( 328 ) 



also in the spectrum of 6 Orionis observed by Huggins in 1894 and 

 1897 (An Atlas of representative Stellar Spectra, p. 140), etc. In those 

 cases the explanation snggested by Ebert would require the addition 

 of special hypotheses. 



Our fundamental hypothesis that the structure of most stai-s is 

 similar to that of the Sun (it being admitted, of course, that the 

 stars may greatly differ as to the extent of their respective gaseous 

 envelopes, the average steepness of the density gradients in them, 

 their chemical composition, temperature, etc.) seems to admit of the 

 interpretation of a greater variety of facts. It makes displacements 

 of the dispersion bands towards the long and the short waves almost 

 equally probable — if we leave the asymmetry in the form of the 

 dispersion curves out of question and provisionally assume the directions 

 of the axes of the stars to be distributed at random through space. 



The direction in which we see a star may be regarded as a steady 

 line in space, allowance being made for aberration and parallax. If, 

 now, the distribution of the matter constituting that celestial body 

 remains nearly unchanged for a long time, then after each rotation 

 of the star our line of sight will again pass through the same points 

 of the "optical system", and we shall observe an accurately perio- 

 dical course in the star's brightness and in the appearance of its 

 spectral lines. In most cases, however, currcuts and vortices will 

 cause more or less considerable alterations to arise in the distribution 

 of the density of the gaseous mass, and, consequently, in the com- 

 position of the beam of light reaching the Earth at a given phase 

 (»f the star's I'Otary motion. Thus the strictly periodical succession 

 of phenomena is open to any degree of disturbance. The very irregular 

 and sometimes rapid changes in the brightness of objects like o Ceti, 

 SS Cygni, ft Cephei, etc. are much more intelligible from this point 

 of view, than tVom intei'pretations based on the assumption of violent 

 eruptions, large spots, or eclipses caused by dark companions. And 

 it is so diflicult to make a sharp distinction between variables of 

 long period and Novae, that we sliould not resent the idea of com- 

 paring even the appearance of a new star to the sudden gleam of 

 a revolving coast-light when the optical system, giving to the beam 

 a considerable decrease in divergence, passes our line of sight. 



Chemistry. — Prof. C. A. Lobry de Bruyn presents a paper of 

 J. Olie Jr. : "-The transformation of the phenylpotassiiun 

 sulphate into p-phenolsulphonate of potassium" . 

 ((Communicated in the meeting of June 25, 1904). 

 (^Ti.is paper will not be published in these Proceedings). 



