a small town of Livonia, situated on the south-side of the river Aa, about ten German leagues southwest of Dorpt.

ÆACEA, in Grecian antiquity, solemn festivals and games celebrated at Ægina, in honour of Æacus; who, on account of his justice upon earth, was thought to have been appointed one of the judges in hell.

ÆCHMALOTARCHA, in Jewish antiquity, the title given to the principal leader or governor of the Hebrew captives residing in Chaldea, Assyria, and the neighbouring countries.

ÆDES, in Roman antiquity, besides its more ordinary signification of a house, likewise signified an inferior kind of temple, consecrated to some deity.

ÆDICULA, a term used to denote the inner part of the temple, where the altar and statue of the deity stood.

ÆDILATE, the office of ædile, sometimes called æditia. See the next article.

ÆDILE, in Roman antiquity, a magistrate whose business it was to superintend buildings of all kinds, but more especially public ones, as temples, aqueducts, highways, bridges, &c.

ÆEDITUS, in Roman antiquity, an officer belonging to the temples, who had the charge of the offerings, treasure, and sacred utensils. The female deities had a woman-officer of this kind called æditia.

ÆGAGROPILA, a ball composed of a substance resembling hair, generated in the stomach of the chamois-goat. This ball is of the same nature with those found in cows, hogs, &c.

ÆGILETHRON, in botany, an obsolete name of the mercurialis. See MERCURIALIS.

ÆGIAS, among physicians, a white speck on the pupil of the eye, which occasions dimness of sight.

ÆGILOPS, among physicians, a species of abscess. See Surgery, title, Of abscess, or tumors.

ÆGILOPS, in botany, a genus of the polygamia monoeia class. There are five species of this plant, which is a kind of grass, viz. the ovata, caudata, squarrota, triuncialis, and incurvata, only the last of which is a native of Britain, and grows by the sea-shore. The English name is sea-hard-grass.

ÆGINETIA, in botany, a synonyme of a species of orobanche. See OROBANCHE.

ÆGIPAN, in heathen mythology, a denomination given to the god Pan, because he was represented with the horns, legs, feet, &c. of a goat.

ÆGIS, in heathen mythology, is particularly used for the shield or cuirass of Jupiter and Pallas.

ÆGIUCHUS, in heathen mythology, a surname of Jupiter. piter, given him on account of his having been suckled by a goat.

ÆGLEFINUS, or Haddock, in ichthyology, a species of the gadus. See Gadus.

ÆGOCEPHALUS, in ornithology, an obsolete name of a species of tringa. See Tringa.

ÆGOCERAS, in botany, an obsolete name of a species of ononis. See Ononis.

ÆGOCERATOS, in botany, a synonyme of the hugonia. See Hugonia.

ÆGOLETHRON, in botany, an obsolete name of the rhododendron hirtum. See Rhododendron.

ÆGONICHUS, in botany, an obsolete name of the lithospermum. See Lithospermum.

ÆGOPHTHALMUS, a name given to any of the semipellucid gems with circular spots in them, resembling the eye of a goat.

ÆGOFOGON, in botany, an obsolete name of the tragopodon. See Tragapodon.

ÆGOPODIUM, a genus of the pentandria digynia clas. There is but one species of this plant, which is a native of Britain and other parts of Europe. The English name is herb gerard, gout-weed, or ashweed.

ÆGYPTIACUM, in pharmacy, the name of several detergent ointments.

ÆGYPTILLA, the name of a stone variegated with different colours, and said to be capable of giving water the colour and taste of wine.

ÆINAUTAE, in antiquity, a denomination given to the senators of Milatia, because they held their deliberations on board a ship, and never returned to land till matters had been agreed on.

ÆLURUS, in Egyptian mythology, the deity or god of cats; represented sometimes like a cat, and sometimes like a man with a cat's head.

ÆNEATORES, in Roman antiquity, a general name for the musicians of an army.

ÆNIGMA, denotes any dark saying, wherein some well-known thing is concealed under obscure language.

ÆNGMATOGRAPHY, or Ænigmathology, the art of resolving, or making enigmas.

ÆOLIC, in a general sense, denotes something belonging to Æolis.

Æolic dialect, among grammarians, one of the five dialects of the Greek tongue, agreeing in most things with the Doric dialect. See Doric.

