excursions. AERO- M. Garnerin, at eleven o'clock in the evening of the 4th NAUTICS. of August, 1807. He ascended from Tivoli at Paris, under the Russian flag, as a token of the peace that Garnerin's subsisted at that time between France and Russia. nocturnal His balloon was illuminated by twenty lamps, and to obviate all dangers of communication between these and the hydrogen gas, which it might be necessary to discharge in the course of the voyage, the nearest of the lamps was fourteen feet distant from the balloon, and conductors were provided to carry the gas away in an opposite direction. After his ascent, rockets which were let off from Tivoli, seemed to him scarcely to rise above the earth, and Paris, with all its lamps, appeared a plane studded with luminous stops. In forty minutes he found himself at an elevation of 13,200 feet, when, in consequence of the dilitation of the balloon, he was under the necessity of discharging a part of the inflammable air. About 12 o'clock, when 3,600 feet from the earth, he heard the barking of dogs; about two o'clock in the morning he saw several meteors flying around him, but none of them so near as to create apprehension; at half past three he beheld the sun emerging in brilliant majesty above an ocean of clouds, and the gas being thereby expanded, the balloon soon rose 15,000 feet above the earth, where he felt the cold extremely intense. In seven hours and a half from this departure, M. Garnerin descended near Loges, forty-five leagues distant from Paris. Second nocturnal ascent. On the 21st of September, 1807, the same intrepid aeronaut undertook a second nocturnal voyage, in the course of which he was exposed to the most imminent danger. M. Garnerin, prognosticating an approaching storm from the state of the atmosphere, refused to be accompanied by a second person, who earnestly requested it. He ascended, therefore, alone from Tivoli, and was carried up, with unexampled rapidity, to an immense height above the clouds; the balloon was there dilated to an alarming degree, and M. Garnerin, having been prevented, from the impatience of the mob before his ascent, from regulating those parts of the apparatus which were meant to conduct the gas away from the lamps on its escape, was totally unable to manage the balloon; he had no alternative left, therefore, but, with one hand, to make an opening two feet in diameter, through which the inflammable air was discharged in great quantities, and with the other to extinguish as many of the lamps as he could possibly reach. The adventurer was now without a regulating valve, and the balloon, subject to every caprice of the whirlwind, was tossed about from current to current. When the storm impelled him downwards, he was obliged to cast out his ballast to restore the ascending tendency, and, at length, every resource being exhausted, no expedient was left him to provide against future exigencies. In this forlorn condition the balloon rose through thick clouds, but afterwards sunk, and the ear having struck against the ground with a violent impulse, rebounded from it to a considerable altitude. The fury of the storm dashed him against the mountains, and after many rude agitations and severe shocks, he was reduced to a state of temporary insensibility. On recovering from this perilous situation, he reached Mount Tonnere in a storm of thunder. A very short time after his anchor hooked in a tree, and in seven hours and a half after his departure, he landed at the distance of three hundred miles from Paris, which is at the rate of forty miles AEROper hour, supposing his course to have been straight. NAUTICS This is only about half the velocity with which this gentleman, in one of his excursions in this country, was conveyed from London to Colchester, a distance of sixty miles, which he passed over in three quarters of an hour. Dublin to We shall close this account of aerial excursions with Sadler's e that of our intrepid countryman, Sadler, who undertook cursion from the perilous task of passing from Dublin to Liverpool, Liverpool. on the 1st of October, 1813. He ascended from Belvidere House, about one o'clock on the above day, with the wind at south-west, and in 35 minutes had sight of the mountains in Wales; he continued in the same direction till three o'clock, when being nearly over the Isle of Man, the wind blowing fresh, he found himself approaching the Welch coast; and at four o'clock had a distinct view of the Skerry light-house, with the prospect of consummating his ardent hopes of a speedy arrival in Liverpool. The wind now shifting, he was taken off, and lost sight of land; when after hovering about a long time, he discovered five vessels beating down Channel; and in hopes of their assistance, he determined to descend with all possible expedition, and precipitated