LANTERN SLIDES 505 



After fixing the negatives should be thoroughly washed 

 and then placed in a rack to dry. 



A negative or lantern slide that is too dark may some- 

 times be reduced (made lighter) by placing it for a little 

 while in the following solution : 



Solution No. 1 : 



Potassium ferricyanicle 1 oz. 



Water 16 oz. 



Solution No. 2: 



Sodium hyposulphite 1 oz. 



Water 16 oz. 



Dissolve the ferricyanide in a dark bottle (or wrap the 

 bottle in opaque paper) as it is affected by the light. Re- 

 duction should be carried out in subdued light, never by a 

 strong daylight. Take a sufficient quantity of No. 2 to 

 cover the negative in a tray and add a small quantity of 

 No. 1, then immerse the negative. Remove several times 

 during the operation and wash off the chemicals to avoid 

 staining. Wash thoroughly after the desired reduction 

 has been obtained. 



Lantern slides if made from negatives are printed in a 

 printing frame in the same manner as that in which a print 

 is made. The slide is then developed in the same way as a 

 negative is developed and in the same developing solution. 



It is to be noted that lantern slide plates are 3%x4 

 inches in dimensions, i. e., a quarter of an inch shorter than 

 the corresponding standard dry plate which is 314x414 

 inches. This size of plate is used to make the negatives 

 from which the lantern slides are printed. 



It often happens that in the laboratory lantern slides can 

 be made up directly from the objects themselves without the 

 labor and expense of making negatives. This is especially 

 true for slides of black tracings such as are made in pharma- 

 cological experiments. The method is as follows : Kits 

 will generally have to be used to step the size of the plate 

 holder down to 814x414 inches. A narrow strip of wood 

 (about the size of a tooth-pick) is glued into the inner edge 



