154 



OPTICAL PROJECTION 



or base; and that a small table, adjustable for height, can 

 also be fixed anywhere on the same base. On this table any 

 piece of sufficiently small apparatus can be adjusted, and 

 projected as if it were a slide. The objective is surrounded 

 by a shade to keep stray light from the screen. Ordinary 



FlG. 81. German Lantern 



slides or diagrams are placed in the spring holder, and pro- 

 jected as usual. 



This arrangement has been a great deal popularised in 

 England by Mr. W. Lant Carpenter in connection with the 

 Gilchrist Lecturing Trust; and where actual physical apparatus, 

 and diagrams, are the principal subjects of projection, it can 

 hardly be improved upon for handiness, cheapness, and sim- 

 plicity ; but it is not so well adapted for optical and acoustical 

 experiments, on account of the stray light. Fig. 82 is an 

 American modification of it, arranged with a special view to 



