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one hundred years before Schwartz was born ; and M. Dutens carries the antiquity of gunpowder still much higher, and refers to the writings of the ancients themselves for the proof of it. It appears too, from o authors and many circumstances, that this composition has been known to the Chinese and Indians for thousands of years. For some time after the invention of artillery, gunpowder was of a much weaker composition than that now in use, or that described by Marcus Graecus, which was chiefly owing to the weakness of their first pieces. Of twenty-three different compositions, used at different times, and mentioned by Tartaglia in his “Ques. and Inv. lib. 3, ques. 5;” the first, which was the oldest, contained equal parts of the three ingredients. But when guns of modern structure were introduced, gunpowder of the same composition as the present came into use. In the time of Tartaglia the cannon powder was made of four parts of nitre, one of sulphur, aud one of charcoal; and the musketpowder of forty-eight parts of nitre, seven parts of sulphur, and eight parts of charcoal; or of eighteen parts of nitre, two parts of sulphur, and three parts of charcoal. But the modern composition is six parts of nitre to one of each of the other two ingredients: though Mr. Napier says, he finds the strength commonly to be greatest when the proportions are, nitre three pounds, charcoal about nine ounces, and sulphur about three ounces. See his paper on gunpowder in the Transactions of the Royal Irish Academy, vol. ii. The cannon-powder was in meal, and the musket-powder grained; and it is certain, that the graining of powder, which is a very considerable advantage, is a modern improvement. To make gunpowder duly, regard is to be had to the purity or goodness of the ingredients, as well as the proportions of them, for the strength of the powder depends much on that circumstance, and also on the due working or mixing of them together. See Nithy. These three ingredients in their purest state being procured, long experience has shown that they are then to be mixed together in the proportion before mentioned, to have the best effect, viz. three quarters of the composition to be nitre, and the other quarter made up of equal parts of the other two ingredients, or, which is the same thing, six parts nitre, one part sulphur, and one part charcoal. But it is not the due proportion of the

materials only, which is necessary to the making of good powder; another circumstance, not less essential, is the mixing them well together; if this be not effectually done, some parts of the composition will have too much nitre in them, and others too little; and in either case there will be a defect of strength in the powder. After the materials have been reduced to fine dust, they are mixed together. and moistened with water, or vinegar, or urine, or spirit of wine, &c. and then beaten to#. for twenty-four hours, either by and or by mills, and afterwards pressed into a hard, firm, solid cake. When dry, it is grained or corned, which is done by breaking the cake of powder into small pieces, and so running it through a sieve: by which means the grains may have any size given them, according to the nature of the sieve employed, either finer or coarser; and thus also the dust is separated from the grains, and again mixed with other manufacturing powder, or worked up into cakes again. Powder is smoothed or glazed, as it is called, for small arms, by the following operation : a hollow cylinder or cask is mounted on an axis, turned by a wheel; this cask is half filled with powder, and turned for six hours, and thus, by the mutual friction of the grains of powder, it is smoothed or glazed. The fine mealy part, thus separated or worn off from the rest, is again granulated. The velocity of expansion of the flame of gunpowder, when fired in a piece of artillery, without either bullet or other body before it, is prodigiously great, viz. seven thousand feet per second, or upwards, as appears from the experiments of Mr. Robins. But M. Bernoulli and M. Euler suspect it is still much greater; and Dr. Hutton supposes it may not be less, at the moment of explosion, than four times as much. It is this prodigious celerity of expansion of the #. of gunpowder which is its peculiar excellence, and the circumstance in which it so eminently surpasses all other inventions, either ancient or modern ; for as to the momentum of these projectiles only, many of the warlike machines of the ancients produced this in a degree far surpassing that of our heaviest cannon slipt or shells; but the great celerity given to these bodies cannot be in the least approached by any other means but the flame of powder. To prove gunpowder. There are several ways of doing this. 1. By sight; thus if it be too black, it is a sign that it is moist,

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or else that it has too much charcoal in it; so also, if rubbed upon white paper, it backens it more than good powder does; but if it be of a kind of azure colour, somewhat inclining to red, it is a sign of good powder. 2 By touching; for if, in crushing it with the fingers’ ends, the grains break easily and turn into dust, without feeling hard, it has too much coal in it; or if, in pressing it under the fingers upon a smooth hard board, some grains feel harder than the rest, it is a sign the sulphur is not well mixed with the nitre. Also by thrusting the hand into the parcel of powder, and grasping it, as if to take out a handful, you will feel if it is dry and equal grained, by its evading the grasp and running mostly out of the hand. 3. By burning; and here the method most commonly followed for this purpose with us, says Mr. Robins, is, to fire a small heap of it on a clean board, and to attend nicely to the flame and smoke it produces, and to the marks it leaves behind on the board; but besides this uncertain method, there are other contrivances made use of, such as powder-triers, acting by a spring, commonly sold at the shops, and others again that move a great weight, throwing it upwards, which is a very bad sort of eprouvette.

