[ 4 *« ] 
fore, the Refra&ions and Reflexions will happen 
every-where alike, and the Figure of a circular 
Crown, with the ufual Order of Colours, will be the 
Confequence. 
As to the Halo, that attends 'Parhelia, being 44 
or 45 Degrees in Diameter, he adopts Gajfendi’s 
Opinion as probable, who applies to it the Geome- 
trical Theorem : *De Angulo ad Centrum , dnplo An- 
guli ad Peripheriam . For when a Halo furrounds 
the Sun, the Sun is in the Centre, and the Eye out 
of it, as it were on the Surface of the Phenomenon-, 
whereas, when the Rainbow appears, the Eye is 
placed in a Line drawn from the Sun to the Centre of 
the Rainbow : And thus the Eye ferves for a Centre, 
from which the Diameter of the Iris is beheld, the 
Sun being placed on the Circumference. Yet he 
fays, it ftill remains to be accounted for, Why, when 
Two Haloes appear at once, the Greater is double the 
Diameter of the Lefs,/'. e. about 90 Degrees? 
1 6th> But as Haloes often appear about the Sun 
and Moon, without Parhelia or Parafelina , there 
muft be a peculiar Difpofvtion of Vappurs requifite 
for forming Parhelii. 
Parhelii , he fays, are fituate either in the Inter- 
fedion of a vertical Halo , and the horizontal An- 
nuliiSy which paflfes through the Sun } or in the 
Sedion of feme horizontal Bands and the Corona : 
And the angular Figure of Parhelia leaves us no 
room to doubt, that it is produced by Planes of the 
Annulus or Bands running into the Corona. Now 
Newtons Theory of Colours, and the Experiments 
it is built upon, fhew, that Whitenefs, which is a 
heterogeneous Light, is reftored by blending or coL- 
kding 
