56 LEWIS: 



a complete circle around the sun, but was more in the shape 

 of a rainbow with an arc of about i8o°, the tangent of the 

 centre of which was parallel to the southeastern horizon. 

 This arc had another peculiar feature more closely resembling 

 the rainbow, in that the colors of the spectrum were very 

 much more pronounced and much less confused than in the 

 inner halo. Red, however, as is typical of phenomena of this 

 nature, was most predominant in the outer as well as the 

 inner circle, and fringed the inside of the halos. 



At Media and at some other localities within the field 

 where the halos were visible, there were three additional 

 circles that could be plainly seen. All of the additional 

 circles were greater in diameter than the small halo, but 

 considerably smaller than the outer halo. The most pro- 

 minent of these three rings was a circle of dazzling white, 

 without a tinge of coloring, that fairly outshone either of the 

 halos. This circle was more narrow and more clean cut than 

 the rings encircling the sun, and is one that is common and 

 C3.n most always be seen in compound displaj^s of solar or 

 lunar halos. This band of light is known in science as the 

 parhelic circle, and always, as in this case, passes through the 

 exact centre of luminary. Unlike the halos, this circle is due, 

 not to refraction, but to reflection of light. According to 

 Thomas Young the parhelic circle is caused by the reflection 

 from the vertical faces of long prisms and from the bases of 

 the short ones. The centre of the parhelic circle fell on the 

 same line as that assumed by the shadow of the sun, and was 

 at a point io° or 15° outside and northwest of the inner halo. 



The other two circles were but slightly smaller than the 

 parhelic circle and also lay to the northwest of the sun. Both 

 of these rings of light were decidedly less brilliant than the 

 other circles and intersected the parhelic circle and were 

 tangent to each other on the shadow line, as well as being 

 tangent to the inner halo. Of the two, the circle that 

 appeared on the northeastern side of the line of symmetry 

 was the brightest and was pure white. The circle on the 