himself into the sea. In this most critical situation, he had the mortification to find that the vessels took no notice of him. Obliged, therefore, to reascend, he now threw out a quantity of ballast, and quickly regained his lofty situation to look out for more friendly aid. It was a length of time before he had the satisfaction of discovering any, but now observed a vessel which gave him to understand, by signals, that she intended to assist him. Two others also, at this time, appeared in sight, and one of them, tacking about, hoisted the Manx colours. Night coming on, he was determined to avail himself of their proffered kindness, and accordingly once more descended to the sea. Here the wind, acting upon the balloon as it lay on the water, drew the car with so much velocity that the vessel could not overtake it; and notwithstanding he used his utmost efforts, and finally tied his cloaths to the grappling iron, and sunk them to keep him steady, still the balloon was carried away so fast, that he was under the necessity of expelling the gas; upon which the car actually sunk, and he had now nothing but the netting to cling to. His perilous situation and the fear of getting entangled, deterred the men from coming near him; until in danger of being drowned, Mr. Sadler begged they would run their bowsprit through the balloon and expell the remaining gas. Having done this, and thrown out a line which he wound round his arm, he was dragged a considerable way, but was fortunately, at length, got on board nearly exhausted. The representation of the car of this balloon in its ascent, is shown in plate 2. Having given this sketch of the history and progress Practice of aeronautics, it remains for us to offer some remarks constructi relative to the art of constructing and filling aërostatic and filling machines. With respect to the form best suited for a balloon, practice seems to have confirmed the globular or elliptical, although mere theorists have contended for a far different figure. Supposing the globular form, the following method Forming has been recommended for forming the several gores the gores of which the balloon is to be composed. Referring to fig. 7, plate 1, AERONAUTICS, the breadths of each slip, FRO at the several distances from the point to the middle, Unes where it is broadest, are directly as the sines of those distances, radius being the sine of half the length of the slip, or of the distance from either point to the middle of the slip. That is, if a ABCD represent one of these gores, AB being half the circumference, or AE a quadrant, conceived to be equal to AC or AD; then will CD be to ab, as radius, or the sine of AC to the sine of A a. So that if the quadrant AE or AC be divided into any number of equal parts, as, for instance, nine, and the quadrant or 90° be divided by 9, the quotient 10 is the number of degrees in each part; and hence the arcs AC, Aa, Ac, &c. will be respectively 90°, 80°, 70°, &c. and CD being radius, the several breadths ab, cd, ef, &c. will be respectively the sines of 80°, 70°, 60°, &c. which are, in the figure, placed opposite, the radius being 1. Therefore, when it is proposed to cut out slips for a globe of a given diameter, we must compute the circumference, and make AE, or AC, equal to one quarter of that circumference, and CD of any breadth, as 3 feet, or 2 feet, or any other quantity; then multiply each of the decimal numbers set opposite the figure by the breadth of CD, so will the several products be the breadths of a b, c d, ef, &c. required. This construction, it will be observed, applies only to the spherical balloon; another, very simple in its operation, and answering to any figure whatever, is described by Mr. Evans, in the Philosophical Magazine for November, 1815. Having by one or other of the above methods formed the gores, and united them in their required form, the next object is to render the whole impervious to the gas with which they are to be filled; for which purpose the following varnish is said to answer best. In order to render linseed oil drying, boil it with two ounces of sugar of lead and three ounces of litharge for every pint of oil, till they are dissolved, which will be in about half an hour. Then put a pound of birdlime and half a pint of drying oil into an iron vessel, whose capacity should be about a gallon, and let it boil very gently over a slow charcoal fire, till the bird-lime ceases to crackle, which will be in about three quarters of an hour; then pour upon it about two pints and a half more of the drying oil, and let it boil another hour, stirring it frequently with an iron or wooden spatula. As the varnish, when boiling, and especially when nearly done, swells very much, care should be taken to remove, in those cases, the pot from the fire, replacing it when