Illyria should do nothing in that province without his knowledge and approbation." Plutarch. sult the records and public instruments preserved in cities which he had visited in his travels. He took a particular journey to Sparta, to search the archives of that famous commonwealth, to understand thoroughly the model of their ancient government, the history of their legislators, their kings, and their ephori; and digested all their memorable deeds and sayings with much care. He took the same methods with regard to many other commonwealths; and thus was enabled to leave us in his works such a rich cabinet of observations upon men and manners, as, in the opinion of Montaigne and Bayle, have rendered him the most valuable author of antiquity. The circumstances of Plutarch's life are not known, and therefore cannot be related with any exactness. According to the learned Fabricius, he was born under Claudius, 50 years after the Christian era. He was married to a most amiable woman of his own native town, whose name, according to the probable conjecture of Rualdus, was Timoxena, and to whose sense and virtue he has borne the most affectionate testimony in his moral works. He had several children, and among them two sons; one called Plutarch after himself, the other Lamprias in memory of his grandfather. Lamprias was he, of all his children, who seems to have inherited his fathers's philosophy; and to him we owe the table or catalogue of Plutarch's writings, and perhaps also his apophthegms. He had a nephew, Sextus Chæroneus, who taught the learned emperor Marcus Aurelius the Greek tongue, and was much honoured by him. Some think, that the critic Longinus was of his family; and Apuleius, in the first book of his Metamorphoses, affirms himself to be descended from him. On what occasion, and at what time of his life, he went to Rome, how long he lived there, and when he finally returned to his own country, are all uncertain. It is probable, that the fame of him went thither before him, not only because he had published several of his works, but because immediately upon his arrival, as there is reason to believe, he had a great resort of the Roman nobility to hear him: for he tells us himself, that he was so taken up in giving lectures of philosophy to the great men of Rome, that he had not time to make himself master of the Latin tongue, which is one of the first things that would naturally have engaged his attention. It appears that he was several times at Rome; and perhaps one motive for his living there was he intimacy he had contracted in some of these journeys with Sossius Senecio, a great and worthy man, who had been four times consul, and to whom Plutarch has dedicated many of his lives. But the great inducement which carried him first to Rome, was undoubtedly that which had carried him into so many other parts of the world; namely, to make observations upon men and manners, and to collect materials for writing the lives of the Roman worthies, in the same manner as he had already written those of the Grecian and accordingly he not only conversed with all the living, but searched the records of the Capitol, and of all the libraries. Not but, as we learn from Suidas, he was intrusted also with the management of public affairs in the empire, during his residence in the metropolis. "Plutarch (says he) lived in the time of Trajan, who bestowed on him the consular ornaments, and also caused an edict to be passed, that the magistrates or officers of Plutarch, When and how he was made known to Trajan is likewise uncertain: but it is generally supposed that Trajan, a private man when Plutarch first came to Rome, was, among other nobility, one of his auditors. It is also supposed, that this wise emperor made use of him in his councils; at least, much of the happiness of his reign has been imputed to Plutarch. Fabricius asserts that he was Trajan's preceptor, and that he was raised to the consular dignity by him, and made procurator of Greece in his old age by the emperor Adrian. We are equally at a loss concerning the time of his abode in the imperial city; which, however, at different times, is not imagined to fall much short of 40 years. The desire of visiting his native country, so natural to all men, and especially when growing old, prevailed with him at length to leave Italy: and at his return he was unanimously chosen archon or chief magistrate of Charonea, and not long after admitted into the number of the Delphic Apollo's priests. We have no particular account of his death, either as to the manner of it or the year; only it is evident that he lived, and continued his studies, to a good old age. The most probable conjecture is that of Fabricius, who says he died in the fifth year of Adrian, at the age of 70. His works have been divided, and they admit of a pretty equal division, into Lives and Morals: the former of which, in his own estimation, were to be preferred as more noble than the latter. His style, as we have already observed, has been excepted to with some reason he has also been criticised for some mistakes in Roman antiquities, and for a little partiality to the Greeks. On the other hand, he has been justly praised for the copiousness of his fine sense and learning, for his integrity, and for a certain air of goodness which appears in all he wrote. His business was not to please the ear, but to instruct and charm the mind; and in this none ever went beyond him. Of his moral writings it is to be regretted that we have no elegant English translation. Even his Lives were chiefly known to the English reader by a motley and miserable version, till a new