light at the surfaces of different media. 



Image at the Surface of Prism A. 



Oil of Camomile. — Two good periods. 

 First limit about 60°. 



Oil of Wormwood. — Three good periods. 

 First limit at 71°, but not well de- 

 fined. 



Bhela /mc^.— Three faint orders at low 

 temperatures, but finely brought out 

 by heat. First limit at 73°. 



Muriatic Acid. — Traces of tints. 



Sulphuric Acid. — Two pretty good or- 

 ders. 



Vitreous Humour of the Haddoch. — 

 Traces of colours. 



Oil of Rhue. — No colours. 



Oil of Boxwood. — No colours. 



Alcohol. — Traces of reddish, bluish, and 

 greenish yellow tints. 



Water. — Traces of tints. 



Image at the 

 Surface of Prism B. 



Bright yellowish 

 white. 



Yellowish white. 



Yellowish white. 



Yellowish white. 

 Yellowish white. 



Bright. 



Bright. 

 Bright. 

 Bright. 



Bright. 



The experiments * recorded in the preceding pages may be 

 divided into two classes. 



I. Those which establish the existence of reflecting forces 

 at the confines of media of the same refractive power ; and, 



II, Those in which periodical colours are produced at the 

 confines of particular kinds of glass, and various fluids and 

 soft solids. 



From the first of these classes of facts the following conclu- 

 sions may be drawn. 



1. The reflective and refractive forces in media of the same 

 refractive power do not follow the same law. This result is 

 clearly established by the experiments with the prism B, which 

 produced no orders of colours. Not only was there a strong 



• These experiments have been extended to a great number of mixed 

 oils and to soft solids, gums and resins, combined with the prisms A and 

 B. I have also substituted for these prisms others of different kinds of 

 glass, which give similar results ; and 1 have examined the phenomena at 

 the confines of different fluids and a great number of minerals of various 

 refractive powers between chromate of lead and fiuor spar. 



