182 G. Tait, Esq., on producing White or Neutral Light, 



neutralised by the orange of the light. If less intense, it 

 becomes a dull orange, being the excess of the orange of the 

 •light combined with the neutral grey produced by the re- 

 mainder of the orange combined with the blue. If more in- 

 tense, it becomes of a very dark grey, slightly tinged with 

 the excess of blue. Green, if pale, becomes of a dull orange, 

 less or more tinged with gi*ey. If more intense, so that the 

 orange of the light may be neutralized by the blue of the 

 green, it becomes of a dark muddy tinge, more or less of a 

 ^ yellowish cast. Purple, if pale, becomes hardly distinguish- 

 able from orange. If more intense, so that the orange of 

 the light may be neutralized by the blue of the purple, it 

 becomes of a dark muddy tinge, more or less of a reddish 

 cast. The appearance of all the more compound colours is 

 altered in the same manner ; the white forming light tints 

 becoming orange ; the blue entering into the various com- 

 pounds of green and purple being almost lost, from the want 

 of blue in the light ; and the red and yellow entering into 

 compounds, being much heightened. 



The difference of effect of the two lights will perhaps be 

 more striking, by now exhibiting on the front of the box, 

 another paper, on the upper and lower halves of which I 

 painted with transparent water-colours, by daylight, two 

 sketches precisely similar to each other. It will be particu- 

 larly observed how much the blues and the compounds of 

 blue are destroyed. 



It is thus obvious how very much ordinary artificial light 

 is inferior to white light, or rather how unfit it is to be used, 

 wherever it is necessary to distinguish the colours of objects, 

 or desirable to perceive them in their natural pleasing and 

 harmonious appearance. 



In obtaining white or neutral light by the method now 

 proposed, there is of course a loss of a large portion of the 

 artificial light. This loss consists partly of the light which 

 would be lost by reflection and extinction in passing through 

 colourless transparent glass, except that there is no reflec- 

 tion from the glass on the side which is painted, instead of 

 its being from both sides as usual ; which loss appears, ac- 

 cording to observations made by Sir William Herschel, to 



