DR. BREWSTER ON REFLECTED LIGHT. 191 
Colours. 
~ Yellow 
Angles of Incidence 
RrE. 
o 
Angles of Incidence 
on Surface 
CoD*. 
. . 83 33 
Orange 
.... 63 
. . 81 13 
1st OrderX Red 
.... 61 
. . 80 27 
Pink 
.... 59J 
. . 79 51 
LLimit of pink and blue 
.... 58 
. . 79 14 
f Bluish pink .... 
.... 57 
. . 78 46 
Full blue 
.... 55 
. . 77 54 
Greenish blue . . . 
.... 52 
. . 76 30 
Yellowish blue . . . 
.... 48 
. . 74 32 
2nd Orders 
Yellow 
.... 41 
. . 70 46 
Reddish yellow . . . 
.... 34 
66 46 
Redder still .... 
.... 26 
. . 61 54 
Red 
.... 21 
. . 59 4 
Pink red 
.... 17 
. . 56 11 
^Limit of pink and blue 
.... 14 
. . 54 14 
'"Blue 
. . . . + 9 
. . 50 57 
Bluish green .... 
.... 0 
. . 45 0 
3rd Orders 
Yellowish 
.... —15 
. . 35 46 
Full yellow .... 
.... -22 
. . 30 37 
Reddish yellow . . . 
.... —31 
. . 25 21 
LPink 
. . . -52 
. . 13 30 
The colour of the pencil psn produced by the other separating surface Gp 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 psn 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 
* This column is calculated from the formula A = 45° + 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. 
