and many other experiments manifest the same virtue, which is the cause of many phenomena. Alhazen, the Arabian, who lived about the year 1100, it seems was more inquisitive into the nature of refracs tion than former writers. But neither Alhazen, nor his follower Vitello, knew any thing of its just quantity, which was not known, to any tolerable degree of exactness, till Tycho Brahe, with great diligence, settled it. But neither did Tycho nor Kepler discover in what manner the rays of light were refracted by the atmosphere. Tycho thought the refraction was chiefly caused by dense vapours, very near the earth's surface: while Kepler placed the cause wholly at the top of the atmosphere, which he thought was uniformly dense; and thence he determined its altitude to be little more than that of the highest mountains. But the true constitution of the density of the atmosphere, deduced afterwards from the Torricellian experiment, afforded a juster idea of these refractions, especially after it was found, that the refractive power of the air is proportional to its density. By this variation in the den-, sity and refractive power of the air, a ray, of light, in passing through the atmosphere, is continually refracted at every point, and thereby made to describe a curve, and not a straight line, as it would have done were there no atmosphere, or were its density uniform.

The atmosphere, or air, has also a reflective power; and this power is the means by which objects are enlightened so uniformly on all sides. The want of this power would occasion a strange alteration in the appearance of things; the shadows of which would be so very dark, and their sides enlightened by the sun so very bright, that probably we could see no more of them than their bright halves; so that for a view of the other halves, we must turn them half round, or if immoveable, must wait till the sun could come round upon them. Such a pellucid unreflective atmosphere would indeed have been very commodious for astronomical observations on the course of the sun and planets among the fixed stars, visible by day as well as by night; but then such a sudden transition from darkness to light, and from light to darkness, immediately upon the rising and setting of the sun, without any twilight, and even upon turning to or from the sun at noon day, would have been very inconve

nient and offensive to our eyes. However, though the atmosphere be greatly assistant in the illumination of objects, yet it must also be observed that it stops a great deal of light.

The knowledge of the component parts of the atmosphere is among the discoveries of the moderns. The opinions of the earlier chemists were too vague to merit any particular notice. Boyle, however, and his contemporaries, put it beyond doubt that the atmosphere contained two distinct substances, viz. an elastic fluid, distinguished by the name of air, and water in the state of vapour. Besides these two bodies, it was supposed that the atmosphere containwhich were continually mixing with it from éd a great variety of other substances, the earth, and which often altered its properties, aud rendered it noxious or fatal. Since the discovery of carbonic acid gas by Dr. Black, it has been ascertained that this elastic fluid always constitutes a part of the atmosphere. The constituent parts of the atmosphere are, according to Mr. Murray, By measure.

Nitrogen gas.......... 77.5
Oxygen gas ... 21.0
Aqueous vapour...... 1.42
Carbonic acid gas...

By weight. 75.55

23.32

1.03

.10

.08

being combined with the water than of the nitrogen. It is difficult, even by long boiling, to expel from water the whole of the oxygen which it holds dissolved; and, if exposed again to the atmosphere, it very quickly imbibes it.

Atmospheric air is an important agent in many of the operations of nature. Besides serving as the vehicle of the distribution of water, it is, by its mobility, the great agent by which temperature is in some measure equalized, or at least its extremes moderated. Animals, as we have seen, are dependent on it for life. It is essential to respiration; in the more perfect animals its deprivation cannot be sustained for a few moments; and even in the less perfect, the abstraction of it is followed, though not so immediately, by death. Its agency depends chiefly on its oxygen, a quantity of which is spent in every inspiration in producing chemical changes in the blood. A part of its nitrogen also is consumed, while a portion of carbonic acid gas is formed and expired. Vegetable life is also in part dependent on it; it conveys water, and perhaps carbonic acid gas, and other principles, to the leaves of plants, and is thus subservient to their nutrition and growth.

ATOMICAL philosophy denotes the doctrine of atoms, or a method of accounting for the origin and formation of all things from the supposition of atoms endued with gravity and motion. The atomic physiology, according to the account given of it by Dr. Cudworth, supposes that body is nothing else but an extended bulk; and resolves, therefore, that nothing is to be attributed to it but what is included in the nature and idea of it, viz. more or less magnitude, with divisibility into parts, figure, and position, together with motion or rest; but so as that no part of body can ever move itself, but is always moved by something else. And consequently it supposes that there is no need of any thing else besides the simple elements of magnitude, figure, site, and motion, which are all clearly intelligible as different modes of extended substance to solve the corporeal phenomena by; and, therefore, not of any substantial forms distinct from the matter, nor of any other qualities really existing in the bodies with out, besides the results or aggregates of those simple elements, and the disposition of the insensible parts of bodies in respect of figure, site, and motion, nor of any intentional species or shews, propagated from the objects to our senses; nor, lastly, of

