180 G. Tait, Esq., on producing White or Neutral Lights 



approximation. It could be ascertained more accurately, by 

 comparing the artificial light transmitted through " coloured" 

 glass with that transmitted through colourless transparent 

 glass of the same quality. There is rather a larger portion 

 to be absorbed in a duller flame, as has just been remarked. 

 The very great excess of orange thus ascertained to exist in 

 artificial light, accounts for the very great difference between 

 its effect and that of white light upon the appearance of the 

 colours of objects, and may give some idea of the extent of 

 that difference to those who have not seen them distinctly 

 contrasted. 



I shall now exhibit white or neutral light and ordinary 

 artificial light in contrast. This may be done in different 

 ways. It is done conveniently and distinctly, by transmitting 

 the lights through paper, or other pellucid substance, by 

 means of the simple apparatus represented by the following 

 diagram. It is, of course, to be used in a dark apartment. 



B 



E 



K 



A B C D, box of tin-plate of such size as may be neces- 

 sary, bright within, opening at the front, A B, and the back, 

 CD. 



