JULIAN period, in chronology, a system or period of 7980 years, found by multiplying the three cycles of the sun, moon, and indiction into one another. See CHRONOLOGY.

This period was called the Julian, not because invented by Julius Cæsar; since the Julian epocha was not received till the year 4669, but because the system consists of Julian years. This epocha is not his torical but artificial, being invented only for the use of true epochas; for Scaliger considering that the calculation was very intricate in using the years of the creation, the years before Christ, or any other epocha whatever, in regard that another person could not understand what year this or that writer meant; to remove such doubts in the computation of time, he thought of this period: which commencing 710 years before the beginning of the world, the various opinions concerning other epochas may commodiously be referred to it. See EPOCHA.

The most remarkable uses of the Julian period are as follow: 1. That we can explain our mind to one another, for every year in this period has its peculiar cycles, which no other year in the whole period has; whereas, on the contrary, if we reckon by the years of the world, we must first enquire how many years any other reckons from the creation to the year of Christ, which multiple-inquisition is troublesome and full of difficulties, according to the method of other periods. 2. That the three cycles of the sun, moon, and indiction, are easily found in this period. 3. That if it be known how the chronological characters are to be found in this period, and how the years of any other epocha are to be connected with the years of it, the same characters also may, with little labour, be applied to the years of all other epochas.

JULUS, in natural history, a genus of insects of the order Aptera. Lip crenate,

emarginate; antennæ moniliform; two feelers, filiform; body long, semi-cylindrical, consisting of numerous transverse seg. ments; legs numerous, twice as many on each side as there are segments of the body. There are fourteen species, of which we shall notice the J. indus, or great Indian julus, which is six or seven inches long; found in the warmer parts of Asia and America, inhabiting woods and other retir ed places. It has 115 legs on each side, the body is ferruginous; legs yellow; the last segment of the body is pointed. The most common species is the J. sabulosus, about an inch and a quarter long; the colour brownish black, except the legs, which are pale or whitish; it is an oviparous animal; and the young when first hatched are small and white, and furnished with only three pair of legs, situated near the head, the remaining pairs, in all 120, do not make their appearance till some time after. This species inhabits Europe, and is found in damp places and in nuts. The juli tribe are nearly allied to the scolopendræ, or centipedes, but their body instead of being flattened, as in those insects, is nearly cylindrical, and every joint or segment is furnished with two pair of feet, the number on each side doubling that of the segments, but in the scolopendra the number of joints and of feet is equal on each side. The eyes of the juli are composed of hexagonal convexities, as in most of the insect tribe, and the mouth is furnished with a pair of denticulated jaws. When disturbed the juli roll themselves up into a flat spiral: their general motion is rather slow and undulatory.

JUNCUS, in botany, rush, a genus of the Hexandria Monogynia class and order. Natural order of Tripetaloidea. Junci, Jussieu. Essential character: calyx six-leaved; corolla none; capsule one-celled. There are twenty-nine species. The rushes have a simple grassy stem, without leaves or knots, or else knotty, with a sheathing leaf at each knot; flowers terminating or lateral, corymbed or panicled, with the branchlets spathaceous at the base.

These plants agree with the grasses in the glumes of their flowers, and the sheaths of their leaves; they differ in having the stems filled with pith, whereas in grasses it is hollow. The rushes form an intermediate link between the grasses and some of the liliaceous plants, as anthericum, &c.

They form naturally two divisions, one without leaves allied to scirpus, &c. and the other with leafy stems. But all classical

botanical writers, says Dr. Smith, have judiciously preserved this very natural genus entire, notwithstanding the capsule is in some species one-celled, in others threecelled. The sea-rushes are planted on the sea-banks in Holland; the roots running deep into the sand, and matting very much so as to hold it together. In the summer, when they are full grown, they cut them, and when dry work them into baskets.

JUNGERMANNIA, in botany, so named from Louis Jungermannus of Leipsic, Professor of Botany at Atorff, a genus of the Cryptogamia Alga, Linnæus, class and order. Natural order of Hepaticæ, Jussieu. Thirty species of these mosses are arranged in five subdivisions, in the fourteenth edition of "Systema Vegetabilium.” Dr. Withering has forty-eight species in the third edition of his "Arrangement of British Plants;" he says many of them are beautiful microscopic objects.

JUNGIA, in botany, so named from Joachim Jungius, M. D. a genus of the Syngenesia Polygamia Segregata class and order. Natural order of Compositæ Oppositifoliæ. Cinarocephalæ, Jussieu. Essential character: calyx common, three-flowered; receptacle chaffy; florets tubular, twolipped; outer lip ligulate; inner two-parted. There is but one species, viz. J. ferruginea, the stems of which are woody, covered with a ferruginous down; leaves alternate, five-lobed, cordate at the base; lobes rounded, blunt; they are hirsute, and underneath hoary; panicle terminating, large, decompounded; heads of flowers small, heaped. It is a native of South America.

