the sole powers of his memory, and of his genius it was when he was embarrassed in his domestic affairs by a dreadful fire, that had consumed great part of his property, and forced him to quit a ruined house, every corner of which was known to him by habit, which in some measure supplied the want of sight. It was in these circumstances that Euler composed a work which alone was sufficient to render his name immortal. Some time after this, the famous oculist Wenzell, by couching the cataract, restored our author to sight; but the joy produced by this operation was of short duration. Some instances of negligence on the part of his surgeons, and his own impatience to use an organ, whose cure was not completely finished, deprived him a second time, and for ever of his sight: a relapse which was also accompanied with tormenting pain. With the assistance of his sons, however, and of Messrs. Krafft and Lexell, he continued his labours: neither the infirmities of old age, nor the loss of his sight, could quell the ardour of his genius. He had engaged to furnish the academy of Petersburgh with as many memoirs as would be sufficient to complete its acts for twenty years after his death. In the space of seven years he transmitted to the academy above seventy memoirs, and above two hundred more, left behind him, were revised and completed by a friend. Such of these memoirs as were of ancient date were separated from the rest, and form a collection that was published in the year 1783, under the title of " Analytical Works." The general knowledge of our author was more extensive than could well be expect ed in one who had pursued, with such unremitting ardour, mathematics and astro nomy as his favourite studies. He had made a very considerable progress in medical, botanical, and chemical science. What was still more extraordinary, he was an excellent scholar, and possessed in a high degree what is generally called erudition. He had attentively read the most eminent writers of ancient Rome; the civil and literary history of all ages and of all nations was familiar to him; and foreigners, who were only acquainted with his works, were astonished to find in the conversation of a man, whose long life seemed solely occupied in mathematical and physical researches and discoveries, such an extensive acquaintance with the most interesting branches of literature. In this respect, no doubt, he was much indebted to a very uncommon memory, which seemed to retain every idea that was conveyed to it, either from reading or from meditation. He would repeat the Æneid of Virgil, from the beginning to the end, without hesitation, and indicate the first and last line of every page of the edition he used. Several attacks of a vertigo, in the beginning of September, 1783, which did not prevent his computing the motions of the aerostatic globes, were however the forerunners of his mild passage out of this life. While he was amusing himself at tea with one of his grand children, he was struck with an apoplexy which terminated his illustrious career at seventy-six years of age. M. Euler's constitution was uncommonly strong and vigorous. His health was good, and the evening of his long life was calm and serene, sweetened by the fame that follows genius, the public esteem and respect that are never with-held from exem. plary virtue, and several domestic comforts which he was capable of feeling, and therefore deserved to enjoy. The catalogue of his works has been printed in fifty pages, fourteen of which contain the manuscript works. The printed ones consist of works published separately, and works to be found in the memoirs of several academies, viz. in thirty-eight volumes of the Petersburgh acts, (from six to ten papers in each volume); in several volumes of the Paris acts; in twenty-six volumes of the Berlin acts, (about five papers to each volume); in the Acta Eruditorum, in two volumes; in the Miscellanea Taurinensia; in vol. ix. of the Society of Ulyssingue; in the Ephemerides of Berlin; in the Memoires de la Société Oeconomique, for 1766. EVOLUTE, in the higher geometry, a curve, which, by being gradually opened, describes another curve. Such is the curve BCF; (Plate V. Miscel. fig. 7.) for if a thread, FCM, be wrapped about, or applied to, the said curve, and then unwound again, the point, M, thereof will describe another curve, AM M, called by M. Huygens, a curve described from evolution. The part of the thread, MC, is called the radius of the evolute, or of the osculatory circle described on the centre, C, with the radius, M C. Hence, 1. When the point, B, falls in A, the radius of the evolute, M C, is equal to the arch, BC; but if not, to A B, and the arch B C. 2. The radius of the evolute, CM, is perpendicular to the curve, A M. 3. Because the radius, M C, of the evolute continually touches it, it is evident, from its generation, that it may be described through innumerable points, if the tangents in the parts of the evolute are produced until they become equal to their corresponding arches. 