one executed with fidelity and spirit was presented to the public by the Langhornes in 1770. On the whole, it is to be wished that this most amiable moralist and biographer had added a life of himself to those which he has given to the world of others, as the parti culars which other writers have preserved of his personal history are very doubtful and imperfect. PLUTO, in Pagan worship, the king of the infer nal regions, was the son of Saturn and Ops, and the brother of Jupiter and Neptune. This deity finding himself childless and unmarried, mounted his chariot to visit the world; and arriving in Sicily, fell in love with Proserpine, whom he saw gathering flowers with her companions in the valley of Enna, near Mount Etna: when, forcing her into his chariot, he drove her to the river Chemarus, through which he opened himself a passage back to the realms of night. See CERES and PRO 2 Plute H that his helmet had the quality of rendering the wearer invisible, and that Minerva borrowed it in order to be Plymouth. concealed from Mars when she fought against the Trojans. Pluto was greatly revered both by the Greeks and Romans, who erected temples and altars to him. To this god sacrifices were offered in the night, and it was not lawful to offer them by day. PLUTUS, in Pagan worship, the god of riches, is frequently confounded with Pluto. He was represented as appearing lame when he approached, and with wings at his departure; to show the difficulty of amassing wealth and the uncertainty of its enjoyment. He was also frequently represented blind, to show that he often bestowed his favours on the most unworthy, and left in necessity those who had the greatest merit. PLUVIALIS, a species of plover. See CHARADRIUS, ORNITHOLOGY Index. PLUVIUS, a surname of Jupiter. He was invoked by that name among the Romans whenever the earth was parched up by continual heat, and was in want of refreshing rains. He had an altar in the temple on the capitol. PLYERS, in fortification, denote a kind of balance used in raising or letting down a draw-bridge. They consist of two timber levers, twice as long as the bridge they lift, joined together by other timbers framed in the form of a St Andrew's cross to counterpoise them. They are supported by two upright jams, on which they swing; and the bridge is raised or let down by means of chains joining the ends of the plyers and bridge. PLYING, in the sea language, the act of making, or endeavouring to make, a progress against the direction of the wind. Hence a ship that advances well in her course in this manner of sailing, is said to be a good plyer. See the articles BEATING, PITCHING, and TACK ING. PLYMOUTH, a town of Devonshire, in England, about 215 miles from London, stands between the rivers Plym and Tamar, just before they fall into the British channel. From a mere fishing village it has become one of the largest towns in the county; and is one of the chief magazines in the kingdom, on account of its port, which is one of the safest in England, and which is so large as to be able to contain 1000 sail. It is defended by several different forts, mounting altogether nearly 300 guns; of which the chief is the Royal Citadel erected in the reign of Charles II. opposite to St Nicholas island, which is within the circuit of its walls, and contains a large store-house and five regular bastions. In time of war the outward-bound convoys generally rendezvous at Plymouth, and homeward-bound ships generally put in to provide pilots up the Channel. It is also a place of resort for men of war that are windbound. It contained 56,000 inhabitants in 1811. The mouth of the Tamar is called Ham-Ooze, and that of Plym Catwater, which are both commanded by the castle on St Nicholas island. About two miles up the mouth of the Tamar there are four docks, two of which were built in the reign of William III. one wet and the other dry, and two which have been built since. They have every conveniency for building or repairing ships. One of the docks is hewn out of a mine of slate, and lined with Portland stone. This town enjoys a pilchard fishery of considerable importance, and carries VOL. XVI. Part II. on an extensive trade with Newfoundland and the Straits. Plymouth. There is a customhouse in it; and though there are two churches (and besides several meeting-houses), yet each church has so large a cure of souls, that the parish clerks were till very lately in deacons orders, to enable them to perform all the occasional and other offices. The seat-rents are given to the poor. The lecturers are chosen every three years by the corporation, which was constituted by Henry VI. and consists of a mayor, 12 aldermen, and 24 common-council men. The mayor is elected by a jury of 36 persons, chosen by four others, two of whom are appointed by the mayor and aldermen, and the other two by the common-council. There is also a recorder and a town-clerk. The population in 1801 exceeded 43,000. The town consists of four divisions, which were anciently governed by four captains, each of whom had three constables under him. It is well supplied with fresh water, which was brought from the distance of seven miles, by Sir Francis Drake a native of the town. The toll of the markets and of the cotton, yarn, &c. with the profit of the mill, which is very considerable, belongs to the corporation, as do the revenues of the shambles, which are farmed out for the mayor's kitchen. There is a charity school in Plymouth, four hospitals, and a workhouse, in all which 100 poor children are clothed, fed, and taught; and there are two printing-houses. To one of the hospitals Colone! Jory