the varnish subsides, otherwise it will boil over. While the boiling is going on, the operator should occasionally examine whether it has boiled enough, which may be known by observing whether, when rubbed between two knives, and then separated from one another, the varnish forms threads between them: if it do it must then be removed from the fire. When nearly cold, add about an equal quantity of spirit of turpentine. In using the varnish the silk of the balloon must be stretched, and the varnish luke-warm. In twenty-four hours it will be dry. As the elastic resin, known by the name of Indian rubber, has been much extolled for a varnish, the following method of making it, as practised by M. Blanchard, may not prove unacceptable. Dissolve elastic resin, cut small, in five times its weight of rectified essential oil of turpentine, by keep ing them some days together; then boil one ounce of AEROthis solution in eight ounces of drying linseed oil for a NAUTICS. few minutes; strain the solution and use it warm. The car, or boat, is best made of wicker work, covered with leather, and painted; and the proper method of suspending it is by ropes proceeding from the net which goes over the balloon. The net should be formed to the shape of the balloon, and fall down to the middle of it, with various cords proceeding from it to the circumference of a circle, about twenty feet below the balloon; and from this circle other ropes should go to the edge of the boat. The meshes of the net may be small at top, against which part of the balloon the inflammable air exerts the greatest force, and increase in size as they recede from the top. All things being thus prepared, the manner of filling Filling a is as follows:-When the balloon is small, as, for small example, three or four feet in diameter, it may be filled balloon. by passing the hydrogen gas through water, by means of the apparatus represented (fig. 8, plate II). A is a bottle containing the ingredients which are to produce the gas; BCD is a tube in the form of a siphon, fastened by one extremity into the neck of the bottle, and passing through a hole in the stopper of another bottle E; it extends so far as almost to touch the bottom of this bottle, which is nearly full of water. To another hole in the cork of the bottle E, is adapted another tube, to the outward extremity of which a bladder or aperture of the balloon is tied. The inflammable air coming out of the aperture D of the tube, passes through the water of the bottle E, and thenenters into the balloon. Two small casks might be employed instead of the bottles A and E. Another apparatus for producing hydrogen gas, and conveying it into the balloon, is represented (fig. 9), where ABC is a vessel made of clay or of iron, in the form of a Florence flask, and the substance yielding gas is introduced into it, so as to occupy about four-fifths or less of its cavity. If the substance swell much by the action of the fire applied to it, a tube of brass, or first of brass and then a leaden tube, must be luted to the neck C of the vessel. The extremity of the tube is made to pass through the water of a vessel HI, and to terminate under an inverted vessel EF; to the upper aperture of which the balloon, or a tube going to the balloon, is adapted. When the part AB of the vessel is put into the fire and made red hot, the inflam mable air that is generated will come out of the tube CD, and passing through the water in the vessel, it will at last enter into the balloon G. As a considerable quantity of common air remains in the inverted vessel EF, before the operation is begun, it should have a stop-cock K, through which it may be drawn out by suction, and then the water will ascend as high as the stop-cock. The aperture of the vessel EF should be at least one foot below the surface of the water in HI, and the fire should be at a sufficient distance from the vessel HI, that the inflammable air, if any of it should escape, may not take fire and do injury. balloon.. The apparatus for filling an inflammable air balloon Filling a of a larger kind, is represented fig. 10. AA are two large tubs about three feet in diameter, and nearly two feet deep, inverted in larger vessels. At the bottom of each of the inverted vessels there is a hole, to which is adapted a tin tube E, about seven inches in diameter and seven or eight inches long. To these tubes the AERO- silken tubes of the balloon are tied; each of the tubes NAUTICS. B is surrounded by several strong casks, so regulated in number and capacity, as to be less than half full when the materials are equally distributed. In the top of each of these casks are two holes, and to one of the holes is adapted a tin tube, formed so as to pass over the edge of the tube B, and through the water, and to terminate with its aperture under