4. The evolute of the common parabola, is a parabola of the second kind, whose parameter is, of the common one. 5. The evolute of a cycloid is another cycloid equal and similar to it. 6. All the arches of evolute curves are rectifiable, if the radii of the evolute can be expressed geometrically. EVOLUTION. See ALGEBRA. EVOLUTION, in the art of war, the motion made by a body of troops, when they are obliged to change their form and disposition, in order to preserve a post, or occupy another, to attack an enemy with more advantage, or to be in a condition of defending themselves the better. It consists in doublings, counter-marches, conversions, &c. A battalion doubles the ranks, when attacked in front or rear, to prevent its be ing flanked, or surrounded; for then a battalion fights with a larger front. The files are doubled either to accommodate them selves to the necessity of a narrow ground, or to resist an enemy which attacks them in flank; but if the ground will allow it, conversion is much preferable, because, after conversion, the battalion is in its first form, and opposes the file leaders, which are generally the best men to the enemy; and Likewise, because doubling the files in a new or not well disciplined regiment, they may happen to fall into disorder. EVOLVULUS, in botany, a genus of the Pentandria Tetragynia class and order. Natural order of Campanacea. Convolvuli, Jussieu. Essential character: calyx five-leaved; corolla five-cleft, rotate; capsule three-celled; seeds solitary. There are seven species, all natives of the East or West Indies. EUONYMUS, in botany, English spin dle-tree, a genus of the Pentandria Monogynia class and order. Natural order of Dumosæ. Rhamni, Jussieu. Essential character: calyx five-petalled; capsule fivesided, five-celled, five-valved, coloured; seeds calyptred, or veiled. There are eight species. These are trees or shrubs; the smaller branches, or twigs four-cornered; the leaves opposite; peduncles axillary, so litary, opposite, one-flowered, sometimes many-flowered, disposed in umbels. EUPAREA, in botany, a genus of the Pentandria Monogynia class and order. Essential character: calyx five-leaved; corolla five or twelve petalled; berry superior, one-celled; seeds very many, adhering to a free receptacle. There is only one species, viz. E. amoena, a native of New Holland and Terra del Fuego. EUPATORIUM, in botany, English hemp agrimony, a genus of the Syngenesia Polygamia Æqualis class and order. Natural order of Composite Discoideæ. Corymbiferæ, Jussieu. Essential character: calyx imbricate, oblong; style cloven half-way, long; down plumose; receptacle naked. There are forty-nine species. These are mostly tall growing perennial herbaceous plants; the greater part are natives of North America, many however from South America and the West Indies; several are found wild in the East Indies, and one only in Europe. EUPHEMISM, in rhetoric, a figure which expresses things in themselves disagreeable and shocking, in terms implying the contrary quality: thus, the Pontus, or Black Sea, having the epithet as, i. e. inhospitable, given it, by reason of the savage cruelty of those who inhabited the neighbouring countries, this name, by euphemism, was changed into that of Euxinus. In which signification nobody will deny its being a species of irony: but every euphemism is not irony, for we sometimes use improper and soft terms in the same sense with the proper and harsh. EUPHONY, in grammar, an easiness, smoothness, and elegance in pronunciation. Euphony is properly a figure, whereby we suppress a letter that is too harsh, and convert it into a smoother, contrary to the ordinary rules: of this there are abundance of examples, in all languages. EUPHORBIA, in botany, English euphorbium, spurge, a genus of the Dodecandria Trigynia class and order. Natural order of Tricoceæ. Euphorbiæ, Jussieu. Essential character: corolla four or five petalled, placed on the calyx; calyx oneleafed, bellying; capsule tricoceous. There are ninety-eight species. These are milky plants, mostly herbaceous, a few shrubby, upright for the most part, very few of them creeping; some are leafless; stems angular or tubercled, or more frequently cylindric or columnar; unarmed, or in the angular sorts resembling the upright cactuses; armed with prickles, which are either solitary or in pairs, placed in a single row on the top of the ridges. EUPHRASIA, in botany, English eyebright, a genus of the Didynamia Angiospermia class and order. Natural order of Personatæ. Pediculares, Jussieu. Essential character: calyx four-cleft, cylindric; capsule two-celled, ovate, oblong; lower anthers have a little thorn at the base of one of the lobes. There are nine species. EURYA, in botany, a genus of the Dodecandria Monogynia class and order. Essential character: calyx five-leaved, calycled; corolla five-petalled; stamina thirteen; capsule five-celled. There is but one species, viz. E. japonica, a native of Japan. EURYANDRA, in botany, a genus of the Polyandria Trigynia class and order. Natural order of Coadunatæ. Magnolia, Jussieu. Essential character: calyx fiveleaved; corolla three-petalled; filament much dilated at the tip, with twin disjoined anthers; follicles three. There is only one species, viz. E. scandens, a native of New Caledonia. EUSTACHIAN tube, in anatomy, begins from the interior extremity of the tympanum, and runs forward and inwards in a bony canal, which terminates with a portion of the temporal bone. See ANATOMY. EUSTEPHIA, in botany, a genus of the Hexandria Monogynia class and order. Corolla superior, tubular, cylindrical, bifid; nectary six cavities in the tube of the corolla; filaments tricuspidate, distinct. There is but a single species, viz. the coccinea. EUSTYLE, in architecture, a sort of building in which the pillars are placed at the most convenient distance one from another, the intercolumniations being just two diameters and a quarter of the column, except those in the middle of the face, before and behind, which are three diameters distant. EWRY, in the British customs, an office in the king's household, which has the care of the table linen, of laying the cloth, and serving up water, in silver ewers, after dinner. EXAGGERATION, in rhetoric, a kind of hyperbole, whereby things are augmented or amplified, by saying more than the truth, either as to good or bad. There are two kinds of exaggeration, the one of things, the other of words. The first is produced, 1. By a multitude of definition. 