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wards the point, and marked below the under mandible by a triangular prominence,by their light body, supported by large wings, by slender legs, palinated feet, and a small hind toe. They are timid and cowardly, except in defence of their young. Generally seen in large flocks, the old and young separate; the larger species frequent the sea, the smaller, lakes or rivers. They walk with tolerable ease, and swim well, but are incapable of diving. They keep much on the wing, and their flight is rapid, strong, and long sustained, even in heavy gales. In sitting, they contract their neck, and rest on one foot. They are extremely voracious, fighting with each other for prey. They are patient of hunger, but will feed on every kind of animal food, either dead or alive, putrid or fresh. Their principal food, however, is fish, of which they will follow the shoals; they catch them with great agility, darting down like an arrow. They breed only once a year, laying from two to four eggs. The species are exceedingly numerous, and resemble each other greatly. The gulls are continually fighting with each other, and the strong plundering the weaker. No sooner does one rise from the water, with a fish in its bill, than it is immediately pursued by others, stronger than itself, and the first that reaches it tears away the spoil. Should, however, the latter not instantly swallow the booty it has acquired, it is, in turn, pursued by others; and, even if it has performed this process, it is oftentimes obliged to disgorge it, when it is seized by one of the pursuers, before it can reach the water. The facility which the gulls have of vomiting their food has been taken notice of, even in their captive state. Some of these birds have been tamed, but, even then, they have always discovered the same quarrelsome and voracious habits. When two are kept together, the weaker generally becomes the victim of the ill nature of the other. Almost all the gulls that appear on our coast are also inhabitants of Europe. This genus is not well understood by naturalists, and much confusion exists as to the species.

GUM; one of the proximate principles of vegetables, distinguished by the following properties :--It is an insipid, inodorous, uncrystallizable solid, more or less transparent, the various colors which the different kinds possess being derived from mixture with coloring principles while exuding in a fluid state. It is insoluble in alcohol, and extremely soluble in water, in which properties it is the reverse of resin. It differs from mucilage only

in being deprived of the water which rendered it fluid; and, of course, when water is added, it again becomes mucilage. This mucilage is apparently not susceptible of fermentation, and may be kept for a long time, as it is less disposed to spontaneous changes than almost any vegetable product. Its chemical composition so nearly approaches sugar, that it may be converted into it by means of nitric acid. Gum, as above defined, is identical in all vegetables, and the different kinds vary only in the quantity and quality of the substances united with them. It exists naturally almost pure in gun Arabic and gum Senegal, and, more or less mixed, in the gum which exudes from the plum, cherry and other fruit-trees, as also in the mucilage of flaxseed, slippery elm, &c. Various resins and gum-resins are commonly confounded under this appellation.

GUM ARABIC is the product of the mimosa nilotica and some other species of the same genus, inhabiting the sandy parts of Arabia, Egypt, Senegal and Central Africa. It exudes spontaneously, in a fluid state, and remains attached to the branches after it has concreted and become solid. This exudation takes place continually, during the whole of the dry season, from October to June, but more copiously immediately after the rains. December and March are the two months in which this gum is collected by the Arabs, with whom it is an important aliment, those tribes that are continually wandering in the desert often making it their principal article of food during a great part of the year. Gum Arabic is obtained in rounded masses, transparent, or of a light yellow color, capable of being easily reduced to a powder, insipid to the taste, or possessing a slight acidity, which, however, is only perceptible by those who use it habitually. It is easily soluble in water, and the solution has the property of conveying pulverized solids through a filter, which would separate them were they suspended merely in water: thus it is impossible, by this means, to separate powdered charcoal from gum water. In pharmacy, gum Arabic is employed to suspend in water substances which, otherwise, could not be kept equally diffused, as balsams, fixed oils, resins, &c.; but its principal consumption is in manufactures, forming the basis of crayons and cakes of water-colors, as well as of writing-ink, and several liquid colors, serving to increase the consistency of these colors, and to prevent their spreading in calico printing, affording

a clear cement for joining light substances which may be prepared in a moment, giving a lustre to ribands, silks, &c., which, however, is destroyed by the application of water. It is, besides, used for a great variety of purposes. In medicine, it is frequently employed, especially in dysenteries, as a demulcent, and enters into the composition of a variety of emollient preparations. Gum Senegal does not differ in its sensible properties; indeed, the chief part of the gum Arabic of commerce is brought from Senegal, and constitutes the most important article of trade with that country.

GUM RESINS apparently combine the properties of gums and resins, being partly soluble in water, partly in alcohol; but they are evidently compound substances, formed of two or more vegetable principles, which, indeed, are often in a state of mere mechanical mixture. Aloes, ammoniac, assafoetida, galbanum, gamboge, olibanum, scammony, and a great variety of concrete juices, are referred to this head.

