PERSPECTIVE. 



r, 2; 8, 1; all parallel to WV. In this 

 instance all the intervals, R, 9; 9, 10 ; 

 10, W ; and W, V ; being equal, the 

 proximate superior ray will always give 

 that parallel : thus the ray of R cuts 

 X W exactly at the point 6, which gives 

 the line 6, 3, parallel to 7, 2 ; and so of 

 all in succession. The lines YZ and 

 W V are parallel ; they determine the 

 height of the front standards, and by 

 means of the lines YX and ZX cut the 

 other standards at their proper heights. 

 Their descent towards X shew them to 

 be above the line n O, which is level 

 with the spectator's eye. The summits of 

 the couples are ascertained by the line 

 ^ X. They will all have their centres 

 over the centres of the lines 5, 4 ; 6, 3 ; 

 7, 2 ; and 8, 1 : ascertained by drawing a 

 line from B to X. 



Fig. 5, exhibits the wall of a monaste- 

 ry, supported in some parts by reinforce- 

 ments, or pillars, between which the wall 

 is less substantial. The measurement of 

 the pillars and of the intervals is given on 

 the base-line AB, while G F shews the 

 horizon and line of sight. The rays from 

 a, c, e, and g, shew the places where the 

 several divisions take place on the 

 {round-line A E, and shew the projec- 

 tions of b, d.f, h. The upper line is also 

 determined by CD, and the crosses in like 

 manner are made to diminish towards the 

 vanishing point F. The small mark at A 

 in the middle of the wall's thickness, as 

 shewn by the shaded part, gives rule for 

 each projection of. the several pillars, as 

 shewn by the shaded parts : their sum- 

 mits and bases will, however, have their 

 fronts, i. e. the parts parallel with C A, 

 terminated by horizontal lines parallel 

 with A B. We must once more impress, 

 that all fronting horizontals in nature 

 must be so represented in perspective, 

 provided they do not extend beyond 60 ; 

 also, that in every instance perpendicu- 

 lars in nature are so delineated in per- 

 spective. 



The reader will have seen, that the 

 base-line, and the depth below it, give 

 the measure of the figure when obliqued. 

 To render this more perfectly intelligible, 

 let us say that it were necessary to place 

 the square W, V, 13, T in perspective be- 

 tween W, V and X (fig. 4). This being 

 a square is readily done ; the more so, as 

 it is proximate to the line ; because the 

 quadrant T W is so readily acted upon ; 

 W V being equal to V T. But say that 

 it were needful to place the line T K 

 (fig. 4) in perspective on the line V X. 

 Braw the quadrant T, W ; and the quad- 



VOL. tf 



rant K, 10 ; the line W, I, drawn to $, 

 will shew the place of T, and the line 8, 2, 

 will shew the place of K : therefore the 

 line T K will be found in perspective be- 

 tween the points 1 and 2 on the line V 

 X. Thus any line or object may be re- 

 presented ; observing that the distance at 

 which it stands below the base-line must 

 be measured on the base-line ; when, 

 by drawing rays to the horizontal line, 

 (whereon all the vanishing points must 

 rest) its place on the oblique line, or scite, 

 will be determined. Some authors on 

 this subject have directed that the back 

 ground should be limited by a semicircle, 

 describing the half-horizon, and that all 

 the vanishing 1 points ought to be placed 

 thereon. This, however well it may an- 

 swer in a panoramic point of view, can 

 never be so appropriate as the horizontal 

 line, in a picture which includes only the 

 sixth part of a circle. 



What has been said relates entirely to 

 mathematical perspective, and forms the 

 basis of architectural design, and governs 

 (though rather occultly) every kind of 

 landscape painting : with regard to the 

 perspective of living objects, and of va- 

 ried nature, that can only be acquired by 

 attention to models, and to the real 

 figures. 



PKRSPECTIVT:, aerial, is the art of giving 

 a due diminution or degradation to the 

 strength of the light, shade, and colours 

 of objects, according to their different 

 distances, the quantity of light which falls 

 on them, and the medium through which 

 they are seen. 



As the eye does not judge of the dis- 

 tance of objects entirely by their apparent 

 size, but also by their strength of colours, 

 and distinction of parts : so it is not suf- 

 ficient to give an object its due apparent 

 bulk according to the rules of stereogra- 

 phy, unless at the same time it be express- 

 ed with that proper faintness and degra- 

 dation of colour which the distance re- 

 quires. Thus if the figure of a man, at a 

 distance, were painted of a proper magni- 

 tude for the place, but with too great a 

 distinction of parts, or too strong colours, 

 it would appear to stand forward, and 

 seem proportionally less, so as to repre- 

 sent a dwarf situated nearer the eye, and 

 out of the plane on which the painter in- 

 tended it should stand. 



By the original colour of an object is 

 meant, that colour which it exhibits to the 

 eye when duly exposed to it in a full open 

 uniform light, at such a moderate distance 

 as to be clearly and distinctly seen. This 

 colour receives an alteration from niajiy 



55 



