December 17, 1891] 



NATURE 



167 



the spectrum of hydrogen are given, or approximately given, by 

 Balmer's law, viz. 



■(■-,J) 



where k — 274-263. In this formula n becomes the oscillation 

 frequency of the successive lines, when for m we write the in- 

 teger numbers 3, 4, 5, &c. Similarly, Profs. Kayser and Range 

 have found that A, B, and C can be determined so that the 

 empirical formula, 



A + 



+ C 



shall approximately represent the positions of the lines in any 

 one of the three series that present themselves in the spectra of 

 the other light monad elements — Li, Na, K, Rb, Cs. These 

 formulae have an important physical meaning. They indicate 

 that « is a function of l/;// ; in other words, that although the 

 periodic times of the successive rays are not themselves a funda- 

 mental period with its harmonics, as is the case with the vibra- 

 tions that give rise to musical sounds, they in some way depend 

 on an event of this simple character which is going on in the 

 molecules from which the spectrum emanates. Balmer's law 

 may be represented by a very simple diagram which places this 

 relationship in evidence. Draw the parabola 



and place its axis horizontal. Erect an ordinate at the distance 

 k from the vertex. Double this out, and using its double 

 length as unit, set off upon it the harmonics 1/3, 1/4, i/S, &c. 

 From each of the points so determined draw horizontal lines to 

 the curve : these are the values of n for the successive lines of 

 the hydrogen spectrum. Now, having regard to the fact that 

 the light monad elements, H, Li, Na, K, Rb, Cs, have all 

 of them series of lines which appear to belong to the same 

 general type, we are justified in assuming that Balmer's law is 

 the simplest case of a general law which prevails throughout all 

 the light monads. Hence, if the oscillation-frequencies be 

 plotted down as the horizontal lines of a diagram constructed as 

 above with x = n and/ — ijm, the curve passing through the 

 ends of the lines in the other monads should be some curve of 

 which the parabola is a particular case. This may happen in 

 different ways, but the simplest hypothesis is that they are 

 hyperbolas or ellipses. Accordingly, the author has tried this 

 hypothesis in the case of the sodium spectrum, with the result 

 that hyperbolas approximately represent series P (the principal 

 series) and series S (the series of sharp lines), and that a para- 

 bola represents the third series, series D (the series of diffuse 

 lines) ; and with the further interesting result that the only line 

 in the sodium spectrum which has not hitherto fallen into its 

 place as a member of one or other of the three series proves to 

 be in reality the first term of series S, with a value for n which 

 is negative instead of positive. The physical meaning of this is 

 that the revolution going on within the molecules round that 

 elliptic partial which gives rise to this double line is in the 

 opposite direction to what it would have been if its n had been 

 positive (see memoir by the author "On Double Lines in 

 Spectra," recently published in the Transactions of the Royal 

 Dublin Society). The equation of an hyperbola being 



(a - xf = P(3 + 1000 . y-), 



the values to be attributed to the constants for series P of the 

 sodium spectrum are approximately — 



log P = 37740300 



a = 3337*4120 



b = 1438-35 



and their values for series S are — 



log P = 2-5263843 

 a = 434'0587 

 b = 108-514. 



The equation of a parabola being 



j; = a - 1000 , by^, 

 the values of the constants for series D are — 

 a = 244-93, 

 log* = 0-04357. 

 NO. I 155, VOL. 45] 



The investigation shows that in series P and series S of 

 the sodium spectrum, the curve of nature is not an exact hyper- 

 bola, but a curve slightly less curved in the neighbourhood of its 

 vertex. It also indicates that there is probably a line in the sodium 

 spectrum, belonging to series P, at or a little less than the wave- 

 Iength2i30. — Mr. J. Joly exhibited and described a shutterforuse 

 in stellar photography. This shutter enables any bright star in the 

 field of the telescope to be covered at will, so as to secure better 

 definition. The shutter is a small watch-spring magnet, adjust- 

 able to any part of the field, and pivoted so that it can be 

 rotated by the action of a current which circulates round the 

 field in a narrow coil. In one position of the magnet the >tar 

 is exposed, in the other covered. A modification for parallax 

 work, suggested by Mr. A. A. Rambaut, and used at Dunsink 

 Observatory, has the magnet and coil to one side of the field, 

 and the shutter, which is carried on a needle attached to the 

 magnet, fixed in the centre of the field. There is no vibration 

 in these shutters, owing to the small mass of the moving parts. 

