152 SPECIAL RESULTS IN THE URANOLOGICAL PORTION 



according to Argelander's observations, it is not to be ranked 

 in the class of periodically variable stars. 



The careful consideration and enumeration of vanished 

 stars, or stars which are supposed to have disappeared, are 

 important in respect to the research for the great number of 

 small planets which are probably belonging to our solar 

 system ; but notwithstanding the exactness of the modern 

 registration of telescopic fixed stars, and of our modern star- 

 maps, very great care is still required for the attainment of 

 full certainty and conviction, that any particular star has 

 actually disappeared from the heavens within any definite 

 period. Errors of observation, of reduction, or of the 

 press, ( 273 ) often disfigure the best catalogues. The disap- 

 pearance of a celestial body from the place where it had 

 certainly been seen before, may be occasioned either by its 

 having moved from thence, or by the luminous process on 

 its surface or in its photosphere being so far enfeebled, that 

 the luminous undulations no longer sufficiently stimulate our 

 visual organs. What we no longer see has not on that 

 account ceased to exist. The idea of the " destruction" or 

 the " burning out" of stars which are gradually becoming 

 invisible, belongs to the Tychonian period., Pliny also, in 

 the fine passage upon Hipparchus, asks : " Stellse an obirent 

 nascerenturve ?" The continual apparent change in the 

 Universe, such as the disappearance of what was before seen, 

 is not annihilation, but only the transition of material sub- 

 stances into new forms, or into compositions dependent on 

 new processes. Dark cosmical bodies may suddenly shine 

 forth afresh by a renewed luminous process. 