GUN; a fire-arm, or weapon of offence, which forcibly discharges à ball, shot, or other offensive matter, through a cylindrical barrel, by means of gunpowder. Gun is a general name, under which are included divers, or even most species of fire-arms. They may be divided into great and small. Great guns, called, also, by the general name cannons, make what we also call ordnance, or artillery, under which come the several sorts of cannon. (See Cannon, Artillery, &c.) Great guns, of all sorts, cannons, carronades, &c., whether of iron or brass, are cast in sand, and afterwards bored. Small guns, muskets, fowling-pieces, &c., are forged from bars of malleable iron, hammered to a proper width, and then turned over a mandril, or cylindrical rod, so as to form a tube with a bore smaller than that of the intended piece. The edges overlap about half an inch, and are firmly welded together. The tube is then hammered, in semicircular grooves, on an anvil hollowed for the purpose. It is afterwards bored with several instruments, of different sizes, in succession, till the hollow is sufficiently large and smooth. A strong plug is firmly screwed into the breech, so as to make it perfectly close. The projecting parts of the barrel, the sight, the loops which fasten it to the stock, &c., are soldered

on.

GUNNERY signifies the science of using artillery against an enemy judiciously, and to the greatest effect. Besides an accurate

acquaintance with the management of ordnance of all kinds, the range and force of every kind, the charge and direction necessary for different distances, their materials, the manner of making and of preserving them, with the component parts, the kinds, the fabrication, the effect of gunpowder, and the method of preserving it, with the manner of preparing and managing every thing that appertains to ammunition, the artillerist must be able to instruct his men in their exercises, both on horseback and on foot; he must be well acquainted with the management of the horses, that are used to transport the cannon and to mount the flying artillery; must know how to harness them to the cannon; how to move and manoeuvre with them on ground of every kind; how to repair, at the moment, any sudden damage; and must be thoroughly acquainted with tactics, especially with the peculiarities of the ground, and with the art of availing himself of them most judiciously in the disposition of his artillery. He must, finally, be able to attack or defend any position; he must have an accurate acquaintance with the science of fortification; but especially he must be practically skilled in throwing up batteries and other fieldworks, so that he may be able, by disposing his artillery before or within a strong place, to assist the engineer most effectually in its attack or defence. Besides, the artillerist has often the regulation of the lights, and other signals, in time of war, of the fire-works in peace, &c. All this must be learned by experience, and by the study of auxiliary sciences. Mathematics (particularly the doctrine of curves, to calculate the path of the balls), physics and chemistry are very necessary, in order to understand the effect of powder, and the manufacturing of ammunition, as well as that of all kinds of fire-works. A knowledge of mechanics is, also, very useful, for understanding the theory of carriages, for moving large loads, when necessary, and on many other occasions.

GUNPOWDER is a mixture of saltpetre, sulphur and charcoal. If we may believe the relations of the missionaries, and the reports of the Chinese historians, the Chinese were first acquainted with the application of gunpowder. Perhaps it proceeded from them to the Arabs; for, in 1331, the Moors used it in their operations before Alicant, and certainly in 1342, at Algesiras; in 1250, the Arabs probably used a mixture similar to gunpowder before Damietta, and perhaps also in a naval

engagement in the year 1085. Among the Europeans, the traces of this invention are still more ancient; for the Greek fire, which was first employed in 668, must have, at least, contained saltpetre mixed with pitch, naphtha, &c., since it was customary, by means of it, to hurl stones from metallic tubes. The first information of the knowledge of the Europeans with regard to the chemical mixture of powder, is found in the 9th century, in a book composed by Marcus Gracchus, preserved in the university of Oxford, which also accurately explains its composition. Roger Bacon (who died in 1294) was likewise acquainted with the power which saltpetre has, when set on fire, of producing a thundering report. The discoverer of the power of powder, when confined and set on fire, of propel ling heavy bodies, was, according to common report, Berthold Schwartz, a monk, who is said to have lived at Mayence, between 1290 and 1320. He, in some of his experiments in alchemy, had put the mixture into a mortar, and, having accidentally dropped into it a spark of fire, to his astonishment, saw the pestle fly off into the air. Other traditions attribute this invention to Constantine Antlitz of Cologne (see De Boucher's Mémoire sur l'Origine de la Poudre à Canon). However this may be, powder was scarcely applied to military uses before 1350, and the accounts of the use of cannons in the battles of Crécy (1346), Poictiers, and still earlier engagements, have arisen from the various significations of the word cannon. In 1356, powder is mentioned in the accounts of the treasury of Nuremburg; in 1360, the house of assembly at Lübeck was burned by the imprudence of the powder manufacturers; and, in 1365, the margrave of Misnia had pieces of artillery. In the course of a few years afterwards, it was known over all Europe. Thus the first traces of this invention would appear to be found in Germany; other nations, however, have put in their claims to this honor. The proportion of the ingredients in the composition of gunpowder, is different in different countries: in the Prussian powder-mills, 75 parts of saltpetre, 114 parts of sulphur, and 134 parts of charcoal are used; but in the French mills, 75 parts of saltpetre, 124 of coal, and 124 of sulphur. In the manufacture of this article, which is carried on in very different ways, much depends upon the goodness of the ingredients. The crude saltpetre is broken up, moistened and exposed to the action of a slow fire, contin

