Isreal Smith Clare.

The London encyclopaedia, or Universal dictionary of science, art, literature, and practical mechanics, comprisiong a popular view of the present state of knowledge (Volume 11) online

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.1. H addon, Printer, Castle Street, London.










Sic oportet ad librum, presertim miscellanei generis, legendum accedere lectorem, nt solct ad convivium conviva
civihs. Convivator annititur omnibus eatisfacere ; et tamen si quid apponitur, quod hujus ant illius palato non
respondeat, et hie et ille urbane dissimulant, et alia fercula probant, ne quid contristent coimvatorem.


A reader should sit down to a book, especially of the miscellaneous kind, as a vrell-behaVed visitor does to a ban-
quet. The master of the feast exerts himself to satisfy his guests ; but if, after all his care and pains, something should
appear on the table that does not suit this or that person's taste, they politely pass it over without notice, and commend
other dishes, that they may nol distress a kind host. Translation.









HA'LO, n.s, A red circle round the sun or

If the hail be a little flatted, the light transmitted
may grow so strong, at a little less distance than" that
of twenty-six degrees, as to form a halo about the sun
or moon ; which halo, as often as the hail-stones are
duly figured, may be coloured. Newton.

I saw by reflection, in a vessel of stagnated water,
three halos, crowns or rings of colours about the sun,
ike three little rainbows, concentrick to his body.


HALO, or Corona, in optics, is a luminous
Circle surrounding the sun, moon, planets, or
fixed stars. Sometimes these circles are white,
and sometimes colored like the rainbow. Some-
times one only is visible, and sometimes several
concentric halos appear at the same time. Those
which have been seen about Sirius and Jupiter
were never more than 3, 4, or 5 in diameter ;
those which surround the moon are, also, some-
times no more than 3 or 5 ; but these, as well
as those which surround the sun, are of very dif-
ferent magnitudes, viz. of 120', 22 35', 30 0',
38 0', 41 2', 45 0', 46 24', 47 0', and 90,
or even larger than this. Their diameters also
sometimes vary during the time of observation,
and the breadths both of the colored and white
circles are very different, viz of 2, 4, or 7.
Their colors are more diluted than those of the
rainbow ; and they are in a different order, ac-
cording to their size. Mr. Huygens observed
red .next the sun, and a pale blue outwards.
Sometimes they are red on the inside and white
on the outside. M. Weidler observed one that
was yellow on the inside and white on the out-
side. In France one was observed, in 1683, the
middle of which was white ; after which followed
a border of red, next to it was blue, then green,
and the outermost circle was a bright red. In
1728 one was seen of a pale red outwardly,
then followed yellow, and then green, terminated
by a white. In Holland, M. Muschenbroeck
says, fifty may be seen in the day-time, al-
most every year; but they are difficult to be ob-
served, except the eye be so situated, that not
the body of the sun, but only the neighbouring
parts of the heavens, can be seen. Mr. Middle-
ton says, that this phenomenon is very frequent
in North America ; for that there is generally
one or two about the sun every week, and as
many about the moon every month. Halos
round the sun are very frequent in Russia. M.
^Epinus says, that from the 23d of April, 1758, to
the 20th of September, he himself had observed
P"> fewer than twenty-six, and that he has sometimes
s>. n twice as many in the same space of time.

Similar, in some respects, to the halo, was the
remarkable appearance which M. Bouguer de-
scribes, as observed on the top of Mount Pichinca,
in the Cordilleras. When the sun was just ris-
ing behind them, so as to appear white, each of

