378 PERSPECTIVE. 



the point of sight, strictly speaking, being in the 

 spectator's eye, and consequently, not any point in 

 the picture. Although, from its name, we should 

 expect to find it always in the middle of the repre- 

 sentation, yet this is by no means the case, for 

 sometimes it is near one of the sides, particularly in 

 what is called parallel perspective ; though gene- 

 rally in oblique perspective, it is in the middle of 

 the picture. And here it should be observed, that, 

 strictly and properly, it should always be in the 

 middle of the picture, when circumstances of con- 

 venience will admit of it ; for it is that point which 

 the spectator is supposed to look full against, or 

 which is exactly opposite to his eye when he views 

 a picture, and surely the best way to see a picture, 

 is to look directly against the middle of it. How- 

 ever, in many kinds of perspective drawings, it is 

 not convenient, on account of room, to have this 

 point in the middle, as may easily be imagined by 

 considering Plate 6. Fig. 1., where G is the centre 

 of the picture. 



It will be easily conceived, from the description 

 of vanishing points, and the centre of the picture, 

 that this last must be the vanishing point of all lines 

 that are in Nature perpendicular to the picture. 



If a plane be supposed to proceed from the eye, 

 as before, parallel to the floor or level ground till 

 it arrives at the picture, the line where it meets it 

 is called the vanishing line of the horizon, or hori- 

 zontal line. This line is of great importance in 

 perspective : the centre of the picture is always 

 somewhere in this line. Its height is necessarily 

 regulated by the height of the eye from the 

 ground ; in landscapes, and views of places, it is 

 generally kept one-third of the height of the pic- 

 ture from the bottom, though this rule is not 



