HAL 
Halo. eneesat Paris. In 1737, he was seized with a paraly- 
"tic affection in his right hand; but this did not prevent 
him from attending the Reyal Society Club every Thurs- 
day: His disorder, however, gradually increased > and 
he died: on'the 14th January 1742, in the 86th year of 
his age. He was buried in the church-yard of Lee, near 
Blackheath. Dr Halley’s Tabule Astronomice were 
published in 1749. They were for a long time the most 
complete and accurate; but they have long since been 
superseded by others more correct and valuable.” 
There are few individuals who have been so distin- 
guished as Dr Halley, both for their industry and their 
genius. He was the author of no fewer than 78 papers: 
in the Philosophical Transactions, wpon almost every 
branch of natural philosophy ; and a great number of 
these are remarkable for their originality, and for the 
new and ingenious views which they unfold. The 
name of Halley, however, is not associated in the his- 
tory of science with any brilliant effort, or any striking 
discovery. His reputation was widely extended, both 
as a profound philosopher and as a man of taste ; and 
almost every department of physical science received 
some improvement from his labours. The upright cha- 
racter of Halley was strikingly displayed in his refusal 
to assume the mask of religion, when it would have 
conducted him to a professorship in Oxford. But while 
we admire this example of sincerity and disinterested-’ 
ness in his unbelief, we cannot but feel that a stain is 
left upon his.reputation, when history records that he 
was a ‘ banterer of religion.” In an-age when a phi- 
losopher like Newton was an open defender of Christi- 
anity, it was indelicate in a philosopher like Halley to 
assume in public the character of an infidel. 
HALO, or Corona, is a luminous circle, sometimes 
containing all the prismatic colours, which occasionally 
appears about the sun and moon, and other luminous 
bodies. 
In the northern regions of the globe, the sun and moon 
frequently appear surrounded with halos, or coloured 
circles, having their diameter about 44° or 92°. When 
a horizontal white circle intersects these halos, parhelia 
or brighter spots appear near their intersections, and al- 
so portions of inverted arches of various curvatures. In 
the horizontal circle, there are often anthelia or bright 
spots nearly opposite to the sun. ; 
In order to lay before our readers a pretty full ac- 
count of this curious class of phenomena, we shall be- 
gin with describmg the most interesting halos that have 
itherto been observed, and then give an account of the 
theories which have been employed to: explain them. 
As the most minute accuracy is necessary in the de- 
scription of the phenomena, we shall generally give it 
in the words of the observers themselves. 
Onthe 20th March 1649, Scheiner observed at Rome 
asingolar halo which Huygens describes in the follow- 
ing manner from the writings of Descartes and Gas- 
sen 
Roman phe- 
nomenon 
observed by 
Scheiner. 
PLATE 
CCLXXXVII 
Pig. 1. 
“‘A is the place of the observer at Rome, B the vertex 
or point over his head, C the true sun, AB a vertical 
plane passing through the observer's eye, the true sun 
and the vertex B, which areall projected in the straight 
line ACB, About the sun C, there appeared two con- 
centric rings not complete, but diversified with colours. 
The lesser and inner ot them DEF, was fuller and more 
perfect ; and though it was open from D'to F, yet these 
ends D and F were perpetually endeavouring to unite. 
Sometimes they did unite and complete the ring, and 
then opened again. The other exterior and fainter and 
scarce discernible circle, was GKI; it had a variety of 
612 
HAL 
colours, but was very inconstant. The third circle 
KLMN was very large, and all over of a white colour, 
such as are often seen with paraselenz about the moon. 
This was an eccentric circle passing t ‘the middle . 
of the sun, at first entire, but towards the end of the 
appearance it was weak and and scarce discern- 
ible from M towards N. In common intersection 
of this circle, and of the outward iris GKI, there broke 
out two parhelia N and K, not entirely perfect ; K was 
somewhat weak, but N shone irs and stronger. 
The brightness in the middle of them both resembled 
that of the sun; but towards their edges, they were . 
tinged with colours like those of the rainbow. They 
were not perfectly round and even at their edges, but 
uneven and ragged. The parhelion N was a little wa« 
vering, and sent out a spiked tail NP, ofa colour some- 
what fiery, which had a continual reci ition. The 
parhelia at L and M, beyond the zenith B, were not so 
bright as the former, but rounder and white like the 
circle which they’ were placed in. They resembled milk 
or clean silver. The parhelion M was almost quite ex- 
tinct at half an hour past two o'clock, excepting that 
some faint remains would revive now and then, and the 
circle itself vanished in that place. The parhelion N’ 
disappeared before K did; and while M became fainter: 
K grew brighter, and vanished last of all.” This has 
been generally called the Roman Phenomenon. 
On Sunday February 20th 1661, new style, Heveli« p71, oy. 
us observed at Dantzie a very curious halo, which he ‘served by , 
thus déscribes in. the appendix to his Mercurius:in Sole Hevelius 
Visus, page 174. “ A little before 11 o’clock, the sun Dantzie 
being towards the south, and the sky ‘very. clear, there in 1661. 
appeared seven suns er in several circles, some PraTE 
white and some coloured, and these with very: long tails, ccixxx 
waving and pointing from the true sun, together with Fig. 2. 
certain white arches crossing one another. Ist, The 7 
true sun at A being about 25° high, was surround-- 
ed almost entirely by a circle whose diameter was 45°, 
and which was coloured like the rainbow with pur- . 
ple, red, and yellow, its under limb being scarce 23°. 
above the horizon. 2d, On each side of the sun at 
and C, towards the west and east, there appeared two 
mock suns, coloured especially towards sun, with 
very long splendid tails of'a whitish colour, and termi~ 
nating ina point. 3d, A far greater circle YXHVZ, 
almost 90° degrees in diameter, encompassed the sun 
and the former lesser’ circle GBIC, and extended itself’ 
down to the horizon. It was very strongly coloured in 
its upper part, but was somewhat duller and fainter on 
each side. 4th, At the tops of these two circles at G 
and H were two inverted arches, whose common cen- 
tre lay in the zenith, and these were very bright/and 
beautifully coloured. The diameter of the lower arch. 
QGR was 90°, and that of the upper one THS was 45°.’ 
In the middle of the lower arch at G, where it coincided 
with the circle BGC, there a; another mock sun ; 
but its light and colours were dull and faintish. 5th, 
There appeared a circle BEF DC much bigger than the 
former, of an uniform whitish colour, parallel to the 
horizon at the distance of 25°, and 130° in diameter, 
which arose as it were from the collateral mock suns 
B and C, and passed through three other parhelia of 
an uniform whitish colour like silver: one at D, almost 
90° from the true sun towards the east; another at E, 
towards the west ; and a third at F in the north, dia- 
metrically opposite to the true sun, all of the same co- 
lour and brightness. There passed also two other white 
arches EN, DP, of the greatest circle of the sphere 
through the eastern and westeyn mock suns E, D, and 
4 