the inverted tub A. The other hole, which serves for supplying the cask with materials, is stopped with a wooden plug. These tin tubes may be about three inches and a half in diameter, and the other holes may be smaller. Two masts, with a rope, &c. are used for this machine, although they are not absolutely necessary; because the balloon, by means of a narrow scaffold, or other contrivance, may be elevated above the level of the tubs AA. When the balloon is to be filled, the net is put over it, and suspended as exhibited in the figure. Having expelled all the common air from the balloon, its silk tubes are fastened round the tin tubes EE, and the materials in the casks being properly proportioned, by putting in first the iron, then the water, and lastly the vitriolic acid, the balloon will soon be inflated by the inflammable air, and support itself without the aid of the rope As the filling advances, the net is adjusted round it; the ropes proceeding from the net are fastened to the hoop MN; the boat IK, is suspended from the hoop MN, and every thing necessary for the voyage is deposited in it. When the balloon is a little more than three quarters full, the silken tubes are separated from the tin tubes, and their extremities being tied, they are placed in the boat. Finally, when the aeronauts are seated in the boat, the lateral ropes are slipped off, and the machine with its appendages ascends into the atmosphere. Proportion It would be excessively laborious, if not absoof materials. lutely impossible, to collect hydrogen gas as it exists in its natural state, therefore such artificial means as those described above, are always had recourse to as the most convenient and productive. The materials commonly consist of a solution of iron, or zinc, in sulphuric acid The iron best adapted for the purpose consists of the turnings produced by the boring of cannons; but when this cannot be obtained, chips of iron should be preferred to filings. It is of importance to attend to the purity of the metal, for rust produces hydrocarbonate, a gas specifically heavier than atmospheric air; grease also is injurious, because it resists the action of the acid. The sulphuric acid must be diluted with five or six times its weight of water; iron yields about 1700 times its own bulk of gas; therefore, four and a half ounces of iron, with the same weight of sulphuric acid, and 22 of water, will produce a cubic foot of inflammable air; and of zine six ounces, with the same quantity of acid, and 30 ounces of water, will produce a cubic foot of air. The gas is collected, as stated above, into a number of casks, which should be lined with tin. M. Garnerin, in 1802, used thirty six casks, every twelve of which communicated with a collar, and three tubes from three collars conveyed the gas into one large tube, which joined to the balloon. Professor Robertson and Sacharof, of whose voyage we have given the detail, had twenty-five vessels communicating with a collar, into each of which they put 120lbs. of iron filings, chiefly from cast iron, with 600 lbs. of water, and 120 lbs. of sulphuric acid poured over it. The filling of the balloon occupied five hours. M. Lu- NAUTIC Blanchard filled a balloon twenty-one feet in diameter AERO from only four casks, each holding 120 gallons. nardi, of whom we have also spoken, reduced his apparatus to still greater simplicity, employing only two casks, from which the gas was transmitted into the balloon without passing through the water; and in the short space of half an hour he filled the balloon by which he ascended from Edinburgh and Glasgow. The shape of this machine resembled a pear, being twenty-three feet in diameter and thirty in height. M. Blanchard used 1000 lbs. of iron and 1250 lbs. of sulphuric acid, for the production of the gas to fill a balloon of twenty-one feet. Lunardi, on the occasion just mentioned, employed 2000 lbs of each, and 12,000 lbs. of water. The latest writer on this subject, computes that this quantity should suffice for a balloon of thirty feet in diameter, which is 14,137 feet in capacity. The balloon of thirty-three feet, in which Lunardi first ascended in England, and one that ascended at Nantz about the same time, were filled from zinc instead of iron. Making allowance for the expansion of the gas during the ascent, the balloon ought never to be filled above three-fourths. There is also another method of procuring hydrogen gas, by passing water over tubes, or through tubes previously heated to redness, but there is a danger of the metal running to a slag before any considerable quantity of gas is obtained; a balloon, however, thirty-two feet in diameter, has been filled by this process in the space of eight hours. The above may, we believe, be considered to con- Theoretic tain all that has been practically