them saw his own shadow projected upon it, and
no other. The distance was such that all the
parts of the shadow were easily distinguishable,
as the arms, the leg, and the head; but what
surprised them most was, that the head was
adorned with a kind of glory, consisting of three
or four small concentric crowns, of a very lively
color, each exhibiting all the varieties of the pri-
mary rainbow, and having the circle of red on
the outside. The intervals between these chcles
continued equal, though the diameters of them
all were constantly changing. The last of them
was very faint; and at a considerable distance
was another great white circle, which surrounded
the whole. As near as M. Bouguer could com
pute, the diameter of the first of these circles
was about 5, that of the second 11, that of the
third 17, and so on ; but the diameter of the
white circle was about 76. This phenomenon
never appeared but in a cloud consisting of
frozen particles, and never in drops of rain like
the rainbow. When the sun was not in the ho-
rizon, only part of the white circle was visible,
as M. Bouguer frequently observed afterwards.
Similar to this curious appearance was one seen
by Dr. M'Fait in Scotland ; who observed a
rainbow round his shadow in the mist, when he
was upon an eminence above it. In this situa-
tion the whole country round seemed buried un-
der a vast deluge, and nothing but the tops of
distant hills appeared here and there above the
flood. In those upper regions, the air, he says,
is at that time very pure and agreeable. At
another time he observed a double range of co-
lors round his shadow. The colors of the outer-
most range were broad and very distinct, and
every where about two feet distant from the
shadow. Then there was a darkish interval,
and after that another narrower range of colors,
closely surrounding the shadow, which was very
much contracted. He thinks that these ranges
of colors are caused by the inflection of the
rays of light, the same that occasioned the riug
of light which surrounds the shadow of all bo-
dies, observed by M-. Maraldi, and this author.
Halos may be produced by placing a lighted
candle* in the midst of steam in cold weather.
If glass windows be breathed upon, and the
flame of a candle be placed some feet from it,
while the spectator is also at the distance of some
feet from another part of a window, the flame
will be surrounded with a colored halo. And if
a candle be placed behind a glass receiver, when
air is admitted into the vacuum within it, at a cer-
tain degree of density, the vapor with which it is
loaded will make a colored halo round the flame.
This was observed by Otto Guericke. In De-
cember 1756 M. Muschenbroeck observed, that,
when the glass windows of his room were cover-
ed with a thin plate of ice on the inside, the
moon appearing through it was surrounded witn



a large and variously colored halo ; and, open-
ing the window, he found that it arose entirely
from that thin plate of ice, for none was seen
except through it. Dr. Kotelnihow, having, like
Dr. Halley, made very accurate observations to
determine the number of possible rainbows,
considers the colored halo, which appears about
a candle, as the same thing with one of those
bows which is formed near the body of the sun,
but which is not visible on account of his exces-
sive splendor. See OPTICS.

Descartes observes,. that the halo never appears
when it rains; from which he concludes that this
phenomenon is occasioned by the refraction of
light in the round particles of ice, which are then
floating in the atmosphere ; and, though these
particles are flat when they fall to the ground, he
thought they must be protuberant in the middle
before their descent; and according to this pro-
tuberancy he imagined that the diameter of the
halo would vary. In treating of meteors, Gas-
sendi supposed, that a halo is of the same nature
with the rainbow, the rays of light being in both
cases twice refracted and once reflected within
each drop of rain or vapor, and that all the dif-
ference there is between them arises from their
different situation with respect to the observer.
For whereas, when the sun is behind the spec-
tator, and consequently the rainbow before him,
his eye is in the centre of the circle ; when he
views the halo, with his face towards the sun, his
eye is in the circumference of the circle ; so that,
according to the known principles of geometry,
the angle under which the object appears, in
this case, must be just half of what it is in the

M. Dechales endeavours to show that the ge-
neration of the halo is similar to that of the rain-
bow. If, says he, a sphere of glass or crystal,
full of water, be placed in the beams of the sun,
there will not only be two circles of colored light
on the side next the sun, and which constitute
the two rainbows ; but there will also be another
on the part opposite to the sun, the rays belong-
ing to which afterwards diverge, and form a
colored circle, such as will be visible, if the light
that is transmitted through the globe be received
on a piece of white paper. The reason why the
colors of the halo are more dilute than those of
the rainbow, he says, is owing principally to their
being formed not in large drops of rain, but in
very small vapor ; for, if the drops of water were
Wge, the cloud would be so thick, that the rays
of the sun could not be regularly transmitted
Jirough them ; and, on the other hand, he ob-
erved, that when the rainbow is formed by very
thin vapors, the colors hardly appear. As for
those circles of colors which are sometimes seen
round candles, it was his opinion that they arc
owing to nothing but moisture on the eye of the
observer ; for that he could never produce this
appearance by means of vapor only, if he wiped
his eyes carefully; and he had observed that
such circles are visible to some persons and not
to others, and to the same persons at one time
and not another.