JUNIPERUS, in botany, juniper-tree, a genus of the Dioecia Monadelphia class and order. Natural order of Coniferæ. Essential character: male, calyx of the ament a scale; corolla none; stamina three: female, calyx three-parted; petals three; styles three; berry three-seeded, irregular, with the three tubercles of the calyx. There are twelve species; some of these are lofty handsome trees; but the J. communis, common juniper, is a low shrub, seldom more than three feet in height, sending out many spreading tough branches, inclining on every side, covered with a brown or reddish bark, with a tinge of purple. The male flowers are sometimes on the same plant with the females, but at a distance from them; they are commonly on distinct plants. The female flowers are succeeded by roundish berries, which are at first

green, and when ripe are of a dark purple colour. They continue on the bush two years, and are sessile in the axil of the leaves. Juniper is common in all the northern parts of Europe, in fertile or barren soils, on hills or in valleys, in open sandy plains, or in moist and close woods. In England it is found chiefly on open downs, in a chalky or sandy soil.

-IVORY, a hard, solid, and firm substance, of a white colour, and capable of a very good polish. It is the tusk of the ele. phant, and is hollow from the base to a certain height. It is brought to us from the East Indies, and from the coast of Guinea. Tusks are valuable in proportion to their size; and it is observed, that the Ceylon ivory, and that from the island of Achem, do not become yellow by wear, as all other ivory does: hence the teeth of these places bear a larger price than those of the coast of Guinea.

IVORY black, is prepared from ivory, or bones burnt in a close vessel. This, when tinely ground, forms a more beautiful and deeper colour than lamp-black; but, in the common methods of manufacturing, it is apt to be adulterated with charcoal dust, so as to be almost, or altogether, unfit for

use.

JUPITER, 2, in astronomy, one of the superior planets, remarkable for its great brightness. See ASTRONOMY.

Jupiter is the brightest of all the planets except Venus. He moves from west to east in a period of 4332 days, exhibiting irregularities similar to those of Mars. Before he comes into opposition, and when distant from the sun about 115°, his motion becomes retrograde, and increases in swiftness till he comes into opposition. The motion then becomes gradually slower, and becomes direct when the planet advances within 115° of the sun. The duration of the retrograde motion is about 121 days, and the arch of retrogradation described is about 10°. But there is a considerable difference both in the amount and in the duration of this retrograde motion.

Jupiter has the same general appearance with Mars, only that the belts on his sur face are much larger and more permanent. They are said to have been first discovered by Fontana and two other Italians; but Cassini was the first who gave a good account of them. Their number is very variable, as sometimes only one, and at others no fewer than eight, may be perceived. They are generally parallel to one

another, but not always so; and their breadth is likewise variable, one belt having been observed to grow narrow, while another in its neighbourhood has increased in breadth, as if the one had flowed into the other, and in this case Dr. Long observes, that a part of an oblique belt lay between them, as if to form a communication for this purpose. The time of their continuance is very uncertain, sometimes remaining unchanged for three months; at others, new belts have been formed in an hour or two. In some of these belts large black spots have appeared, which moved swiftly over the disk from east to west, and returned in a short time to the same place; from whence the rotation of this planet about its axis has been determined.

The figure of Jupiter is evidently an oblate spheroid, the longest diameter of his disk being to the shortest as 13 to 12. His rotation is from west to east, like that of the sun, and the plane of his equator is very nearly coincident with that of his orbit; so that there can scarcely be any difference of seasons in that planet. His rotation has been observed to be somewhat quicker in his aphelion than his perihelion: The axis of rotation is nearly perpendicular to the plane of the ecliptic, and the planet makes one revolution in about 9 h. 55′ and 37". The changes in the appearances of these spots, and the difference in the time of their rotation, make it probable that they do not adhere to Jupiter, but are clouds transported by the wind, with different velocities, in an atmosphere subject to violent agitations.

Four little stars are observed around Jupiter, which constantly accompany him. Their relative situation is continually changing. They oscillate on both sides of the planet, and their relative rank is determined by the length of these oscillations. That one in which the oscillation is shortest is called the first satellite, and so on. These satellites are analogous to our moon. See ASTRONOMY. They are all supposed to move in ellipses; though the excentricities of all of them are too small to be measured, excepting that of the fourth; and even this amounts to no more than 0.007 of its mean distance from the primary.

