ty, on the supposition that it is receivable yearly.

PERPETUITY, in law, is where, if all that have interest join the conveyance, yet they cannot bar or pass the estate; for, if by concurrence of all having interest the estate may be barred, it is no perpetuity.

PERRY, a drink made of pears, in the same manner as cyder is made from apples. See CYDER. The pears must be perfectly ripe, and to give the liquor a greater degree of tartness, some mix crabs with them. The best fruit for making perry is such as is least fit for eating, as the choak-pear, boreland-pear, horsepear, and the barberry-pear.

PERSEUS, in astronomy, a constellation of the northern hemisphere, which, according to the catalogues of Ptolemy and Tycho, contains twenty-nine stars; but in the Britannic catalogue,sixty-seven. PERSIAN wheel, an engine, or wheel, turned by a rivulet, or other stream of water, and fitted with open boxes at its cogs to raise water for the overflowing of lands, or other purposes. It may be made of any size, according to the height the water is to be raised to, and the strength of the stream by which it is turned. This wheel is placed so, that its bottom only is immersed in the stream, wherein the open boxes at its cogs are all filled one after another with water, which is raised with them to the upper part of the wheel's circuit, and then naturally empties itself into a trough, which carries it to the land.

PERSON, in dramatic poetry, the character assumed by an actor, or he who is represented by the player. Thus, at the head of dramatic pieces, is placed the dramatis personæ, or list of the persons that are to appear on the stage. Father Bossu observes, that in the epic and dramatic poem, the same person must reign throughout; that is, must sustain the chief part through the whole piece, and the characters of all the other persons must be subordinate to him.

PERSON, in grammar, a term applied to such nouns or pronouns, as, being either prefixed or understood, are the nominatives in all inflexions of a verb; or it is the agent or patent in all finite and personal verbs. See GRAMMAR.

PERSONAL tithes, tithes paid of such profits as come by the labour of a man's person, as by buying and selling, gains of merchandise, and handicrafts, &c.

PERSONALITY, an action is in the personality, where it is brought against

the right person, or the person against whom in all law it lies.

PERSONATE, in law, is the representing a person by a fictitious or assumed character, so as to pass for the person represented. Personating bail, is by stat. 21 Jac. I. c. 26, a capital felony. By various other statutes, personating seamen entitled to wages, prize-money, &c. is also a capital felony.

PERSONATÆ, in botany, masked, the name of the fortieth order in Linnæus's Fragments of a Natural Method, consisting of a number of plants whose flowers are furnished with an irregular gaping petal, which, in figure, somewhat resembles the snout of an animal. Most of the genera of this natural order arrange themselves under the class and order "Didynamia Angiospermia." The rest, although they cannot enter into the artificial class just mentioned, for want of the classic character (the inequality of the stamina), yet, in a natural method, which admits of greater latitude, may be arranged with the Personatæ, which they resemble in their habit and general appearance, and particularly in the circumstance expressed in the title. This order furnishes both herbaceous and woody vegetables of the shrub and tree kind. The roots are generally fibrous and branched; in gerardia and tozzia, they are tuberous. The roots of broom-rape are parasitical; that is, attach themselves to the roots of other plants, from which they derive their nourishment. The stems and branches are cylindrical when young, except in some species of fig-wort, in which they are square. The leaves are simple, generally placed opposite in pairs at the bottom of the branches, but in many genera stand alternate towards the top. Some species of trumpet-flower have the common footstalk of their winged leaves terminated by a tendril, with three or five branches. In a species of cornutia is observed a stipula or scale, in form of a half moon, of the same substance with the leaves between which it is placed. The flowers are universally hermaphrodite. They proceed either singly, or in clusters, from the wings of the leaves, as in American viburnum, or terminate the branches in a spike, panicle, or head, as in cornutia, vervain, &c. In the latter, they seem placed in whorls. The calyx, or flower-cup, is of one leaf, which is cut into two, three, four, or five divisions, that are permanent. In the trumpet-flower, the calyx falls off early, and generally resolves itself into five distinct leaves. The corolla is com

posed of one irregular petal, with two lips, resembling the head or snout of an animal. In toad-flax, the petal is terminated behind by a nectarium in form of a spur. The stamina in plants of the first section, are two or four in number. In hedge-hyssop, and some species of vervain, the filaments are four in number, but two of these only are terminated by anthers; so that the number of perfect stamina in these plants is only two. The seed-bud is single, and placed above the receptacle of the flower. The style is single, thread-shaped, bent in the direction of the stamina, and crowned with a stigma, which is generally blunt, and sometimes divided into two. The seedvessel is a capsule, generally divided in ternally into two cavities, and externally into the same number of valves. The seeds are numerous, and affixed to a receptacle in the middle of the capsule.

