162 THE BOOK OF THE LANTERN. 



Hitherto I have regarded the picture as possessing a 

 plain glass surface to represent the sky, and this will be 

 found to be the case with most photographic slides. But 

 we all know that a plain white sky in a photograph is, from 

 an artistic point of view, an abomination. By the simple 

 process of colouring we get over the difficulty ; still, if we 

 can produce upon a photographic transparency natural 

 clouds either existing in the original negative by the virtue 

 of a properly-constructed shutter, which will only give a 

 fraction of the normal exposure to the sky, or by a system 

 of printing-in from a separate negative in a way that need 

 not be described here, it will be a great artistic gain. In 

 colouring such a sky the painter has a great advantage, for 

 irregularities in laying on the colour, which would other- 

 wise be distinctly visible, are hidden by the details of the 

 clouds in the picture. 



In colouring such a sky we may commence, as usual, by 

 dabbing on the blue in the spaces which represent rifts 

 between the clouds, and we can then add tender tints made 

 up by mingling such colours as crimson lake, and the 

 various yellows at our disposal, and we can also add to the 

 richness of the general effect by putting in different tones 

 of lavender, mauve, and purple, made up with crimson lake, 

 the madders, and blue. These colours, after the blue has 

 been dabbed on, can best be painted in with the brush, 

 using as a medium Canada balsam in turpentine. This is 

 a good, quick-drying medium, and it has the advantage of 

 being so pale in colour that it will not affect the most deli- 

 cate tints. 



Before proceeding farther with the work, the picture 



