218 COSMOS. 



yet seems to justify us in regarding all new stars as variable 

 in long periods, "which from their very length have remained 

 unknown to us. If, for instance, the self-luminosity of all 

 the suns of the firmament is the result of an electro-magnetic 

 process in tlieir photospheres, we may consider this process 

 of light as variable in many ways, without assuming any 

 local or temporary condensations of the celestial ether, or any 

 intervention of the so-called cosmical clouds. It may either 

 occur only once or recur periodically, and either regularly or 

 irregularly. The electrical processes of light on our earth, 

 which manifest themselves either as thunder-storms in the 

 regions of the air, or as polar effluxes, together with much 

 apparently irregular variation, exhibit nevertheless a certain 

 periodicity dependent both on the seasons of the year and the 

 hours of the day ; and this fact is, indeed, frequently observed 

 in the formation for several consecutive days, during per- 

 fectly clear weather, of a small mass of clouds in particular 

 regions of the sky, as is proved by the frequent failures in 

 attempts to observe the culmination of stars. 



The circumstance that almost all these new stars burst 

 forth at once with extreme brilliancy, as stars of the 1st 

 magnitude, and even with still stronger scintillation, and that 

 they do not appear, at least to the naked eye, to increase 

 gradually in brightness, is, in my opinion, a singular 

 peculiarity, and one well deserving of consideration. Kepler 6 

 attached such weight to this criterion, that he refuted the 

 idle pretension of Antonius Laurentinus Politianus, to having 

 seen the star in Ophiuchus (1604) before Bronowski, simply 

 by the circumstance that Laurentinus had said " Apparuit 

 nova stella parva et postea de die in diem crescendo apparuit 

 lumine non multo inferior Venere, superior Jove." There 

 are only three stars which may be looked upon in the light 

 of exceptions, that did not shine forth at once as of the 1st 



6 Kepler, De Stella nova in pede Serp., p. 3. 



