■656 



SCmNGE. 



[N. S. Vol. IX. No. 227. 



cially upon the transmission of light through 

 ordinary media. The chief difference between 

 his treatment of the subject and the classical 

 one of Maxwell lies in the fact that Gold- 

 hammer considers what are usually called the 

 constants of the medium, the specific resistance 

 or the dielectric constant, for instance, not to be 

 constants, but to be functions of the wave fre- 

 quency, developable in poiver series. It may be 

 remarked that this view receives a certain 

 amount of support from the researches of Blond- 

 lot and J. J. Thomson, which show that the 

 dielectric constants of certain materials do de- 

 pend upon the frequency. 



Developing mathematically the preceding 

 hypothesis, Goldhammer arrives at very general 

 equations for the velocity and absorption of 

 light in a given medium. It is worthy of re- 

 mark that the formulas given by Helmholtz,Sell- 

 meier and Lommel can all be considered as 

 special cases of that of Goldhammer and can be 

 derived from it. 



In Wied. Ann., No. 3, Band 67, Goldhammer 

 applies the theory which has just been sketched 

 to the Zeeman eflTect, and thus obtains a new 

 theoretical explanation of the phenomenon. 

 Considering the absorption spectra first, he 

 shows that any alteration in the specific con- 

 stants of the medium will cause a change in the 

 position of the absorption lines. He then as- 

 sumes that the magnetic field does cause such 

 an alteration in these quantities ; in support of 

 this assumption, he calls attention to a paper by 

 Bolzmann (Wied. Ann., 31, p. 789), in which 

 it is shown that a magnetic field increases the 

 resistance of a gas placed in it. 



KirchofF's laws allow one to pass from the 

 absorption spectrum to that of emission. Then 

 in a bright-line spectrum the effect of a mag- 

 netic field is to cause displacements in the lines 

 and might give rise to doublets and triplets. 



In order to account for the polarization phe- 

 nomena, Goldhammer makes a further assumjj- 

 tion that the magnetic field causes the medium 

 to become seleotropic and double-refracting. 

 The circular polarization of the doublets, when 

 viewed along the lines of force, is very closely 

 connected with the well-known magnetic rota- 

 tion of the plane of polarization. 



It will be noticed that this theory of Gold- 



hammer's differs materially from those pro- 

 posed by Lorentz and Larmor. Goldhammer 

 makes the whole of the phenomena depend 

 upon changes in the medium, while Lorentz 

 and Larmor attribute them to the electrody- 

 namic forces developed by the motion of elec- 

 trified ions in a magnetic field. 



At present it seems that the ionic is the more 

 promising of the two theories, since it gives an 

 explanation, incomplete it is true, of the com- 

 plexity of structure of the lines and of their 

 polarization. The numerical value of the ratio 

 between the mass of a vibrating ion and the 

 charge carried by it as derived from the Zeeman 

 efl^ect is in good agreement with that obtained 

 by J. J. Thomson from the phenomena of 

 cathode rays. 



DAYLIGHT-PHOSPHORESCENCE. 



MOUEELO (Comptes Bendus, t. CXXVIIL, p. 

 557) has made the curious discovery that 

 sulphides of strontium, calcium, barium and 

 zinc, prepared in a particular way, show 

 much more brilliant phosphorescence after 

 exposure to diffused daylight than they do 

 after exposure to direct sunlight, and, further, 

 that periodic exposure to diffused daylight in- 

 creases very remarkably the power of phos- 

 phorescing. After being brought to this sensi- 

 tive state one phosphorescing portion is able to 

 excite phosphorescence in another non- lumi- 

 nous portion either when the two portions are 

 in contact or when they are contained in sepa- 

 rate glass tubes. 



A. St.C. D. 



NOTES ON INORGANIC CHEMISTRY. 

 An analysis of the water of the Great, or II- 

 lecilliwaet Glacier, British Columbia, has been 

 published in the Chemical Neivs by F. T. Shutt 

 and A. T. Charron. The waters were taken a 

 few feet from the face of the glacier, and were 

 of characteristic turbid or milky appearance. 

 Analysis showed water of great organic purity, 

 the free ammonia being 0.018 parts per million; 

 albumenoid ammonia 0.027 to 0.037 ; nitrogen 

 as nitrates and nitrites 0.0246 to 0.0442; 

 chlorinO.l; solids 12 to 30.8. On sedimenta- 

 tion the waters became perfectly clear, and 

 microscopic examination of the deposit showed 



