252 THE BOOK OF THE LANTERN. 



Whiting's patent arrangement for facilitating the ex- 

 hibition of slides is extremely ingenious, but seems to me 

 to be an adaptation of Samuels' changing box, for photo- 

 graphic cameras. At any rate, the same principle is 

 involved. It consists of a pusher of wood working be- 

 tween grooves on the lantern stage. Close against it is a 

 box of slides with a powerful spring at the back of them, 

 so that they are forced up against the pusher, the front 

 one being always in the right position to be pushed for- 

 ward on to the stage. The act of moving the pusher 

 sends a picture on to the stage, removes that previously 

 shown, which goes into another box, or drops down an 

 inclined plane out of the way, and at the same time the 

 lens is covered so that there is momentary darkness on 

 the sheet. This darkness is, I think, preferable, and less 

 trying to the eyes of the audience than if the actual 

 change of picture took place visibly. 



Other forms of carriers provide in a different manner 

 for the lens being covered at the moment of change. One 

 very good one consists of a pair of wings, which open and 

 close automatically over the front of the objective lens 

 as the change is made. In this case the first picture 

 seems to darken down on the screen towards the centre, 

 'the reverse action immediately discovering the next 

 slide. 



The following remarks, which were written by me, and 

 were published in the Yearbook of J ^ holography -, will 

 describe the kind of carrier which I myself use : " When 

 a man is in the habit of travelling about from place to 

 place on lecturing intent, he will, if wise, reduce his 