gave a charity for 12 poor widows, as he did a mace worth 120l. to be carried before the mayor, and six good bells, valued at 500l. to Charles-Church, so called from our kings in whose reigns it was begun and finished. In the entrace of the bay lies the famous Eddystone rock, which is covered at high water, and on which the ingenious Mr Winstanley built a light-house, that was blown down in the terrible hurricane of Nov. 27th 1703, and himself, with others that were with him in it, never more heard of. However, another was erected in the room of it, by the corporation of the Trinity-house, in the time of Queen Anne, which was destroyed by an accidental fire Dec. 4th 1755, but rebuilt in 1759: which was also burnt down, and rebuilt by the celebrated Smeaton in the year 1770. In the reign of Edward III. the French landed, and burnt part of the town, but were soon repulsed by Hugh Courtenay earl of Devon. In the reign of Henry IV. the French landed here again, and burnt 600 houses. Between this town and the sea is a hill called the Haw, which has a delightful plain on the top, having a pleasant prospect all round it, and a good landmark for the use of mariners. The list of parliament-men for this borough, formerly divided into two parts, by the names of Sutton-Valtort and Sutton-Prior, commences the 26th of Edward I. and continues to the 14th of Edward III. after which we find no return made for it till the 20th of Henry VI. when the privilege was renewed. On the Haw is a fort, which at once commands the town and defends the harbour. Here is a ferry over the Tamar, called Crumwell or Crimble Passage, the west side of which is called Westone-House, and is in Devonshire, though most of the parish wherein it stands is in Cornwall. In April 1759 parliament granted 25,1591. for the better fortifying the town and dock of Plymouth. N. Lat. 50. 26. W. Long. 4. 15. PLYMOUTH, in New England, a sea-port town, and capital of the county of the same name, in the province 4 P of Plymouth, of Massachusets Bay, in North America, with about Plynteria 2000 inhabitants. It is remarkable for having been the first settlement in New England, and for having had the first place of worship. It is seated at the south end of Plymouth bay. W. Long. 70. 40. N. Lat. 41. 58. PLYNTÉRIA, a Grecian festival in honour of Aglauros, or rather of Minerva, who received from the daughter of Cecrops the name of Aglauros. The word is derived from zλvvuy, lavare, because during the solemnity they undressed the statue of the goddess and washed it. The day on which it was observed was looked upon as unfortunate and inauspicious; and therefore no Plynteti person was permitted to appear in the temples, as they were purposely surrounded with ropes. The arrival of Alcibiades in Athens that day was thought very unfortunate, but the success that ever after attended him proved it to be otherwise. It was customary at this festival to bear in procession a cluster of figs; which intimated the progress of civilization among the first inhabitants of the earth, as figs served them for food after they had found a dislike for acorns.. I Definition PNEUMATICS. of the term. THIS term is restricted, in the present habits of our language, to that part of natural philosophy which treats of the mechanical properties of elastic fluids. The word, in its original meaning, expresses a quality of air, or more properly of breath. Under the article PHYSICS we observed, that in a great number of languages the term used to express breath was also one of the terms used to express the animating principle, nay, the intellectual substance, the soul. It has been perhaps owing to some attention to this chance of confusion that our philosophers have appropriated the term PNEUMATICS to the science of the mechanical properties of air, and PNEUMATOLOGY to the science of the intellectual phenomena consequent on the operations or affections of our thinking principle. Extent of We have extended (on the authority of present custhe science.tom) the term PNEUMATICS to the study of the mechanical properties of all elastic or sensibly compressible fluids, that is, of fluids whose elasticity and compressibility become an interesting object of our attention; as the term HYDROSTATICS is applied to the study of the mechanical properties of such bodies as interest us by their fluidity or liquidity only, or whose elasticity and compressibility are not familiar or interesting, though not less real or general than in the case of air and all vapours. No precise limit to the different bodies. We may be indulged in the observation by the bye, that there is no precise limit to the different classes of classes of natural bodies with respect to their mechanical properties. There is no such thing as a body perfectly hard, perfectly soft, perfectly elastic, or perfectly incompressible. All bodies have some degree of elasticity intermixed with some degree of ductility. Water, mercury, oil, are compressible; but their compressibility need not be attended to in order perfectly to understand the phenomena consequent on their materiality, fluidity, and gravity. But if we neglect the compressibility of air, we remain ignorant of the cause and nature of its most interesting phenomena, and are but imperfectly informed with respect to those in which its elasticity has no share; and it is convenient to attend to this distinction in our researches, in order to understand those phenomena which depend solely or chiefly on compressibility and elasticity. This observation is important; for here elasticity appears in its most simple form, unaccompanied with any other mechanical