PROJECTIONS FOR THE SCHOOL-ROOM. 5 



upon the opposite wall, and then will be seen what 

 further conveniences will be wanted, such as curtains, 

 screen, table, mounting for lenses, etc. 



THE DARKENED ROOM. 



Exhibitions with the stereopticon are almost always 

 given at night, and there is no trouble from exterior 

 light ; but the illustrations and demonstrations which 

 are part of the work of schools and colleges need to he 

 given in the daytime, and this necessitates a provision 

 for shutting out the light which will interfere with the 

 experiment. 



The light may be excluded from a room by tight- 

 fitting shutters, or with curtains It is very difficult to 

 make shutters so tight that all light is excluded by 

 them. It can be done much better and cheaper by 

 having some frames made the size of the window frames, 

 and covering them with what is known as enamelled 

 cloth, such as is used in upholstery and carriage trim- 

 ming. These should fit tight enough in their places to 

 remain when placed. 



The same kind of cloth can be attached to common 

 curtain fixtures, and rolled up and down as wanted ; 

 but it will be found that a great deal of light will pass 

 by the edge of these curtains. This can be obviated 

 by tacking strips of the same material a foot wide to 

 the side of the casing, so that the curtain will roll down 

 inside of the strips. When sunlight or the lime-light 

 is used, it is not always necessary that the room should 

 be totally dark ; and, indeed, some of the best experi- 

 menters think it a part of their success that their work 

 is done in a room that is light enough for one to see to 

 read a newspaper. Yet there are some experiments 

 which require that extraneous light be shut out from 



