MADRIER, in the military art, a long and broad plank of wood, used for supporting the earth in mining and carrying on a sap, and in making coffers, caponiers, galleries, and for many other uses at a siege. Madriers are also used to cover the mouths of petards, after they are loaded, and are fixed with the petards to the gates or other places designed to be forced open.

MADRIGAL, in the Italian, Spanish, and French poetry, is a short, amorous poem, composed of a number of free and unequal verses, neither confined to the regularity of a sonnet, nor to the point of an epigram, but only consisting of some tender and delicate thought, expressed with a beautiful, noble, and elegant simplicity. The madrigal is usually considered as the shortest of all the lesser kinds of poetry, except the epigram; it will ad. mit of fewer verses than either the sonnet or the roundelay; no other rule is regard. ed in mingling the rhymes, and the different kinds of verse, but the fancy and convenience of the author: however, this poem allows of less licence than many others, both with respect to rhyme, measure, and delicacy of expression.

MAGAZINE, a place in which stores are kept, of arms, ammunition, provisions, &c. Every fortified town ought to be furnished with a large magazine, which should contain stores of all kinds sufficient to enable the garrison and inhabitants to hold out a long siege, and in which smiths, carpenters, wheelrights, &c. may be employed, in making every thing belonging to the artillery, as carriages, waggons, &c.

MAGAZINE, powder, a place in which

powder is kept in large quantities, and which, on account of the nature of the substance preserved, should be arched and bomb-proof. According to the plan of Vauban, they are sixty feet long and twenty-five feet broad in the inside. The foundations are eight or nine feet thick, and about as many feet high from the foundation to the spring of the arch. As some inconveniences have arisen from this structure, Dr. Hutton proposes to find an arch of equilibration, which he would have constructed to a span of twenty feet, the pitch being ten feet; the exterior walls at top forming an angle of 113°, and the height of the angular point above the top of the arch to be seven feet.

MAGGOT. See MUSCA.

MAGI, or MAGIANS, an ancient religious sect in Persia, and other eastern countries, who maintained that there were two principles, the one the cause of all good, the other the cause of all evil; and abominating the adoration of images, worshipped God only by fire, which they looked upon as the brightest and most glorious symbol of Oromasdes, or the good God; as darkness is the truest symbol of Arimanius, or the evil god. This religion was reformed by Zoroaster, who maintained that there was one supreme independent being; and under him two principles or angels, one the angel of goodness and light, and the other of evil and darkness: that there is a perpetual struggle between them, which shall last to the end of the world; that then the angel of darkness and his disciples shall go into a world of their own, where they shall be punished in everlasting darkness; and the angel of light and his disciples shall also go into a world of their own, where they shall be rewarded in everlasting light. The priests of the magi were the most skilful mathematicians and philosophers of the ages in which they lived, insomuch that a learned man and a magian became equivalent terms. The vulgar looked on their knowledge as more than natural, and imagined them inspired by some supernatural power; and hence those who practised wicked and mischievous arts, taking upon themselves the name of magians, drew on it that ill signification which the word magician now bears among us.

This sect still subsists in Persia, under the denomination of gaurs, where they watch the sacred fire with the greatest care, and never suffer it to be extinguished. See GAURS.

MAGIC, originally signified only the knowledge of the more sublime parts of philosophy; but as the magi likewise professed astrology, divination, and sorcery, the term magi became odious, being used to signify an unlawful, diabolical kind of science, acquired by the assistance of the devil and departed souls. See ASTROLOGY, NECROMANCY, &C.

Natural magic is only the application of natural philosophy to the production of surprising but yet natural effects. The common natural magic, found in books, gives us merely some childish and superstitious traditions of the sympathies and antipathies of things, or of their occult and peculiar properties; which are usually intermixed with many trifling experiments, admired rather for their disguise

than for themselves.

MAGIC lantern. See LANTERN.

MAGIC Square, in arithmetic, a square figure made up of numbers in arithmetical proportion, so disposed in parallel and equal ranks, that the sums of each row, taken either perpendicularly, horizontally, or diagonally, are equal: thus,

extremely surprising, especially in the more ignorant ages, when mathematics passed for magic, and because also of the superstitious operations they were employed in, as the construction of talismans, &c.; for, according to the childish philosophy of those days, which ascribed virtues to numbers, what might not be expected from numbers so seemingly wonderful? The magic square was held in great veneration among the Egyptians, and the Pythagoreans, their disciples, who, to add more efficacy and virtue to this square, dedicated it to the then known seven planets divers ways, and engraved it upon a plate of the metal that was esteemed in sympathy with the pla net.-The square, thus dedicated, was inclosed by a regular polygon, inscribed in a circle, which was divided into as many equal parts as there were units in the side of the square; with the names of the angles of the planet, and the signs of the zodiac, written upon the void spaces between the polygon and the circumference of the circumscribed circle. Such a talisman or metal they vainly imagined would, upon occasion, befriend the person who carried it about him. To Saturn they attributed the square of nine places or cells, the side being three, and the sum of the numbers in every row 15: to Jupiter the square of 16 places, the side being 4, and the amount of each row 34; to Mars the square of 25 places, the side being 5, and the amount of each row 65: to the Sun the square with 36 places, the side being 6, and the sum of each row 111: to Venus the square of 49 places, the side being 7, and the amount of each row 175: to Mercury the square with 64 places, the side being 8, and the sum of each row 260: and to the moon the square of 81 places, the side being 9, and the amount of each row 369. Finally, they attributed to imperfect matter, the square with 4 divisions, having two for its side; and to God, the square of only one cell, the side of which is also an unit, which multiplied by itself undergoes no change. To form a magic square of an odd number of terms in the arithmetic progression 1, 2, 3, 4, &c. place the least term 1 in the cell immediately under the middle or central one; and the rest of the terms in their natural order, in a descending diagonal direction, till they run off either at the bottom, or on the side: when the number runs off at the bottom, carry it to the uppermost cell, that is not occupied, of