affection of matter (if we except gravity), and lies most open to our observation, whether employed for investigating the nature of this action. very property of bodies, or for explaining its mode of We shall even find that the constitution of an avowedly elastic fluid, whose compressibility is so very sensible, will give us the distinctest notions of fluidity in general, and enable us to understand its characteristic appearances, by which it is distinguished from solidity, namely, the equable distribution of pressure through all its parts in every direction, and the horizontality which its surface assumes by the action of gravity: phenomena which have been assumed as equivalent to the definition of a perfect fluid, and from which all the laws of hydrostatics and hydraulics have been derived. And these laws have been applied to the explanation of the pheno mena around us; and water, mercury, oil, &c. have been denominated fluid only because their appearances have been found to tally exactly with these consequences of this definition, while the definition itself remains in the form of an assumption, unsupported by any other proof of its obtaining in nature. A real mechanical philosopher will therefore attach himself with great eagerness to this property, and consider it as an introduc tion to much natural science. liar com pressible Of all the sensible compressible fluids air is the most Air the familiar, was the first studied, and the most minutely most fam examined. It has therefore been generally taken as the example of their mechanical properties, while those me-quid chanical properties which are peculiar to any of them, and therefore characteristic, have usually been treated as an appendix to the general science of pneumatics. No objection occurs to us against this method, which will therefore be adopted in treating this article. But although the mechanical properties are the pro-Different per subjects of our consideration, it will be impossible properties to avoid considering occasionally properties which are of it more of a chemical nature; because they occasion such raodifications of the mechanical properties as would fre quently be unintelligible without considering them in conjunction with the other; and, on the other hand, the mechanical properties produce such modifications of the properties merely chemical, and of very interesting phenomena consequent on them, that these would often pass unexplained unless we give an account of them in this place. By mechanical properties we would be understood to Mechanimean such as produce, or are connected with, sensible cal properchanges of motion, and which indicate the presence and ties. agency of moving or mechanical powers. They are therefore the subject of mathematical discussion; admit ting 7 What is ir? 8 Proofs hat it is matter. Plate ting of measure, number, and direction, notions purely mathematical. air. We shall therefore begin with the consideration of It is by no means an idle question, "What is this air of which so much is said and written?" We see nothing, we feel nothing. We find ourselves at liberty to move about in any direction without any let or hinderance. Whence, then, the assertion, that we are surrounded with a matter called air? A few very simple observations and experiments will shew us that this assertion is well founded.' We are accustomed to say that a vessel is empty when we have poured out of it the water which it contained. Take a cylindrical glass jar (fig 1.) having a small hole in its bottom; and having stopped this hole, cccxxIII. fill the jar with water, and then pour out the water, fig. 1. leaving the glass empty, in the common acceptation of the word. Now, throw a bit of cork, or any light body, on the surface of water in a cistern: cover this with the glass jar A held in the hand with its bottom upwards, and move it downwards, as at B, keeping it all the while in an upright position. The cork will continue to float on the surface of the water in the inside of the glass, and will most distinctly shew whereabouts that surface is. It will thus be seen that the water within the glass has its surface considerably lower at C than that of the surrounding water; and however deep we immerge the glass, we shall find that the water will never rise in the inside of it so as to fill it. If plunged to the depth of 32 feet, the water will only half fill it; and yet the acknowledged laws of hydrostatics tell us, that the water would fill the glass if there were nothing to hinder it. There is therefore something already within the glass which prevents the water from getting into it; manifesting in this manner the most distinctive property of matter, viz, the hindering other matter from occupying the same place at the same time. ssessed of ce, While things are in this condition, pull the stopper pulsive D out of the hole in the bottom of the jar, and the water will instantly rise in the inside of the jar, and stand at an equal height within and without. This is justly ascribed to the escape through the hole of the matter which formerly obstructed the entry of the water; for if the hand he held before the hole, a puff will be distinctly felt, or a feather held there will be blown aside; indicating in this manner that what prevented the entry of the water, and now escapes, possesses another characteristic property of matter, impulsive force. The materiality is concluded from this appearance in the same manner that the materiality of water is concluded from the impulse of a jet from a pipe. We also see the mobility of the formerly pent up, and now liberated, substance, in consequence of external pressure, viz. the pressure of the surrounding water. 