24 ThE ART OF PROJECTING. 



For holding pictures, and other objects, for projec- 

 tion, the retort-holder will answer, in many cases, just 

 as well as a more costly fixture. Not only may the 

 larger pieces, such as photographic transparencies, 

 leaves of trees, and the like, be held well in it, but 

 microscopic specimens in glass slides, also small un- 

 mounted objects, such as parts of flowers, insects, etc., 



may be held in 

 small forceps 



Fi ff- 16. (pi g> l6 ^ which 



in turn may be held in the retort-holder. It will be 

 found convenient to have as many as three of the 

 latter. 



PROJECTIONS. 



TO PROJECT WITH THE PORTE LUMIERE AND A 

 SINGLE LENS. 



Fasten the porte lumiere in its place, and so adjust it 

 that the beam of light / (Fig. 17) is reflected horizon- 

 tally, and falls upon the screen s. It will appear as 



a bright spot, 

 five or six inch- 

 es in diameter. 

 Darken the 

 room, by draw- 

 ing the curtains 

 or closing the 

 shutters, and 

 the beam of 

 Fig. 17. light can then 



