UPON THE DIFFERENTLY COLOURED RAYS OF LIGHT. 9 



It acts more powerfully upon green light than oil of cas- 

 sia. 



20. Arabic, Gum. 



Gum Arabic acts more powerfully upon green light than oil 

 of cassia, balsam of Tolu, and flint -glass. 



When it opposes crown-glass, the uncorrected colour is 

 scarcely perceptible ; the excess of action on green light being 

 on the side of the gum. 



It acts less powerfully upon green light than topaz and rock- 

 crystal. 



2L Beech Nut, Oil of 

 This oil acts less powerfully on green light than crown- 



glass. 



It acts a very little less powerfully upon green light than 

 flint-glass. 



22. Bergamot, Oil of 



This oil acts less powerfully upon green light than flint and 

 crown glass. 



No uncorrected colour is visible when it acts in opposition 

 tp oil of marjoram. 



23. Beryl. 



Beryl acts more powerfully upon green light than flint and 

 ■crown glass. 



24. Borax. 



Borax acts more powerfully upon green light than flint and 

 ■crown glass. 



Vol. VIII. P. I. B 25. Glass 