10 enetra ty, II icity, Also, if we take a smooth cylindrical tube, shut at one end, and fit a plug or cork to its open end, so as te slide along it, but so tightly as to prevent all passage by its sides; and if the plug be well soaked in grease, we shall find that no force whatever can push it to the bottom of the tube. There is therefore something within the tube preventing by its impenetrability the entry of the plug, and therefore possessing this characteristic of matter. In like manner, if, after having opened a pair of com mon bellows, we shut up the nozzle and valve hole, and try to bring the boards together, we find it impossible. There is something included which prevents this, in the same manner as if the bellows were filled with wool; but on opening the nozzle we can easily shut them. viz. by expelling this something; and if the compression be forcible, the something will issue with considerable force, and very sensibly impel any thing in its way. 12 It is not accurate to say, that we move about with- inertia, and out any obstruction: for we find, that if we endeavour mobility. to move a large fan with rapidity, a very sensible hinderance is perceived, and that a very sensible force must be exerted; and a sensible wind is produced, which will agitate the neighbouring bodies. It is therefore justly concluded that the motion is possible only in consequence of having driven this obstructing substance out of the way and that this impenetrable, resisting, moveable, impelling substance, is matter. We perceive the perseverance of this matter in its state of rest when we wave a fan, in the same manner that we perceive the inertia of water when we move a paddle through it. The effects of wind in impelling our ships and mills, in tearing up trees, and overturning buildings, are equal indications of its perseverance in a state of motion. 13 To this matter, when at rest, we give the name AIR; and when it is in motion we call it WIND. Air, therefore, is a material fluid: a fluid, because It is thereits parts are easily moved, and yield to the smallest in-fore a material fluid, equality of pressure. 14 Air possesses some others of the very general, though Heavy, and not essential properties of matter. It is heavy. This appears from the following facts. 1. It always accompanies this globe in its orbit round the sun, surrounding it to a certain distance, under the name of the ATMOSPHERE, which indicates the being connected with the earth by its general force of gravity. It is chiefly in consequence of this that it is continually moving round the earth from east to west; forming what is called the trade-wind, to be more particularly con sidered afterwards. All that is to be observed on this subject at present is, that, in consequence of the disturbing force of the sun and moon, there is an accumulation of the air of the atmosphere, in the same manner as of the waters of the ocean, in those parts of the globe which have the moon near their zenith or nadir: and as this happens successively, going from the east to the west (by the rotation of the earth round its axis in the opposite direction), the accumulated air must gradually flow along to form the elevation. This is chiefly to be observed in the torrid zone; and the generality and regularity of this motion are greatly disturbed by the changes which are continually taking place in dif ferent parts of the atmosphere from causes which are not mechanical. 15 2. It is in like manner owing to the gravity of the supports air that it supports the clouds and vapours which we the clouds see constantly floating in it. We have even seen bodies of no inconsiderable weight float, and even rise in the air. Soap bubbles, and balloons filled with inflammable gas, rise and float in the same manner as a cork rises in water. This phenomenon proves the weight of the air, in the same manner that the swimming of a piece of wood indicates the weight of the water which sufports it. 3. But we are not left to these refined observations for 16 Familiar proofs of its weight. Plate ccccxx11. fig. 2. 17 It may even be for the proof of the air's gravity. We may observe familiar phenomena, which would be immediate consequences of the supposition that air is a heavy fluid, and like other heavy fluids, presses on the outsides of all bodies immersed in or surrounded by it. Thus, for instance, if we shut the nozzle and valve hole of a pair of bellows after having squeezed the air out of them, we shall find that a very great force, even some hundred pounds, is necessary for separating the boards. They are kept together by the pressure of the heavy air which surrounds them, in the same manner as if they were immersed in water. In like manner if we stop the end of a syringe after its piston has been pressed down to the bottom, and then attempt to draw up the piston, we shall find a considerable force necessary, viz. about 15 or 16 pounds for every square inch of the section of the syringe. Exerting this force, we can draw up the piston to the top, and we can hold it there; but the moment we cease acting, the piston rushes down and strikes the bottom. It is called a suction, as we feel something as it were drawing in the piston; but it is really the weight of the incumbent air pressing it in. And this obtains in every position of the syringe; because the air is a fluid, and presses in every direction. Nay, it presses on the syringe as well as on the piston; and if the piston be hung by its ring on a mail, the syringe requires force to draw it down (just as much as to draw the piston up); and if it be let go, it will spring up, unless loaded with at least 15 pounds for every square inch of its transverse section (see fig. 2.). 