The Alaska daily empire., 1919-06-10
People Last Night Witt messed a Strange Sight in the Sky Which Caused
 Much Comment
IS GIVEN
M. B. Summers, of United States Weather Bureau Tells What Caused the
 Strange Sight

The people of Juneau and vicinity were treated to a most interesting optical phenomenon yesterday after noon in the form of numerous cir Speculation was rife as to the cause and nature of the strange sight, ana as to its significance and possible portending some great event or hap pening in the near future. Many per sons of middle age stated that they had never seen the like before. While the circles had some of the characteristics of the rainbow, it was pointed out that rainbows occur only with falling raindrops and sunshine at the same time. The sky was almost clear while the circles pre- vailed. only a thin film of cloud be- ing discernible.
 The Weather Bureau received nu- nerous inquiries by telephone dur ng the period of display of the bands )f light, and inquiring ones were old that the rings were none other han solar halos, and that while
 hey were of unusual form and size,
 hey were by no means unprecedent- ,d and had no significance whatever
 M. B. Summers, in charge of the Weather Bureau office, states that lalos in their simplest form are observed at Juneau nearly every O r1d fhof c;v Cf 'een during the month of May just ;losed. They were all of the solar ype, rings around the sun, and all lad a radius of 22 degrees, which the size most commonly observed Occasionally a lular halo, or circle lround the moon is seen, the las; instance of this type observed by the Weather Bureau being on March II
 md 12.
 As to the cause of halos, Mr Sum ners states that they are due tc iiffraction and refraction of the suns or moons rays by ice particles composing cirro-stratus clouds. These clouds have an altitude of approx imately 30000 feet and even in sum. ner are invariably made up of ice crystals. It has been demonstrated
 hat when these crystals are rela. lively small and of varying sizes
 he halo will be white, or almost white, but when they are large and homogeneous in size, most if not all If the prismatic colors are brought ut. It seems probable, also, that
 he shape and Orientation of the ice particles is responsible for the vari- 'us forms that the halos assume in
 uch cases as that Sof yesterday. MT. Summers states, that while yester. lays halo was unusual in the num- ger and shape of the bands of light,
 ypes much more complex in geo. metric design have been seen. in 'arious parts of the earth's surface.
 1e says halos arc not confined to any particular latitude or longitude, the ,nly requisite being the presence of
 hin Cirro-stratus clouds, with ice articles of the proper size, shapes, ,uantity and orientation. Occasion lily these particles may be precipi-
 ated during the prevalence of a lalo in winter. Such a condition occurred at Boulder, Colorado on January 10, 191S Unfortunately, however no detailed or criticaI exam nation was made of these crystals, sr at least none was reported.
 While the brilliancy and intensity 'f the halo of yesterday varied at different times, five circles or seg- nents of circles were visible during
 he greater portion of the Hme At pm. the Weather Bureau first ob- served the initial halo of 22 degrees 'adius, but it was not until about pm. that the additional circles began to appear Those continued It intervals to about 8:20 It was noted that the smaller circles, those If P degrees radius, had the pris- matic colors ranged with the blue 'nside and the blue outside, while he large circle, having. radius of f6 degrees. was at times composed of white light and again had the rainbow colors When colored. how ever, the arrangement was the re- verse of that in the smaller circles. Most brilliant parhelia, or sundays, were almost continually visible on both sides of the sun from pm. to 8 p.m
 Surveyor General Chas. E. David son. made measurements of the size of the larger circle and found it to be of 46 degrees radius. which coin: cides with measurements made of this type of halo at other places.