ually skimmed and violently agitated, till all the moisture evaporates, and the saltpetre remains in the form of a fine powder. The sulphur is pulverized after having been well purified. The charcoal is that derived from the alder or any other soft wood or bushes, as, for example, hemp stalks, which are burned with great care in a confined room, and reduced to a fine powder. These three ingredients are then moistened, brought under a stamping, or more commonly a rolling mill, where two metallic, or, which are better, marble cylinders, turn round a fixed vertical wooden pillar, and crush to pieces the mixture, which lies upon a round smooth surface of the same material. Other mills effect this bruising operation by several large iron runners, revolving upon a metallic plate, similar to a painter's grinding stone, or by a rapid revolution of the mixture in casks containing metallic balls. After the mixture, in some one of these ways, has been acted on in the mills for the space of six or eight hours, and when the ingredients are united, and form one homogeneous mass, it is pressed, while yet wet, by means of cylindric rollers of wood, through a sieve of perforated parchment, by which the powder is formed into grains. In other mills, this process of forming it into grains takes place after the powder has been pressed between two boards into a solid cake, and then submitted twice to the operation of a grooved roller, The powder, after it has been grained, is spread upon boards in the drying-houses, and exposed to the strong heat of an oven for two days. In order to prevent its taking fire, the oven is well lined with clay and copper. Of late years, this process of drying has been sometimes effected by means of steam. Finally, the powder is sorted by being passed through several sieves. In the first, or coarsest, remains what is entirely useless; through the second passes the second-sized, or cannon powder; and through the third and last the finest, or musket powder. The powder, thus prepared, is packed in oaken casks. In order to provide against accidents, the English use copper casks or vessels, with the tops screwed on. Copper vessels are also used in the U. States. der must be of a slate color, uniform, round and pure grain, and also have a uniform color on being broken up ; nor should it leave behind it, either on the hand or on paper, any black spots. When set on fire, it should burn at once, without crackling or leaving upon paper any ap

Good gunpow

pearances of its combustion. When applied to the tongue, the taste should be extremely cooling. In order to prove its strength, let any person apply an accurate ly fitting ball to a small mortar, and the distance to which the ball is thrown will prove the strength of the powder. The French government eprouvette is a mortar seven French inches in diameter, and three ounces of powder must throw a copper globe, of 60 pounds weight, 300 feet; otherwise the powder is not admissible. An eprouvette is sometimes used which is inaccurate; the powder throws back the cover of a small mortar, and with it a wheel, which catches in a steel spring; the strength is determined by the tooth, at which the wheel remains fixed. This method is defective, because the spring is weakened by use. Another method is, to suspend a small cannon as a pendulum, and to judge of the strength of the powder by the force of the recoil, which will describe a greater or less arc of a circle. In the preservation of powder, fire and water must both be carefully guarded against. Powder destined for military purposes, should be deposited in an airy building, removed at least 1000 paces from any habitation, provided with lightning rods, and surrounded with walls, ditches and palisadoes; there should be a guard constantly set, to prevent the introduction of fire, and to hinder all persons from entering, who have things about them that will produce fire. These buildings should contain openings for the free passage of the air; the casks should stand upon a platform of wood, at a distance from the wall, and the powder itself should be sunned and dried every one or two years. If the powder is to be kept in damp places, as, for example, in the casemates (arched passages under ground) of fortresses, the walls should be internally covered with lead, and a vessel filled with unslacked lime placed in the middle of the apartment, so that the moisture of the atmosphere may be attracted by the lime. In the transportation of gunpowder, dust, which is liable to penetrate the cracks and joints of the casks, should be carefully guarded against, as the friction may produce explosion. It is also necessary for its good preservation, that the carriages and vessels in which it is transported should be water-tight. We may effectually preserve it from moisture, by dipping the cask and the sackcloth covering into melted pitch. Vessels prepared in this way, and containing powder, may be immersed in the water for weeks, without