PERSOONIA, in botany, so named in honour of C. H. Persoon; a genus of the Tetrandria Monogynia class and order. Essential character: calyx none; petals four, staminiferous towards the base; glands four at the base of the germ; stig ma blunt; drupe one-seeded. This genus consists of subvimineous shrubs; leaves commonly alternate, without stipules; corolla smooth within: anthers linear, finally bent back; style permanent, smooth; drupe eatable in most; flowers yellow. Natives of the islands in the Southern Ocean.

PERSPECTIVE is the foundation of all the polite or liberal arts that have their basis in drawing; though colouring, taken abstractedly, does not come within its rules, yet the painter, as well as the sculptor and architect, cannot but derive essential advantages from a knowledge of perspective; it is indeed difficult to conceive how a person, who has not either been instructed in, or been gifted by nature with some idea of the effects produced by locality and distance, can form any thing like a correct opinion of the merits of those imitations of nature which come under the heads of portrait, landscape, figure, or architectural drawing.

Perspective is, in brief, the art of representing, upon a plane surface, the appearance of objects, however diversified, similar to that they assume upon a glassplane, interposed between them and the eye at a given distance. The representation of a solid object on a plane surface can show the original in no other point of view but that from which it is at the time

beheld by the draughtsman; the least change in any of the parts requires a change in the whole; unless in fancy drawings, where a fac-simile is not required. Nor can any deviation from the several lines, which will be hereafter explained, and on which the truth and correctness of representation depend, be allowed, without changing the bearings, directions and tendency of all the perspective lines which constitute the basis of that faithful and converging series which unite all the component parts in the most pleasing and harmonious concinnity.

By perspective we are taught to delineate objects on a plane, upon geometrical principles, and in exact ratio with their several magnitudes, governed by their distance. But it is not in the power of art to represent any single figure (exact as it appears in nature) on a plane, except it be a circle; and then the point of sight, or direct position of the eye, must be perfectly centrical. The reasons for this are obvious; every object which recedes from the eye (such as a row of houses in an oblique direction), inevitably requires that its more remote parts should be represented as being of less magnitude than those more in front, that is, nearer to the spectator. Now, although it is considered an axiom in perspective that all objects standing parallel to the base line, or bottom of the picture, should be represented as preserving in every instance the real proportions of the scale from which their parts were taken; yet, when we analyze the object, according to the various angles those several parts make with the eye, we shall find that even such full pointing figures require their more remote parts to be reduced in proportion, as they become more distant from the centre, or point of sight. But it will be obvious, that where the object is very remote, there must be the less necessity for such scrupulous attention; therefore, when we draw an extensive mansion, full fronting, at a great distance, we describe all the horizontal lines in the building_by_horizontal lines in the drawing; so long as they are comprehended within an angle of 60 degrees; which is the natural range of sight, and beyond which no picture should ever extend; when beyond that angle, we cannot take the whole picture at one view; but must treat it as a panorama, and view the several parts abstractedly. When a building is so near, as to occasion turning our heads round for the purpose of sceing its several parts,

they have the same effect, and compel us to have recourse to various vanishing points, in which we seek the termination of those lines that converge, and in fact divide the building, though full fronted and uniform, into several parts; each of which seems to assume a distinct character, and to demand separate consideration. This will be more fully understood when we treat of the general rules which govern perspective. The reader must recollect, that, as it would be impossible to represent more than one view of the object, in one plane, or picture, so there can be but one point of sight; that is, but one par. ticular spot, where the eye of the spectator is supposed to be fixed; from which, as from a very minute point, all the figures represented must appear as under one general system. The same attention must of course be paid to shadows; for we cannot suppose the dark side of a house to result from any thing but the light being in such a quarter as does not allow it to strike on that side; consequently, we attribute the bright side of the same object to its being illuminated by the rays which act peremp torily upon it. Speaking of common ef. fects, we consider the light to be solitary; such as the sun, or the moon, or one candle, &c.; hence we perceive both the necessity, and the reason, for exhibiting all objects as bright, which are within the range of, or show themselves openly to, the light, and all parts to which its rays cannot reach direct as being in the shade, and more or less dark, according as they may be more retired and confined. When two lights are found in the same picture, such as two candles on a table, there will be to every object under their mutual influence a half shade, and a whole shade; the former, called the penumbra, showing that extent which results from one light being obscured, or cut off; and the latter, or the umbra, showing those parts which are not acted upon by either of the lights. This will be obvious to any person who may place two candles behind him, as he sits with his back to a table; they being about two feet asunder. He will then see, on the wall, the influence of each candle: and his shadow will increase with the remoteness of the plane, or wall, on which it is represented.

