wood, and its diameter should be somewhat less than that of the machine. On each side of the scaffold are erected two masts HI, KL, each of which has a pulley at the top, and rendered firm by means of ropes KG, KP, HP, HG. The machine to be filled is to be placed on the scaffold, with its neck round the aperture of the well. The rope passing over the pulleys of the two masts, serves, by pulling its two ends, to lift the balloon about 15 feet or more above the scaffold; and the rest of the machine is represented by the dotted lines in the figure MNO. The machine is kept steady, and held down, whilst filling, by ropes passing through loops or holes about its equator; and the ropes may easily be disengaged from the machine, by slipping them through the loops when it is able to sustain itself. The proper combustibles to be lighted in the well, are those which burn quick and clear, rather than such as produce much smoke; because it is hot air, not hot smoke, that is required to be introduced into the machine. Small wood and straw have been found to be very fit for this purpose. Mr Cavallo observes, as the result of many experiments with small machines, that spirit of wine is upon the whole the best combustible; but its price may prevent its being used for large machines. As the current of hot air ascends, the machine will soon dilate, and lift itself above the scaffold and gallery which was covered by it. The passengers, fuel, instruments, &c. are then placed in the gallery. When the machine makes efforts to ascend, its aperture must be brought, by means of the ropes annexed to it, towards the side of the well a little above the scaffold; the fire place is then suspended in it, the fire lighted in the grate, and the lateral ropes being slipped off, the machine is abandoned to the air. (See Montgolfier's balloon, Plate III.) It has been determined by accurate experiments, that only one-third of the common air can be expelled from these large machines and therefore the ascending power of the rarefied air in them can be estimated as only equal to half an ounce avoirdupoise for every cubic foot.

The conduct of balloons, when constructed, filled, and actually ascending in the atmosphere, is an object of great importance in the practice of aerostation. The method generally used for elevating or lowering the balloons with rarefied air, has been the increase or diminution of the fire: and this is entirely at the command of the aeronaut, as long as he has any fuel in the gallery. The inflammable air balloons have been generally raised or lowered by diminishing the weight in the boat, or by letting out some of the gas through the valve but the alternate escape of the air in descending, and discharge of the ballast for ascending, will by degrees render the machine incapable of floating; for in the air it is impossible to supply the loss of ballast, and very difficult to supply that of inflammable air. These balloons will also rise or fall by means of the rarefaction or condensation of the enclosed air, occasioned by heat and cold. It has been proposed to aid a balloon in its alternate motion of ascent and descent, by annexing to it a vessel of common air, which

might be condensed for lowering the machine, and rarefied again, by expelling part of it, for raising the machine: But a vessel adapted to this purpose must be very strong; and, after all, the assistance afforded by it would not be very considerable. M. Meunier, in order to attain this end, proposes to enclose one balloon filled with common air in another filled with inflammable air as the balloon ascends, the inflammable air is dilated, and of course compresses the internal balloon containing the common air: and by diminishing its quantity, lessens its weight. If it should be necessary to supply this loss, he says it may be easily done by a pair of bellows fixed in the gallery. Others have proposed to annex a small machine with rarefied air to an inflammable air balloon by ropes, at such a distance that the fire of the former might not affect the inflammable air of the latter: the whole apparatus, thus combined, of balloons formed on the two principles of heated and inflammable air, might be raised or lowered by merely increasing or diminishing the fire in the lower balloon.

Wings or oars are the only means of this sort that have been used with some success: and, as Mr Cavallo observes, they seem to be capable of considerable improvement; although great effects are not to be expected from them, when the machine goes at a great rate. The best methods of moving those wings are by the human strength applied similarly to the oars of a waterman. They may be made in general of silk stretched between wires, tubes, or sticks; and when used, must be turned edgewise when they are moved in the direction in which the machine is intended to be impelled, but flat in the opposite direction. but flat in the opposite direction. Fig. 8. is the representation of one of Mr Blanchard's wings. Fig. 9. is one of those used by Mr Lunardi, which consists of many silk shutters or valves, ABCD, DECF, &c. every one of which opens on one side only, viz. ADBC opens upon the line AB, DECF opens upon the line DC, &c. In consequence of this construction, this sort of oars does not need being turned edgewise. Fig. 10. represents one of the wings used by the brothers Roberts in the aerial voyage of the 19th September 1784; and fig. 11. represents one of the wings constructed by Count Zambeccari, which consists of a piece of silk stretched between two thin tubes set at an angle; but these wings are so contrived as to turn edgewise by themselves when they go on one direction. Öther contrivances have been made to direct aerostatic machines, but they have mostly been invented to effect a power upon them as upon a ship. It appears, however, that they can have no effect when a machine is only moved by the wind alone, because the circumambient air is at rest in respect to the machine. The case is quite different with a vessel at sea, because the water on which it floats stands still whilst the vessel goes on; but it must be time and experience that can realize the expectations suggested by these contrivances.

A view of the principles of this science, and of the more recent aerial voyages, is given under the article AERONAUTICS in the SUPPLEMENT.

AERSCHOT,

Aerschot

AERSCHOT, a town of the Austrian Netherlands in the duchy of Brabant, and capital of the duchy of schines. Aerschot. It is seated on the river Demur, ten miles east of Malines or Mechlin, and eight north of Louvain. E. Long. 5. 44. N. Lat. 51.