Bb

the same column that it would have fallen in below, and then proceed descending diagonalwise again as far as you can, or till the numbers either run off at bottom or side, or are interrupted by coming at a cell already filled: now when any number runs off at the right-hand side, then bring it to the furthest cell on the left-hand of the same row or line it would have fallen in towards the right hand: and when the progress diagonalwise is interrupted by meeting with a cell already occupied by some other number, then descend diagonally to the left from this cell till an empty one is met with, where enter it; and thence proceed as before. Thus,

First place the 1 next below the centre cell, and thence descend to the right till the 4 runs off at the bottom, which therefore carry to the top corner on the same column as it would have fallen in ; but as that runs off at the side, bring it to the beginning of the second line, and thence descend to the right till they arrive at the cell occupied by 1; carry the 8 therefore to the next diagonal cell to the left, and so proceed till 10 runs off at the bottom, which carry therefore to the top of its column, and so proceed till 13 runs off at the side, which therefore bring to the beginning of the same line, and thence proceed till 15 arrives at the cell occupied by 8; from this therefore descend diagonally to the left; but as 16 runs off at the bottom, carry it to the top of its proper column, and thence descend till 21 runs off at the side, which is therefore brought to the beginning of its proper line; but as 22 arrives at the cell occupied by 15, descend diagonally to the left, which brings it into the first column,

but off at the bottom, and therefore it is carried to the top of that column; thence descending till 29 runs off both at bottom and side, which therefore carry to the highest unoccupied cell in the last column; and here, as 30 runs off at the side, bring it to the beginning of its proper column, and thence descend till 35 runs off at the bottom, which therefore carry to the beginning or top of its own column; and here, as 36 meets with the cell occupied by 29, it is brought from thence diagonally to the left; thence descending, 38 runs off at the side, and therefore it is brought to the beginning of its proper line; thence descending, 41 runs off at the bottom, which therefore is carried to the beginning or top of its column; from whence descending, 43 arrives at the cell occupied by 36, and therefore it is brought down from thence to the left; thence descending, 46 runs off at the side, which therefore is brought to the beginning of its line; but here, as 47 runs off at the bottom, it is carried to the beginning or top of its column, from whence descending with 48 and 49, the square is completed, the sum of every row and column and diagonal making just 175. Dr. Franklin carried this curious speculation further than any of his predecessors in the same way. He constructed both a magic square of squares, and a magic circle of circles, the description of which is as follows. The magic square of squares is formed by dividing the great square into 256 little squares, in which all the numbers from 1 to 256, or the square of 16, are placed in 16 columns, which may be taken either horizontally or vertically. Their chief properties are as follow. 1. The sum of the 16 numbers in each column or row, vertical or horizontal, is 2056. 2. Every half column, vertical and horizontal, makes 1028, or just one half of the same sum 2056. 3. Half a diagonal ascending, added to half a diagonal descending, makes also the same sum 2056; taking these half diagonals from the ends of any side of the square to the middle of it, and so reckoning them either upward or downward, or sideways from right to left, or from left to right. 4. The same with all the parallels to the half diagonals, as many as can be drawn in the great square: for any two of them being directed upward and downward, from the place where they begin, to that where they end, their sums still make the same

2056. Also the same holds true down ward and upward; as well as if taken sideways to the middle, and back to the same side again. Only one set of these half diagonals and their parallels is drawn in the same square upward and downward; but another set may be drawn from any of the other three sides. 5. The four corner numbers in the great square, added to the four central numbers in it, make 1028, the half sum of any vertical or horizontal column, which contains 16 numbers; and also equal to half a diagonal or its parallel. 6. If a square hole, equal in breadth to four of the little squares or cells, be cut in a paper, through which any of the 16 little cells in the great square may be seen, and the paper be laid upon the great square, the sum of all the 16 numbers, seen through the hole, is always equal to 2056, the sum of the 16 numbers in any horizontal or vertical column.

MAGISTERY, an old chemical term, very nearly synonymous with precipitate, but is now rarely used, except in the following combinations; magistery of bismuth, which is the white oxide of this metal precipitated from the nitrous solution by the addition of water, magistery of sulphur, which is sulphur precipitated from its alkaline solution by an acid.

