-14 ON THE ACTION OF TRANSPARENT BODIES 



When flint-glass acts in opposition to balsam of Capivi, nut 

 ml, oil of rhodium, and oil of rosemary, no secondary spectrum is 

 visible. 



46. Glass, Opal-coloured. 



This glass acts more powerfully upon green light than oil of 

 cassia, and balsam of Tolu. 



It acts less powerfully upon green light than flint-glass. 



47. Glass, Orange-coloured. 



This glass acts less powerfully upon green light than crown- 

 glass, and very little less than flint-glass. 



It acts more powerfully upon green light than oil of amber, 

 and oil of anise-seeds. 



48. Glass, Red^coloured. 



This glass acts less powerfully upon green light \h&n flint 

 .and crown glass. 



49. Hyssop, Oil of 



This oil acts less powerfully upon green light than crown- 

 glass, and a little less powerfully than flint-glass, and oil of pep- 

 permint. 



50. Ice. 



When ice is opposed to flint-glass, it forms a secondary spec- 

 trum, having the same position, and nearly the same magni- 

 tude, as when water is combined with flint-glass. 



51. Juniper, Gum. 



This gum acts less powerfully upon green light than crown- 



tglass. 



52. Juniper, 