The most considerable and generally received
theory, respecting halos, is that of Huygens, pub-
lished in the English Philosophical Transactions.

See Lowthorp's Abridgment, Vol. II., p. 189.
Sir Isaac Newton mentions it with respect. This
article contains the heads of a discourse which
he afterwards composed, but never quite finished ;
and which has been translated, with some addi-
tions, by Dr. Smith, from whom the following
account is chiefly extracted. Mr. Huygens was
first led to think particularly upon this subject,
by the appearance of five suns at Warsaw, in
1658 ; after which, he says, he hit upon the true
cause of halos and mock suns. If we can con-
ceive any kind of bodies in the atmosphere,
which, according to the known laws of optics,
will, either by reflection or refraction, produce
the appearance in question, when nothing else
can be found that will do it, we must acquiesce in
the hypothesis, and suppose such bodies to exist,
even though we cannot give a satisfactory account
of their generation. Two such bodies are as-
sumed by M. Huygens ; one of them a round
ball, opaque in the centre, but covered with a
transparent shell ; and the other is a cylinder, of
a similar composition. By the help of the for-
mer he endeavours to account for halos, and by
the latter for those appearances which are called
mock suns. Those bodies which M. Huygens
requires, in order to explain these phenome
are not, however, a mere assumption ; for so e
such, though of a larger size than his purpos
quires, have been actually found, consisting, of
snow within and ice without. They are particu-
larly mentioned by Descartes. The balls with
the opaque kernel, which he supposed to have
been the cause of them, he imagines not to exceed
the size of a turnip-seed.

M. Marriotte accounts for the formation of the
small coronas by the transmission of light through
aqueous vapors, where it suffers two refractions
without any intermediate reflection. He shows
that light which comes to the eye, after being re-
fracted in this manner, will be chiefly that which
falls upon the drop nearly perpendicular ; because
more rays falling upon any given quantity of sur-
face in that situation, fewer of them are reflected
with small degrees of obliquity, and they are not
so much scattered after refraction. The red will
always be outermost in these halos, as consisting
of rays which suffer the least refraction. And
whereas he had seen, when the clouds were driven
briskly by the wind, halos round the moon, vary-
ing frequently in their diameter, being sometimes
of 2, sometimes of 3, and sometimes of 4 ;
sometimes also colored, sometimes only white,
and sometimes disappearing entirely ; he con-
cluded that all these variations arose from the
different thickness of the clouds, through which
sometimes more and sometimes less light was trans-
mitted. He supposed, also, that the light which
formed them might sometimes be reflected, and
at other times refracted. As to those coronas
which consist of two orders of colors, he ima-
gined that they were produced by small pieces of
snow, which, when they begin to dissolve, form
figures which are a little convex towards their ex-
tremities. Sometimes, also, the snow will be
melted in different shapes ; and, in this case, the
colors of several halos will be intermixed anc
confused ; and such, he says, he had sometimes
observed round the sun. M. Marriotte then


proceeds to explain the larger halos, viz. those
that are about 45 in diameter, and for this pur-
pose he lias recourse to equiangular prisms of
ice, in a certain position with respect to the sun;
and he takes pains to trace the progress of the
rays of light for this purpose ; but this hypothe-
sis is very improbable. In some cases he thought
that these large coronas were caused by hail-
stones, of a pyramidal figure; because, after two
or three of them had been seen about the sun,
there fell the same day several such pyramidal
hail-stones. M. Marriotte explains parhelia by
the help of the same suppositions. See PARHE-

M. Muschenbroeck concludes his account of
coronas with observing, that some density of
vapor, or some thickness of the plates of ice,
divides the light in its transmission through the
small globules of water, or their interstices, into
its separate colors : but what that density was,
or what was the size of the particles which com-
posed the vapor, he could not determine.