The orbits of these planets were thought by Galileo to be in the same plane with that of their primary: but M. Cassini has found that their orbits make a small angle with it; and as he did not find any differVOL. IV.

ence in the place of their nodes, he concluded that they were all in the same place, and that their ascending nodes were in the middle of Aquarius. After observing them for more than thirty-six years, he found their greatest latitude, or deviation from the plane of Jupiter's orbit, to be 2° 55'. The first of these satellites revolves at the distance of 5.697 of Jupiter's semi-diame. ters, or 1′ 51′′, as measured by proper instruments; its periodical time is 14. 184. 27' 34". The next satellite revolves at the distance of 9.017 semi-diameters, or 2′ 56'', in S. 13h. 13′ 43′′; the third at the distance of 14.584 semi-diameters, or 4′ 42′′, in 7a. 3h. 42′ 36′′; and the fourth at the distance of 25.266, or 8′ 16′′, in 16. 16h. 32′ 09′′. Since the time of Cassini it has been found that the nodes of Jupiter's satellites are not in the same place; and from the different points of view in which we have an opportunity of observing them from the earth, we see them sometimes apparently moving in straight lines, and at other times in elliptic curves. All of them, by reason of their immense distance, seem to keep near their primary, and their apparent motion is a kind of oscillation like that of a pendulum; going alternately from their greatest distance on one side to the greatest distance on the other, sometimes in a straight line, and sometimes in an elliptic

curve.

When a satellite is in its superior semicircle, or that half of its orbit which is more distant from the earth than Jupiter is, its motion appears to us direct, according to the order of the signs; but in its inferior semi-circle, when it is nearer to us than Jupiter, its motion appears retrogade; and both these motions seem quicker the nearer the satellites are to the centre of the primary, slower the more distant they are, and at the greatest distance of all they ap pear for a short time to be stationary.

From this account of the system of Jupiter and his satellites, it is evident that occulta. tions of them must frequently happen by their going behind their primary, or by coming in betwixt us and it. The former takes place when they proceed towards the middle of their upper semi-circle; the latter, when they pass through the same part of their inferior semi-circle. Occultations of the former kind happen to the first and second satellites; at every revolution, the third very rarely escapes an occultation; but the fourth more frequently, by reason of its greater distance.

C

It is seldom that a satellite can be discovered upon the disk of Jupiter, even by the best telescopes, excepting at its first entrance, when by reason of its being more directly illuminated by the rays of the sun than the planet itself, it appears like a lucid spot upon it. Sometimes, however, a satellite in passing over the disk appears like a dark spot, and is easily to be distinguished. This is supposed to be owing to spots on the body of these secondary planets; and it is remarkable, that the same satellite has been known to pass over the disk at one time as a dark spot, and at another so luminous that it could not be distinguished from Jupiter himself, except at its coming on and going off. When the satellites pass through their inferior semi-circles, they may cast a shadow upon their primary, and thus cause an eclipse of the sun to his inhabitants if there are any; and in some situations this shadow may be observed going before or following the satellite. On the other hand, in passing through their superior semi-circles, the satellites may be eclipsed in the same manner as our moon, by passing through the shadow of Jupiter; and this is actually the case with the first, second, and third of these bodies; but the fourth, by reason of the largeness of its orbit, passes sometimes above or below the shadow, as is the case with our moon.

The beginnings and endings of these eclip. ses are easily seen by a telescope when the earth is in a proper situation with regard to Jupiter and the sun; but when this or any other planet is in conjunction with the sun, the superior brightness of that luminary renders both it and the satellites invisible. From the time of its first appearing after a conjunction until near the opposition, only the immersions of the satel lites into his shadow, or the beginnings of the eclipses, are visible; at the opposition, only the occultations of the satellites, by going behind or coming before their primary, are observable and from the apposition to the conjunction, only the immersions, or end of the eclipses, are to be seen. This is exactly true in the first satellite, of which we can never see an immersion with its immediately subsequent emersion and it is but rarely that they can be both seen in the second; as, in order to their being so, that satellite must be near one of its limits, at the same time that the planet is near his perihelion and quadrature with the sun. With regard to the third, when Jupiter is more than forty-six degrees

:

from conjunction with, or opposition to the sun, both its immersions and immediately subsequent emersions are visible; as they likewise are in the fourth, when the distance of Jupiter from conjunction or opposition is twenty-four degrees.

JURATS, magistrates in the nature of Aldermen, for the government of several corporations. Thus we meet with the Mayor and Jurats of Maidstone, Rye, &c.

