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as b* a . ed on paper ? It can no way be represented so clearlypla c {P a . cln o it on one side, as shown in the figure, or bytew,,® u vertically bemjj ente d in Figure J2.

°' ) ject TV ^ ateVei means the representation tu, Figure 2 of anvie We( j A BCD > is obtained, if the outline be accurate, and0 y a * a Proper distance, it is plain it will make an out-i he colon"; Same fo, ' m in the eye as the object itself; and iffign re °“ r »'g were equally perfect, the eye might mistake theemploy l 1 " tlie original. But even when colours are nota Pp«'iJ econ 'ect dimensions- r "ranee, and

»- n S it vertically beneath the object to be drawn, as

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give the whole a pleasingconstitute the first great requisite to every

tivg l i lus endeavoured to explain the nature of perspec-’■ e ma y next advert to the limits of vision. We may

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side:

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r the

e ye, in whatever direction we look, as situated

Centre of a sphere, which we may suppose to be repre-ss held 'J ^ le c irele ekfi, Figure 3. The hemisphere elf' 8 als Q n(i tde . e ye> and therefore obviously invisible ; and itto k, c Certa ' n ’ that the eye, looking forward horizontallyfay p| not take in at once the whole of the hemisphere e k f.Hi^ j‘° m this, it cannot take in a larger angle than set,^ tl l(; 8 )u t half a hemisphere, or equal to 90 degrees. And^Ual w hich the eye takes in, extend all round to ank liol e o |i s tance from the central ray k b, it follows that the°tm () p t le rays which enter the eye at once, will be in the? c °ne Cone , of which the apex is at the eye ; and of such

Hey p i y s > set may be considered as the profile. It is

°bjec ts fjtnd, that to have an agreeable view of large

found, that

Su<dl as buildings, the

k'oivi 60 degrees, or one-third *, » ' n h\eet

Ut)!, 8 ’ . t!l at we cannot distinctly see the who e . P j t ’.

lts distance from the eye be at least equal to its hei B ,n ot Tn '® appearance of

angle of vision should notof an hemisphere; in other

hiad "‘'t^avance of a picture will be more agreeable, ifie e ,] ® to comprehend above 45, or at most 50 degrees ;a ° r . sma ll objects, or such as do not exceed the length0t ln any of their dimensions, it is not advisable toI^er ® n an gl« of 30 degrees,a ( ?* >r ‘ Se *nore than

*W l dls 'ance

As a picture therefore shouldthe eye can easily take in at oneof 25 degrees on either side of the point ofo considered a standard limit. Fifty degrees tofj Cat , ’ are comprehended in the angle x E y ; and wet{^ c ® it t;!]. °hserve, that the measure of an angle, is theJ® Point r S U P on the circumference of a circle, which hasm^osed 0 the angle for its centreL® t'lft °. Coll tain 360 degrees.

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°ne of

a circle being alwaysHence, if the lines form-*Ew were extended, the angle vnt would still

fifty degrees, because, whatever were the

^ if thj llC l e drawn from the point e, through its twotk^se ^ , R ' r< 'le were divitid into 360 parts, the numbera fifty atts enclosed by the angle, could not be more

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• a tin» l ° VV P rocee d to the definition of the terms used^tk^'nto °*' P ers pective, and then show the method ofk 6 fils,,, 0 Perspective, those forms which may be consideredh? E <'r ts °f a11 Alters.

g’ Wl,j C | , Ns —1. An original object is any object what-V],,'- 0r;,.- ls . rendered the subject of a picture,a'kal (,i,: planes or lines are the surfaces or lines of

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! j. ( ' a te ( |P ec ^' l ’ e plane is the surface on which a picture is'kiftjP'hte 0 f niay be here observed, that painters regardoh; a P' otu re merely as an aperture through which1 iii ** are seen > an d they therefore consider the5 ii|L, 0| > this** a, ' e to transparent, to admit of this view.d tfie ' "ocount that the perspective plane is frequently^parent plane.

4. Ground-plane is the earth or surface on which standthe objects to be delineated, as well as the spectator.

5. Ground-line is the line on which the perspective planeis supposed to rest.

6. Visual rays are those which, passing through thetransparent plane, render original objects visible.

7. Principal visual ray is that which passes through theaxis or centre of the eye, and the course of which, therefore,from the perspective plane, is shorter than any other,because it is perfectly direct. Its height above the ground-line is, of course, always the same as that of the eye.

8. Point of sight is that fixed point from which the spec-tator looks upon the perspective plane, when any originalobject is delineated.

9. Centre of the picture is that point of the perspectiveplane which is exactly opposite the point of sight, that is,where the principal visual ray enters the transparent orperspective plane. It must, therefore, be carefully distin-guished from the measured centre of any picture, as it cannever exceed the height of the eye from the ground-line.

10. The distance of the picture, or point of distance, is thedistance between the eye and point of sight, and the centreof the picture.

11. Vanishing points are those points to which all linesinclined to the picture appear to converge, and which thoselines meet when produced. Vanishing points have no placein a finished picture ; they are used to facilitate drawing inperspective.

12. The horizontal line is a line parallel with the horizon,at the height of the eye,—that is, it passes horizontallythrough (lie centre of the picture.

j Distance of a vanishing point is the distance upon thevanishing point on the picture to the eye of the spectator.It may also be proper to remind some, of the differencebetween a perpendicular and a vertical line or plane : a ver-tical line points directly to the centre of the earth ; it istherefore at right angles to the plane of the horizon, and isthe same with the direction of a plumb-line : a perpendicularline is any line which is at right angles to another ; it maytherefore be sometimes a vertical line, sometimes a horizontalone, or in any other position, according to the direction ofthe line or surface with which it forms a right angle.

Methods of putting squares into perspective. —Suppose asquare to be traced upon the ground at some distance beforeus ; that we find, upon admeasurement, the length of eachside to be 8 feet, and that we are opposite the centre of thenearest side, at the distance of 18 feet. We know, that ifwe wish to obtain what is called a ground-plan of thissquare, we must represent it by a square upon paper, as inFigure 4, and thus we shall have its real appearance, sup-posing the eye to be looking down upon it, just over itscentre ; but looking upon it obliquely, as we have stated,and with the eye at the height of 6 feet from the ground, weare convinced, from the nature of perspective, as beforeexplained, that the side nearest to us will make a longer lineupon the retina than any of the rest. The question is,therefore, to obtain the true appearance of the whole square,

—that is, the true form of the image it makes on the retina.

In the first place, determine the scale to be observed,—thatis, what space shall correspond to a foot of the original. Forexample, suppose one-tenth of an inch; then draw a line, a b,Figure 5, eight-tenths of an inch long, and another line, ii d,parallel with this base-line, at the height of six-tenths of an inchfrom it. Raise a perpendicular from the centre of the line a b,and the point c, which cuts the horizontal line, will be thecentre of the picture. From c on the horizontal line, set offthe distance at which the square is seen, which will here be

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