The following definitions of the principal features in the science and application of perspective will prove useful to the student, viz. projection delineates

objects in plano, by means of right lines called rays, suppose to be drawn from every angle of the object to particular points. When the objects are angular, these rays necessarily form pyramids, having the plane or superficies, whence they proceed, for their basis; but when drawn from, or to, circular objects, they form a cone.

Ichnography, or ichnographic projec tion, is described by right lines parallel among themselves, and perpendicular to the horizon, from every angle of every ob. ject, on a plane parallel to the horizon; the points where the perpendicular lines or rays cut that plane being joined by right lines. The figure projected on the horizontal plane is likewise called the plan or seat of that object on the ground plane. The points are the scites, or seats, of the angles of the object. The lines are the seats of the sides. By this we are to understand how the bases of figures represented as superstructures stand, or are supported; and we are further enabled to judge of, indeed to measure, their several parts, and their areas.

Orthography represents the vertical position and appearance of an object: hence orthographic projection is called the elevation. When we thus see the front of a house, we give it that term; but when the side is displayed, we call it the profile. If we suppose a house, or other object, to be divided by a plane · passing perpendicularly through it in a line at right angles with the point, we call it the lateral section; but if the plane pass in a direction parallel with the front, it is termed a longitudinal section. If the plane passes in neither of the former directions (not however deviating from the vertical) it is said to be an oblique section.

These give us the modes of laying down plans, of showing the parts, and the manner in which the interiors of edifices are arranged; consequently are indispensable to the architect, surveyor, and indeed should be understood by every person in any way connected with building or designing. Nor should the following be neglected, viz. scenography, which shows us how to direct the visual rays to every point, or part, of a picture; and stereography, which enables us to represent solids on a plane, from geometrical projection; whence their several dimensions, viz. length, breadth, and thickness, may all be represented, and be correctly understood at sight.

We suppose our readers to have some knowledge of geometry before they commence upon this, or any other of the abstract sciences which are founded thereon. Should such, however, not be the case, we beg leave to refer them to that head, where they will find sufficient instruction to enable them to prosecute their inquiries on the subject now before

US.

An original object, is that which be comes the subject of the picture, and which is the parent of the design. Any plane figure may become an object, as may any of its parts, as a broken pillar, the ruins of a house, the stump or the branch of a tree; but we generally speak of objects as relating to entire figures represented as solids, or to as much rural or other scenery as may be embraced under an angle of 60 degrees formed by two lines meeting at the eye. This will explain why we are enabled to represent so great a number of distant objects, while the front, or fore-ground, will contain, comparatively, but a very few: it being obvious, that as the lines forming the angle become more distant, the more may be included between them.

Original planes, or lines, are the surfaces of the objects to be drawn; or they are any lines of those surfaces; or it means the surfaces on which these objects stand.

Perspective plane is the picture itself, which is supposed to be a transparent plane, through which we view the ob. jects represented thereon.

Vanishing planes are those points which are marked upon the picture, by supposing lines to be drawn from the spectator's eye parallel to any original lines, and produced until they touch the picture.

Ground plane is the surface of the earth, or plane of the horizon, on which the picture is supposed to stand.

The ground line is that formed by the intersection of the picture in the ground plane.

The horizontal line is the vanishing point of the horizontal plane, and is produced in the same manner as any other vanishing line, viz. by passing a plane through the eye parallel to the horizontal plane.

The point of sight is the fixed point from which the spectator views the perspective plane.

Vanishing points are the points which are marked down in the picture by sup.

posing lines to be drawn from the spectator's eye, parallel to any original lines, and produced until they touch the pic

ture.

The centre of a picture is that point on the perspective plane where a line, drawn from the eye perpendicular to the picture, would cut it; consequently it is that part of the picture which is nearest to the eye of the spectator.

The distance of the picture is the distance from the eye to the centre of the picture. If what has been already said and repeated, regarding the angle of 60 degrees, is understood, the spectator will never bring the picture so near to himself as to occasion the eyes to expand, indeed to strain, so as to embrace more than that angle.

The distance of a vanishing point is the distance from the eye of the spectator to that point where the converging lines meet, and after gradually diminishing all the objects which come within their direction and proportion, are reduced so as in fact to terminate in nothing. All parallel lines have the same vanishing point; that is to say, all such as are in a building, parallel to each other, when not represented exactly opposite to, and parallel with the eye, will appear to converge towards some remote point, i. e. their vanishing point. Circles, when retiring in such manner, are represented by ellipses, proportioned to their distances: their dimensions in perspective are ascertained by enclosing them, or the nearest of them, where a regular succession is to be pourtrayed, within a square, which, being divided into any number of equal parts or chequers, will show all the proportions of those more remote. We trust it scarcely requires to be repeated, that the further any object is from the eye or foreground of a picture, the less it will appear in nature, and the more it must be reduced in exhibiting its perspective.

