HOME-MADE PROJECTION APPARATUS 



[Cn. IX 



blocks of the required size for the special purpose. The blocks can 

 be made as heavy as desired by adding sheets of lead (fig. I58A). 



For the guides to follow the track, one can make V-shaped 

 grooves, or more easily, strips of the proper thickness can be screwed 

 to the block (fig. 159). One of the strips should be screwed tightly 

 to the block, and the other should have screw holes through the 

 strip considerably larger than the screws, then it will be possible to 

 make slight changes in position to get an exact fit. When in the 

 exact place desired the screws can be set firmly. As the large holes 

 in the strips will be larger than the heads of the screws, metal 

 washers should be employed (fig. 159). 



430. Sockets for the stems of the apparatus. There is first 

 screwed to the top of the block, a railing flange, and into this is 

 screwed a short tube of the size to receive the stem or post of the 



FIG. I58A. SHIELD FOR A PROJECTION ORJECTIVE. 



This shows the method of supporting an objective in a shield. The shield is 

 supported by a bolt with a fan shaped end (p). 



The bolt or stem enters the socket and is held in place by a screw (s). 



U Apparatus block composed of U-ad sheets above and a block of wood 

 below. The block of wood has V-shaped grooves for sliding along the track. 



b Baseboard with track, end view. 