 In the first form, the current in the one coil may control 

 shutters placed in any part of the field of the tele-cope, so that, 

 if desirable, more than one star may be covered.— Prof. T. 

 Johnson described the structure and function of the peculiar 

 swellings (callosities) of Nitophylluvi versicolor, Harv., and 

 pointed out the bearing of his observations on the specific char- 

 acter of N. versicolor, and Schmitz's views on the structure of the 

 Floridean thallus. — Mr. E. W. L. Holt read a list of the rarer 

 shore and deep-sea fishes obtained during the cruise of the s.s. 

 Harlequin on the west coast of Ireland (1891). One fish, 

 Cenirophorus squamosus (Gm. L. ), taken in deep water off the 

 Mayo coast, is new to the British fauna. The following are 

 new to the Irish fauna : Raia oxyrhynchus (Linn.), from 500 to 

 375 fathoms, and from shallow water ; Raia viicrocellata 

 (Mont.), from shallow water— coast of Mayo and Donegal ; 

 Rhombus norvegicus (Gthr.), from shallow water— Donegal 

 Bay; Arnoglossus grohmanni (Bonap.) was again taken; 

 Crystallogobius nilssoni (Dub. and Kor.) proved to be abun- 

 dant everywhere, between 10 and 35 fathoms. The follow- 

 ing were amongst the forms, usually inhabiting littoral 

 water, which were taken at more than 100 fathoms : Scyllium 

 canicula, Acanthias vulgaris, Galeus vulgaris, Raia oxyrhyn- 

 chus, Gadus (Eglifinus, Conger vulgaris. 



Paris. 



Academy of Sciences, December 7. — M, Duchartre in the 

 chair. — Reply to a note by M. Besson on phosphides of boron, 

 by M. Henri Moissan. The author points out that he re- 

 marked upon the reaction between boron ond phosphorus in a 

 paper presented on April 6, 1891, and more fully described 

 its properties on July 6, 1891. He therefore claims priority 

 over M. Besson, who first presented a note on the subject on 

 July 13. — On the theory of linear differential equations,;by M. 

 Andre Markoff, — On modifications of the adiabatism of a con- 

 tracted gaseous stream, by M. H. Parenty.— The vapour ten- 

 sions of cobalt chloride solutions, by M. Georges Charpy. The 

 graphic representation of the tensions at different temperatures 

 of a solution saturated in the cold (containing 32 per cent, of 

 C0CI2) gives two right lines from 20' to 40'', and from 75° on- 

 wards respectively, joined by a curve. Each of these right lines 

 corresponds to a definite state of hydration of the salt ; the 

 lower represents the tension of a red solution, the upper of a 

 blue one. These results agree with those of M. Etard, but the 

 interval of passage between the two states is from 40° to 75° 

 instead of from 35° to 50", as found by this observer, a difference 

 explained by the use of saturated solutions in his experiments. — 

 Action on some metals of sodammonium and potassammonium, 

 byM.Joannis. (See Notes.)— Calculation of the temperature of 

 ebullition of isomeric ethers of the fatty acids, by M. G. Hin- 

 richs, —Thermal data concerning active malic acid and potassium 

 and sodium malates, by M. G, Massol. The heat of solution of 

 the anhydrous acid is (per mol. in 4 litres), - 3-31 Cal. ; heats 

 of neutralization— by K = -^ 26-23 Cal., by Na = -f 2486 Cal.; 

 heats of solution of the anhydrous salts : 



C4H5O5K in 6 litres = - 578 Cal. 

 CiHjOsKj in 8 litres = -f- r55 Cal. 

 C4H805Na in 6 litres = - 166 Cal. 

 C4H405Na2 in 8 litres = -i- i -78 Cal. 



The heats of formation of the salts indicate that malic acid lies 

 between succinic and oxalic acids in the energy of its action. — 



