174 HALOS AND PARHELIA. [Lesson XXVJI. 



through it will seem surrounded with a large and 

 various coloured Halo. 



Parhelia are far more rarely seen, but their ap- 

 pearance is singularly curious. Their apparent size 

 is generally the same as the true sun ; but they 

 are not always round, nor always so bright as the 

 sunj and, when several appear, some are brighter 

 than o'thers. They are tinged externally with 

 colours like the rainbow; and many of them have 

 a long fiery tail, opposite to the sun, becoming 

 paler towards the extremity. These tails mostly 

 appear in a* white horizontal circle, commonly 

 passing through all the Parhelia, and would go 

 through the centre of the sun, if it were entire. 



We have on record, an account of Parhelia 

 seen at Rome, in March 1629 : at this time four 

 were observed, one of which was very much tinged 

 with various colours like the rainbow ; and the 

 others were faintly so. Some were also observed 

 by Cassiniy in 1C83. In England and Scotland, 

 two have frequently been seen at a time. In 

 North America they are often seen, and continue 

 for hours, nay sometimes for several days, being 

 visible from sun-rise to sun- set : when these dis- 

 appear, rain or snow is there generally expected. 



M. Huygens, on applying his attention to these 

 appearances, was soon sensible that they could not 

 arise from such globules as formed the Halos : yet 

 since Parhelia are always attended with Halos, he 

 was satisfied that their causes must be much alike. 

 Considering, then, what other figures hail-stones 



might 



