PERSPECTIVE. 



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, divid- 

 ed into eight equal parts, whose perspec- 

 tive 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 A C and B C 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 intersecta- 

 ble by perpendiculars from the base line, 

 A B, and the other opposite angles inter- 

 sectable by horizontal lines parallel to 

 A B. But A C being longer than B C, 

 gives the whole of the trapezia a cast to- 

 wards E, This shews that the two va- 

 nishing points, while, (in this instance) 

 they serve to intersect each other, con- 

 tain 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 extensix*e 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 BC It will also be observed, that 

 as the trapezia become more distant, they 

 become smaller, while their angles point- 

 ing towards C, and towards the base line, 

 thai 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 hy two 

 ranges of buildings, each of which has a 

 different vanishing point. N O is the per- 

 pendicular edge of the angle ; N Q O, and 

 N PO, 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 pro- 

 duced. The mode of proving the due 

 direction of lines in perspective, such as 



X Q, and W P, which appear like tne 

 bands or fillets that separate the different 

 stories of an edifice, is very simple ; name- 

 ly, 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 tye, 

 they will appear to ri.se as O Q. The tri- 

 angle O Q N being more acute will give a 

 more direct view of the houses, and ap- 

 pear to recede less from the eye than 

 N P Q, which is more obtuse, and makes 

 every house appear narrower. 



Fig. 3, shews the front of a house, 

 I H F G, which, when thrown into per- 

 spective by the vanishing point, Q, being 

 made high, and several rays proceeding 

 from o p q r s t to k being carried too high, 

 give an outre 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, opqrs t, intersect the 

 ground-line F M in those parts which cor- 

 respond with the places of the doors ; 

 whose heights are ascertained or deter- 

 mined by the line S Q, equal at S F to 

 their height in the original front I II F 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 inten- 

 tion of shewing the immense dispropor- 

 tions which are generated by a false 

 placing of the point to which the rays 

 proceed; and which point is always form- 

 ed to advantage rather below than above 

 the centre of a picture. When the horizon 

 is too much raised, numberless distortions 

 take place. 



Fig. 4, gives the ground plan of a gal- 

 lery, R S V 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 n <t> becomes 

 the horizontal line, on which X is the va- 

 nishing point, and <I> the point to which 

 the rays R 0, 9 4>, 10 <J>, and W 0>, being 

 drawn, cut V X in the places marked 

 4, 3, 2, 1, respectively, and give the si- 

 tuations of tne standards for the right side. 

 The places for those on the left side arc 

 found by drawing the lines 4, 5 ; 6, 3 ; 



