PERSPECTIVE. 



We suppose our readers to have some 

 knowledge of geometry before they com- 

 mence upon this, or any other of the ab- 

 stract sciences which are founded there- 

 on. Should such, however, not be the 

 case, \ve beg leave to refer them to that 

 head, where they will find sufficient in- 

 struction 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 re- 

 presented as solids, or to as much rural 

 or other scenery as may be embraced un- 

 der 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 con- 

 tain, 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 sur- 

 faces of the objects to be drawn ; or they 

 are any lines of those surfaces ; or it 

 means the surfaces on which these ob- 

 jects 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 

 spectators^ 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 pro- 

 duced 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 per- 

 spective plane. 



Vanishing points are the points which 

 are marked down in the picture, by sup- 



posing lines to be drawn from the spec- 

 tator'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 dis- 

 tance 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 thir di- 

 rection and proportion, are reduced so as 

 in fact to terminate in nothing. All paral- 

 lel lines have the same vanishing point ; 

 that is to say, all such as are in a build- 

 ing, parallel to each other, when not re- 

 presented exactly opposite to, and paral- 

 lel with the eye, will appear to converge 

 towards some remote point, i. e. their va- 

 nishing point. Circles, when retiring in 

 such manner, are represented by ellipses, 

 proportioned to their distances : their di- 

 mensions in perspective are ascertained 

 by enclosing them, or the nearest of them, 

 where a regular succession is to be pour- 

 trayed within a square, which being di- 

 vided 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 na- 

 ture, 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 re- 

 sembles 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 asy height, and ob- 

 serving how low those objects, which are 

 near thereto, will appear, when compared 