ascertained upon this notions. interesting subject; and it would be useless to enter at much length into the illustration of theories, which only exist in the imagination of their respective authors. One of the greatest defects attending the machines we have been describing consists in the difficulty, perhaps we might say the impossibility, of conducting them in the atmosphere; they are immersed in strong currents of air, with which they are irresistibly borne away, in any direction, at hazard, without the navigator having it at all in his power to restrain or direct their course. When we consider that M. Garnerin was taken from London to Colchester at the rate of eighty miles per hour, any idea of force existing in the aeronaut, or in any wings or sails with which he may be furnished to direct his course, seems perfectly hopeless; yet numerous plans are frequently suggested under a view of effecting such a purpose. are by no means disposed to check the spirit of scientific pursuit, and freely acknowledge that many things are accomplished by perseverance, which, in the first instance, appeared almost as impossible as that of directing a balloon at the pleasure of the voyager; but still we must confess that our hopes of success in this case are very little removed from despair. We Mr. John Evans has published, at different times, his ideas on this subject, in Tilloch's Philosophical Magazine; and proposes to attain any desired direction by means of oblique ascents and descents, in the same manner as a ship frequently reaches its destined port, with the wind full a-head, by repeated oblique traverses. See Phil. Mag. No. 211. Sir George Cayley has also directed much of his attention to this subject, and has many ingenious speculations connected with it, published in Nicholson's AERO- Journal, and in the Philosophical Magazine; and parNAUTICS. ticularly in the former, on the construction and opera TORES. tions of parachutes. In a number of the latter work ERUSCA- for February, 1816, we have a paper by this philosopher, in which he suggests the power of steam, not only for alling the balloon, but for working machinery in it to serve for its direction; and concludes by stating, that he thinks it very possible that the lines by Darwin, with reference to the power of steam, may be eventually realized. "Soon shall thy arm, unconquer'd STEAM! afar For our own parts, we must confess that such flights of imagination seem to us to become poetry much better than philosophy. ÆRUGO (anp, air, or ether, from its blue colour), the rust or oxid of metal, particularly of copper. It is formed naturally, as in the copper mines, or artificially, as in verdigrise, and is produced by the action of vinous acid on the metal. Eruginous is an adjective that has been formed from this word. ERUGO PREPARATA, prepared verdigrise. In the Pharmacopeia Londinensis this is the basis of the unguentum æruginis. ÆRUSCATORES, in Antiquity, from the Latin æruscari, to beg. A sort of vagabonds, whose character appears to have answered to that of our gypsies. Certain priests of the goddess Cybele were also called @ruscatores of the great mother, because of their employment of begging, or alms-gathering, in public streets. These priests attracted attention by the ringing of little bells. Hence, probably, the custom of some mendicant orders abroad; and of lepers appearing formerly in some parts of our own country, with bell and clapper. It was a term also applied to oppressive tax-gatherers. Æ, Es, light, fire, ether; in Ancient Metallurgy, brass or copper, probably from the bright colour of those metals. In more modern usage, Æs signifies brass, and cuprum is applied to copper. ES FLAVUM was a name sometimes given to this compound. Amongst the Romans, Es signified money generally, their first coinage having been brass and some nations still call their money by the name of that particular metal, in which it is of most frequent currency; as the siller or silver of the Scotch. The ancients had various sorts of the Es, such as Es caldarium, or Æs olarium, cast brass, or pot brass, which was not malleable. Es candidum was of a pure and white kind, found, it is said, under the veins of silver in the mine, and seems to have been similar to talc; or it was nothing more than a whiter brass. Es uxorium was a sum paid by Roman bachelors for living single to old age. ES CORINTHIUM. This was accounted the most costly and precious composition of all the brasses of the ancients. Pliny affirms that it was first discovered at the sacking of Corinth, from which it obtained its name. It was said to be a mixture of gold, silver, and the common brass; and was divided into the red, the white, and the common money-colour; but no gold can be obtained, after the most accurate analysis, from some pieces of this compound