Iridescent Colours. 155 



tion, I have here a few objects exhibiting iridescent colours, 

 which, by trial, will be found to give the following results : — 

 The crest of this humming bird, CJirysolampis mosquitus, 

 which, to the unaided eye, appears resplendent with all shades 

 of red, orange, yellow, or green, according to the angle of 

 the incident light, appears, when examined by the mirror, of 

 one unvarying red tint, disappearing when the object is 

 moved, but absolutely unchanging in tint. Such an object, 

 therefore, I should describe as "iridescent red;" all else regard- 

 ing its colour may be inferred. Again, the breast, or gorget, of 

 the same bird reflects all shades of orange, yellow, or green 

 to the eye alone ; with the mirror it is seen of a deep 

 orange, which, as before, is unchanged in tints by any 

 variation in position. Such an object I would describe as 

 " iridescent orange." The gorget of another humming bird, 

 CallipJdox amethystina, to the eye alone appears crimson, 

 orange, yellow, or green ; with the mirror it is iridescent 

 crimson only, spectroscopically a red of the 2nd order. 

 Amongst insects, instances of iridescent species are number- 

 less, the results of examination are just the same as in other 

 iridescent bodies. This butterfly, Morpho, to the eye alone 

 appears either greenish-blue, blue, or violet, as its inclination 

 to the light varies ; examined with the mirror it appears 

 green, and should be described as iridescent green, or 

 iridescent bluish-green. This beetle, Poropleura bacca, 

 appears any shade of red, yellow, or green to the eye 

 alone ; with the mirror only iridescent red. In this extra- 

 ordinary beetle, CJirysochroa fulminans, we have all the 

 colours of the spectrum in their natural sequence, beginning 

 with red at the tip of the wing case, and ending with violet 

 higher up the elytron. These colours vary in an indescribable 

 manner when attentively examined at different angles of 

 incident light with the eye alone ; with the mirror the wing 

 cases are seen to be coloured successively from base to tip 

 iridescent green, yellow, orange, and red, and these tints 