The best eprouvette consists in a small

cannon, the bore of which is about one inch in diameter, and is usually charged with two ounces of powder, and with powder only, as a ball is not necessary, and the strength of the powder is accurately shewn by the arc of the gun’s recoil. The whole machine is so simple, easy, and expeditious, that, as Dr. Hutton observes, the weighing of the powder is the chief part of the trouble, and so accurate and uniform, that the successive repetitions,or firings,with the same quantity of the same sort of powder, hardly ever yield a difference in the recoil of the one hundreth part of itself. To recover damaged powder. The method of the powder merchants is this: they put part of the powder on a sailcloth, to which they add an equal weight

of what is really good, then with a sho-,

vel they mingle it well together, dry it in the sun, and barrel it up, keeping it in a dry and proper place. Others again, if it be very bad, restore it by moistening it with vinegar, water, urine, or brandy; then they beat it fine, sift it, and to every pound of powder add an ounce, or an ounce and a half, or two ounces (according as it is decayed) of melted nitre, and afterwards

these ingredients are to be moistened and well mixed, so that nothing may be discerned in the composition, which may be known by cutting the mass, and then they granulate it is as usual. In case the powder be quite spoiled, the only way is to extract the salt-petre with water, in the usual way, by boiling, filtrating, evaporating, and crystallizing, and then with fresh sulphur and charcoal to make it up afresh. On the subject of gunpowder, see also Euler on Robins's Gunnery, Antoni Examen de la Poudre, Baume's Chemistry, and Thompson's Experiments in the Philosophical Transactions for 1781. Soon after the discovery of the oxygenated-muriatic acid and its combination with potash, it was found that this oxymuriate produced a much more violent detonation with combustible bodies, than is afforded by nitre. It has been estimated to possess more than double the force; but on account of this extraordinary power of gunpowder made with the new salt, and some fatal accidents by its exploding, in consequence of friction or percussion, to which it is liable, as well during the manufacture as afterwards, this modern compound has not been brought into use in military operations, but is likely to continue among the articles of scientific curiosity. GUN powden and CoMhust1B LEs. No person shall make gunpowder but in the regular manufactories established at the time of making the statute 12 George III. c. 61, or licensed by the sessions, pursuant to certain provisions, under forfeiture of the gunpowder, and two shillings per pound; nor are pestle mills to be used under a similar penalty. Only forty pounds of powder is to be made at one time under one pair of stones, except Battle-powder, made at Battle and elsewhere in Sussex. Not more than forty hundred weight to be dried at one time in one stove; and the quantity only required for immediate use to be kept in or near the place of making, except in brick or stone magazines, fifty yards at least from the mill. Not more than twenty-five barrels to be carried in any land carriage, nor more than two hundred barrels by water, unless going by sea or coastwise, each barrel not to contain more than one hundred pounds. No dealer to keep more than two hundred pounds of powder, nor any person, not a dealer, more than fifty pounds, in the cities of London and Westminster, or within three miles thereof, or within any other city, borough, or market-town, or one mile thereof, or within two miles of the king's palaces or magazines, or half a mile of any parish church, on pain of forfeiture, and two shillings per pound, except in licensed mills, or to the amount of three hundred pounds for the use of collieries, within two hundred yards of them. GUNTER (En MUN p,) an English mathematician of the seventeenth century, was descended from an ancient and respectable family in Brecknocshire, South Wales, and was born in the county of Herefordshire in the year 1580. He received his classical education on the royal foundation at Westminster School, whence he was elected at about eighteen years of age to Christ Church College, in Oxsord. He was admitted to the degree of B. A. in 1603, and to that of M. A. in 1606; after which he entered into orders, and proceeded bachelor of divinity in the year 1615. His genius had early led him to the pursuit of mathematical studies; and at the time when he took his degree of M. A. he had merited the title of an inventor by his new projection of the sector, of which he then wrote a description in Latin, and permitted his friends to transcribe it, though the English account of his invention was not pubIished till several years afterwards. In the year 1618, he had invented a small portable quadrant, for the more easy finding the hour and azimuth, and more useful astronomical purposes. The reputation which he had now acquired in the mathematical world occasioned his introduction to the acquaintance of some of the most able mathematicians of his time, by whose recommendation and interest he was elected professor of astronomy at Gresham College, London, in the year 1619. In this situation he soon distinguished himself by his lectures and his writings, which contributed greatly to the improvement of science, and reflected credit to the choice that had been made of him to that professorship. His first publication after his election appeared in 1620, and was entitled “Canon Triangulorum, sive Tabulae sinuum artificialium ad radium 10.0000000, et ad Scrupula prima Quadrantis,” 8vo. This treatise

was accompanied with the first 1,000 of:

