CH. X] 



MAGNIFICATION OF DRAWINGS 



355 



MAGNIFICATION OF WALL DIAGRAMS, AND DRAWINGS MADE WITH 

 THE OPAQUE LANTERN 



509. Scale of wall diagram. Make the diagram any desired 

 size as directed in 457. Then remove the negative or lantern 

 slide from the holder and insert a lantern slide or negative of the 

 metric rule (fig. 178, 211). The image of the metric rule on the 

 drawing surface will, of course, be magnified exactly as much as the 

 diagram. By using a metric measure, one can find the magnifica- 

 tion of the screen image exactly as described in 508. 



For wall diagrams, it is not usually very important to know the 

 magnification. All that is necessary is to get it large enough to be 

 seen well. But if one wishes to show the relative size of objects 

 such as blood corpuscles of different animals, then the magnifica- 

 tion must be known. 



\_j 



FIG. 199. MODEL 4-5 DELINEASCOPE WITH THE PROJECTION MICRO- 

 SCOPE IN A HORIZONTAL POSITION. 



(Cut loaned by the Spencer Lens Co.). 



With the microscope in this position the image may be thrown down on a 

 horizontal surface for drawing by pushing the totally reflecting prism up in 

 the microscope tube to intercept the light (see fig. 109, 175). 



