Dec. 2 1, 1876] 



NATURE 



159 



of this new star with the Eastern Equatorial of the Paris 

 Observatory. On the first evening of observation I was 

 only able to establish the presence of bright lines in the 

 spectrum, two days after the atmospheric conditions 

 enabled me to make a more thorough examination, and to 

 take measurements as exact as the feeble light of the 

 star permits. The following is the result of the spectro- 

 scopic investigations : — 



The spectrum of the star is composed of a certain 

 number of bright lines standing detached on a sort of 

 luminous background, almost completely interrupted 

 between the green and the blue, so that at first sight the 

 spectrum appears to consist of two separate parts. In 

 order to study it qualitatively, I made use of a spectro- 

 scopic eye-piece, specially constructed, which utilises the 

 greatest portion of the light, and allows us to vary its con- 

 centration. For the measurements I employed a Duboscq 

 direct-vision spectroscope, fitted with a scale visible by 

 means of lateral reflection. The accompanying sketch 

 gives an idea of the appearance of the spectrum, and 

 represents the position of lines measured according to 

 the readings of the auxiliary scale, in the most complete 

 series of measurements. 



I have only noticed bright lines ; the dark lines, if 

 they exist, must be very fine and must have escaped me 

 on account of the very feeble hght of the star. The order 

 a^y . . . ^ is that of their intensity, taking into account 

 the visibility of the colour. The following figures are the 

 divisions of the scale which define their position : — 



a S y ^ 7] 6 e 



30 44 60 66 73 81 100 113 

 The flame of a spirit lamp, observed immediately after, 

 gave the line D at the division 42 ; but a slight obliquity 



of the slit relatively to the lines of the scale, introduces a 

 constant difference of one to two divisions in the direction 

 of the re-establishment of the coincidence with the line S. 

 The sky being covered soon after that measurement, I 

 left the spectroscope in position without touching it, and 

 next morning I compared the position of the Fraunhofer 

 lines visible with the light of the clouds -^ 



C D ^(mean) F G 



31 43-5 653 79-5 116 



This is the spectroscope which I employed to observe 

 the spectrum of the Aurora Borealis of February 4, 1872. 

 The relative distance of the lines C, D, F, was the same, 

 2i> 33) 69. There may easily be deduced from these data 

 the correspondence of the divisions of the auxiliary scale 

 with the scale of wave-lengths. The following are the 

 results calculated for the bright lines observed, as also a 

 table of bright lines of various elements expressed in 

 millionths of a millimetre : — 



661 



656(C)' 



7 P 

 531 517 



500 483 451 435 

 - 486(F)- 434 



— 5l7((5mean) — 

 532 — — 



Observ. 



Hydrogen 



Sodium ... — 589(D) 



Magnesium... — 



Line in Solar \ 



Corona . . . / 

 LiueinChro.|_ g 



mosphere. .J •' ' 



This comparison shows that if we take into account 

 the small apparent displacement caused by the obliquity 

 of the slit (which makes all the numbers a little too large), 

 and the inevitable uncertainty presented by measurements 

 of such feeble lights, it may be admitted that the lines 

 a, r], €, coincide with that of hydrogen, S with that of 



sodium, and /3 with the triple line 3 of magnesium. The 

 feeble dispersing power of the spectroscope used did not 

 enable me to distinguish whether the bright line was 

 single, double, or triple, for any of the three cases may 

 occur {CojHptes Rendus, t. Ixxiii., p. 332). 



But the most curious coincidence, which I give here 

 with much reserve, but which it will be interesting ulti- 

 mately to verify, is the coincidence of the line y, very 

 bright in the spectrum of the star, with the green line 

 X = 532 (1474 of Kirchhoff's scale), observed in the spec- 

 trum of the solar corona and in the chromosphere ; the 

 feeble band 6 corresponds also to a band X = 447 of the 

 chromosphere ; one is thus led to think that the line 8 

 corresponds rather to the bright line of the chromosphere 

 X = 587 (helium), than to that of sodium, 589. If this 

 interpretation be accurate, the bright lines of the spec- 

 trum of the star comprehend exclusively the brightest 

 and most frequent lines of the chromosphere. The fol- 

 lowing, in fact, according to Young's Catalogue of the 

 Chromospheric Lines {Phil. Mag., November, 1 871), is 

 the designation of the Isrightest lines and their relative 

 occurrence : — 



Wave-lengths 656(C) 587 532 5i7(^) 486(F) 447 434 



Relative frequence ... loo 100 75 15 100 75 100 



All the other bright lines have a relative frequency 

 lower than 10, with the exception of the fourth bright line 

 of hydrogen X = 410 (/?), to the extreme violet, whose fre- 

 quency is represented by 100, I believe, moreover, that 

 I have often seen this line without always being able to 

 measure it. 



To sum up, the light of the star appears to pos- 

 sess exactly the same composition as that of the solar 

 envelope known as the chromosphere. Notwithstanding 



the great temptation there exists 10 araw irom this fact 

 inductions relative to the physical condition of this new 

 star, its temperature, the chemical reactions of which it 

 may be the seat, I shall abstain from all comment and all 

 hypothesis on this subject ; I believe the facts necessary 

 to arrive at a useful conclusion are wanting, or at least at 

 a conclusion capable of verification. Whatever attractions 

 these hypotheses may have, it is necessary not to forget 

 that they are unscientific, and that, far from serving 

 science, they greatly tend to trammel her. 



D' 



JUST INTONATION 

 R. STONE'S lectures on "Sound and Music," just 

 published, lead one to expect that notwithstanding 

 the formidable appearance of some of the key-boards ex- 

 hibited at South Kensington, the cause of scientific music 

 and of just intonation in particular will be materially 

 advanced by the Loan Exhibition. 



Certainly we may look for something practicable and 

 little short of perfect in the " Natural Finger-board " of 

 Mr. Colin Brown, the Euing Lecturer on Music in the 

 Andersonian University, Glasgow. As supplementary 

 to the descriptions given by Dr. Stone and by Mr. 

 Brown himself, I trust the following remarks will help to 

 elucidate the construction of the instrument, and to make 

 still more obvious its simplicity and " naturalness." 



The vibration numbers of the diatonic scale being 

 represented by — 



, 9 5 4 3 5 15 2 

 ''8' 4' 3' 2' 3' 8' "' 



if we build the scale upon the dominant ^ the vibration 

 numbers will be— 