2. By a multitude of adjuncts. 3. By a detail of causes and effects. 4. By an enumeration of consequences. 5. By comparisons. And, 6. By the contrast of epithets and rational inference. Exaggeration by words is effected, 1. By using metaphors. 2. By hyperboles. 3. By synonymous terms. 4. By a collec. tion of splendid and magnificent expressions. 5. By periphrasis. 6. By repetition. And lastly, by confirmation with an oath; as for example, "Parietes, medius fidius, gratias tibi agere gestiunt." EXACUM, in botany, a genus of the Tetrandria Monogynia class and order. Natural order of Rotaceæ. Gentianæ, Jussieu. Essential character: calyx fourleaved; corolla salver-shaped, with an inflated tube; capsule two-furrowed, twecelled, many-seeded, bursting at the top. There are ten species. EXANTHEMA, among physicians, denotes any kind of efflorescence or eruption, as the measles, purple spots in the plague, or malignant fevers, &c. According to Dr. Cullen it is an order in the class pyrexia, and includes all contagious diseases, beginning with fever, and followed by an eruption on the skin. EXCELLENCY, a title anciently given to kings and emperors, but now to embassadors, and other persons, who are not qualified for that of highness, and yet are to be elevated above the other inferior dignities. In England and France the title is now peculiar to embassadors, but very common in Germany and Italy. Those it was first appropriated to, were the princes of the blood of the several royal houses; but they quitted it for that of highness, upon several great lords assuming excellency. EXCENTRIC, in geometry, a term applied to circles and spheres which have not the same centre, and consequently are not parallel; in opposition to concentric, where they are parallel, having one common cen tre. EXCENTRIC circle, in the Ptolemaic system, the very orbit of the planet itself, which it was supposed to describe about the earth. EXCENTRIC circle, in the new astronomy, a circle described from the centre of the orbit of the planet, with half the axis as a radius. EXCENTRIC place of a planet, is the very point of the orbit, where the circle of incli nation coming from the place of a planet in its orbit, falls thereon with right angles. EXCENTRICITY, in astronomy, is the distance of the centre of the orbit of a planet from the centre of the sun, that is, the distance between the centre of the ellipsis and the focus. See ASTRONOMY table. EXCEPTION to evidence, at common law, is the same as a bill of exceptions, which is a formal exception made in writing, to be signed by the judge, when any evidence is improperly refused or received, and is a record of such matter, which the judge is afterwards called upon to acknowledge in court, and then being made part of the record, it is argued in the same manner as any other point of error appearing upon the record. This proceeding is founded on the Stat. of Westminster, 2. EXCEPTION, in law, is a clause whereby the party contracting, excepts, or takes a particular thing out of a general thing granted or conveyed, and it must be something which is not inseparable from it. It must not be the whole thing granted, but part thereof only, and must be conformable, and not repugnant, to the grant, for then the exception is void. It must also be described with certainty. EXCHANGE, in political economy. The reciprocal payments of merchants are made in bills of exchange, the amount of which is expressed in the money of the country upon which they are drawn. In calculating the par of exchange, the coin of different countries is supposed to contain that quantity of gold or silver, of a determinate purity, which, agreeably to the regulations of their respective mints, it ought to contain. Thus an English guinea is supposed to contain Alb. troy of gold; and a shilling lb. of silver, each of a certain degree of fine ness. When a bill of exchange upon Lisbon can be procured in London for the same weight of gold or silver which the sum of Portuguese money for which it is drawn is supposed to contain, exchange between London and Lisbon is said to be at par; when it can be procured for less, exchange is said to be below par, or in favour of London; when more must be given, exchange is said to be above par, or against London. The value of all the bills of exchange which the merchants of London can draw upon the merchants of any other place, aust in general be regulated by the value of the consignments which they have made to that place, and consequently the course of exchange affords an indication of the state of the trade between different countries. When bills upon Lisbon, for instance, are scarce in London, and exchange consequently above par, it is a sign that London owes more to Lisbon, than Lisbon to London; and the reverse is a sign of the contrary. But there are other circumstances by which the course of exchange is very materially affected. Should the circulating coin of any country, v. g. be considerably debased, and its real value, the quantity of gold or silver which it really contains be much less than its nominal value, exchange may appear to be against a country, while actually it is in favour of it. Before the reformation of our silver coinage in the reign of William III. we are informed by Dr. Smith, the exchange between England and Holland computed by the standard of their respective mints, was 25 per cent. against England; but the current coin of England was at that time rather more than 25 per cent. below its standard value, and consequently exchange was really in favour of England. The issue of assignats during the revolution, depreciated the currency of France in a greater degree than was ever known in any other instance, and accordingly the exchange between London and