206 PREPARATION OF LANTERN SLIDES [CH. VIII 



and filtered through filter paper. The slides are coated with the 

 gelatin as described for the varnish. When the gelatin is dry the 

 surface receives a pen or brush well. Gelatin slides are not so 

 satisfactory as the varnished slides. 



FIG. 115. AMERICAN LANTERN SLIDE OF FULL SIZE WITH GUIDE LINES 

 FOR MAKING SLIDES DIRECT. 



The thumb tacks at the four corners are to hold the slide firmly in position 

 while writing or drawing upon it. The lined area represents about the maxi- 

 mum size of opening projected in ordinary work (65 x 75 mm.), (2>i X2 %in.). 



319. Inks and pens. One can use any ink and any pen on 

 the varnished or gelatinized slides. 



For making tables, etc., it is best to use water-proof India ink 

 and a fine pen, a crow-quill, steel pen is excellent. 



320. Drawing diagrams on varnished slides. One can draw 

 freehand on these varnished slides as well as upon paper. For 



