542 Scientific Proceedings, Royal Dublin Society. 



drawn a picture of an- almost identical display of solar halos which he had 

 witnessed on the. forenoon of September 22nd in that year at Greystones, 

 Co. Wicklow. 



. I have much pleasure in showing the tennis-ball in question, and also a 

 picture, drawn from it by Mr. Thomas Mason, photographer, Dame Street, 

 Dublin. In the picture the sun should be in the centre of the circle of 

 22° radius. 



While touching on the subject of halos, I may allude to a beautiful 

 double corona which encircled the moon on the evening of Friday, March 

 22nd, 1918. 



Following on a summer's day of warmth and sunshine, that evening was 

 signalized by the appearance of a " glory " round the gibbous moon of 

 unusual beauty. In the afternoon a thin film of cirrus cloud spread over 

 the sky at a great height from the westward. Although the thermometer 

 at the surface of the ground in Dublin rose to 63 deg. in the shade under the 

 combined influence of bright sunshine and a brisk south-westerly wind, that 

 cloud was evidently composed of prismatic ice-crystals of singular tenuity, 

 for at 8 p.m. and again at 9.30 p.m. a double-coloured corona developed round 

 the moon. It consisted of two concentric circles outside an ordinary " glory." 

 Both circles showed prismatic colours as in a rainbow. The inner circle, with 

 a radius of 6 degrees from the moon's centre, displayed the colours - red, 

 orange, yellow, green, blue, and violet from within outwards. The outer circle 

 showed these tints' in a fainter degree and in the reverse order. 



The phenomenon was a corona, or " glory " — not a halo, which is a great 

 circle, with a radius of 22 degrees 30 minutes of arc, or less commonly of 

 45 degrees, round the sun or moon. In a halo all the colours of the rainbow 

 may be seen, and the phenomena attending it can be explained only by the 

 refraction of light through ice-crystals composing the feathery cirrus clouds 

 which float at a vast height in the atmosphere. The beautiful coloured corona 

 observed on the evening of March 22nd was of a like origin. 



