100 SPECTRES AND GHOSTS. 



" Because, if they were," said John, " they would not dare 

 to go about nights as much as they do." 



" They could have a man, then," said Lawrence, " and he 

 could pretend to shoot the ghost, which it would be very 

 safe for him to do, since he would only shoot at nothing 

 in the air. The real person by which the appearance was 

 produced would be on the other side of the glass, far 

 away." 



" He might break the glass, then," said John. 



" No," replied Lawrence, " for the image is not in the 

 glass, but far behind it as far behind it, in fact, as the real 

 object is before it. The image of my little ghost, for in- 

 stance, appears, not on the surface of the window-pane, but 

 out on the shelf, where the cat is as far, in fact, from the 

 glass on the outside as I hold the paper from it on the in- 

 side." 



Here Lawrence moved his card backward and forward, 

 nearer to and farther from the glass, and showed that the 

 image seemed to advance and recede in a manner exactly 

 corresponding to the movement of the object. 



Any i-eader of this book can see how this was done by 

 cutting out such an image and holding it up near the win- 

 dow, with a lamp or candle near, to illuminate it strongly. 

 The effect will be greater if this is done in the evening, be- 

 fore it is quite dark, so that there shall be no bright light 

 shining upon the objects in the street, but only enough to 

 make them visible. 



"If I wished to make a representation of the ghost at 

 the other side of the street," continued Lawrence, " then I 

 should have to carry back my paper ghost to the back side 

 of the room, and make it a great deal larger. I might have 

 a real person, with a sheet over his arms, to represent the 

 ghost, so that he might make gestures and walk about, but 

 the principle would be the same in that case as in this. 



