124 ELEMENTARY PHOTO-MICROGRAPHY. 



The least fogging of the lights, it should be 

 noted, will spoil the slide, and the image must 

 stand out well denned on a perfectly transparent 

 background. Spoiled plates make good cover 

 glasses, if stripped of gelatine by steeping in boil- 

 ing water and soda. When the plates are ready 

 for mounting, a square or circular mask is placed 

 between the cover and picture. If there is room 

 on the margin of the mask, which is usually black, 

 the title may be written upon it with white ink, 

 not forgetting to put a white spot in each top 

 corner when looking at the picture the right way 

 about. These are for the guidance of the lanternist, 

 who puts the slide into the lantern upside down 

 with the spots toward the condenser. Nothing is 

 more awkward for both audience and operator 

 than pictures projected in a wrong position. 



It often happens that a slide which appears all 

 right by mere daylight inspection will show very 

 badly when enlarged on the screen through the 

 lantern to a loft. disc. Then any defects in focus 

 are plainly visible, and if the slide be too dense 

 or too thin, it is at once apparent. It is therefore 

 advisable before exhibiting any slide in public to 

 have it tested. If not already a member of a 

 local photographic society, here is an inducement 

 to join one, because most societies give special 

 opportunities for testing the slides of members 



