268 



PROJECTION OF HORIZONTAL OBJECTS 



[CH. IX 



PROJECTION OF HORIZONTAL OBJECTS 



397. As with the magic lantern, so with the projection micro- 

 scope some objects must be left in a horizontal position for projec- 

 tion. This requires that the microscope be in a vertical position. 

 As the light source is for giving light in a horizontal direction 

 (fig. 121), it is necessary to use a mirror or prism to reflect the 

 horizontal light upward through the vertical microscope and then 

 another mirror or prism above the microscope to reflect the vertical 

 light horizontally to the screen. This is shown in fig. 147, 175. 



The ordinary mirror of the microscope serves very well for mak- 

 ing the light vertical, but for reflecting it horizontally to the screen 

 a prism or a plane mirror silvered on the face is best, as it gives a 

 single image, not a double image as would the ordinary glass mirror 

 silvered on the back. 



398. Avoidance of stray light with a vertical microscope. 



This is easily accomplished by using a vertical piece of blackened 

 cardboard just beyond the microscope as shown in fig. 147. If 

 light escapes from the sides one can use pieces of black cardboard 

 or asbestos to enclose the microscope more completely. Ordi- 

 narily, however, the single black shield beyond the microscope 

 will answer. 



399. Sample Objects Suitable for Projection with the Differ- 

 ent Objectives (see also 39ga). 



PHOTOGRAPHIC TYPE OF OHJECTIVES (Micro-Planars, etc.) 

 Xo Tube (fig. 138) 



