light at* the surfaces of different media. 



219 



Image at the Surface of Prism A. 



Balsam of Peru. — Slight tinges of red ; 

 blue as above. Two faint orders of 

 colours brought out by heat. 



Oil of Anise-seeds. — The tinges of two 

 orders of colours. Heat of 200° brings 

 out two good orders of colours. Li- 

 mit of pink and blue of the first or- 

 der at an incidence less than Q5°. 



Balsam of Styrax.- — Tinges of two or- 

 ders of colours. Improved by heat. 



Canada Balsam. — Above two orders of 

 colours ; pink of second the best. Im- 

 proved by heat. 



Oil of Tobacco. — Two faint orders of co- 

 lours. Heat brings out nearly three. 



Oil of Cloves. — Two faint orders. Heat 

 brings out part of a third. First li- 

 mit of pink and blue about Q5P of in- 

 cidence. 



Oil of Sassafras. — Two orders. First 

 red pale. First blue good. 



Balsam ofCapivi. — See page 213. 



Muriate of A7itimo7iy. — Two tolerably 

 distinct orders of colours. 



Oil of Cummin. — Two beautiful orders. 

 A fine yellow in the second order. 

 Heat spoils them all. 



Nut Oil. — Two faint orders, the second 

 red and second blue being tolerably 

 good. Heat brings out two fine or- 

 ders, the first limit of pink and blue 

 ending at about 76*' of incidence. 



Oil of Pimento. — Three good orders of 

 colours. First hmit of pink and blue 

 at QB" of incidence. 



Image at the 

 Surface of Prism B, 



Yellowish white. 



Grayish or bluish 

 white. 



Bright white. 



Grayish or bluish 

 white. 



Grayish white. 



Yellowish white ; 

 but bluish gray 

 with heat. 



Grayish white. 



Grayish white. 



Faint grayish, be- 

 coming more in- 

 tense and yellow 

 by heat. 



Yellowish white. 



Pale blue, very faint 

 at great incidences. 



