THE MAGIC LANTERN. 



mounted on one side of the screen, and the spectators placed on the 

 other, as shown in fig. 2 (p. 193). In this case, the screen should 

 be made of white muslin or fine calico stretched upon a frame, its 

 transparency being increased by wetting it well with water. In 

 some cases the muslin is prepared with wax or oil, which may be 

 convenient to save the trouble of wetting it, but which in other 

 respects does not answer the purpose better. 



8. When the pictures are produced through a transparent 

 screen, the exhibitor being concealed from the spectators, may 

 make them vary in magnitude : first gradually increasing, and 

 then gradually diminishing. This is accomplished by moving the 

 lantern gradually and alternately from and towards the screen, 

 varying the focus during the motion, so as to render the picture 

 upon the screen always distinct. 



Let us suppose for example, that the nozzle of the lantern is 

 first placed in actual contact with the screen. The picture on the 

 screen will then be exceedingly small, and the spectators, to whom 

 the screen is invisible, will imagine the object to be at a great 

 distance. Let the exhibitor then move back the lantern slowly 

 from the screen, keeping the focus constantly adjusted, the 

 picture on the screen will then be gradually enlarged, and the 

 impression produced on the spectators will be that its increased 

 magnitude is produced by the gradual approach of the object 

 towards them ; and so complete is this delusion, that the rapid 

 increase of magnitude of the picture actually startles even persons 

 who are most familiar with the optical causes which produce the 

 effect. It sometimes appears as if the object would approach so 

 as to come in actual collision with the spectator. 



When the object seems thus to be brought near the spectator, 

 it is made to retire gradually by moving the lantern towards the 

 screen, the effect being produced by the gradual diminution of 

 the image upon the screen, and this is continued until the nozzle 

 of the lantern coming again in contact with the screen, the object 

 seems again to be lost in the distance, its magnitude being 

 reduced to a mere point. The exhibitor seizes this moment to 

 change the picture, displacing one slider by the introduction of 

 another, a manoeuvre which, when adroitly performed, will escape 

 the notice of the spectators. The new picture is then exhibited in 

 the same way. 



Effects of this kind have been denominated " phantasmagoria," 

 from the Greek words ^avraff^a (phantasma), a spectre, and 

 ayopaop.a.1 (agoraomai), 1 meet. 



9. Interesting and amusing effects are produced by placing two 

 lanterns of equal power, so as to throw pictures of precisely equal 

 magnitude on the same part of the same screen. A sliding cover 



JOG 



