nual motion in her orbit. The word is compounded of ab from, and erro to wander, because the stars appear to wander from their true situations. This apparent motion is so minute, that it could never have been discovered by observations, unless they had been made with extreme care and accuracy; and although it naturally arises from the combination of the two causes just mentioned, yet as it was never even suggested by theorists, until it was discovered by observation, it furnishes us with one of the strongest proofs of the truth of the Copernican system. The discovery is owing to the accuracy and ingenuity of Dr. Bradley, astronomer royal: he was led to it accidentally by the result of some careful observations, which he had made with a view of determining the annual parallax of the fixed stars.

Aberration, in optics, that error or deviation of the rays of light, when inflected by a lens or speculum, whereby they are hindered from meeting or uniting in the same point, called the geometrical focus; it is either lateral or longitudinal The lateral aberration is measured by a perpendicular to the axis of the speculum, produced from the. focus, to meet the reflected or refracted ray: the longitudinal aberration is the distance of the focus from the point in which the same ray intersects the axis.

ABEYANCE, in law-books, something that only exists in expectation, or in the intendment, or remembrance of the law.

ABJURATION. A forswearing, or renouncing by oath: in the old law it signified a sworn banishment, or an oath taken to forsake the realm for

ever. In its modern, and now more usual signification, it extends to persons, and doctrines, as well as places. Thus for a man to abjure the pretender by oath, is to bind himself not to own any regal authority in the person called the Pretender, nor even to pay him any obedience, &c.

ABLUTION, à ceremonious washing of the whole, or part of the body, instituted by the several founders of the religions of the East, for the prevention of those disorders that, especially in warm climates, result from the filth in which the greater part of the people were, and still are condemned to live. For this purpose it was made a religious rite; and by an easy transition of idea, the purity of the body was made to typify the purity of the soul: an idea the more rational, as it is perhaps physically certain that outward wretchedness debases the inward mind. A frequent change of the clothes next the skin, affords, perhaps, especially in cold countries, the same advantages as ablution; and hence, in Europe, the custom has almost universally fallen into disuse. Ablution is still practised in Turkey, as well as in most other parts of the ancient continent.

ABOMASUS, a name used for the fourth stomach of ruminating beasts, or such as chew the cud. These have four stomachs: the last, where the chyle is formed, and from which the food descends into the intestines, is called the Abomasus.

ABORIGINES, Originally a proper name, given to a certain people in Italy, who inhabited the ancient Latium, or country now called Campayna di Roma. Whence this people came by the appellation is much disputed. The name is now given to

the primitive inhabitants of a country, in contradistinction to colonies, or new races of people.

ABRIDGEMENT, in a literary sense, is the compression of the matter of a work into a smaller compass than that in which it has been originally written. With respect to private abridgements and commonplace books, theorists in education have frequently taken pains to engage youth in their compilation. On this subject, however, it may be doubted whether the practice will confer any advantage, and even suspected that it may do much mischief. If the mind is desirous of acquiring a thorough knowledge of any particular subject, the notation of facts, dates, &c. will, no doubt, most effectually enable it to accomplish the purpose; but where this is not the design, the time that is devoted to the tedious task of copying one author, had better be employed in reading twenty. If, as has been said before, any minute study is the object, copying is useful; but if it be done merely to assist the memory with sentiments, terms of expression, &c. it is wrong for the habit of making memorandums, by discharging memory from its office, takes from it every opportunity of improvement.

ABSCISS, or ABSCISSA, of a conic section, or other curve, is a part or segment cut off by a line at some certain point, which is determined by an ordinate to the curve.

ABSORBENTS, calcarious earths, or other medicines which soak up the redundant humours of the body. Also, a system of vessels that absorb and convey fluids from every cavity of the body to the thoracic duct, which is their common trunk. These last are likewise denominated lymphatics, and those of the

smaller intestines, from the milky hue of the fluid in most animals, lacteals.

ABSTINENCE may be defined, the habit of refrain ing from what is either useful, agreeable, or pernicious. The Christian system more particularly enjoins the discipline of the passions, and an abstinence from those pleasures which have a tendency to degrade our nature. In England, certain days have been appointed, called vigils and fasts, in which flesh is prohibited, and fish enjoined: this, however, being more a political restriction than a religious obligation, was first enacted in the reign of queen Elizabeth, with a view to encourage our fisheries. Of the brute animals, many are remarkable for their long abstinence from food, such as the serpent, the rattlesnake, tortoise, bear, dormouse, elephant, &c. Instances may also be found of men who have been abstemious to a degree almost incredible; and experience has demonstrated that, from habit and use, the power of abstinence may be either increased or diminished.

ABYSSINIA, is bounded on the north by Nubia ; on the east by the Arabian gulf, or Red Sea, and the kingdom of Adel; on the south by the kingdoms of Ajan, Alaba, and Gingiro; and on the west by the kingdom of Gorem, and part of Gingiro. In this country the famous river Nile has its source. On the mountains the air is pretty temperate; therefore their towns and fortresses are generally placed on them; but in the valleys the heat is intense. The torrents of water in the rainy seasons wash a great deal of gold from the mountains. These seasons commence in May, and end in September. The inhabitants of this country, in

general, are of an olive complexion, tall, graceful, and well featured. Their language is the Ethiopic, which bears a great affinity to the Arabic. Gold, silver, copper, and iron, are the principal ores which abound there, but not above one third part of their gold is converted into money, or used in trade.

ACADEMICS, a sect of philosophers, who followed the doctrine of Socrates and Plato, as to the uncertainty of knowledge, and the incomprehensibility of truth. Academic, in this sense, amounts to much the same with Platonist; the difference between them being only in point of time. They who embraced the system of Plato, among the ancients, were called Academici; whereas those who did the same since the restoration of learning, have assumed the denomination of Platonists.

ACADEMY, in the modern acceptation, is a society of persons united for the pursuit of some objects of study and application, as the Royal Academy of Arts of London, and the Royal Academy of Sciences of Berlin. The term is derived from a house and gardens, once the residence of Academus, a celebrated Athenian, in which Plato and his disciples held philosophical conversations.

ACCELERATION, in mechanics, the increase of velocity in a moving body. Accelerated motion is that which continually receives fresh accessions of velocity, and is either equally or unequally accelerated. Acceleration stands directly opposed to Retardation, which denotes a diminution of velocity. See MECHANICS.

ACCENT, is 1. The manner of speaking or pronouncing. 2. The sound of a syllable. 3. The