PERSPECTIVE 



75 



objects themselves. The distance and position of 

 objects affect both their distinctness and apparent 

 form, giving rise to a sulxlivision of perspective 

 into linear perspective, which, as its name denotes, 

 considers exclusively the effect produced by the 

 position and distance of the observer upon the 

 apparent/ormand grouping of objects; while aerial 

 perspective confines itself to their distinctness, as 

 modified by distance and light. The necessity of 

 attending to the principles of perspective in all 

 pictorial drawing is apparent when we consider, 

 for instance, that a circle when seen obliquely 

 appears to be not a circle but an ellipse, with its 

 shortest diameter in line with the spectator, and 

 its longest at right angles to this. A square, when 

 looked at from a position opposite the middle of 

 one of its sides, appears as a trapezoid, the sides 

 which are perpendicular to the direction of vision 

 appearing to be parallel, while the other two appear 

 to converge to a point in front of the spectator, &c. 

 For the same reason two rows of parallel pillars of 

 equal height, seen from a point between and equi- 

 distant from each row, appear not only to converge 

 at the further end, but to necome gradually smaller 

 and smaller. An excellent 

 idea of a perspective plan can 

 l>e easily obtained by inter- 

 posing a vertical transparent 

 plane (as of glass a window, 

 for instance) between the 

 observer and the objects of 

 his vision, and supposing that 

 the objects he sees are not 

 seen through the glass, but 

 painted on it. A sketch made 

 on a glass plane in this posi- 

 tion by following with a pencil 



vertical lines in nature being parallel to it in the 

 picture. The point of sight, being the point directly 

 opposite to the observer, is properly placed in the 

 centre of the picture, for it is most natural that 

 the view should lie symmetrically on each side of 

 the principal visual line ; but this is not by any 

 means a universal rule, fcr we very frequently lind 

 it on the right or left si<J.e, but always, of course, 

 on the horizontal line. All lines which in nature 

 are perpendicular to the ground line, or to a ver- 

 tical plane which is raisedupon it as a base, meet 

 in the point of sight, which is thus their vanishing 

 point (see the line of the tops and bottoms of the 

 pillars in fig. 1 ). The points of distance are two 

 points in the horizontal line on each side of the 

 point of sight, and in a ' direct ' sketch are at a 

 distance from it equal to the horizontal distance 

 of the sketcher's eye from the ground line. The 

 equality of distance of these points from the point 

 of sight is not, however, necessary, as it occurs only 

 in those cases where the lines, of which the points 

 of distance are the vanishing points, are inclined 

 ( in nature ) at an angle of 45 to the base line ; 

 but in all cases the two points of distance are 



Fig. 1. 

 Illustrating the more Important points and lines ; PVR is the principal visual ray. 



all the lines and shades of the objects seen through 

 it, the eye being all the time kept quite steady, 

 would form a picture in perfect perspective. In 

 practice, however, it is found unfortunately that 

 glass is not a suitable material for sketching on, 

 and that the vertical position is not the most con- 

 venient ; it is therefore preferable to make a care- 

 ful studv of the effects produced by change of posi- 

 tion and distance on the appearance of objects in 

 nature, and from the results of this to compile a 

 IMM!V <>f rules, by the observance of which painters 

 may Ix- enabled to produce an effect true to nature. 

 After the 'scope' (i.e. the numlier of objects to be 

 introduced, and the distance at which they are to 

 be viewed ) of the picture has been determined, and 

 before the design is commenced, it is necessary to 

 draw upon the perspective plan three lines: (1) 

 Th-> Imse line, or ground line, limits the sketch to- 

 wards the operator, and is the base line of the 

 pirturi-. (2) The horizontal line represents the 

 ordinary position of the sensible horizon. The 

 hHght of the horizontal line is about one-third 

 of tlm height of the picture, when the sketcher is 

 placed at or little alx>ve the level of the horizon ; 

 but it may rise in a degree corresponding to his 

 increase of elevation till it reaches near to the top 

 of the perspective plan. The general rule is to 

 have a nigh horizontal line when the view is taken, 

 or supposed to l>e taken, from an eminence; but 

 when the station is on a level, either actual or 

 assumed, as is the case when a statue or a moun- 

 tainous landscape is figured, the horizontal line 

 must be low. The horizontal line in nearly all 

 cases is supposed to be level with the spectator's 

 eye. ( 3 ) The vertical line is drawn from the sup- 

 IKmition of the sketcher, perpendicular to 

 tin- i/rimml and horizontal lines, meeting the latter 

 in a point which is called the point of sight, or 

 c-ntr<- of the picture. The vertical line has no 

 ri'].ii-~i-ntative in nature, and is merely a mechan- 

 ical adjunct to the construction of the picture, all 



about twice as far apart as the eye is from the 

 picture. One important use of the points of dis- 

 tance is to define the distance of objects in a row 

 (fig. 1 ) from each other. For this purpose two 

 points of distance are not necessary, as when the 

 position of one pillar is found, that of the one 

 opposite is at once obtained by drawing a line 

 parallel to the base or ground line. We have 

 seen that the point of sight is the vanishing point 

 of all level lines which meet the ground line or 

 a vertical plane on it at right angles, and that the 

 points of distance (in a direct picture) are the van- 

 ishing points of all lines which cut the ground line 

 at an angle of 45 ; but there are many other 



froups of parallel lines in a picture which have 

 ifferent situations, and therefore different vanish- 

 ing points. Such lines with their vanishing points 

 (called for distinction's sake accidental points) 

 are represented in fig. 2. If the accidental point 

 is above the horizontal line, it is called the acci- 

 dental point aerial ; if below, the accidental point 

 terrestrial ; and a little consideration makes it 

 evident that these points may or may not be 

 situated within the plane of the picture. Such are 

 the points and lines necessary for the construction 

 of a plan in true perspective ; and from the above 

 explanation we may deduce the two general prin- 

 ciples : ( 1 ) that all parallel straight lines in nature 

 are no longer parallel when projected on the per- 

 spective plane, lint meet in a point which is called 

 the vanishing point, and is some one of the three 

 above descril>ed, unless these lines happen 'to be 

 also parallel to the ground line or the vertical line, 

 in which case they remain parallel when trans- 

 ferred to the picture ; and (2) that, since the bodies 

 drawn below the horizontal line are seen as if 

 from above, those above as if from below, and 

 those to the right and left of the point of sight as 

 if observed from the left and right, it follows that 

 straight lines which in the picture are above the 

 horizontal line lower themselvts, those below raise 



