Sidebilder
PDF
ePub

is a native of New Zealand and the South Sea Islands. It is in length about sixteen inches. Its food consists of shell-fish and putrid carcases. Its legs are long, red, and naked a little above the knees.

VAGRANTS are all persons threatening to run away, and leave their wives and children to the parish. All persons unlawfully returning to the parish or place whence they have been legally removed by order of two justices, without bringing a certificate from the parish or place whereto they belong. All persons who have not wherewith to maintain themselves, live idle, and refuse to work for the usual wages given to other labourers in the like work, in the parishes or places where they are. All persons going from door to door, or placing themselves in the streets, highways, or passages, to beg or gather alms in the parishes or places where they dwell. All these shall be deemed idle and disorderly persons, and one justice may commit such offenders (being thereof convicted before him, by his own view, confession, or oath of one witness) to the house of correction, to hard labour, not exceeding one month. And any person may apprehend and carry before a justice any such persons going from door to door, or placing themselves in the streets, highways, or passages, to beg alms in the parishes or places where they dwell; and if they shall resist, or escape from the person apprehending them, they shall be punished as rogues and vagabonds. And the said justice, by warrant under his hand and seal, may order any overseer, where such of fender shall be apprehended, to pay five shillings to any person in such parish or place so apprehending them, for every of fender so apprehended; to be allowed in his accounts, on producing the justice's order and the person's receipt to whom it was paid. 17 George II. c. 5. The same statute also enacts, that such justice shall order the person so apprehended to be publicly whipped by the constable, petit-constable, or some other person to be appointed by such constable or petit-constable of the place where such offender was apprehended, or shall order him to be sent to the house of correction; and by 27 George III. c. 11, the common gaol, until the next sessions, or for any less time, as such justice shall think proper. To defray the expenses of apprehending, conveying, and maintaining rogues, vagabonds, and incorrigible rogues, and all other expenses necessary, the justices, in sessions, may cause such sums as shall be necessary to be raised, in the same

manner as the general county rate. 17 George III. c. 5.

VAHLIA, in botany, so named in honour of Martin Vahl, regius professor of botany, at Copenhagen, a genus of the Pentandria Digynia class and order. Natural order of Succulenta. Onagræ, Jussieu. Essential character: calyx fiveleaved: corolla five-petalled; capsule inferior, one-celled, many-seeded. There is only one species, viz. V. capensis, a native of the Cape of Good Hope, in sandy places.

VAIR, in heraldry, a kind of fur, consisting of divers little pieces, argent, and azure, resembling a Dutch U, or a bellglass. Vairs have their point azure oppo. site their point argent, and the base argent to the base azure.

VAIRY, VAIRE, VERRY, or VARRY, in heraldry, expresses a coat, or the bearings of a coat, when charged or chequered with vairs and hence, vairy cuppy, or vairy tassy, is a bearing composed of pieces representing the tops of crutches.

:

VALANTIA, in botany, cross-wort, a genus of the Polygamia Monoecia class and order. Natural order of Stellatæ. Rubiaceæ, Jussieu. Essential character : hermaphrodite, calyx none; corolla fourparted; stamens four; style bifid; seed one; male, calyx none; corolla three or four-parted; stamens three or four; pistil obsolete. There are nine species.

VALENTINIA, in botany, a genus of the Octandria Monogynia class and order. Essential character: calyx five-parted, coloured, spreading; corolla none; capsule berried, four-seeded, pulpy. There is but one species, viz. V. illicifolia, a native of Hispaniola, on the most barren rocks towards the ocean; also in Cuba, about the Havannah.

VALERIANA, in botany, valerian, a genus of the Triandria Monogynia class and order. Natural order of Aggregatæ. Dipsacea, Jussieu. Essential character: calyx none; corolla one-petalled; gibbous on one side of the base, superior; seed one. There are thirty-one species.

