(io^7) 
extends itfelf from the Sun to our Eye ^ than of a certain angle, 
do ntcefTarily hinder the rays-, which fall on them, from co- 
ming to our Eyes , in regard thu the opaque kernel is che caufe 
that there is behind every fuch grain a (pace of a conicwil figure, 
asM NOin the II. Figure, in which the Eye of the Srea-a- 
tor being fcitaated cannot fee the Sun through that grain,though 
it may fee him when pofited elfewhere , as fomewhere in P. 
And to make the L:ompany the more diftin(5ily to underftand 
theeffed, which theft ©rains fufpended in the Air muft pro- 
duce, he drew the I II Figure 5 in which, B is the place of the 
Eyes B A, the axis which pafTeth from the Eye to the Suns 
C^M> F5 fome of the icy Grains with their feeinel , making 
them half opaque : Among which, the Grain C> being in the 
/fj^Af B-Aj and the lines C Kj L H, reprefenting the rays of the 
Sun neareft to the axis^ the pafTage of which isnot hindred by 
the opacity of the kernel, 'tis certain , not only that the grain 
C will not be able to tranfmit any ray of the Sun towards 
but alfothat, imagining the fuperficies of a Gone, whofe top 
is in the Eye 3 and its fides BD, BE, parallel to the rays CK, 
L H 5 all the grains MM , which this fupeificies fiiall comprife^ 
willUkewife not fuffer any ray to pafs to the Eye, becaiife it 
muft needs beintheirConeof obfcurity 5 but tli ;fe^ thatfliali 
be without this fup^rficies, as the grains F F will let them 
pafs, becaufe the Eye is without their Cone of obfcurity. 
Whence it follows , that the Angle of this Cone B D E is that, 
which determins the Diameter of the Halo^ which depends 
from the proportion , the opaque grain hath to the tranfpa- 
rent 3 in ,vhich it is incloted. For, if this Diameter is of 44 
degrees, as is obfeived in moft ladle's, the bign^fs of the o- 
paque grain will betothe tranfparent as 40 to ip. But he faid^ 
that this proportion was not always the fame , and that the di- 
verfity of it was thecaufe , that fometimes there were feen ma» 
ny mlo^ , one about the other , all having the Sun for their 
Center. 
He adc^ed, that it was eafy to know , why thefe Hal&'s were 
always of ^ round figure , whether the Sun be little or much 
raifed abov^ the Horizon*, asalfo togive a^reafonof their Co- 
lourSj which is the fame with that in the Tnangn'ar Gl fs- 
Pfifmes ^ 