any other kind of motion or action really distinct from local motion, such as genera tion and alteration, they being neither intelligible as modes of extended substance, nor any ways necessary. Forasmuch as the forms and qualities of bodies may well be conceived to be nothing but the result of those simple elements of magnitude, figure, site, and motion, variously combined together in the same manner as syllables and words, in great variety, result from the different combinations and conjunctions of a few letters, or the simple elements of speech; and the corporeal part of sensation, particularly that of vision, may be solved only by local motion of bodies, that is, either by corporeal effluvia streaming continually from the surface of the objects, or rather, as the later and more refined atomists conceived, by pressure made froin the object to the eye, by means of light in the medium. So that the sense taking cognizance of the object by the subtle interposed medium, that is tense and stretched, (thrusting every way from it upon the optic nerves) doth by that as it were by a staff touch it. Again, generation and corruption may be sufficiently explained by concretion and secretion, or local motion, without substantial forms and qualities. And, lastly, those sensible ideas of light and colours, heat and cold, sweet and bitter, as they are distinct things from the figure, site, and motion of the insensible parts of bodies, seem plainly to be nothing else but our own fancies, passions, and sensations; however, they be vulgarly mistaken for qualities in the bodies without us.

ATRA bilis, in ancient medicine, the black bile, one of the humours of the ancient physicians; which the moderns call melancholy. Dr. Percival suggests that this disorder is occasioned by the stagnation of the gall, by which it is rendered too viscid by the absorption of its fluid parts. Bile in this state discharged into the duodenum occasions universal disturbance until it be evacuated. It brings on vomiting, purging, &c. previous to which are fever, delirium, &c.

ATRACTYLIS, in botany, a genus of the Syngenesia Polygamia class of plants, with radiated flowers and compressed seeds, coronated with a plumose down, and standing on a plane villose receptacle. There are eight species, of which we may notice the A. gummifera, gummy-rooted attractylis; root perennial, sending out many narrow leaves which are deeply sinuated, and armed with spines on the edges; these lie

close on the ground, and between them the flower is situated; it is a native of Italy and the islands of the Archipelago. It flowers in July, but the seeds never come to perfection in England.

ATRAGENE, in botany, a genus of the Polyandria Polygynia class of plants, the flower of which consists of twelve petals, and its seeds are caudated. There are five species. This genus is allied to Ranunculus, but has a double row of petals, in the outer row four large ones, in the inner many small ones, which are properly nectaries. The A. alpina may be increased by cuttings or layers, in the same manner as clematis; in a strong soil, and trained against a wall it will rise to the height of six or eight feet. The flowers appear early, and if the season prove favourable they make a handsome figure; but as this plant is apt to put out leaves very early in the spring it is frequently nipped by the frosts; as are many plants and trees of Siberia and Tartary of which this is a native.

ATRAPHAXIS, in botany, a genus of the Hexandria Digynia class of plants, the flower of which consists of two roundish, sinuated, and permanent petals; and its cup incloses a single, roundish, and compressed seed. There are two species: 1. the spinosa, a shrub that rises four or five feet high, sending out many weak lateral branches, armed with spines, and garnished with small ashcoloured leaves. The flowers come out at the ends of the shoots in clusters, each consisting of two white petals tinged with purple, included in a two-leaved calyx of a white herbaceous colour. 2. A. undulata, which sends out many slender branches, trailing on the ground; leaves about the size of those of knot-grass, waved and curled on their edges, embracing the stalk half round at their base. This is a native of the Cape.

ATRIPLEX, orach, in botany, a genus of the Polygamia Monoecia class of plants, without any flower petals; the cup of the female flower is composed of two leaves, inclosing a single and compressed seed; whereas that of the hermaphrodite flower is composed of five leaves, and incloses a single, roundish, and depressed seed. There are fourteen species.

ATROPA, in botany, a genus of the Pentandria Monogynia class of plants, the flower of which consists of a single funnelfashioned petal; the fruit is a globose berry containing two cells, wherein the seeds inclosed are numerous and kidney-shaped.