VALLISNERIA, in botany, a ge nus of the Dioecia Diandria class and order. Natural order of Palma. Hydrocharides, Jussieu. Essential charac ter: male, spathe two-parted; spadix covered with floscules; corolla threeparted; female, spathe bifid, one-flowered; calyx three-parted: superior; stigma three-parted: capsule one-celled, many-seeded. There are two species, viz. V. spiralis, two-stamened vallisneria; and V. octandria, eight-stamened vallis. neria.

VALUE, in commerce, denotes the price or worth of any thing: hence the intrinsic value denotes the real and effective worth of a thing, and is used chiefly with regard to money, the popular value whereof may be raised and lowered at the pleasure of the prince; but its real, or intrinsic value, depending wholly on its weight and fineness, is not at all affected by the stamp or impression there

on.

VALVE, in hydraulics, pneumatics, &c. is a kind of lid, or cover, of a tube or vessel, so contrived as to open one way; but which, the more forcibly it is pressed the other way, the closer it shuts the aperture; so that it either admits the entrance of a fluid into the tube or vessel, and prevents its return; or admits its escape, and prevents its re-entrance.

VALVE, in anatomy, a thin membrane, applied on several cavities and vessels of the body, to afford a passage to certain humours going one way, and prevent their reflux towards the place from whence they came. The veins and lymphatics are furnished with valves which open towards the heart, but keep close towards the extremities of those vessels; that is, they let the blood and lymph pass towards the heart, but prevent their returning towards the extreme parts from whence they came.

VAN, in naval affairs, the foremost division of a naval armament, or that part which leads the way to battle, or advances first in the order of sailing.

VANDELLIA, in botany, a genus of the Didynamia Angiospermia class and order. Natural order of Personatæ. Scrophulariæ, Jussieu. Essential character: calyx four-parted; corolla ringent; filaments the two outer from the disk of the lip of the corolla; anthers connected by pairs; capsule one-celled, many-seeded. There are two species, viz. V. diffusa, and V. pratensis.

VANGUERIA, in botany, a genus of the Pentandria Monogynia class and order. Natural order of Aggregatæ. Rubiaceæ, Jussieu. Essential character: calyx five-toothed; corolla tube globular, with a hairy throat; stigma bilamel late; berry inferior; four or five-seeded. There is but one species, viz. V. edulis, supposed to be a native of China.

VAPOUR, in meteorology, a thin humid matter, which, being rarefied to a certain degree by the action of heat, ascends to a particular height in the atmosphere, where it is suspended, until it returns in the form of dew, rain, snow, &c. On this subject we refer our readers

to the articles EVAPORATION and METEOROLOGY, and shall make a few additional observations on dew, which is a phenomenon proper to clear weather. It begins to be deposited about sun-set, is most constant in vallies, and on plains near rivers, and other collections of waters, and abounds on those parts of the surface which are clothed with vegetation. It is often suspended when rain is approaching, as likewise in windy weather, and before thunder storms: an unusually copious deposition however sometimes precedes rain. The following is said to be the usual appearance in the valley through which the Thames passes. After a clear warm day there is gradually formed on the horizon a continuous haze, rising sometimes to a considerable height, and often tinged by the setting sun with a fine gradation of red and violet shades. This is the precipitated water become faintly visible in its descent. Dew is always to be found on the grass by the time that this haze has become conspicuous, and its abundance is proportioned to the density and permanence of the latter. The following facts are deserving of notice.

In this country the dew is observed more copiously in the mornings of spring and summer than at other times in the year. Sometimes, however, in autumn and winter, an abundant dew is deposited in the night. In countries nearer the equator, the dews are generally observed in the morning throughout the whole year; and in some places they are so very copious as in a great measure to supply the deficiency of rain, which seldom falls in those places. The condensation of the vapour which forms the dew mostly takes place while the sun is below the horizon; the greatest deposition taking place soon after the setting of the sun.