having their contents in the least injured. The effects of this substance, when set on fire, are truly wonderful. When powder is heaped up in the open air, and then inflamed, it detonates without report or effect. A small quantity of powder left free in a room, and fired, merely blows out the windows; but the same quantity, when confined in a bomb within the same chamber, and inflamed, tears in pieces and sets on fire the whole house. Count Rumford loaded a mortar with one-twentieth of an ounce of powder, and placed upon it a 24 pound cannon, weighing 8081 pounds; he then closed up every opening as completely as possible,and fired the charge, which burst the mortar with a tremendous explosion, and raised up this immense weight. Whence such and similar effects arise, no chemist as yet has been able, satisfactorily, to explain; and the greater part of the explanations hitherto made are, nothing but descriptions of facts. The best explanation is, that the azote and oxygen gases of the saltpetre, and the carbonic acid gas from the charcoal, which had hitherto been in a solid state, are set free, and the expansive power of all these gases requires much more room than they previously occupied. They now endeavor to overcome the obstructions to their expansion, and this tendency is very much increased by the intense heat generated by the gases. The confined steam operates in the same way, although this is not the only cause of the phenomenon, as Rumford supposes.

GUNPOWDER PLOT; a conspiracy formed in the second year of the reign of James I (1604), for the purpose of destroying the king and parliament at a blow. The Roman Catholics having been disappointed in their expectations of indulgence from James, Catesby and Percy, two Catholic gentlemen of ancient family, with a few others of their persuasion, determined to run a mine below the hall in which parliament met, and, on the first day of the session, when the king and the royal family would be present, involve all the enemies of the Catholic religion in one common ruin. A vault below the house of lords, which had been used to store coals, was hired, two hogsheads and 36 barrels of powder lodged in it, the whole covered with fagots, and the doors thrown open so as to prevent suspicions. As the young prince Charles and the princess Elizabeth would be absent, measures were taken to have them seized, and Elizabeth proclaimed queen. The secret of the conspiracy was communicated

to more than 20 persons, and had been faithfully kept for near a year and a half. Ten days, however, before the meeting of parliament, a Catholic peer received a note from an unknown hand, advising him not to attend at the parliament, as it would receive a terrible blow. This he communicated to the secretary of state, lord Salisbury, who, although apprehending nothing, thought proper to lay it before the king. James saw the matter in a more serious light; and, on searching the vaults below the houses of parliament (Nov. 5, 1605), Guy Fawkes, an officer in the Spanish service, who had been employed to fire the powder, was found at the door, with the matches in his pocket, and the gunpowder in the vault was discovered. Fawkes was put to the torture, and made a full discovery of the conspirators, who, with their attendants, to the number of 80 persons, had assembled in Warwickshire, determined to defend themselves to the last. Percy and Catesby were killed in the attack; the others were made prisoners and executed. Lingard (History of England, vol. ix, chap. 1) gives a very full account of the conspiracy, which does not materially differ from the statement above given. It has been, however, asserted by others, that it was all a plot of Salisbury's, to effect the ruin of the Catholics, and that the warning came from his hands. In support of this, they allege that most of the conspirators declared themselves ignorant of the extent of the conspiracy, the Jesuits, who were implicated in it, protested their innocence, and that the French ambassador, who made inquiries on the spot, entirely exculpates them. (See Lettres et Négociations d'Antoine Lefevre de la Boderie.) In the calendar of the church of England, the 5th of November is duly noticed as a holyday at the public offices; and the Common Prayer Book contains "A Form of Prayer with Thanksgiving, to be used yearly upon the Fifth day of November, for the happy Deliverance of King James I," &c. It is customary for boys in England, as it was for merly in New England, to make an effigy representing Guy Fawkes, which they carry about, singing certain verses,* and

*These verses are:

"Remember, remember
The fifth of November,
Gunpowder treason and plot !
We know no reason
Why gunpowder treason
Should ever be forgot.
Holla, boys! Huzza!

"A stick and a stake,
For king William's sake;

asking for materials to burn the figure. Scuffles between boys of different quarters of the town were common on this occasion, at least in Boston, Massachusetts.

GUNTER, Edmund; an excellent English mathematician, who flourished in the reign of James I, and distinguished himself by his inventions, which have never yet been superseded, though some of them have been subsequently much improved.

GUNTER'S CHAIN; the chain in common use for measuring land according to the true or statute measure; so called from the name of its inventor. The length of the chain is 66 feet, or 22 yards, or four poles of five yards and a half each; and it is divided into 100 links of 7.92 inches each. 100,000 square links make one acre.

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 it arithmetically. It is usually divided into a hundred parts, every tenth of which 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 so on; and the intermediate division will, in like manner, represent one hundredth parts of an integer. If each of the great divisions represent ten integers, then will the lesser divisions stand for integers; and if the great divisions be supposed each 100, the subdivisions will be each 10.Use of Gunter's Line :-1. To find the product of two numbers. From 1 extend the compass to the multiplier; 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 find a fourth proportional to three given numbers. Suppose the numbers 6, 8, 9: extend the compasses from 6 to 8; and this exten. A stick and a stump For Guy Fawkes' rump.

Holla, boys! Huzza!"

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