Æolic verse, in prosody, a verse consisting of an iambus, or spondees; then of two anapests, separated by a long syllable; and lastly, of another syllable. Such as,

O stelliferi conditor orbis.

ÆOLIPILE, a hollow metallic ball with a slender neck, or pipe; which after being filled with water, and a great degree of heat applied to it, the water issues out with great velocity in the form of an elastic vapour. See Pneumatics.

ÆOLIS, in ancient geography, a country lying upon the western coast of Asia Minor.

ÆOLUS, the god of the winds.

ÆON, signifies the age or duration of any thing.

ÆON, among the Platonists, was used to denote any virtue, attribute, or perfection.

Æon, in mythology, the first woman, according to the Phoenician writers.

Æon, among anatomists, an obsolete name for the spinal marrow.

ÆONIAN, in botany, an obsolete name of the sedum majus. See Sedum.

ÆRA, in chronology, a series of years commencing from a certain fixed point of time, called an epocha; thus we say, the Christian era, that is, the number of years elapsed since the birth of Christ. See Astronomy, Of the division of time.

Æra of Nabonassar. See Nabonassar.

Æra of the Hegira. See Hegira.

Ærarium, in Roman antiquity, the treasury or place where the public money was deposited.

Ærarium privatum, was the emperor's privy purse, or place where the moneys arising from his private patrimony were deposited.

Æarius, in a general sense, denotes any person employed in coining or managing the public monies.

Æarius was more particularly used by the Romans for a degraded citizen, whose name had been struck off the list of his century.

The æarii were so called on account of their being liable to all the taxes and other burdens of the state, without enjoying any of its privileges. Hence, inter ararios referri, was a more severe punishment than tribu moveri.

Ærial, in a general sense, denotes something partaking of the nature of air; thus, aerial substance, aerial particles, &c.

Ærians, in church-history, a branch of Arians, who, to the doctrines of that sect, added some peculiar dogmas of their own; as, that there is no difference between bishops and priests; a doctrine maintained by many modern divines, particularly of the presbyterian and reformed churches.

Ærica, in ichthyology, a synonyme of the clupea herengus, or herring. See Clupea.

Flor Æris, among alchemists, small scales procured from copper melted by a strong heat; it is sometimes used for ærgo or verdigris.

Aerography signifies a description of the air, especially of its dimensions, and other most obvious properties; in which sense it differs but little from aerology, which is a scientific account of the nature and less obvious properties of air. See Pneumatics.

Aeromancy, a species of divination performed by means of air, wind, &c. It is also used for the art of foretelling the various changes of the air and weather, by means of barometers, hygrometers, &c.

Aerometry, the art of measuring the motion, gravity, elasticity, rarefaction, condensation, &c. of air. See Pneumatics.

Aerophobia, among physicians, signifies the dread of air.

Aerophylacea, a term used by naturalists for caverns or reservoirs of air, supposed to exist in the bowels of the earth. ÆSTUARIA, in geography, denotes an arm of the sea, which runs a good way within land. Such is the Bristol channel, and many of the friths of Scotland.

ÆSTUARIES, in ancient baths, were secret passages from the hypocaustum into the chambers. See Bath, and Hypocaustum.

ÆSTUARY, among physicians, a vapour-bath, or any other instrument for conveying heat to the body.

ÆTH, or Ath, a strong little town in the Austrian Netherlands, and province of Hainault, situated on the river Dender, about twenty miles S.W. of Brussels.

ÆTHALE, a term used by the ancients for the cadmia fornacum. See Cadmia.

ÆTHALIES, a name given by the Greeks to the sedum. See Sedum.

ÆTHER, the name of an imaginary fluid, supposed by several authors, both ancient and modern, to be the cause of gravity, heat, light, muscular motion, sensation, and, in a word, of every phenomenon in nature. Anaxagoras maintained that ether was of a similar nature with fire; Perrault represents it as 7200 times more rare than air; and Hook makes it more dense than gold itself. Whoever has an inclination to know the various hypotheses concerning æther, may consult Shebbeere, Perrault, Hook's posthumous works, Acta Erud. Lips. 1716, Bernouilli's Cogitatio de gravitate aetheris, &c., &c.