which have come down to us. ES CYPRIUM, a copper, from which superior brass was made, found in the island Cyprus. ES HEPATICON, was of a silverish colour, and is sometimes thought to have been bronze. Es USTUм, or as veneris, æs crematum, crocus veneris, cinis æris, terms applied to an ancient chemical preparation used in the famous art of staining glass. It appears to have been an oxid of copper mixed with sulphur, and was sometimes applied as a drying and detersive quality in ointments. ÆSCHYNOMENE, the bastard sensitive plant; class and order Diadelphia, Decandria. ESCULAPIUS, in Ancient Mythology, the god of medicine, and son of Apollo, by Coronis; or, according to others, by Larissa, daughter of Phlegias. Apollo set a crow to watch the nymph Coronis after his union with her; and discovering that she admitted the embraces of Ischys of Emonia, he destroyed her with lightning, but preserved the infant, and gave him to Chiron, the centaur, to be educated in the art of medicine. By some authors it is represented, that Coronis left her father to avoid his discovering her pregnancy, and exposed her child near Epidaurus. A goat suckled Esculapius, and a dog of the flock of Aresthanus sheltered the infant from injury. He was found by the master, Aresthanus, whilst in search of his lost goat, and the head of the child was then perceived to be illuminated with a radiance of light. Minerva presented to him some of the blood of the Gorgon which she had slain, and with this Esculapius brought several dead people to life. Pluto was displeased with the successful efforts of the physician, and lest his dominions should want inhabitants, complained to Jupiter. The father of the gods struck Esculapius with thunder; and Apollo, in revenge, killed the Cyclops who made the thunder-bolts. Goats, bulls, lambs, and pigs were sacrificed to this god of physic; and he was first worshipped at Epidaurus, Pergamos, Athens, Smyrna, Cyrene, and Crete. Rome, being delivered from a plague A. v. c. 462, built a temple to Esculapius, who, it was said, had concealed himself under the form of a serpent on the banks of the Tyber, and effected their deliverance from the direful disease. At Epidaurus his statue was erected of gold and ivory, with a large beard; one hand contained a staff with a serpent wreathed around it, and his other hand supported a serpent. He is generally accompanied by the symbol of vigilance, a cock. ESCULUS, in Botany, the horse-chesnut; class and order Heptandria, Monogynia. ESTIMATIO CAPITIS, a term of Saxon law for a fine payable on account of offences against persons of rank, the sum being proportioned to the quality of the persons aggrieved. SYMNIUM, in Antiquity. Pausanias mentions a monument of this name, built by Esymnus, who, hav AERONAUTICS. SYMNIUM. ÆTHER. 66 ESYM- ing consulted the Delphian oracle respecting the best NIUM.. method of governing the Megareans, was answered, By holding consultation with the most numerous." Understanding the deceased heroes and sages of former times to be intended by this, he built and consecrated a monument to them, and enclosed it with a senate 'house; in which the illustrious dead were thus believed to be present with the deliberations of the living. ETHALIA, or ILUA, in Ancient Geography, from aaλŋ, smoke, which seems to denote that it formerly contained a volcano; the present well-known island of Elba. See ELBA. ETHER (audely, to burn), in Physiolgy, a subtle, penetrating fluid, which has been supposed, both in ancient and modern times, to be diffused through the universe at the extremity of the earth's atmosphere; to pervade the air itself, and to occupy all the pores and interstices of matter. The existence of such a fluid is wholly hypothetical, and has given birth to conjectures as indefinite as the space that has been assigned to its circulation. With some of the ancient philosophers, it was the origin of all things, an attenuation of fire, which, according to Hippocrates, was "immortal; knows all things; sees, hears, and determines whatsoever is, or shall hereafter be." From this fluid, existing in perfection only in the highest heavens, and encircling the whole of the material universe, all grosser elements were said to be first derived, and from them the various productions of nature. Here the gods were enthroned, and the stars rolled along in all the music of the spheres. We need not be surprised that such philosophy readily furnished language to poetry, and assimilated itself with all the grosser and more refined notions of the ancient mythologies. It was poetry and mythology in itself. As a speculation of science, it would long since have been exploded from all connection with the inductive philosophy, but for the sanction that has been given to it by some conjectures of Sir Isaac Newton. Finding, after all his endeavours to procure a vacuum, and after the exclusion of the common air from the receiver of the air-pump, that there still was a medium through which heat would act, and the thermometer be affected by it, as in the open air, he suggested that an elastic vibrating Æther might remain in the vessel, as the only solution of the attending phenomena. He also connected it with his doctrine of gravitation, and subjoins it as a question "concerning its cause."