( 326 ) 



A much simpler explaiicitioii of the phenomena may be derived 

 from GUI' conception of the irregiihir fields of radiation cansed by 

 the stars. 



We need only snppose that the outer parts of ö Orionis and 

 of Nova Persei, like those of so many other stars, contain much 

 hydrogen and helinm, little calcium and sodium. The currents and 

 \'ortices in the gaseous mass, which produce the irregularities of the 

 field of the star's radiation, bring about very broad dispersion bands 

 in the viciuily of the lines of hydrogen, helium, etc. The darkest 

 parts of these bands Avill be displaced when, by the star's rotation, 

 masses in which the density is variously distributed, pass Qiw line 

 of sight. The disj)ersion bands of calcium and sodium, on the other 

 hand, are so narrow, (hat the vai-ying position of their darkest parts 

 cannot be distinguished from the fixed position of the corresponding 

 absorption lines. The constant displacement of the latter indicates 

 that d Orionis recedes from the Sun >vith a xelocity of 16 km., 

 Nova Persei of 7 km. a second. 



According to our opinion (f Orionis, therefore, is na spectroscopic 

 binary. 



In the spectra of a great many stars oscillations and duplications 

 have only been observed with diifuse lines. In those cases too the 

 dis))lacemejits are, as usual, e.\j»i-essed iji so many kilometers a 

 secojid, because no other iinerprelalion than motion in the line of 

 sight is thought of. From the al)ove consideralions it follows, however, 

 that the observed oscillations are very likel>- to be executed by 

 dis|)ersion bands and Jiol by llie absorption lines; then Jio sufficient 

 ground remains for classijig such slars among sj)ec1roscoj)ic binaries 

 and for calculating orbital elements. 



Sövei-al difficulties to which the conclusions derixed from DoppLKii's 

 [)rinci[)le lead us, will then disaj)pear at the same time. How, for 

 instance, are we to realize the physical conditions of the orbital 

 motion in such so-called binaries as i Orionis, 57 Cygni, 6> Orionis 

 and many others, all of which ai-e involved in nebulous matter, but 

 whose motion in the line of sight is nevertheless — according to 

 Fhost and Adams — subject to periodical variations of 70, 90, 

 140 km. a second, in spite of our physical notions concerning 

 resistant media? When, on the other hand, the observed displacements 

 of spectral lines, as well as the oscillations of the l>rightness of 

 similar stars, ai-e supposed not to result from motion in orbits, but 

 from irregularities in their fields of radiation, there remains nothing 

 astonishing in the fact that such variations often occur with stars 

 involved in nebulosity. 



