140 THE BOOK OF THE LANTERN. 



large expanse of sky, the quickest method is to gum over 

 it a piece of orange-coloured paper with a jagged edge. 



A lantern slide, otherwise perfect, will sometimes re- 

 quire a little strengthening. I believe that the best 

 method of intensification is that long ago published by 

 Mr. England. Here it is : 



Mercuric bi-chloride (corrosive sublimate) ... | oz. 

 Sal ammoniac ... ... ... ... ... \ 



Water 12 



(Dissolve, and mark " Poison.") 



The picture, after well soaking in plain water, is im- 

 mersed in this mixture, in which it will first turn grey, 

 and afterwards quite white if left long enough. The 

 white stage should not be reached unless a very great 

 additional intensity is requisite. Remove from the solu- 

 tion, wash most thoroughly under a tap for three or four 

 minutes, and immerse in the following solution, which will 

 almost immediately turn the film to a brown black : 



Liq. ammonia-fort ... ... ... ... drachm. 



Water ... ... ... ... ... ... Bounces. 



Rinse under the tap, and the operation is complete. Many 

 people object to the use of the mercuric salt, on the 

 ground that it is unstable, and that the picture will ulti- 

 mately fade. I have not found this to be the case if the 

 washing operation be thoroughly carried out, but as a rule 

 I should give an intensified film a protecting layer of 

 varnish. Prevention is better than cure, and the amateur 

 should endeavour to produce pictures that will require no 

 doctoring. 



When the lantern transparency is complete it must be 

 mounted before it can be considered out of hand. It is as 