-“ A question, I say," he adds, in his premonition to the reader, prefixed to the second edition of Optics, in 1717, "for I do not hold it as a thing established." His ideas were, that this fluid or " ethereal medium," being much rarer in the pores of bodies and in their immediate neighbourhood, than at a distance from them, and in the vicinity and body of the sun exceedingly rare, and denser as we recede from it, it would be repelled by all other bodies, and impel them toward the sun. Dr. Hartley ventured to construct upon this theory of a vibrating æther, the celebrated system of vibration, and vibratiuncles of the medullary substance of the nerves and brain; by which he accounts for all our sensations and ideas. He even thinks it a consequence of this theory, that could matter be endowed with the most simple kinds of sensation, it might arrive at all the intelligence of which the human ETI mind is possessed! The metaphysical difficulties of this system are ably stated by Dr. Reid. "Our sensations arise from vibrations, and our ideas from vibratiuncles, ÆTI or miniature vibrations; and he (Dr. Hartley) comprehends, under these two words of sensations and ideas, all the operations of the mind. But how can we expect any proof of the connection between vibrations and thought, when the existence of such vibrations was never proved. The proof of their connection cannot be stronger than the proof of their existence. For, as the author acknowledges, that we cannot infer the existence of the thoughts from the existence of the vibrations, it is no less evident, that we cannot infer the existence of vibrations from the existence of our thoughts. The existence of both must be known before we can know their connection. As to the existence of our thoughts, we have the evidence of consciousness; a kind of evidence that never was called in question. But as to the existence of vibrations, in the medullary substance of the nerves and brain, no proof has yet been brought." Upon the scientific objections to this theory, though the great name of NEWTON is concerned, it has been inquired, whether the imperfection of the instruments employed, or other causes, may not induce us to suppose that the air is not wholly exhausted from the receiver of the air-pump, rather than that it leaves behind a fluid distinct from itself; and, with regard to the supposed connection of this fluid with gravitation, it been suggested, that it will answer none of the purposes for which it is produced. As a fluid unequally dense and elastic, according to the hypothesis, its particles are not in contact, and are elastic only by mutual repulsion; that is, by acting on each other at a distance; a repulsion which, only in operating through all the space, between the earth and the sun (to say nothing of its action in remoter parts of the universe), must multiply in every particle of the conformation of this fluid the very difficulties for which its existence is supposed to account. The conjectural shape in which Newton left his few thoughts upon this subject, would have rendered any remark upon the difficulties of establishing it, perhaps, unnecessary at this period of the world, but for the general authority of his name, its connection with Hartley's system, and with the still wilder conjectures of the ancients. ETHER, in Chemistry, a light gaseous fluid, produced by the mixture of alcohol and a concentrated acid. See CHEMISTRY, Div. ii. ETHER, in Medicine. See MEDICINE, Div. ii. ÆTHEREAL OIL, in Distillation, a subtle essential oil, nearly a spirit; thus, the ethereal oil of turpentine, is the liquor rising next after the spirit. ETHUSA, in Botany, Fool's Parsley; a genus of plants, of the order Digynia, class Pentandria. ÆTITES, or EAGLE-STONE, in Natural History, a flint, or crustated and hollow stone, found in slates of our common pebbles: it rattles on being shaken, and contains a nucleus. Many miraculous were properties attributed to it by the ancients; such as the prevention of abortion, the discovery of thieves, &c. There is also an idle popular story, that the female eagle (acros, from whence its name atites) takes up this stone into her nest, while she is sitting, to prevent her eggs being rotten. They are at first soft, and become hard by their exposure to the atmosphere. Near Trevoux, in France, they are very numerous. |