Before the method of philosophizing by induction was known, the hypotheses of philosophers were wild, fanciful, ridiculous. They had recourse to æther, occult qualities, and other imaginary causes, in order to explain the various phenomena of nature: But since the days of the great Lord Verulam, who may be styled the parent of genuine philosophy, a contrary course has happily been followed. He convinced the world, that all knowledge must be derived from experiment and observation; and that every attempt to investigate causes by any other means must be unsuccessful. Since his time, the best philosophers have followed the track which he pointed out. Boyle, Locke, Newton, Hales, and a few others, in little more than one century, have improved and extended science far beyond what the accumulated force of all the philosophers since the creation had been able to effectuate: A striking proof both of the comprehensive genius of Bacon, and of the solidity of his plan of investigation.

It must indeed be acknowledged, that there is a propensity in the human mind, which, unless it be properly restrained, has a direct tendency both to corrupt science, and to retard our progress in it. Not contented with the examination of objects which readily fall within the sphere of our observation, we feel a strong desire to account for things which, from their very nature, must, and ever will, elude our researches. Even Sir Isaac Newton himself was not proof against this temptation. It was not enough that he had discovered the nature of light and colours, the application of gravity to the motions of the heavenly bodies, &c.; he must go further, and attempt to assign the cause of gravity itself. But, how does he proceed in this matter? Not in the the way of experiment, which had led him to his former discoveries, but in the way of conjecture, which will never lead any man to truth. He had recourse to a subtle elastic æther, not much different from that of the ancients, and by it accounted for every thing he did not know, such as the cause of gravitation, muscular motion, sensation, &c.

Norwithstanding the reputation of Sir Isaac, philosophers have generally looked upon this attempt as the foible of a great man, or, at least, as the most useless part of his works; and accordingly peruse it rather as a dream or a romance, than as having any connection with science. But we are sorry to find, that some late attempts have been made to revive this doctrine of æther, particularly in a dissertation De ortu animalium caloris, published in May last.

As the revival of an old doctrine becomes in some measure a new one, we shall plead no other apology for inferring a specimen of the method of reasoning employed in this dissertation.

The author makes frequent use of a species of argument termed dilemma by logicians. For example, in the first part of the work, after endeavouring to prove that animal heat cannot be owing to fermentation, the motion of the fluids, and other causes that have usually been assigned, he draws this conclusion:

"If none of these causes are sufficient to produce the effect; therefore, by dilemma," says he, "it must be sought for in the nature and action of the nerves."

This is a new species of dilemma: — If the author had proved, that the cause of heat in animals could not possibly exist anywhere, but either in fermentation, the motion of the fluids, &c. or in the nerves, after having disproved its existence in all the rest, his conclusion in favour of the nerves would have been just; but, as he has not so much as attempted this, the conclusion is not only false, but ridiculous.

However, upon the authority of this dilemma, the author first gives what he calls a Compend of a new doctrine concerning the nerves, and then proceeds to inquire in what manner the nerves produce animal heat: He tells us, "That thought (cogitation) and sensation depend upon impulses either on the extremities of the nerves, or the sensorium commune, and the consequent motions produced by these impulses: That these motions are so quick, as to be almost instantaneous: That as all motion is mechanical; therefore thought, sensation, and muscular motion, must likewise be mechanical: That such quick motions cannot be produced without the intervention of some extreme ly elastic power; and, as Sir Isaac Newton has shown, that the impulses which occasion the different sensations must be owing to an elastic power; therefore the muscular motions of animals must be occasioned by the oscillations of some elastic power."

"But," says he, "as this elastic power cannot exist in the solid nervous fibres, nor in any inelastic fluid; therefore, by dilemma, it must exist in an elastic fluid; and hence also, by the former dilemma, this elastic fluid must be seated, either in the nerves, or in their medullary substance."