4. But the most direct proof of the weight of the air weighed. is had by weighing a vessel empty of air, and then weighing it again when the air has been admitted; and this, as it is the most obvious consequence of ita weight, has been asserted as long ago as the days of Aristotle. He says (Пg Ouganov, iv. 4.), That all bodies are heavy in their place except fire; even air is heavy; for a blown bladder is heavier than when it is empty. It is somewhat surprising that his followers should have gone into the opposite opinion, while professing to maintain the doctrine of their leader. If we take a very large and limber bladder, and squeeze out the air very carefully, and weigh it, and then fill it till the wrinkles just begin to disappear, and weigh it again, we shall find no difference in the weight. But this is not Aristotle's meaning; because the bladder, consider ed as a vessel, is equally full in both cases, its dimensions being changed. We cannot take the air out of a bladder without its immediately collapsing. But what would be true of a bladder would be equally true of any vessel. Fig. 3. Therefore, take a round vessel A (fig. 3.), fitted with a stopcock B, and syringe C. Fill the whole with water, and press the piston to the bottom of the syringe. Then keeping the cock open, and holding the vessel upright, with the syringe undermost, draw down the piston. The water will follow it by its weight, and leave part of the vessel empty. Now shut the cock, and again push up the piston to the bottom of the syringe; the water escapes through the piston valve, as will be explained afterward: then opening the cock, and again drawing down the piston, more water will come out of the vessel. Repeat this operation till all the water have come out. Shut the cock, unscrew the syringe, and weigh the vessel very accurate ly. Now open the cock, and admit the air, and weigh the vessel again, it will be found heavier than before, and this additional weight is the weight of the air which fills it; and it will be found to be 523 grains, about an ounce and a fifth avoirdupois, for every cubic foot that the vessel contains. Now since a cubic foot of water would weigh 1000 ounces, this experiment would show that water is about 840 times heavier than air. The most accurate judgment of this kind of which we have met with an account is that recorded by Sir George Shuckburgh, which is in the 67th vol. of the Philosophical Transac tione, p. 560. From this it follows, that when the air is of the temperature 53, and the barometer stands at 29 inches, the air is 836 times lighter than water. But the experiment is not susceptible of sufficient accuracy for determining the exact weight of a cubic foot of air. Its weight is very small; and the vessel must be strong and heavy, so as to overload any balance that is sufficiently nice for the experiment. To avoid this inconvenience, the whole may be The m weighed in water, first loading the vessel so as to make convers it preponderate an ounce or two in the water. By this m doing t means the balance will be loaded only with this small preponderancy. But even in this case there are considerable sources of error, arising from changes in the specific gravity of the water and other causes. The experiment has often been repeated with this view, and the air has been found at a medium to be about 840 times as light as water, but with great variations, as may be expected from its very heterogeneous nature, in consequence of its being the menstruum of almost every fluid, of all vapours, and even of most solid bodies; all which it holds in solution, forming a fluid perfectly transparent, and of very different density according to its composition. It is found, for instance, that perfectly pure air of the temperature of our ordinary summer is considerably denser than when it has dissolved about half as much water as it can hold in that temperature ; and that with this quantity of water the difference of density increases in proportion as the mass grows warmer, for damp air is more expansible by heat than dry air. We have had occasion to consider this subject when treating of the connection of the mechanical properties of air with the state of the weather. See METEOROLOGY. d knowled ed by the master Such is the result of the experiment suggested by This Aristotle, evidently proving the weight of the air; and per yet, as has been observed, the Peripatetics, who profess by the to follow the dictates of Aristotle, uniformly refused it rate this property. It was a matter long debated among thoug the philosophers of the last century. The reason was that Aristotle, with that indistinctness and inconsistency, which is observed in all his writings which relate to matters of fact and experience, assigns a different cause to many phenomena which any man led by common observation would ascribe to the weight of the air. Of this kind is the rise of water in pumps and syphons, which all the Peripatetics had for ages ascribed to something which they called nature's abhorrence of a void. Aristotle had asserted (for reasons not our business to adduce at present), that all nature was full of being, and that nature abhorred a void. He adduces many facts, in which it appears, that if not absolutely impos sible, it is very difficult and requires great force, to produce a space void of matter. When the operation of pumps and syphons came to be known, the philoso phers of Europe (who had all embraced the Peripatetic doctrines) |