50 LEWIS : 



to advance new theories and ideas in contradiction of the sci- 

 entific, underlying and arbitrary, yet generally accepted, 

 causes of the phenomenon that have been revealed to us by 

 the authorities who have made the sun, or solar, and the 

 moon, or lunar, halos and kindred phenomena a subject of 

 years of careful study and exhaustive investigation. Rather 

 is it the purpose to avoid as much as possible the purely tech- 

 nical treatment of the various and intensely interesting feat- 

 ures in connection with the subject, and confine the discussion 

 to observations taken in a very simple manner with the ori- 

 ginal intention of preserving for private record as full and as 

 complete a description as possible of the most unusual and 

 brilliant spectacle that attracted the attention of thousands of 

 people on Thursday morning, May 20th, 1915. 



The observations taken by the writer are supplemented by 

 and are compared with those made by several other members 

 of the Institute, and their kindness is acknowledged for sup- 

 plying necessary data. The courtesy of Mr. George S. Bliss, 

 Director of the United States Weather Bureau at Philadel- 

 phia, is also acknowledged for his kindness in furnishing 

 department records and data. It is certain that this addi- 

 tional information will add very materially to the interest and 

 value of this paper as a record. 



Compound solar or lunar halos are due to the refraction 

 and reflection of rays of light from the sun or moon, respect- 

 ively, through a comparatively thin plane or cloud composed 

 of innumerable particles or crystals of frozen moisture. In 

 this latitude these conditions, occurring usually in very filmy 

 cirrus cloud strata, are produced by abnormally low tempera- 

 tures of the upper atmosphere, which convert the minute 

 globules of water into ice crystals of many varied forms and 

 shapes. The general form of these crystals is that of a hex- 

 agonal prism. 



Simple or single halos, often seen around the luminary, 

 are due to the refraction of light rays only. The cause of 

 and the wonderful effects that appear in the display of double 



