THE BOOK OF THE LANTERN. 151 



what is in reality a coloured varnish ; and this must be 

 quickly applied to the picture before it has time to thicken 

 by evaporation of the solvents. 



For greens, to be used mostly in foliage and for grass, 

 yellow and blue must be mixed together in varying pro- 

 portions. There is no such thing as a satisfactory trans- 

 parent green which can be bought ready made, and suit- 

 able for the purposes of the slide-painter ; but the use of 

 the two colours named, if we take care to vary the pro- 

 portion of each, can be made to give a great variety of 

 tints. But it should be pointed out that, if used alone, this 

 compounded green will be far too raw, and will exhibit a tint 

 which is never seen in nature. 



We mix, therefore, with the yellow and blue, some red 

 or brown, to take off this rawness. An endless variety of 

 tints may be made by taking three colours only, and using 

 them in different proportions, and I would advise the slide- 

 painter to mix some of these tints, and put them side by 

 side on a bit of glass, with a ticket attached to each 

 describing their constituents. This specimen glass will be 

 useful for future reference. I give in the next chapter a 

 few compound tints, which can be made easily, and can be 

 used for foliage, etc. 



The list of colours given will be found more than 

 sufficient for all needs, and many slide-painters do very 

 good work with only half their number, for there is no 

 limit to the number of tints which one may get by 

 judicious blending. Mathematicians are able to tell us 

 the number of chances against a whist-player turning 

 up the same cards on two different occasions, and we 