Here again the author calls Sir Isaac into his assistance.—"What confirms this opinion," says he, "is the Newtonian æther, which pervades all nature, and which, with a few variations in its modification, Sir Isaac has shown to be the cause of cohesion, elasticity, gravity, electricity, magnetism, &c. in the following manner: 1. As the rays of light, when reflected, do not touch the solid parts of bodies, but are reflected a little before they reach them, it is plain that the æther not only fills the pores of bodies, but likewise floats upon their surfaces; and hence it becomes the cause of attraction and repulsion.—2. All metals, and inelastic fluids, are non-electrics; on the other hand, all solid bodies, metals excepted, are electrics, i.e. proper for accumulating æther. But æther, thus accumulated in such a variety of bodies, may produce various motions in the parts of these bodies, without inducing any change in the bodies themselves. Hence æther, with some variations in its modification, is sufficient to account for all the phenomena of electricity. 3. As iron, by accumulating æther around it, exhibits all the wonders of magnetism; so this magnetic æther is more analogous to the nervous æther of animals than any other kind of it. For, as the magnetic æther passes along iron without changing any part of the iron; so the nervous æther, in like manner, passes along the medullary substance of the nerves, and excites motion in any part, that is continuous with them, without inducing any change in the nerves.—4. The irritability and life of plants, which very much resemble those in animals, cannot be explained by any inelastic cause, and must therefore be attributed to an ætherial one.

Lastly, As the common æther is differently modified in each of the substances above taken notice of, and also produces various motions or effects peculiar to each, it likewise varies and has some peculiar qualities when residing in animal bodies; so that the nervous or animal æther is not exactly the same, but differs in some respects from those species of æther which give rise to cohesion, gravity, magnetism, electricity," &c.

Having thus explained the nature and qualities of æther, our author starts a very important question, viz. "Whence is æther derived? and whether does it leave any body after having once got possession of it?" In answer to this, he observes, "That certain bodies have the power of collecting the electrical matter from every circumjacent body, and of accumulating it in their pores and on their surfaces, but do not suffer it again to transmigrate into any other body. There are other substances of an opposite nature, which do not accumulate the electric matter, but instantly allow it to pass into others, unless prohibited by an electric. Hence," says he, "nothing more is necessary for substances of the former kind, but to be in such circumstances as allow them to accumulate the electric matter. In the same manner," proceeds our author, "the nervous æther, which is diffused through every part of nature, flows..." flows copiously into the medullary part of the nerves, when no obstacle stands in its way; but, when once it has got there, it keeps firm possession, and never afterwards leaves it. Now," says he, "a quan- tity of ether probably constitutes one of the stami- nal parts of animal bodies, and increases in propor- tion to their age and growth: For nothing is more ridiculous than to suppose that what is commonly called the nervous fluid can be daily wasted by la- bour and exercise, and daily repaired by a new se- cretion from the brain. To refute this vulgar no- tion, nothing more is necessary than to say, That it is one of Boerhaave's theories, and must be false, as all Boerhaave's other theories have been proved to be ill-founded! But ether is of a more fixed and determinate nature; whenever it gets possession of any substance, it never forsakes it, unless the texture and constitution of the body itself be chan- ged. Hence," continues our author, "the ether of an acid body remains as long as the body conti- nues to be acid; the same observation holds with regard to the ether of an alkaline body: But, if these two be blended together into a neutral salt, the ether must likewise be changed into a neutral; and therefore, in the formation of the medullary or staminal part of animals, the ether which before belonged to, or had the properties of some other sub- stance, is instantaneously changed into animal ether, and remains so till the dissolution of that animal."

Our author next observes, "That bodies require to be in a certain state or condition in order to the for- mation of an ether that is proper for them. This condition of bodies is called an excited state: Thus, as sulphur, when fluid, does not receive the electric matter, but, when solid, instantly receives it; in the same manner, the nerves, though properly formed, do not admit an ether adapted to their nature, unless they be in an excited state. Hence," says he, "the ether of a dead, and that of a living person, are very different, although the texture and figure of the nerves be the same. The state neces- sary for constituting the ether of a living animal, seems to depend on heat and moisture; because these things are absolutely necessary in the constitution of life: And hence," concludes our author, "the ex- cited state of the nerves depends on heat and mois- ture. There are also certain circumstances," says he, "which contribute to render the state of the nerves more or less apt for accumulating ether: A spasmodic fever, for example, renders the nerves of the whole body less pervious to the motion of the ether; and hence, in cases of this nature, health, and all the vital functions, must be injured."

"There," our author observes, "are the outlines of a new doctrine concerning the nature and func- tions of the nerves;" and, upon this foundation, proceeds to give his new theory of animal heat.

