LUMINOUS PHENOMENA. 
67 
IX. 
Classification of certain Luminous Appearaitces which result 
‘from the Reflection or Refraction of Light by Clouds, and 
which are commonly called Halos, Rainbows, Parhelia, tSfc. 
By A/r. Thomas Forster, F. L. S*. 
"TI^VERY on# who is conversant in meteorology, must be Luminous ap- 
Ji-A well acquainted with such luminous appearances, occa- 
lonally seen about the sun, moon, and planets, and caused by pour. 
tl.«%efraction of their light through a cloud of peculiar struc- 
ture, as are usually called halos, coronae, burrs, glories, &c. 
■But these phaenomena have hitherto received no definite names 
whereby they may be distinguished from each'other, though 
they differ considerably in appearance. Meteorologists have 
spoken of halos and coronae indiscriminately, without dis- 
tinguishing between the corona or luminous disk, and the halo, 
or lumiiijus ring. 
The ancient writers, too, sjwke differently of halones, circuli, 
coronae, halyses, parhelia, and other the like phaenomena, as ap- 
pears by the works of Aristotle,| Pliny, J Seneca § and others. 
'Aristotle appearsto have written with the most perspicuity of all • 
of them. 
With a view to obviate the inconvenience and misunderstand- 
ing which might arise from the confusion or promiscuous use of 
terms not sufficiently definite, I subjoin the following classifica- 
tion, which, though imperfect, may serve, till a better shall be 
found, to enable meteorologists, in their journals, to express, 
•with tolerable precision, the kind of appearance which they wish 
to commemorate. 
I endeavour to classify them (for want of a better criterion) Clasiificatioo 
ficcordins to 
►according to the various shapes or flgures which they present their figure. 
• From his “ Researches into Atmospheric Phenomena.” 
t Aristot. Meteor, lib. iii. cc. 2, 3. 
t Plin. Hist. Nat. lib. ii. cc. 29, SO, 31, 32. lib. xviii. 35. ' 
) fieuec. Optra Philos. Ub. i. cc. 2, 3, 4, 5, 6,7, 
It 