In cloudy weather there is little or no dew deposited: the most considerable quantity is observed in a morning, subsequent to a clear, still, and cool night, which has followed a pretty warm day. The lower parts of bodies that are exposed to the ambient air are first covered with dew. The most singular circumstance is, that dew is not deposicriminately: it falls upon certain bodies ted upon all kinds of substances indismuch more abundantly than on others, and upon some even not at all. The drops of dew attach themselves to glass, crystals, and porcelain, much more readily than to other bodies; next to these the leaves of vegetables, wood, especially when varnished, and common earthen ware; but the dew adheres least

come

of all to all sorts of metallic bodies. We may now notice Mr. Dalton's observations, which are the result of a variety of well conducted and very accurate experiments on this subject. 1. That aqueous vapour is an elastic vapour sui generis, diffusible in the atmosphere, but forming no chemical combination with it. 2. That temperature alone limits the maximum of vapour in the atmosphere. 3. That there exists at all times, and in all places, a quantity of aqueous vapour in the atmosphere, variable according to circumstances. 4. That whatever quantity of aqueous vapour may exist in the atmosphere at any time, a certain temperature may be found, below which a portion of that vapour would unavoidably fall or be deposited, in the form of rain or dew, but above which no such diminution could take place with chemical agency. This point may be called the extreme temperature of vapour of that density; and 5. That whenever any body, colder than the extreme temperature of the existing vapour, is situated in the atmosphere, dew is deposited upon it, the quantity of which varies as the surface of the body, and the degree of cold below the extreme temperature. The reader may be referred to an excellent and elaborate article on this subject in Dr. Rees's New Cyclopedia, a work, of which it may be fairly and honourably said, that as it advances in its progress, it increases in merit and reputation.

VARIABLE quantities, in geometry and analytics, denote such as are either continually increasing or diminishing; in opposition to those which are constant, remaining always the same. Thus, the abscisses and ordinates of an ellipsis, or other curve line, are variable quantities, because they vary or change their magnitudes together. Some quantities may be variable by themselves alone, while those connected with them are constant: the abscisses of a parallelogram, whose ordinates may be considered as all equal, and therefore constant. The diameter of a circle, and the parameter of a conic section, are constant, while their abscisses are variable. Variable quantities, (see FLUXIONS,) are usually denoted by the last letters of the alphabet z, y, x, while the constant ones are denoted by the first letters a, b, c.

as

VARIANCE, in law, signifies any alteration of a thing formerly laid in a plea, or where the declaration in a cause differs from the writ, or from the deed upon which it is grounded. If there be a vari

ance between the declaration and the writ, it is error, and the writ shall abate; and if there appear to be a material variance between the matter pleaded and the manner of pleading it, this is not a good plea, for the manner and matter of pleading ought to agree in substance, or there will be no certainty in it. Cro. Jac. 479.

VARIATION of curvature, in geometry, is used for that inequality or change which happens in the curvature of all curves except the circle; and this variation, or inequality, constitutes the quality of the curvature of any line. Sir Isaac Newton makes the index of the inequality, or variation of curvature, to be the ratio of the fluxion of the radius of curvature to the fluxion of the curve; and Mr. Maclaurin, to avoid the perplexity that different notions, connected with the same terms, occasion to learners, has adopted the same definition; but he suggests, that this ratio gives rather the variation of the ray of curvature, and that it might have been proper to have measured the variation of curvature, rather by the ratio of the fluxion of curvature itself to the fluxion of the curve: so that the curvature being inversely as the radius of the curvature, and consequently its fluxion as the fluxion of the radius itself directly, and the square of the radius inversely, its variation would have been directly as the measure of it, according to Sir Isaac's definition, and inversely as the square of the radius of curvature.

VARIATION of the needle, in magnetism. Although the north pole of the magnet in every part of the world, when suspended, points towards the northern parts, and the south pole to the southern parts, yet it seldom points exactly north and south. The angle, in which it deviates from due north and south is called "The variation of the needle," or, "The variation of the compass," and this variation is said to be east or west, according as the north pole of the needle is eastward or westward of the meridian of the place. This deviation from the meridian is not the same in all parts of the world, but is different in different places, and it is almost perpetually varying in the same place. When the variation was first observed, the north pole of the magnetic needle declined eastward of the meridian of London, but it has since that time been changing towards the west; so that in the year 1657, the needle pointed due north and south; at present, it declines towards the west between 24° and 25°

and it seems to be still advancing westward.