JURY, a certain number of persons sworn to inquire of and try some matter of fact, and to declare the truth upon such evidence as shall be laid before them. The

jury are sworn judges upon all evidence in any matter of fact. Juries may be divided into two kinds, common and special. A common jury is such as is returned by the sheriff, according to the directions of the statute 3 George II. cap. 25, which appoints that the sheriff's officer shall not return a separate pannel for every separate cause, but one and the same pannel for every cause to be tried at the same assizes, containing not less than forty-eight, nor more than seventy-two jurors; and their names being written on tickets shall be put into a box or glass, and when each cause is called, twelve of those persons whose names shall be first drawn out of the box shall be sworn upon a jury, unless absent, challenged, or excused. When a sufficient number of persons are impannelled, they are then separately sworn well and truly to try the issue between the parties, and a true verdict give according to the evidence.

Special juries were originally introduced in trials at bar, when the causes were of too great nicety for the discussion of ordinary freeholders. To obtain a special jury, a motion is made in court, and a rule is granted thereupon, for the sheriff to attend the master, prothonotary, or other proper officer, with his freeholder's book, and the officer is to take indifferently fortyeight of the principal freeholders, in the presence of the attornies on both sides, who are each of them to strike off twelve, and the remaining twenty-four are returned upon the pannel..

Jurors are punishable for sending for, or receiving, instructions from either of the parties concerning the matter in question.

In causes of nisi prius, every person whose name shall be drawn, and who shall not appear after being openly called three times, shall, on oath made of his having been lawfully summoned, forfeit a sum not

exceeding 51., nor less than 40s., unless some reasonable cause of absence be proved, by oath or affidavit, to the satisfaction of the judge. If any juror shall take of either party to give his verdict, he shall, on conviction, by bill or plaint, before the court where the verdict shall pass, forfeit ten times as much as he has taken; half to the King, and half to him who shall sue. A man who shall assault or threaten a juror for giving a verdict against him, is highly punishable by fine and imprisonment; and if he strike him in the court, in the presence of the judge of assize, he shall lose his hand and his goods, and the profits of his lands during life, and suffer perpetual imprison

ment.

JURY mast, whatever is set up in room of a mast that has been lost in a storm or in an engagement, and to which a lesser yard, ropes, and sails are fixed.

JUSSIÆA, in botany, so named from Antoine de Jussieu, a genus of the Decandria Monogynia class and order. Natural order of Calycanthemæ. Onagræ, Jussieu. Essential character: calyx four or five parted, superior; petals four or five; capsules four or five celled, oblong, gaping at the corners ; seeds numerous, minute. There are eleven species. These are mostly herbaceous plants, natives of North and South America, also of the East and West Indies.

JUSTICE signifies he who is deputed by the King to do right by way of judgment.

JUSTICES in eyre, in ancient times, were sent with commission into several counties to hear such causes especially as were termed pleas of the crown. And this was done for the ease of the people, who must otherwise have been hurried to the King's Bench, if the case were tco high for the county court: they differed from the justices of oyer and terminer, because they were sent upon one or for special causes and to one place; whereas the justices in eyre were sent through the province and counties of the land, with more indefinite and general commissions.

JUSTICES of gaol delivery, such as are sent with commission to hear and determine all causes appertaining to such as for any offence are cast into the gaol.

JUSTICES of nisi prius, are the same with justices of assize, for it is a common adjournment of a cause, to put it off to such a day, nisi prius justiciarii venerint ad eas partes ad capiendas assisas; and upon this elause of adjournment, they are called jus

tices of nisi prius, as well as justices of assize, by reason of the writ or action they have to deal in.

JUSTICES of oyer and terminer. As the jus tices of assize and nisi prius are appointed to try civil cases, so are the justices of oyer and terminer, and gaol delivery, to try indictments for all crimes all over the kingdom, at what are generally denominated the circuits or assizes; and the towns where they come to execute their commission are called the assize towns, and are generally the county towns.

JUSTICES of the peace, are persons appointed by the King's commission, to attend to the peace of the county where they dwell. They were called guardians of the peace till the thirty-sixth year of Edw. III, c. 12, where they are called justices. A justice of the peace must, before he acts, take the oath of office, which is usually done before some persons in the county, by virtue of a dedimus protestatem out of chancery. Sheriffs, coroners, attorneys, and proctors, may not act as justices of the peace.

The power, office, and duty of this mygistrate extends to an almost infinite number of instances, specified in some hundreds of acts of parliament, and every year accumulating. The commission of the peace does not determine by the demise of the King, nor until six months after, unless sooner determined by the successor: but before his demise, the King may determine it, or may put out any particular person, which is most commonly done by a new commission, leaving out such person's name.

Justices of the peace can only be appointed by the King's special commission, and such commission must be in his name ; but it is not requisite that there should be a special suit or application to, or warrant from the King for the granting it, which is only requisite for such as are of a particular nature, as constituting the mayor of such a town and his successors perpetual justices of the peace within their liberties, &c. which commissions are neither revocable by the King, nor determinable by his demise, as the common commission of the peace is, which is made of course by the Lord Chancellor according to his discretion.