90 



NATURE 



[May 2 2, ii^9o 



spectrum of such a diffused mass is likely to possess great 

 interest, and the nebula is so large that it will probably not be 

 difficult to differentiate the spectra of different regions. 



(2) In his catalogue of stellar spectra, published in 1887, 

 Konkoly records an observation of this star, in which bright 

 lines were strongly suspected. Notwithstanding the recent ad- 

 ditions to this group by Prof. Pickering and Mr, Espin, the 

 number is still very small, and it is important that suspected 

 cases should be fully investigated. The lines suspected by 

 Konkoly in 69 Virginis were C, D3, and F — the three com- 

 monly observed in )3 Lyrse and 7 Cassiopeia. It is quite pos- 

 sible that the appearance of the lines is periodic, and observa- 

 tions should therefore be continued for some time. If the lines 

 are of any considerable brightness, the observations ought not 

 to be difficult, as the bright lines in the 8th magnitude stars in 

 Cygnus are easily seen and measured with 10 inches aperture. 

 Any irregularities in the continuous spectrum, especially in the 

 green and blue, should be noted ; and, if possible, comparisons 

 should be made with the carbon flutings. Prof. Lockyer has 

 pointed out that a line near A 447 is associated with D3 in the 

 Orion nebula, and also in the solar chromosphere, and it is im- 

 portant to observe whether this also applies to the bright-line 

 stars. He has demonstrated by photographs that the line in the 

 nebula (447) is coincident with one of the bright lines photo- 

 graphed by Prof. Pickering in P Cygni. 



(3) Duner describes the spectrum of this star as a magnificent 

 one of Group II., particularly in the red end. The bands 1-9 

 are all strongly marked. The star is thus probably a little more 

 advanced in condensation than the mean species of the group, 

 and it will be interesting to know what line-absorptions appear 

 at this stage, and also what is the extent of carbon radiation. 



(4 and 5) These are given in Vogel's catalogue as stars of the 

 solar type and of Group IV. respectively. The usual observa- 

 tions are required in each case. 



(6) This is one of the very few variables with spectra of 

 Group VI. So far, we have no records of any changes in 

 spectra which may accompany the variations in magnitude, and 

 the cause of the variability is, consequently, very imperfectly 

 understood. Duner says that the spectrum consists of three 

 zones rather feebly developed, band 6 (near A. 564) being weak, 

 but he does not state the magnitude of the star at the time of 

 his observation. The next maximum will occur about May 28. 

 The star ranges from about magnitude 7 '5 to < 11 in a period 

 of 461 days. Changes of colour should also be noted. 



A. Fowler, 



Spica. — At the Berlin Academy of Sciences on April 24, 

 Prof. Vogel announced that Spica consists of two close stars 

 revolving round their common centre of gravity. Tbe star's 

 spectrum is that of Class IV., and twice in April 1889 the Y line 

 appeared to be shifted towards the violet end of the spectrum as 

 compared with the H & line given by a vacuum tube, whilst once 

 in the following month the shift appeared to be towards the red 

 end. These observations and others made this year of the 

 star's motion in line of sight are given in the following table, 

 approach to the sun being indicated by ( - ) and recession from 

 the sun by ( + ), both being expressed in German miles per 

 second : — 



Pot>dam Mean Time. 



h. m. 



889 April 21 ... 9 15 



,, 29 ... II 10 



May I ... 10 58 



[890 April 4 ... II 30 



„ 9 ... 10 30 



,, 10 ... II 30 



,, II ... 10 50 



„ 13 ... 10 50 



Observed Relative ^-Ti 



Motion. to the .Sun. "^ 



. - II-6 ... -07 ... - 12-3 



. - 1-2 ... - I '2 ... - I3'2 



. + 7-5 ... -1-3 ... 4- 6-2 



. - 34 ... -0-5 ... - 2-9 



. - I4'2 ... +0'2 ... - I4'0 



.. - 0"3 ... +0'I ... - 0"2 



.. + 7-6 ... 00 ... + 7*6 



.. - 147 ... -o'l ... - 14-8 



11-3 ... -03 



-f II"0 



The observations have been reduced to the epoch 1890, 

 April 2, loh. Potsdam mean time, and the period of revolution 

 of the system determined as 4 days 0*3 hours. The greatest 

 motion in line of sight due to the orbital velocity is about 12 

 miles a second, and the system as a whole is moving towards the 

 earth with a velocity of about 3 miles a second. 