ÆRUGINOUS, an epithet given to such things as resemble or partake of the nature of the rust of copper. ÆRUGO, in Natural History, properly signifies the rust of copper, whether natural or artificial. The former is found about copper mines, and the latter, called verdigris, made by corroding copper plates with acids.

ÆRUSCATORES, in Antiquity, a kind of strolling beggars, not unlike gypsies, who drew money from the credulous by fortune-telling, &c. It was also a denomination given to griping exactors, or collectors of the revenue. The Galli, or priests of Cybele, were called æruscatores magnæ matris; and unrgayuglaı, on account of their begging or collecting alms in the streets; to which end they had little bells to draw people's attention, similar to some orders of mendicants abroad.

AERY, or AIRY, among sportsmen. See AIRY.

ÆS UXORIUM, in Antiquity, a sum paid by bache lors, as a penalty for living single to old age. This tax for not marrying seems to have been first imposed in the year of Rome 350, under the censorship of M. Furius Camillus and M. Posthumus. At the census, or review of the people, each person was asked, Et tu ex anima sententia uxorem habes liberum quærendorum causa? He who had no wife was hereupon fined after a certain rate, called as uxorium.

Æs per et libram was a formula in the Roman law, whereby purchases and sales were ratified. Originally the phrase seems to have been only used in speaking of things sold by weight, or by the scales: but it afterwards was used on other occasions. Hence even in adaptions, as there was a kind of imaginary purchase, the formula thereof expressed, that the person adopted was bought per æs et libram.

Es Flavum, yellow copper, among the Romans, an appellation given to the coarser kinds of brass.

The ancients had different kinds of brass, as æs candidum, æs Corinthium, denoting probably different metallic alloys or mixtures.

Es Caldarium, a term used by the German mineralists, for a substance which sometimes occurs to those who work upon cobalt, and is used for making the fine blue colour called smalt.

Es Ustum, a chemical preparation, made of thin leaves of copper, sulphur, and nitre, placed stratum super stratum in a crucible, and set in a charcoal fire till all the sulphur is consumed; after which, the copper is taken out of the crucible, and reduced to powder. Some quench the leaves of copper in vinegar, and repeat the calcination.-Its principal use is in colouring glass, to which it gives a beautiful tincture. The surgeons use it as a detersive, and some have given it internally; but it is certainly a very dangerous medicine, and should be avoided.

ASCHINES, an Athenian, a Socratic philosopher, the son of Charinus a sausage-maker. He was continually with Socrates; which occasioned this philosopher to say, that the sausage-maker's son was the only

person who knew how to pay a due regard to him. Aschines. It is said that poverty obliged him to go to Sicily to Dionysius the tyrant; and that he met with great contempt from Plato, but was extremely well received by Aristippus; to whom he showed some of his dialogues, and received from him a bandsome reward. He would not venture to profess philosophy at Athens, Plato and Aristippus being in such high esteem; but he opened a school in which he taught philosophy to maintain himself. He afterwards wrote orations for the forum. Phrynicus, in Photius, ranks him amongst the best orators, and mentions his orations as the standard of the pure Attic style. Hermogenes has also spoken very highly of him. He wrote besides several Dialogues, of which there are only three extant: 1. Concerning virtue, whether it can be taught. 2. Eryxias, or Erasistratus; concerning riches, whe ther they are good. 3. Axiochus; concerning death, whether it is to be feared. M. Le Clerc has given a Latin translation of them, with notes and several dissertations, entitled Sylva Philologica.

ÆSCHINES, a celebrated Grecian orator, was born at Athens 327 years before the Christian era. According to his own account, he was of distinguished birth; according to that of Demosthenes, he was the son of a courtezan, and a humble performer in a company of comedians. But whatever was the true history of his birth and early life, his talents, which were considerable, procured him great applause, and enabled him to be a formidable rival to Demosthenes himself. The two orators, inspired probably with mutual jealousy and animosity, became at last the strenuous leaders of opposing parties. Æschines was accused by Demosthenes of having received money as a bribe, when he was employed on an embassy to Philip of Macedon. He indirectly retaliated the charge by bringing an accusation against Ctesiphon the friend of Demosthenes for having moved a decree, contrary to the laws, to confer on Demosthenes a golden crown, as a mark of public approbation. A numerous assembly of judges and citizens met to hear and decide the question: each orator employed all his powers of eloquence; but Demosthenes, with superior talents, and with justice on his side, was victorious; and Æschines was sent into exile. The resentment of Demosthenes was now softened into generous kindness; for when schines was going into banishment, he requested him to accept of a sum of money; which made him exclaim, "How do I regret leaving a country where I have found an enemy so generous, that I must despair of ever meeting with a friend who shall be like him!"

In

Eschines opened a school of eloquence at Rhodes, which was the place of his exile, and he commenced his lectures by reading to his audience the two orations which had been the cause of his banishment. His own oration received great praise; but that of Demosthenes was heard with boundless applause. so trying a moment, when vanity must be supposed to have been deeply wounded, with a noble generosity of sentiment, he said, "What would you have thought if you had heard him thunder out the words himself." -Eschines afterwards removed to Samos, where he died, in the 75th year of his age, Three of his orations only are extant. His eloquence is not without

energy,