122 LETTERS ON NATURAL MAGIC. 



not " start from their frames," they will at least 

 bend upon him their frowns or their approbation. 

 It is in vain that he tries to evade their scrutiny. 

 Wherever he goes their eyes eagerly pursue him ; 

 they will seem even to look at him over their 

 shoulders, and he will find it impossible to shun 

 their gaze but by quitting the apartment. 



As the spectator in this case changes his posi- 

 tion in a horizontal plane, the effect which we 

 have described is accompanied by an apparent 

 diminution in the breadth of the human face, 

 from only seven or eight inches till it disappears 

 at a great obliquity. In moving, therefore, from 

 a front view to the most oblique view of the face, 

 the change in its apparent breadth is so slow that 

 the apparent motion of the head of the figure is 

 scarcely recognized as it follows the spectator. 

 But if the perspective figure has a great breadth 

 in a horizontal plane, such as a soldier firing his 

 musket, an artilleryman his piece of ordnance, a 

 bowman drawing his bow, or a lancer pushing 

 his spear, the apparent breadth of the figure will 

 vary from five to six feet or upwards till it dis- 

 appears, and therefore the change of apparent 

 magnitude is sufficiently rapid to give the figure 

 the dreaded appearance of turning round, and 

 following the spectator. One of the best examples 

 of this must have been often observed in the fore- 

 shortened figure of a dead body lying horizontally, 

 which has the appearance of following the ob- 

 server with great rapidity, and turning round 

 upon the head as the centre of motion. 



The cause of this phenomenon is easily ex- 

 plained. Let us suppose a portrait with its face 

 and its eyes directed straight in front, so as to 