A bird's-eye view is supposed to be taken from some elevated spot, which commands such a prospect as nearly resembles the plane or ichnography of the places seen. Thus the view from a high tower, or from a mountain, whence the altitudes of the several objects on the plane below appear much diminished, gives nearly the same representation as is offered to a bird flying over them; whence the term. Some idea may be formed of this by standing on any height, and observing how low those objects, which are near thereto, will appear, when compared

with those more distant, taking, however, the perspective diminution of the latter into consideration.

We shall now explain the five figures included in the Plate of Perspective. The first figure shews a base line, A B, divided into eight equal parts, whose perspective proportions on the lines A C and B C, are shewn, by drawing from the several divisions, 1, 2, 3, 4, &c. on A B, rays to the vanishing points, D and E, situated on the horizon. If AC and BC were of equal length, the several squares thus made in the area, A C B, would shew trapezia regularly diminishing towards C, having their opposite angles intersectable by perpendiculars from the base line, A B, and the other opposite angles intersectable by horizontal lines parallel to A B. But AC being longer than B C, gives the whole of the trapezia a cast towards E. This shews that the two vanishing points, while (in this instance) they serve to intersect each other, contain distances, considered perspectively, in proportion to their brevity; they are under the same parallels, but the angle, B A C, being smaller than the angle C B A, causes the divisions on A C to be more extensive than those on B C, as may be seen by referring to the lesser spaces occupied by the standard on the latter. The figures 1, 2, 3, &c. correspond with those on the base line, exhibiting their due perspective distances on the lines A C and B C. It will also be observed, that as the trapezia become more distant, they become smaller, while their angles pointing towards C, and towards the base line, that is, their perpendicular angles become more obtuse, and their horizontal angles, i. e. those on the right and left, become more acute: were it otherwise, they could not produce a diminution of the trapezia in proportion to distance.

Fig. 2. shews the angle formed by two ranges of buildings, each of which has a different vanishing point. NO is the perpendicular edge of the angle; NQ O, and NP O, shew the two faces, each of which is intersected by streets of various breadths. In both instances the specta tor's eye is supposed to be situated near two-thirds up the two buildings; that is to say, about X on one face, and about W on the other. This produces a mixed effect, seldom to be found in reality; though, in some cases, where streets lying on a declivity, and joining others with less deviation from the level, this will be produced. The mode of proving the due direction of lines in perspective, such as

XQ and W P, which appear like the band or fillets that separate the different stories of an edifice, is very simple, namely, all horizontal lines in buildings that decline from the plane of a picture, and tend towards some vanishing point, will, when above the spectator's eye, appear to descend towards that point, as from N to Q; but when below the spectator's eye, they will appear to rise as O Q. The triangle OQ N, being more acute, will give a more direct view of the houses, and appear to recede less from the eye than NP Q, which is more obtuse, and makes every house appear narrower.

Fig. 3. shews the front of a house, IHFG, which, when thrown into perspective by the vanishing point, Q, being made high, and several rays proceeding from o p q r s t tok being carried too high, give an outré appearance to the front, as shewn by the outlines I F L M, in which it will be seen that a rude and unpleasant disproportion is given in every part. Nor is this even the manner in which the house would appear when seen from above, or below it, on the principle of a bird's eye view. The places of the seve ral doors and windows being ascertained, the several lines, o p q r s t, intersect the ground-line FM in those parts which correspond with the places of the doors; whose heights are ascertained or determined by the line S Q, equal at S F to their height in the original front IHF G.

The windows being over the doors, must be under the same perpendiculars in both cases; their depth is determined by taking the measurements on the line IS, and drawing rays to the point Q. This figure is given chiefly with the intention of shewing the immense disproportions which are generated by a false placing of the point to which the rays proceed; and which point is always formed to advantage rather below than above the centre of a picture. When the hori zon is too much raised, numberless distortions take place.

Fig. 4. gives the ground plan of a gallery, RSV T, which is to be shewn in perspective with its several standards, and the pitch of the awning on the ground lines V X and W X. Here II becomes the horizontal line, on which X is the vanishing point, and the point to which the rays R, 9, 10, and W, being drawn, cut VX in the places marked 4, 3, 2, 1, respectively, and give the situations of the standards for the right side. The places for those on the left side are found by drawing the lines 4, 5; 6,3 ;