Brigg's logarithms of common numbers. In the second edition of it, which was published in English in 1624, under the title of “Canon Triangulorum, or Table

of artificial Sines and Tangents to a radius of 10.0000000 Parts to each Minute of the Quadrant,” 4to., the logarithms were continued from 1,000 to 10,000, and a rule was given at the end for augmenting them to 100,000. These tables were the first of the kind which had been given to the world, and, if the author had published nothing else, would have preserved his memory to the latest posterity, by the admirable aid which they afforded to students in astronomy; for they greatly facilitated the practical parts of that science, by furnishing a method of solving sperical triangles without the aid of secants or yersed sines: the same thing being ef. fected by addition and subtraction only, which in the use of the former tables of right sines and tangents required multiplication and division. Due praise was bestowed upon him by many of the most eminent mathematicians among his contemporaries, for the service which he rendered to science by this most excellent work; and his right to the improvememt of logarithms, by their application to spherical triangles, was satisfactorily established by Mr. Edmund Windgate, Mr. Robert Burton, and Mr. Henry Bond, sen. In the year 1622, Mr. Gunter made his important discovery, that the variation of the magnetic needle varies. To this discovery he was led in the course of lectures he made on the variation at I)eptford, by which he found, that the declination of the needle had changed almost five degrees in the space of fortytwo years. The truth of this discovery was afterwards confirmed and established by Mr. Gellibrand, his successor at Gresham College. Soon after this he invented his famous “rule of proportion,” which is an easy and excellent method of combining arithmetic and geometry, adapted to the understanding of persons of the most ordinary capacities. It consists in applying the logarithms of numbers and of sines and tangents to straight lines drawn on a scale or rule, by which, proportions in common numbers and trigonometry may be resolved by the mere application of a pair of compasses: a method founded on this property, that the logarithms of the terms of equal ratios are equidifferent. This was called Gunter’s proportion and Gunter's line ; and the instrument in the form of a two foot scale is now in common use for navigation and other purposes, is and commonly called the Gunter. In the year 1624, this invention was carried into France by Mr. Wingate, who not only communicated it

to most of the principal mathematicians then at Paris, but also, at their request, published an account of it in the French language. Mr. Gunter likewise greatly improved the sector, and other instruments for the same uses, the description of all which he published in 1624, in a treatise, entitled “The Cross Staff, in three books,” &c. 4to. In the same year he published, by King James's order, a small tract, entitled “The Description and Use of his Majestie's Dials in Whitehall Garden,” 4to. Mr. Gunter had been employed by the direction of King Charles in drawing the lines on these dials, and at his desire wrote this description, to which we refer those readers who wish to see a particular account of the construction and uses of those dials, which are no longer in existence. Our author was the first who used the word co-sine for the sine of the complement of an arc. He also introduced the use of arithmetical complements into the logarithmical arithmetic; and it has been said, that he first started the idea of the logarithmic curve, which was so called, because the segments of its axis are the logarithms of the corresponding ordinates. To him likewise the mathematical world is indebted for many other inventions and improvements, most of which were the subjects of his lectures at Gresham College, and afterwards disposed into treatises, which were printed in his works. From the genius and abilities which he had displayed in his works already noticed, the highest expectations were formed of his future services in the cause of useful science; but they were unhappily disappointed by his death, in 1626, when he was only in the forty-fifth year of his age. His name, however, will be transmitted with honour to posterity, as that of the parent of instrumental arithmetic. His works have been collected, and various editions of them have been published. The fifth is by William Leybourn, in 1673, 4to, containing the description and use of the sector, crossstaff, bow, quadrant, and other instruments; with several pieces added by Samuel Foster, Henry Bond, and William Leybourn. GUNTER’s chain, the chain in common use for measuring land, according to true or statute measure; so called from Mr. Gunter, its reputed inventor. The length of the chain is 66 feet, or 22 yards or 4 les, of 54 yards each; and it is divided into 100 links, of 7.92 inches each. This chain is the most convenient of anything for measuring land, because the contents

thence computed are so easily turned into acres. The reason of which is, that an acre of land is just equal to 10 square chains, or 10 chains in length and one in breadth, or equal to 100,000 square links. Hence the dimensions being taken in chains, and multiplied together, it gives the content in square chains, which therefore being divided by 10, or a figure cut off for decimals, brings the content to acres; after which the decimals are reduced to roods and perches, by multiplying by 4 and 40. But the better way is to set the dimensions down in links, as integers, considering each chain as 100 links; then having multiplied the dimensions together, producing square links, divide these by 100,000, that is, cut off five places for decimals, the rest are acres, and the decimals are reduced to roods and perches as before. Suppose a field to be measured be 837 links in length, and 750 in breadth, to find its area we say 887

