330 



DRAWING WITH THE MAGIC LANTERN 



[CH. X 



The size of the drawing can be varied without moving the lantern 

 or the drawing surface by using an objective of longer focus for a 

 smaller diagram, or of a shorter focus for a larger diagram (see also 

 57)- 



466. Use of the magic lantern for small drawings. It fre- 

 quently happens that a small drawing of some large object is 

 needed for publication. This may be some natural object or a 

 piece of apparatus. The object or piece of apparatus is placed in a 

 good light and a small negative made on a lantern-slide plate, being 

 careful not to make the negative too dense. After this is dry, it 

 can be put into the lantern-slide carrier and projected upon the 

 drawing paper, and the outlines accurately traced. Then with a 

 pen and India ink one can ink in the lines and add any necessary 

 shading free-hand, having the object or piece of apparatus in view 

 so that it can be accuratclv done. The exact magnification or 



Condenser 



Arc Lamp 



KS 



FIG. 185. SIMPLEST FORM OF MAGIC LANTERN WITH ARC LIGHT FOR USE 



IN DRAWING. 



SW Supply wires. 



So K Socket with its key switch. 



S P Separable attachment plug. 



LW Wires extending from the cap of the plug to the knife switch. 



KS Knife switch for turning the current on and off. 



Rheostat The balancing device for regulating the current. 



Arc Lamp The arc lamp with right-angled carbons. 



Condenser The two-lens condenser with the first (i) and the second (2) 

 elements. 



LS Position of the lantern slide or other large object. 



Objective with r, its center. 



Axis Axis The principal optic axis of the condenser and the objective. 

 The radiant must be centered on this axis. 



Image Screen The drawing surface on which the image is projected. 



