THE SCINTILLATION OF THE STARS. 227 



from the siin; if it is polarized in an opposite plane, the polarization 

 may be due to the refraction of the atmosphere. If it is polarized 

 quaqua versus, (on every side,) that may depend on three causes, viz: 

 on the refraction by the surfaces of the object and eye-glasses; or on 

 an imperfection in the annealing of the glass of which the lenses are 

 formed; or on the circumstance that one or more of the lenses are 

 compressed by the mountings. Supposing it to be an effect of the 

 first of these causes, the openings of the object and of the eye-glasses 

 should be reduced to a central band, which would eliminate the light 

 polarized in an opposite plane, and would leave that which is polarized 

 in a plane perpendicular to the direction. By turning the tube or 

 the lenses the direction of the polarization would be changed. If the 

 polarization is produced by a defect in the manufacture of the glass 

 of the lenses, the existence of such imperfection will be rendered 

 evident by exposing the lenses to the polarized light. If the observed 

 polarization is owing to the reflection of the rays of the sun by the 

 comet or its envelopes, the small stars will be seen more distinctly 

 through it when the polarized light has been extinguished by one of 

 Nicol's prisms." 



L. F. KAMTZ, 

 Editor of the ^^ Bepertormm.'^ 



