is alternately exposed and hidden twelve times. A 

 commutator, ^^ (shown enlarged at Fig. I, B), forms part of the 

 axis of the disk. The commutator is formed of a hollow cylinder 

 of brass round a solid wooden cylinder. The brass is cut into 

 two halves by a saw cut running diagonally to and fro round it, 

 so as to form on each half of the cylinder twelve deeply cut teeth 

 interlocking, and insulated from those on the opposing half 

 cylinder by an air space about 2 mm. across. Only one half, 

 k li h, of the cylinder is used, the other, / i i, being idle ; it 

 might have been cut away altogether were it not for some little 

 use that it is in saving the rubbing-spring, J, from too great fric- 

 tion when passing rapidly over the serrated edge. To a block 

 beneath the commutator are attached two springs, one, /•, rub- 

 bing permanently against the continuous base of the serrated 

 hemicylinder /; /;, and the other, j, rubbing over the points of 

 the teeth of /; /;. By co meeting these springs with the wires 

 from a battery it will be seen that rotation of the com- 

 mutator produces alternate makes and breaks in the current. 

 The spring, 7, rubbing against the teeth is made with a little 

 adjustment sideways, so that it can be said to touch the points 

 of the teeth only, when the breaks will be much longer than the 

 makes, or it can be set to rub near the base of the teeth, when 

 the current will remain on for a much longer time and the 

 intervals of no current will be very short. By means of a screw, 

 / /, attached to the spring, any desired ratio between the makes 

 and the breaks can be obtained. The intermittent primary 

 current is then carried to an induction coil, /«, the secondary 

 current from which passes through the vacuum tube, «, contain- 

 ing the earth under examination. When the commutator, the 

 coil-break, and tlie position of the vacuum tube are in proper 

 adjustment, no light is seen when looked at from the front if the 

 wheel is turned slowly (supposing a substance like yttria is being 

 examined), as the current does not begin till the tube is obscured 

 by an intercepting segment, and it ends before the earth comes 

 into view. When, however, the wheel is turned more quickly, 

 the residual phosphorescence lasts long enough to bridge over 

 the brief interval of time elapsing between the cessation of the 

 spark and the entry of the earth into the field of view, and the 

 yttria is seen to glow with a faint light, which becomes brighter 

 as the speed of the wheel increases. 



To count the revolutions, a projecting stud, 0, is fastened to 

 the rotating axis, and a piece of quill,/, is attached to the fi.xed 

 support, so that at every revolution a click is produced. With 

 a chronograph watch it is easy in this way to tell the time, to 

 the tenth of a second, occupied in ten revolutions of the wheel. 



Under ordinary circumstances it is almost impossible to detect 

 any phosphorescence in an earth until the vacuum is so high that 

 the line spectrum of the residual gas begins to get faint ; other- 

 wise the feeble glow of the phosphorescence is drowned by the 

 greater brightness of the glowing g.as. In this phosphoroscope, 

 however, the light of glowing gas does not last an appreciable 

 time, whilst that from the phosphorescent earth endures long 

 enough for it to be caught in the instrument. By this means, 

 therefore, I have been able to see the phosphorescence of yttria, 

 for example, when the barometer gauge was 5 or 6 mm. below 

 the barometer. 



When the earth under examination in the phosphoroscope is 

 yttria free from samaria, and the residual emitted light is ex- 