There are eight species, of which we notice in this place the A. belladonna, deadly night-shade, which has a perennial, thick, long, and branching root, sending out strong, herbaceous, upright, branching stems; the root-leaves are often a foot long, and five inches broad; peduncles axillary, one-flowered; flowers large, nodding, void of scent; calyx green; berry large, at first green, but when ripe of a beautiful shining black colour, full of purple juice; with roundish, dotted, channelled seeds, immersed in the pulp, and a glandular ring surrounding it. It is a native of Europe, particularly of Austria and England, in churchyards and on dunghills, skulking in gloomy lanes and uncultivated places; in other countries it is said to be common in woods and hedges. The qualities of this plant are malignant, and it is extremely poisonous in all its parts. Numerous instances have occurred of the berries proving fatal after causing convulsions and delirium. Buchanan relates the destruction of the army of Sweno the Dane, when he invaded Scotland, by the berries of this plant, which were mixed with the drink with which the Scots had engaged to supply the Danes. The invaders became so inebriated that the Scottish army fell on them in their sleep and slew such numbers that scarcely enough were left to carry off their king. To children the berries have often been fatal. The symptoms occur in half an hour, and consist of vertigo, great thirst, delirium, swelling, and redness of face. Vinegar liberally drank has been found efficacious in obviating the effects of the poison. See MANDRAKE.

ATROPHY, in medicine, a disease wherein the body or some of its parts do not receive the necessary nutriment, but waste and decay incessantly. See MEDI

CINE.

ATTACHING, or ATTACHMENT, in law, the taking or apprehending of a person by virtue of a writ or precept.

It is distinguished from an arrest in this respect, that whereas an arrest lies only on the body of a man, an attachment is oftentimes on the goods only, and sometimes on the body and goods; there is this farther difference, that an arrest proceeds out of an inferior court by precept only, and an attachment out of a higher court, either by precept or writ.

An attachment by writ differs from distress, insomuch that an attachment does not extend to lands, as a distress does; and a

distress does not touch the body as an attachment does.

In the common acceptation, an attachment is the apprehension of a man's body, to bring him to answer the action of the plaintiff.

ATTACHMENT out of the chancery is obtained upon an affidavit made that the defendant was served with a subpoena, and made no appearance; or it issueth upon not performing some order or decree. Upon the return of this attachment by the sheriff, quod non est inventus in balliva sua, another attachment, with a proclamation, issues; and if he appears not thereupon, a commission of rebellion.

The

ATTACHMENT out of the forest, is one of the three courts held in the forest. lowest court is called the court of attachment, or wood-mote court; the mean, swan-mote; and the highest, the justice in eyre's seat.

This attachment is by three means, by goods and chattles, by body, pledges, and mainprize, or the body only. This court is held every forty days throughout the year, whence it is called forty-days court.

ATTACHMENT of privilege, is by virtue of a man's privilege to call another to that court whereto he himself belongs, and in respect whereof he is privileged to answer some action.

ATTACHMENT, foreign, is an attachment of money or goods, found within a liberty or city, to satisfy some creditor within such liberty or city.

By the custom of London and several other places, a man can attach money or goods in the hands of a stranger to satisfy himself.

ATTAINDER, in law, is when a man has committed felony or treason, and sentence is passed upon him for the same. The children of a person attainted of treason, are, thereby, rendered incapable of being heirs to him, or to any other ancestor; and if he were noble before, his posterity are degraded and made base: nor can this corruption of blood be salved but by an act of parliament, unless the sentence be reversed by a writ of error.

ATTAINDER, bill of, a bill brought into parliament for attainting, condemning, and executing a person for high-treason.

ATTAINT, in law, a writ which lies against a jury that have given a false verdict in any court of record, in a real or personal action, where the debt or damages amount to above forty shillings.

If the verdict be found false the judgment by common law was, that the jurors meadows should be ploughed up, their houses broken down, their woods grubbed up, all their lands and tenements forfeited, &c. but by statute the severity of the common law is mitigated, where a petty jury is attainted, and there is a pecuniary penalty appointed.

But if the verdict be affirmed, such plaintiff shall be imprisoned and fined.

ATTELABUS, in natural history, a genus of insects of the order Coleoptera. Head attenuated behind; antennæ thickening towards the lip.

Of the genus Attelabus, one of the principal species is the Attelabus coryli of Linnæus, which is a smallish insect, found chiefly on hazel trees, and is black with red wing-sheaths; and a variety sometimes occurs in which the thorax is red also; it usually measures about a quarter of an inch in length. A much smaller species is the Attelabus betulæ, which is found on the birch; it is entirely of a black colour, and is remarkable for gnawing the leaves of that tree during the early part of spring, in such a manner that they appear notched on the edges. The thighs of the hind-legs in this insect are of a remarkable thickened form. The larvæ of the attelabi do not seem to have been distinctly described, but they probably bear a resemblance to those of the genus Curculio. Linnæus refers to the genus attelabus some insects which by later entomologists have been otherwise arranged: among these is the elegant species called Attelabus apiarius, so named from the mischief which its larva occasionally commits among bee-hives, destroying the young of those insects. It is about three quarters of an inch in length, and of a beautiful violetblack, with red wing-shells, marked by three black transverse bands. The whole insect is also covered with fine short black hair. It is common in some parts of France, Germany, &c. Its larva above mentioned is of a bright red colour. There are 13 specics.

