DR. BREWSTER ON REFLECTED LIGHT. 



191 



Colours. 



Angles of Tncidence 

 RrE. 



1st Order.< 



2nd Order.-< 



3rd Order.^ 



Yellow 70 



Orange 63 



Red 61 



Pink 59^ 



-Limit of pink and blue .... 58 



Bluish pink h^ 



Full blue 65 



Greenish blue 52 



Yellowish blue 48 



Yellow 41 



Reddish yellow 34 



Redder still 26 



Red 21 



Pink red 17 



Limit of pink and blue .... 14 



fBlue + 9 



Bluish green 



Yellowish —15 



Full yellow —22 



Reddish yellow —31 



Pink —52 



Angles of Incidence 

 on Surface 

 CoD*. 



. 83 33 



. 81 13 



. 80 27 



. 79 51 



. 79 14 



. 78 46 



. 77 54 



. 76 30 



. 74 32 



. 70 46 



. 66 46 



. 61 54 



. 59 4 



. 56 11 



. 54 14 



. 50 57 



. 45 



. 35 46 



. 30 37 



. 25 21 



. 13 30 



The colour of the pencil />*« produced by the other separating surface G/> H 

 is at all incidences a faint yellowish gray, (which is best seen by turning the 

 system of prisms upside down ; and receiving the ray R r upon the prism B, 

 so that the reflected ray p*w may not pass through the oil ;) and its intensity 

 suffers very little change. This fact is a very remarkable one, and arises (as 

 will be presently seen) from some specific property of the glass itself. When 

 the lower prism is of the same glass as A, and produces the colours in the pre- 

 ceding table at different angles of incidence from those of A, the play of colours 



i '. i' 



* This column is calculated from the formula A e= 45° + VI1:S, I being the angles of incidence in 



— m 



the 1st column, A the angles in the 2nd, and m = 1.508 the refractive index of the glass. 