Sir Isaac Newton considered the larger and
I'-'S variable appearances of this kind as pro-
duced according to the common laws of refrac-
t; :i, but that the less and more variable appear-
. 'Ses depend upon the same cause with the
colors of thin plates. He concludes his expli-
t ion of the rainbow with the following obser-
v^tion on halos and parhelia : ' The light which
comes through drops of rain by two refractions,
without any reflexion, ought to appear the
strongest at the distance of about 26 from the
sun, and to decay gradually both ways as the
distance from him increases. And the same is
to be understood of light transmitted through
spherical hailstones : and if the hail be a little
flatted, as it often is, the transmitted light may
be so strong, at a little less distance than that of
26, as to form a halo about the sun or moon ;
which halo, as often as the hail-stones are duly
figured, may be colored, and then it must be
red within by the least refrangible rays, and blue
without by the most refrangible ones ; especially
if the hail-stones have opaque globules of snow
in their centres to intercept the light within the
halo, as Mr. Huygens has observed, and made
the inside of it more distinctly defined than it
would otherwise be. For such hail-stones,
though spherical, by terminating the light by the
snow, may make a halo red within, and colorless
without, and darker within the red than without,
as halos use to be. For, of those rays which
pass close by the snow, the red-making ones
will be the least refracted, and so come to the eye
in the straightest lines.' Some farther thoughts
of Sir Isaac Newton's on halos are subjoined to
the account of his experiments on the colors of
thick plates of glass which he conceived to be
similar to those which are exhibited by thin
ones : ' As light reflected by a lens quicksil-
vered on the back side makes the rings of the
colors above described, so it ought to make the
like rings in passing through a drop of water.
At the first reflexion of the rays within the drop,
some colors ought to be transmitted, as in the
case of a lens, and others to be reflected back
to the eye. For instance, if the diameter of a
small drop or globule of water be about the

s&jth part of an inch, so that a red-making ray,
in passing through the middle of this globule,
has 250 fits of easy transmission within the glo-
bule, and ail the red-making rays, which are at
a certain distance from this middle ray round
about it, have 249 fits within the globules, and
all the like rays at a certain farther distance
round about it have 248 fits, and all those at a
certain farther distance 247 fits, and so on, these
concentric circles of rays, after their transmis-
sion, falling on a white paper, will make con-
centric rings of red upon the paper ; supposing
the light which passes through one single globule
strong enough to be sensible, and in like manner
the rays of other colors will make rings of other
colors. Suppose now that in a fair day the sun
should shine through a thin cloud of such glo-
bules of water or hail, and that the globules are
all of the same siz, the sun seen through this
cloud ought to appear surrounded with the like
concentric rings of colors, and the diameter of
the first ring of red should be 7 15', that of
the second 10 15', that of the third 12 33', and,
according as the globules of water are bigger or
less, the ring should be less or bigger.' This
curious theory our author informs us was con-
firmed by an observation which he made in 1692.
He saw by reflexion, in a vessel of stagnating
water, three halos, crowns, or rings of colors
about the sun, like three little rainbows concen-
tric to his body. The colors of the first or in-
nermost, were blue next the sun, red without,
and white in the middle, between the blue and
red ; those of the second crown were purple
and blue within, pale red without, and green in
the middle ; and those of the third were pale
blue within, and pale red without. These crowns
enclosed one another immediately, so that their
colors proceeded in this continual order from
the sun outward ; blue, white, red ; purple, blue,
green, pale yellow, and red ; pale blue, pale
red. The diameter of the second crown, mea
sured from the middle of the yellow and red on
one side of the sun to the middle of the same
color on the other side, was 9 33', or there-
abouts. The diameters of the first and third he
had not time to measure ; but that of the first
seemed to be about 5 or 6, and that of the third
about 1 2. The like crowns appear sometimes
about the moon : for in the beginning of the
year 1664, on February 19th, at night, he saw
two such crowns about her. The diameter of the
first, or innermost, was about 3, and that of the
second about 5 3Cf. Next about the moon was
a circle of white ; and next about that the inner
crown, which was of a bluish green within, next
the white, and of a yellow and red without; and
next about these colors were blue and green on
the inside of the outer crown, and red on the
outside of it. At the same time there appeared
a halo at the distance of about 22 35' from the
centre of the moon. It was elliptical ; and its
long diameter was perpendicular to the horizon,
verging below farthest from the moon. He was
told that the moon has sometimes three or more
concentric crowns or colors encompassing one
another next about her body. The more equal
the globules of water or ice are to one another,
the more crowns of colors will appear, and the


colors will be the more lively. The halo, at the
distance of 22 30' from the moon, is of another
sort. By its being oval, and more remote from
the moon below than above, he concludes that it
was made by refraction in some kind of hail or
snow floating in the air in an horizontal posture,
the refracting angle being about 50 or 60. Dr.
Smith, however, makes it sufficiently evident,
that the reason why this halo appeared oval, and
more remote from the moon towards the horizon,
is a deception of sight, and the same with that
which makes the moon appear larger in the ho-

HALORAGUS, in botany, a genus of the te-
tragynia order and octandria class of plants :
CAL. quadrifid above ; there are four petals ; a
dry plum, and a quadrilocular nut.