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GUNTER’s line, a logarithmic line, usually graduated upon scales, sectors, &c. It is also called the line of lines and line of numbers; being only the logarithms graduated upon a ruler, which therefore serves to solve problems instrumentally, in the same manner as logarithms do arithmetically. It is usually divided into an hundred parts, every tenth thereof is numbered, beginning with 1, and ending with 10; so that if the first great division marked 1, stand for one tenth of any integer, the next division, marked 2, will stand for two-tenths; 3, three-tenths, and soon; and the intermediate divisions, will in like manner represent 100th parts of the same integer. If each of the great divisions represent 10 integers, then will the lesser divisions stand for integers; and if the great divisions be supposed each 100, the subdivisions will be each 10.

GUNTER’s line, use of 1. “To find the product of two numbers.” From 1 extend the compasses to the multiplief; and the same extent, applied the same way from the multiplicand, will reach to the product. Thus, if the product of 4 and 8 be required, extend the compasses from 1 to 4, and that extent, laid from 8 the same way, will reach to 32, their product. 2. “To divide one number by another.” The extent from the divisor to unity will reach from the dividend to the quotient; thus, to divide 36 by 4, extend the compasses from 4 to 1, and the same extent will reach from 36 to 9, the quotient sought. 3. “To three given numbers, to find a fourth proportional.” Suppose the numbers 6, 8, 9; extend the compasses from 6 to 8, and this extent, laid from 9 the same way, will reach to 12, the fourth proportional required. 4. “To find a mean proportional between any two given numbers.” Suppose 8 and 32 : extend the compasses from 8 in the left-hand part of the line to 32 in the right; then bisecting this distance, its half will reach from 8 forward, or from 32 backward, to 16, the mean proportional sought. 5. “To extract the square root of any number.” Suppose 25: bisect the distance between one on the scale and the point representing 25 ; then the half of this distance, set of from 1, will give the point representing the root 5. In the same manner the cube root, or that of any higher power, may be found, by dividing the distance on the line, between 1 and the given number, into as many equal parts as the index of the power expresses; then one of those parts, set from 1, will find the point representing the root required. GUNTER’s quadrant, one made of wood, brass, &c. containing a kind of stereographic projection of the sphere, on the plane of the equinoctial; the eye being supposed placed in one of the poles. Besides the use of this quadrant in finding heights and distances, it serves also to find the hour of the day, the sun's azimuth, and other problems of the globe. GUNTER’s scale, usually called by seamen the Gunter, is a large plain scale, having various lines upon it, of great use in working the cases or questions in navigation. This scale is usually two feet long, and about an inch and a fift broad, with various lines upon it, both natural and logarithmic, relating to trigonometry, navigation, &c. On the one side are the natural lines, and on the other the artificial or logarithmic ones. The former side is first divided into inches and tenths, and numbered from one to twenty-four

inches, running the whole length near one edge. One half the length of this side consists of two plain diagonal scales, for taking off dimensions to three places of figures. On the other half or foot of this side are contained various lines relating to trigonometry, in the natural numbers, and marked thus, viz. Rumb, the rumbs or points of the compass; Chord, the line of chords; Sine, the line of sines; Tang. the tangents; S. T. The semi-tangents; and at the other end of this half are, Leag, leagues, or equal parts; Rumb, another line of rumbs ; M. L. miles of longitude : Chor, another line of chords. Also in the middle of this foot are L, and P, two other lines of equal parts: and all these lines on this side of the scale serve for drawing or laying down the figures to the cases in trigonometry and navigation. On the other side of the scale are the following artificial or logarithmic lines, which serve for working or resolving those cases; viz. S. R. the sine rumbs; T. R. the tangent rumbs; Numb. line of numbers; Sine, sines; V. S. the versed sines; Tang, the tangents; Meri. Meridional parts; E. P. Equal parts. GUN-WALE, or gunnel, is the uppermost wale of a ship, or that piece of timber which reaches on either side from the quarter-deck to the forecastle, being the uppermost bend which finishes the upper works of the hull, in that part in which are put the stanchions which support the waste-trees. GUSSET, in heraldry, is formed by a line drawn from the dexter or sinister chief points, and falling down perpendicularly to the extreme base. GUST, in sea-language, a sudden and violent squall of wind, bursting from the hills upon the sea, so as to endanger the shipping near the shore. These are peculiar to some coasts, as those of South Barbary and Guinea. GUSTAVIA, in botany, so named in memory of Gustavus III. King of Sweden: a genus of the Monadelphia Polyandria class and order. Natural order of Myrti, Jussieu. Essential character: calyx none: petals several; berry many-celled; seeds appendicled. There is but one species, viz. G. augusta, which is a tree from

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