"From the foregoing reasoning," says he, "the heat, as well as all the functions of animals, seem to be occasioned by the oscillations of the nervous ether betwixt the extremities of the sentient nerves and the brain, or, more properly, betwixt the brain and muscles. But electrical ether, as above ob- served, varies a little from common ether; all in- elastic fluids, as was likewise formerly remarked, are non-electrics; and all solid bodies, metals ex- cepted, are electrics: These circumstances," says our author, "seem to be owing to the oscillations of the electric matter in bodies. In the same manner," says he, "the nature of animals may be such, and the nerves may be so constituted, as to form an ether ad- apted to their nature, and to excite those oscillations which occasion animal heat. The wonderful effects of heat and cold upon the nerves," continues our author, "confirms this theory: Every action, and even life itself, requires a certain degree of heat; for, as the heat of the external air is so variable, it was absolutely necessary that animal bodies should be endowed with the faculty of producing a degree of heat suited to their nature, independent of ex- ternal circumstances: Hence we see the reason why the degree of heat so seldom varies in the same spe- cies of animals. However, although the nervous ether is always ready for exciting heat by its oscil- lations; yet, in order to bring about this effect suc- cessfully, external stimuli are necessary, otherwise the ether would be in danger of stagnating, which would occasion sleep, a pallid, and, last of all, death.

The most permanent of these stimuli is the pulsa- tion of the arteries; which is the reason why heat is so connected with the circulation of the blood, and why many authors have mistaken it for the true cause of animal heat."

Our author now concludes with observing, "That by his theory, the varieties of heat in different parts of the body, the heat and flushing of the face from shame, and all the other phenomena of heat in ani- mal bodies, admit of a better explanation, than by any other theory hitherto invented."

Having thus given a pretty full account of an at- tempt to explain the most abstruse operations of na- ture, as nearly as possible in the very words of the author, we cannot deny ourselves the liberty of mak- ing a few observations.

To give a formal refutation of this author's reason- ing, is no part of our plan. It is, perhaps, wrong to say that he has reasoned; for the whole hypothet- ical part of his essay is a mere farrago of vague affir- mations, non-entities, illogical conclusions, and extra- vagant fancies. His ether seems to be an exceedingly tractable sort of substance: Whenever the qualities of one body differ from those of another, a different mo- dification of ether at once solves the phenomenon. The ether of iron must not, to be sure, be exactly the same with the nervous ether, otherwise it would be in danger of producing sensation in place of mag- netism. It would likewise have been very improper to give the vegetable ether exactly the same quali- ties with those of animal ether; for, in such a case, men would run great risk of striking root in the soil, and trees and hedges might eradicate and run about the fields. Nothing can be more ludicrous than to see a writer treating a mere ens rationis as familiarly as if it were an object of our senses: The notion of compounding the ether of an acid and that of an alkali, in order to make a neutral of it, is completely ridiculous. But if men take the liberty of substituting names in place of facts and experiments, it is an easy matter to account for any thing.

By this method of philosophising, obscurity is forever banished from the works of nature. It is impossible to gravel an ætherial philosopher. Ask him what questions you please, his answer is ready:—"As we cannot find the cause anywhere else; ergo, by dilemma, it must be owing to æther!" For example, ask one of those sages, What is the cause of gravity? he will answer, "This æther! Ask him the cause of thought, he will gravely reply, "The solution of this question was once universally allowed to exceed the limits of human genius: But now, by the grand discoveries we have lately made, it is as plain as that three and two make five:—Thought is a mere mechanical thing, an evident effect of certain motions in the brain produced by the oscillations of a subtle elastic fluid called æther!" This is indeed astonishing!

Such jargon, however, affords an excellent lesson to the true philosopher. It shows to what folly and extravagance mankind are led, whenever they deviate from experiment and observation in their inquiries into nature. No sooner do we leave these only faithful guides to science, than we instantly land in a labyrinth of nonsense and obscurity, the natural punishment of folly and presumption.

When endeavouring to account for that propensity in the human mind which prompts us to attempt the solution of things evidently beyond our reach, we recollected a passage in Swift's works, which explains it in the most satisfactory manner.