VARIEGATION, among botanists and florists, the act of streaking or diversifying the leaves, &c. of plants and flowers with several colours. Variegation is either natural or artificial. Of natural variegation there are four kinds: the first showing itself in yellow spots here and there, in the leaves of plants, called by gardeners the yellow bloach. The second kind, called the white bloach, marks the leaves with a great number of white spots, or stripes; the whitest lying next the surface of the leaves, usually accompanied with other marks of a greenish white, that lie deeper in the body of the leaves. The third, and most beautiful, is where the leaves are edged with white, being owing to some disorder or infection in the juices, which stains the natural complexion or verdure of the plant. The fourth kind is that called the yellow edge. VARIGNON (PETER,) in biography, was born at Caen in 1654. He was the son of an architect, and intended at an early age for the church. Accident threw into his way a copy of Euclid's Elements, which gave him a strong bias towards mathematical learning. So intent was he in the pursuit of science, that he abridged himself of the necessaries of life, to purchase books to aid him in the pursuit. From his relations he met with much opposition, because they imagined that geometry and algebra would ill accord with the course of theological studies. While he was at college he became acquainted with the Abbé St. Pierre; and in their application to learning, they were mutually serviceable to one another. abbé, to enjoy more of Varignon's company, determined to lodge with him; and sensible of his merit, he resolved to give him a fortune, that he might fully pursue the bent of his genius, and improve his talents; and out of only 1800 livres a year, which he had himself, he conferred 300 of them upon Varignon.

The

The abbé, persuaded that he could not do better than go to Paris to study philophy, settled there in 1686, with M. Varignon, in the suburbs of St. Jacques. There each studied in his own way; the abbé applying himself to the study of men, manners, and the principles of government; whilst Varignon was wholly occupied with the mathematics.

"I," says Fontenelle, "who was their countryman, often went to see them, sometimes spending two or three days with them. They had also room for a

couple of visitors, who came from the same province. We joined together with the greatest pleasure. We were young, full of the first ardour for knowledge, strongly united, and, what we were not then perhaps disposed to think so great a happiness, little known. Varignon, who had a strong constitution, at least in his youth, spent whole days in study, without any amusement or recreation, except walking sometimes in fine weather. I have heard him say, that in studying after supper, as he usually did, he was often surprised to hear the clock strike two in the morning; and was much pleased that four hours rest were sufficient to refresh him. He did not leave his studies with that heaviness which they usually create; nor with that weariness which a long application might occasion. He left off gay and lively, filled with pleasure, and impatient to renew it. In speaking of mathematics, he would laugh so freely, that it seemed as if he had studied for diversion. No condition was so much to be envied as his; his life was a continual enjoyment, delighting in quietness.'

دو

In the solitary suburb of St. Jacques he formed, however, a connection with many other learned men; as Du Hamel, Du Verney, De la Hire, &c. Du Verney often asked his assistance in those parts of anatomy connected with mechanics; they examined together the positions of the muscles, and their directions; hence Varignon learned a good deal of anatomy from Du Verney, which he repaid by the application of mathematical reasoning to that subject.

At length, in 1687, Varignon made himself known to the public by a treatise on new mechanics, dedicated to the Academy of Sciences. His thoughts on the subject were, in effect, quite new. He discovered truths, and laid open their sources. In this work he demonstrated the necessity of an equilibrium, in such cases as it happens in, though the cause of it is not exactly known. This discovery Varignon made by the theory of compound motions, and is what this essay turns upon. This new treatise on mechanics was greatly admired by the mathematicians, and procured the author two considerable places, the one of geometrician in the Academy of Sciences, the other of professor of mathematics in the college of Mazarine; to this honour he was the first person raised.

