66 LEWIS: SOLAR HALO. 



appears on the inside of the halos as due to the fact that the 

 least refrangible rays (red) are least turned aside in minimum 

 deviation of light and that violet, being the most refrangible, 

 is deflected in such a manner that it always appears on the 

 outer edge of the rings. 



In "American Weather," by General A. W. Greely, Chief 

 Signal Officer of the United States Army, is found the follow- 

 ing quotation: — "Probably the most remarkable series of 

 solar halos seen in the United States were those of December 

 29th and 31st, 1880, in the Ohio and upper Mississippi and 

 lower Missouri valleys. At the time the temperature was 

 below zero Fahrenheit. The halos were frequently double, 

 being 22° and 46° radii, with brilliant contact arches. Gen- 

 erally the prismatic colors showed with great distinctness, and 

 mock suns varying in number from two to five were frequent." 



An exhaustive treatise on solar halos, by Dr. L,ouis Besson, 

 of the Paris Observatory, appeared in the National Monthly 

 Weather Review of July, 1914, together with a supplementary 

 article by one of the United States officials in the Weather 

 Bureau at San Francisco. A copy of the above magazine is 

 on file in the Philadelphia Weather Bureau. 