"Let us next examine (says the Dean) the great introducers of new schemes in philosophy, and search till we can find from what faculty of the soul the disposition arises in mortal man, of taking it into his head to advance new systems, with such an eager zeal, in things agreed on all hands impossible to be known; from what seeds this disposition springs, and to what quality of human nature these grand innovators have been indebted for their number of disciples; because it is plain, that several of the chief among them, both ancient and modern, were usually mistaken by their adversaries, and indeed by all except their own followers, to have been persons crazed, or out of their wits; having generally proceeded, in the common course of their words and actions, by a method very different from the vulgar dictates of unrefined reason; agreeing, for the most part, in their several models, with their present undoubted successors in the Academy of modern Bedlam. Of this kind were Epicurus, Diogenes, Apollonius, Lucretius, Paracelsus, Des Cartes, and others; who, if they were now in the world, tied fast, and separated from their followers, would, in this undistinguishing age, incur manifest danger of phlebotomy, and white, and chains, and dark chambers, and straw. For what man, in the natural state or course of thinking, did ever conceive it in his power to reduce the notions of all mankind exactly to the same length, and breadth, and height of his own? Yet this is the first humble and civil design of all innovators in the empire of reason.—Now, I would gladly be informed, how it is possible to account for such imaginations as these in particular men, without recourse to my phenomenon of vapours, (i.e. æther), ascending from the lower faculties to overshadow the brain, and there diffusing into conceptions, for which the narrowness of our mother-tongue has not yet assigned any other name besides that of madness or frenzy. Let us therefore now conjecture how it comes to pass that none of these great projectors do ever fail providing themselves and their notions with a number of implicit disciples; and I think the reason is easy to be assigned.—For there is a peculiar string in the harmony of human understanding, which, in several individuals, is exactly of the same tuning. This if you can dextrously screw up to its right key, and then strike gently upon it, whenever you have the good fortune to light among those of the same pitch, they will, by a secret necessary sympathy, strike exactly at the same time. And in this one circumstance lies all the skill or luck of the matter: For if you chance to jar the string, among those who are either above or below your own height, instead of subscribing to your doctrine, they will tie you fast, call you mad, and feed you with bread and water. It is therefore a point of the nicest conduct, to distinguish and adapt this noble talent with respect to the difference of persons and of times.—For, to speak a bold truth, it is a fatal miscarriage to ill to order affairs as to pass for a fool in one company, when in another you might be treated as a philosopher: Which I desire some certain gentlemen of my acquaintance to lay up in their hearts as a very reasonable innuendo."

We would not have dwelt so long upon this article, had it not been to guard, as far as our influence extends, the minds of those who may be unacquainted with the genuine principles of philosophy, from being led into a wrong track of investigation.

Æther, in chymistry, a name given to any volatile spirit. The spirit which generally goes by that name is procured by distilling spirit of wine with oil of vitriol, and then precipitating with an alkali. See Chemistry.

Ætherial, an epithet for anything partaking of the nature of æther.

Æthiopis, in botany, a synonyme of a species of salvia. See Salvia.

Æthiops mineral, a preparation of mercury made by rubbing equal quantities of quicksilver and flour of sulphur in a mortar, till the mercury wholly disappears, and a fine black powder remains.

Æthiops albus, a preparation of mercury made by rubbing rubbing quicksilver with a double quantity of crab's eyes or candied sugar, till it is extinguished.

ÆTHIOPS of Dr Plumber, a medicine prepared by levigating sulphur auratum antimonii with an equal quantity of calomel.

ÆTHUSA, in botany, a genus of the pentandria digynia clas. The volucrum is dimidiated, triphyllous, and pendulous. There is but one species, viz., the æthusa synapium, or fools-parsley, a native of Britain.

ÆTIANS, in church-history, a branch of Arians who maintained, that the Son and Holy Ghost are in all things dissimilar to the Father.

ÆTILOGY, that branch of physic which assigns the causes of diseases.

ÆTITÆ, or ÆTITÆS, a name given to pebbles or stones of any kind which have a loose nucleus rattling in them, called, in English, Eagle-stones.

ÆTNA, a famous burning mountain or volcano of Sicily. It is one of the highest mountains of the whole island, and situated on the eastern coast not far from Catania. It is remarked of this mountain, that its eruptions ceased immediately when those of Vesuvius began. See Vesuvius.

Ætna salt, a name used by some authors for saline substances, found near the opening of mount Ætna and other volcanos.

ÆTOLARCHA, in Grecian antiquity, the principal magistrate or governor of the Ætolians.