Varignon catched eagerly at the science of infinitesimals as soon as it appeared in the world, and became one of its

most early cultivators. Severe and unremitted study injured his health very much, and in 1705 he had a dangerous illness, which confined him to his bed many months, and the effects of which he did not recover for three years. Indeed it can scarcely be said that he ever perfectly regained the vigour which he had formerly enjoyed. He could not lay aside his studies, and these were deemed incompatible with his health. He died in 1722: by Fontenelle he is described as an excellent man, not apt to be jealous of the fame of others; he was as simple in his manners as his understanding was superior. He was at the head of the French mathematicians, and one of the best in Europe. He was apt to be over hasty when a new object presented itself; and too impetuous towards those who oppos ed him. His works, which were published separately, were "Projet d'une nouvelle Mechanique," 4to. "Des nouvelles Conjectures sur la Pesanteur." "Nouvelle Mechanique ou Statique." Besides a vast number of separate memoirs.

VARNISH. Lac varnishes, or lacquers, consist of different resins in a state of solution, of which the most common are, mastich, sandarach, lac, benzoin, copal, amber, and asphaltum The menstrua are either expressed or essential oils, as also alcohol. For a lac varnish of the first kind, the common painter's varnish is to be united, by gently boiling it with some more mastich or colophony, and then diluted again with a little more oil of turpentine. The latter addition promotes both the glossy appearance and drying of the varnish.

Of this sort is the amber varnish. To make this varnish, half a pound of amber is kept over a gentle fire in a covered iron pot, in the lid of which there is a small hole, till it is observed to become soft, and to be melted together into one mass. As soon as this is perceived, the vessel is taken from off the fire, and suffered to cool a little; when a pound of good painter's varnish is added to it, and the whole suffered to boil up again over the fire, keeping it continually stirring. After this, it is again removed from the fire; and when it is become somewhat cool, a pound of oil of turpentine is to be gradually mixed with it. Should the varnish, when it is cool, happen to be yet too thick, it may be attenuated with more oil of turpentine. This varnish bas always a dark-brown colour, because the amber is previously half-burned in this operation; but if it be required of a

bright colour, amber-powder must de dissolved in transparent painter's varnish, in Papin's machine, by a gentle fire.

As an instance of the second sort of lac varnishes with etherial oils alone, may be adduced the varnish made with oil of turpentine. For making this, mastich alone is dissolved in oil of turpentine by a very gentle digesting heat, in close glass vessels. This is the varnish used for the modern transparencies employed as window-blinds, fire-screens, and for other purposes. These are commonly prints, coloured on both sides, and afterward coated with this varnish on those parts that are intended to be transparent. Sometimes fine thin calico, or Irish linen, is used for this purpose; but it requires to be primed with a solution of isinglass, before the colour is laid on.

Copal may be dissolved in genuine Chio turpentine, according to Mr. Sheldrake, by adding it in powder to the tur. pentine previously melted, and stirring till the whole is fused. Oil of turpentine may then be added to dilute it sufficiently. Or the copal in powder may be put into a long-necked mattrass with twelve parts of oil of turpentine, and digested several days on a sand-heat, frequently shaking it. This may be diluted with one fourth or one fifth of alcohol. Metallic vessels, or instruments, covered with two or three coats of this, and dried in an oven each time, may be washed with boiling water, or even exposed to a still greater heat, without injury to the varnish.

A varnish of the consistence of thin turpentine is obtained for aërostatic machines, by the digestion of one part of elastic gum, or caoutchouc, cut into small pieces, in thirty-two parts of rectified oil of turpentine. Previously to its being used, however, it must be passed through a linen cloth, in order that the undissolved parts may be left behind.

The third sort of lac-varnishes consists in the spirit-varnish. The most solid resins yield the most durable varnishes; but a varnish must never be expected to be harder than the resin naturally is of which it is made. Hence, it is the height of absurdity to suppose that there are any incombustible varnishes, since there is no such thing at an incombustible resin. But the most solid resins by them. selves produce brittle varnishes: therefore something of a softer substance must always be mixed with them, whereby this brittleness is diminished. For this purpose, gum elemi, turpentine, or bal

« ForrigeFortsett »