288 



HOME-MADE PROJECTION APPARATUS 



[CH. IX 



the work to be done. For the work of micro-projection, drawing, 

 etc., contemplated in this and the following chapter a table of the 

 following dimensions has served admirably: Height, 100 centi- 

 meters (40 in.). Size of top 125 cm. (50 in.) long; 50 cm. (20 in.) 

 wide. The legs are about 5 cm. (2 in.) square, and have large 

 screw eyes in the lower ends for leveling. The table should be 



FIG. 158. HOME-MADE OPTICAL BENCH. 



t t t t The track of rods or tubes on the baseboard. 



Radiant The block carrying the arc lamp. 



as Asbestos paper between the track rods at the arc lamp end of the optical 

 bench. 



Condenser The block carrying the condenser. 



Stage The block carrying the stage of the projection apparatus or the lan- 

 tern-slide holder. 



Microscope The block carrying the projection microscope or the lantern 

 slide or other projection objective. 



//// The railing flanges holding the sockets. 



base The baseboard. 



rigidly made so that there will be a minimum of vibration. If the 

 table vibrates there is a disagreeable trembling of the screen image. 

 (For pictures of such a table see fig. 133, 182). 



Carrying out the precautions against reflections from light sur- 

 faces, the table is made dull black or brown. This is easily 

 accomplished by using some dull black paint like "dead-black 

 Japalac" or other dull black, or dull brown paint, thinned some- 

 what with turpentine. 



The anilin black stain used for laboratory tables is also most 

 excellent ( 424a). 



To the projection table should be fastened the rheostat, and the 

 ammeter, if one is used ; also the lamp switch and the incandescent 

 lamp (fig. 133). Then the table can be moved from one place to 