From this it is found that the distance between the com- 

 ponents of the system is 660,000 miles, and their total mass 

 ;= I '2 that of the sun. 



It will be remembered that Algol is a spectroscopic double of 

 the same character as the above described. 



NO. 1073, VOL. 42] 



The Meteoric Theory of Comets. — In the Sidereal 

 Messenger for May, Mr. W. H. S. Monck discusses the evidence 

 that has been brought forward in support of this theory, and in 

 connection with the meteoritic origin of the universe. Only four 

 comets are definitely known to be connected with meteor-showers ; 

 and conversely, only four meteor-showers have been connected 

 with comets ; these comets are all periodic, the longest period 

 being 415 years. From this fact it is argued that there is not 

 sufficient evidence to allow the assertion that all comets are 

 connected with meteor-swarms and that the ejection theory 

 advocated by the late Mr, Proctor is supported. It is asserted 

 that, since an ejection from a rapidly cooling body may be partly • 

 solid, partly liquid, and partly gaseous, the gaseous matter might 

 form the comet and the solid (or solidified) matter form the atten- 

 dant meteors ; but for this origin to be true the assumption must 

 be made that two planets exist beyond Neptune. Mr. Monck 

 argues that because Arcturus was seen through 90,000 miles of 

 Donati's comet, whereas Saturn's rings (except perhaps the inner 

 crape ring) are not transparent, the rings must be more than 

 1000 times as dense as the comet at the point where it crossed 

 between us and Arcturus, hence meteoritic collisions should be 

 more frequent and the effect of the increased temperature should 

 be made clearly manifest in the spectrum. The meteoritic 

 hypothesis is not, however, objected to as a working hypothesis, 

 but is said to be on an equality with the older nebular hypothesis ; 

 and the writer does not think the spectroscope will ever afford a 

 crucial test between the two, for the reason that it cannot dis- 

 tinguish between a large solid, surrounded by a gaseous envelope, 

 and a number of small bodies with interspaces filled with 

 gas. 



Mass of Shooting-Stars.— Mr. C. C. Hutchins, in the 

 American yournal of Science for May, gives the result of an 

 inve.stigation undertaken with the object of finding data for 

 determining the mass of shooting-stars. Having determined the 

 radiant energy of the standard candle, it was found that on the 

 supposition that the ra3rs of a meteor have the same ratio of 

 visible to total energy as those of the candle, the mass of a meteor 

 at a distance, of 50 miles, having a magnitude equal to Vega and 

 a velocity of 25 miles per second, would be 0-2936 gram if it 

 continued two seconds. If the meteor in burning produce, for a 

 given expenditure of energy more light than the candle, then a 

 less mass would serve to produce the light given by it. A lump 

 of the Emmett Co. (Iowa) iron meteorite was placed upon the 

 lower carbon of an arc lamp and vaporized by the passage of 

 the current, and it was found that for a given expenditure of 

 energy the arc of meteoritic vapour gave ten times the light of 

 the candle, hence the mass of a meteor giving the light of a first 

 magnitude star moving with parabolic velocity, and lasting for 

 two seconds, is 0*029 gram. 



Photographs of the Moon. — Admiral Mouchez, at the 

 meeting of the Paris Academy of Sciences of May 12, presented 

 a note on some new photographs of the moon obtained by the 

 Brothers Henry at Paris Observatory. The instrument used 

 was the equatorial 0'32 metres aperture, destined for the niap of 

 the heavens. The photographs are said to be far superior to 

 those obtained in Englatid and the United States with larger 

 apertures, the superiority of the results being ascribed not only 

 to the perfection of MM. Henry's objectives, but also to the 

 method of direct enlargement adopted. 



THE ROYAL SOCIETY CONVERSAZIONE. 



T^HE conversazione held by the Royal Society on May 14 was 

 -'■ in every way most successful. The attendance was large, 

 and everyone was pleased and interested by the programme. We 

 note some of the objects exhibited : — 



The Director- General of the Geological Survey exhibited: — 

 (i) A series of specimens illustrating deep borings in the south 

 of England. In this case was arranged a series of cores and 

 specimens from all the deep bores which during the last thirty 

 years have been made in the south of England in search of wafer. 

 They included the borings at Richmond, Crossness, Kentish 

 Town, Meux's Brewery, Strealham, Turnford, Ware, Chatham, 

 Gayton and Orton in Northamptonshire, Harwich, and Swindon. 

 The positions of these bores were shown on the large index 