MAGNESIA, in chemistry, an earth, the properties of which were not fully known, till Dr. Black, about the middle of the last century, investigated its nature. In the pursuit, the Doctor was led to the important discovery of the carbonic acid gas. Magnesia had, before his time, been frequently confounded with lime; he, however, by the most accurate experiments, showed that it possessed properties different from all the other earths. Although magnesia exists in great abundance in combination with other substances, it has never been found perfectly pure in nature. It is an ingredient in many fossils; and several of the salts, which it forms by combination with the acids, are found in mineral springs, and in the water of the ocean. From these combinations magnesia is obtained by different artificial processes. Murray mentions the sulphate of magnesia, or Epsom salt, as well adapted to this purpose. One part of this salt is to be dissolved in twenty of water, and the so-' lution filtered; to this is added, while hot, a solution of pure potash or soda, as long as precipitation is produced. The

Mr.

alkali combines with the sulphuric acid, and the magnesia is separated: being insoluble in water, it falls down in white powder it is then washed in water till the fluid comes off tasteless. This earth exists under the form of a white spongy powder, soft to the touch, without smell, and having a slightly bitter taste. Its specific gravity is 2.3. It slightly changes vegetable colours to a green. Magnesia, when quite pure, is infusible, though exposed to the most intense heat: even in the focus of the very powerful burning mirror, or in the heat excited by oxygen gas, it cannot be melted. When made into a paste with water it contracts like alumina, if exposed to a sudden heat. It is almost insoluble in water. There is no action between magnesia and hydrogen or carbon, and very little between it and phosphorus. It combines readily with the acids, and with them forms neutral salts. Of these the greater number are soluble or crystallizable, and have a bitter taste. It does not enter into combination with the fixed alkalies, but in combination with some of the other earths it is fusible, by means of a very strong heat. With lime, in certain proportions, it forms a greenish yellow glass. It is much used in medicine as a gentle

laxative, and as an absorbent to destroy acidity in the stomach. It is also employed to aid the solution of resinous and gummy substances, as camphor and opium, in water. We shall notice only a few of its combinations.

Magnesia combines with sulphur either in the dry or humid way, forming thereby a sulphuret of magnesia. The solid sulphuret of magnesia decomposes rapidly when exposed to the air.

Sulphate of magnesia is a compound of sulphuric acid and magnesia, and is found in sea water, and in many mineral springs, Those at Epsom once afforded a large part of what was used in commerce; hence the name of Epsom salt. Now indeed it is commonly obtained from sea water. The bittern water, or, as it is usually called, the mother water of common salt, that is, the water which remains after the crystallization, consists chiefly of sulphate of magnesia. The constituent parts are, according to Bergman,

When common carbonate of magnesia is exposed to a moderate heat, it is decomposed; its carbonic acid disengaged. It loses about half its weight, and the magnesia remains nearly pure.

Under the magnesian genus of fossils are comprehended, not only those in which magnesia is the ingredient which is present in largest proportion, but those also, in which, though in a smaller proportion, there exist the characters in some measure peculiar to this genus. These are, softness, unctuosity, and being in general destitute of hardness, lustre, and

many of those which belong to the siliceous and argillaceous genera. Magnesian fossils have usually a green colour, more or less deep.

MAGNET. See MAGNETISM.

MAGNETISM is supposed to have been first rendered useful about the end of the twelfth, or at least very early in the thirteenth century, by John de Gioja, a handicraft of Naples, who noticed the peculiar attraction of metals, iron in particular, towards certain masses of rude ore; the touch of which communicated to other substances of a ferruginous nature, especially iron or steel bars, the same property of attraction: these touched bars he observed to have a peculiar and similar tendency towards one particular point; that when suspended in equilibrio, by means of threads around their centres, they invariably indicated the same point; and that, when placed in a row, however adversely directed, they soon disposed themselves in perfectly parallel order. In this instance, he improved upon the property long known to, but not comprehended or applied to use by the ancients, who considered the loadstone simply as a rude species of iron ore, and curious only so far as it might serve to amuse. Gioja, being possessed of a quick understanding, and of a strong mind, was not long in further ascertaining the more sensible purposes to which the magnet might be appropriated. He accordingly fixed various magnets upon pivots, supporting their centres in such

manner as allowed the bars to traverse freely. Finding, that, however situated within the reach of observation and comparison, they all had the same tendency, he naturally concluded them to be governed by some attraction, which might be ultimately ascertained and acted upon. He therefore removed into various parts of Italy, to satisfy himself whether or not the extraordinary impulse, which agitated these bars that had been magnetised by friction, existed only in the vicinity of Naples, or was general. The result of his researches appears to be, that the influence was general, but that the magnets were rendered extremely variable, and fluctuated much, when near large masses of iron. The experiments of Gioja gave birth to many others, and at length to a trial of the magnetic influence on the surface of the water. To establish this, a vessel was moored out at sea, in a direction corresponding with that of the magnet; and a boat, having a magnet equipoised on a pivot at its cen