HALS'ENING, adj.~) Germ, hals ; Scotch,
UALSE, n. s. shass, the neck. Sound-

HAL'SER, n. s. j ing harshly ; inharmo-

nious in the throat or tongue. Not in use. Hal-
ser, from Sax. balj- neck, and -jeel a rope. It is
now in marine pronunciation corrupted to
hawser. A rope less than a cable.

The crueltee of thee, Quene Medea !
Thy litel children hanging by the hals,
For thy Jason that wos of love so fals.

Chaucer. Prologue to the Man of Lowe's Tale.
A beechen mast then in the hollow base
They hoisted, and with well-wreathed halsers hoise
Their white sails. Chapman.

This hastening horny name hath, as Cornuto in
Italy, opened a gap to the scoffs of many. Carew.

No halsers need to bind these vessels here,
Nor bearded anchors ; for no storms they fear.


HALSTEAD, a market town of Essex, seated
on a rising ground, on the Coin, forty-seven miles
north-east of London. It has an old church, the
steeple of which was once burnt down by light-
ning, but rebuilt at the expense of Robert Fiske,
esq. The town consists of moae than 1000
houses. The inhabitants manufacture bays, ca-
limancoes, &c. There is a free school for forty
boys, and a very antique bridewell. Its market
on Friday is noted for corn.
HALT, v. n., adj. & n. s. } Sax. bealt, lame ;
HALTER, n. s. \ bealtan, to limp.

To limp, or falter in walking ; one who is dis-
abled ; a cripple ; to stop suddenly as soldiers
in a march ; to doubt or hesitate ; to be unde-
cided ; to fail or falter ; in a rel igious sense, to
backslide from former steadfastness.

How long halt ye between two opinions ?

1 Kings.

All my familiars watched for my halting, saying,
Peradventure he will bf enticed, and we shall prevail
against him. Jeremiah.

Bring in hither the poor, the maimed, the halt, and
the blind. Luke.

For false Fortune hath played a game
At chesse with me, alas the while !
The trayteresse, false and full of gyle
That al behoteth and nothing halfe,
She goth upright and yet she hallt.

Chaucer. The Boke of lie Duchesse.
Here's a paper written in his hand ;
A halting sonnet of his own pure brain,
Fashioned to Beatrice. Shafatpeare.

And will she yet debase her eyes
On me, that halt and am mis-shapen thus 1 Id.


Without any halt they marched between the two
armies. Clarendon.

He might have made a halt 'till his foot and artillery
came up to him. Id.

The heavenly bands
Down from a sky of jasper lighted now
In Paradise, and on a hill made halt. Milton.
Scouts each coast light armed scour

Each quarter to descry the distant foe,

Where lodged, or whither fled, or if for fight

In Motion, or in halt. Milton,

Thus inborn broils the factions would engage,
Or wars of exiled heirs, or foreign rage,
Till halting vengeance overtook our age. Dryden.

I was forced to halt in this perpendicular march.


Spenser himself affects the obsolete,
And Sidney's verse halts ill on Roman feet.


The man who pauses on the paths of treason
Halts on a quicksand, the first step ingulphs him.

Hill', Henry V.

HALTER, n. s. & v. a. Sax. pealj-rrie, from
balj-, the neck. A rope to hang malefactors ; to
bind with a cord ; to catch in a noose.

Whom neither halter binds nor burthens charge.


He's fled, my lord, and all his powers do yield ;
And humbly thus, with halters on their necks,
Expect your highness' doom of life or death.


Online LibraryIsreal Smith ClareThe London encyclopaedia, or Universal dictionary of science, art, literature, and practical mechanics, comprisiong a popular view of the present state of knowledge (Volume 11) → online text (page 1 of 189)