92 ELEMENTARY PHOTO-MICROGRAPHY. 



cloth-faced board by springs in such a way that 

 the negative may be moved in any direction to 

 bring the right position opposite the centre. The 

 dry plate is then put on, with film side against 

 film side of negative, and covered with a wood 

 block the same size, which again is pressed by a 

 spring to keep the negative and plate in contact. 

 If any difficulty be experienced in discovering the 

 film side, it may be removed by simply breathing 

 upon the slide, when the glass side will be at once 

 clouded over or steamed by the condensed moisture, 

 but the film side will remain dry and unaffected. 



The exposure varies with the plate used. 

 Ilford " Special " lantern plates for warm and cold 

 tones require twenty seconds at eighteen inches 

 from an ordinary gas bat's-wing burner. Ilford 

 " Alpha " for red and brown tones, two minutes 

 at six inches from the burner. For slides with 

 black ground or contrasty effects, the Cadett 

 11 Black Tone " plates give excellent results. Ex- 

 posure, five seconds at twenty-four inches from 

 gaslight. 



Development and fixing are the same as for 

 negatives. The least fogging of the lights, it should 

 be noted, will spoil the slide, and the image must 

 stand out well defined 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 