Paris became between 60 and 70 per cent. against the latter place. An unfavourable state of the exchange with any country farnishes a motive for exporting commodities to it. The merchant under these circumstances can afford to sell his commodities as much cheaper as the premium which he is obliged to pay for a bill of exchange amounts to. Hence the course of exchange always tends to an equilibrium. Indeed it can never really exceed the expense of sending gold or silver bullion to the place upon which the bill is drawn ; since this is the money of the commercial world, and will every where be accepted in payment. Its apparent rise above this expense is to be ascribed to a depreciation of" the currency or some similar cause. We shall now enter more into the practical part of exchange. In treating this subject, we shall first give an idea of the nature of exchanges; in the second place we propose explaining the peculiar terms in use among merchants relative to bills; and, thirdly, we shall give examples of exchange with the principal countries in commercial intercourse with Great Britain. In transactions between a buyer and seller, both residing in the same place, it is obvious that the mode of payment is extremely simple. It takes place either in cash or by bill, and is attended with no intricacy of computation. Transactions between two towns in the same country are almost equally easy. Payment in cash is out of the question, but the seller either draws on the buyer a bill payable at the residence of the buyer, or if this residence is not a town of extensive trade, the buyer domiciles his acceptance at a place of this description; that is, he makes it payable there. The simplicity of this process arises from the money being of the same denomination in both places, and nearly of the same value. But in dealing with foreign countries, the calculation becomes less simple from the difference of denomination; and although this causes no real difference in the value of money, yet obstacles exist to the conveyance of specie, which almost always prevent money from being of equal value in two different countries at the same time. Among merchants resident in different countries, bills serve nearly the same purpose as cash to the inhabitants of the same town. They are the current coin, by which the buyer in one country repays the seller in another; they pass like money from hand to hand; and this facility of circulation would always make money of nearly equal value in two countries, whose exchange of merchandize should be nearly equal. But it seldom happens that the exchange of merchandize is equal; there is almost always a balance on one side or the other; this balance must be paid in money; and money is consequently of greatest value on the spot where payment must take place. Hence the fluctuations of exchange. These fluctuations are greater or less according to the amount of the balance to be paid, and according to the expense and difficulty of conveying specie. By the expense of conveying specie is meant the carriage and insurance; by the difficulty, is meant the hazard of evading those prohibitory regulations, which in most countries impede its exportation. So powerful is the operation of these causes, that the exchange is often high, even between neighbouring countries; for instance, during 1793, the trade between Holland and England was completely open, insurance was low, and the voyage is known to be short, yet money was worth 10 or 12 per cent. more in England than in Holland; that is, a bill on London cost on the exchange of Amsterdam between 10 and 12 per cent. more than the intrinsic value of the money. This continued until the spring of 1794, when the King of Prussia having promised to act with vigour against the French, on condition of receiving a large subsidy, the remittance of a part of that subsidy through Amsterdam caused an immediate fall in the rate of exchange between England and Holland. At other periods of the war, it has been thought advisable that government should export specie rather than turn the course of exchange against us by the formidable operation of remitting a subsidy in bills. II. Having explained the origin of fluctuations in exchange, we shall next advert to the peculiar terms, used in bill transactions. Usance. This term, derived like many of our mercantile phrases from the Italian, (usanzia) nieans the customary period at which bills used to be drawn from one particular country on another. This period between Holland and England was a month. "At two usance pay to order of, &c." in such a bill means, "at two months after date pay to order, &c." Between England and Hamburgh, and between England and France, usance is also a month. Between England and Portugal or Spain, it is two months; and between England and Italy it is three months. Its length evidently increases with the distance of two countries from each other, and was regulated by the time formerly required for the conveyance of bills. In the American and West India trades, the phrase is not known, and the common term of a bill is sixty or ninety days after sight. The word usance continues to be employ. ed only from conformity to ancient custom; for it has no signification which would not be equally well expressed by the more ge nerally intelligible phrase of months or days. Days of grace. It has been judged fit by the legislatures of different countries, to consider the acceptance of a bill of exchange as an engagement decidedly obligatory on the acceptor. If he fail in paying it, he not only loses his credit, but the holder of the bill may, in most countries, arrest either his person or his property. The policy of these enactments is to give free currency to bills of exchange, by satisfying the |