ATTENDANT, in law, one that owes duty or service to another, or in some manner depends upon him, as a widow endowed of lands by a guardian, ɛhall be attendant upon him.

ATTESTATION, in military affairs, is a certificate made by some justice of the peace, within four days after the enlistment of a recruit. This certificate is to bear testimony that the said recruit has been brought

before him in conformity to the mutiny act, and has declared his assent or dissent to such enlistment; and if duly enlisted, that the proper oaths have been administered, and that the 2nd and 6th sections of the articles of war against desertion have been read to him.

ATTITUDE, in painting and sculpture, the gesture of a figure, or statue; or it is such a disposition of their parts, as serves to express the action and sentiments of the person represented.

ATTORNEY general, is a great officer under the king, created by letters patent, whose office it is to exhibit informations, and prosecute for the crown in criminal causes, and to file the bills in the exchequer, for any thing concerning the king in inheritance or profits. To him come warrants for making of grants, pardons, &c.

ATTORNIES at law, are such persons as take upon them the business of other men, by whom they are retained. By the Geo. II. cap. 23, s. 5, no person shall be permitted to act as an attorney, or to sue out any process in the name of any other person, in any courts of law, unless such person shall have been bound by contract in writing, to serve as a clerk for five years to an attorney, duly sworn and admitted in some of the said courts; and such person, during the said term of five years, shall have continued in such service, and unless such person, after the expiration of the said five years, shall be examined, sworn, admitted, and inrolled. And for every piece of vellum, parchment, or paper, upon which shall be written any such contract, whereby any person shall become bound to serve as a clerk aforesaid, in order to his admission as a solicitor or attorney, in any of the courts at Westminster, there shall be charged a stamp duty of 100l. 34 Geo. III. c. 14. And in order to his admission as a solicitor or attorney in any of the great courts of sessions in Wales, or in the counties palatine of Chester, Lancaster, or Durham, or in any court of record in England, holding pleas to the amount of 40 shillings, and not in any of the said courts of Westminster, there shall be charged a stamp duty of 501. Every attorney, solicitor, notary, proctor, agent, or procurator, practising in any of the courts at Westminster, ecclesiastical, admiralty, or Cinque-port courts, in his Majesty's courts in Scotland, the great sessions in Wales, the courts in the counties Palatine, or any other courts holding pleas to the amount of 40 shillings, or more;

shall take out a certificate annually, upon which there shall be charged, if the solicitor, &c. residing within the bills of mortality, a stamp-duty of 51. in any other part of Great Britain Sl. Persons practising after the 1st day of November, 1797, without obtaining a certificate, shall forfeit 501. and be incapable of suing for any fees. An attorney shall not be elected into any office against his will, such as constable, overseer of the poor, or churchwarden, or any office within a borough; but his privilege will not exempt him from serving in the militia, or finding a substitute. Black. Rep. 1123.

ATTRACTION, a general term, used to denote the power or principle by which bodies mutually tend towards each other, without regarding the cause or action that may be the means of producing the effect.

The philosopher Anaxagoras, who lived about 500 years before the Christian æra, is generally considered as the first who noticed this principle, as subsisting between the heavenly bodies and the earth, which he considered as the centre of their motions. The doctrines of Epicurus and of Democritus are founded on the same opinion.

Nicholas Copernicus appears to have been one of the first among the moderns, who had just notions of this doctrine.

After him, Kepler brought it still ncarer perfection; having determined that bodies tended to the centres of the larger round bodies, of which they formed a part, and the smaller celestial bodies to the great ones nearest to them, instead of to the centre of the universe: he also accounted for the general motion of the tides on the same principle, by the attraction of the moon; and expressly calls it virtus tractoria quæ in luna est; besides this, he refuted the old doctrine of the schools, "that some bodies were naturally light, and for that reason ascended, while others were by their nature heavy and so fell to the ground;" declaring that no bodies whatsoever are absolutely light, but only relatively so, and that all matter is subjected to the law of gravitation.

Dr. Gilbert, a physician at London, was the first in this country who adopted the doctrine of attraction; in the year 1600, he published a work entitled, "De Magnete Magneticisque Corporibus; which contains a number of curious things; but he did not sufficiently distinguish between attraction and magnetism.

The next after him was Lord Bacon, who, though not a convert to the Coperni