48 LIGHT SCIENCE FOR LEISURE HOURS. 



the polariscope is to be applied, though for my own 

 part I have very little faith in the possibility that 

 this instrument can give intelligible and reliable 

 results respecting such a phenomenon as the corona 

 would appear to be. If its light really is of the mixed 

 nature I have described, it can scarcely be but that 

 the polariscopic teachings will be discordant and 

 practically unmeaning. 



Last, but not least, a large array of observers have 

 devoted themselves to the scrutiny of the general 

 features of the eclipse. I wish very strongly to in- 

 dicate the opinion that much remains to be done in 

 this way. It seems to me that in all the eclipses 

 hitherto observed, attention has been somewhat too 

 exclusively directed to the eclipsed sun and its imme- 

 diate neighbourhood. I write this in the full know- 

 ledge of the meteorological and other observations 

 which have been made during eclipses. The class of 

 observation which, as it seems to me, has been insuffi- 

 ciently attended to, includes the special study of the 

 varying illumination of the sky, not near the sun, but 

 at all orders of distance from him. Remembering- 



O 



that we know the actual figure, dimensions, and 

 position, from second to second, of that vast shadow- 

 cone which the moon projects upon our atmosphere, 

 we can interpret in a very satisfactory manner the 

 apparent changes of illumination in different regions of 

 the sky. From such observations, properly made and 

 studied, more could be learned, I do not hesitate to 

 say, respecting the height of the air, the quality of its 



