Mother of Pearl.

Taranaki Daily News, Volume XLVII, Issue 8003, 14 December 1905, Page 4

Mother of Pearl.

The iridscence of mother-of-pearl is an effect o! diffraction of light on the shell's surface. Fine scratches drawn upon glass or pollened metal "reflect waves of light from their sides; and some, being reflected from opposite sides of the same furrow, interfere with and quench each other. But the obliquity of reflection which extinguishes the shorter waves does not destroy the longer ones, hence the phenomena of colour. These are called the colours of striated surfaces, and are beautifully illustrated by mother-of-pearl. This shell is composed of exceedingly thin layers, which, when cut across by the polisher, expose their edges and furnish the necessary small and regular grooves. The most conclusive proof that the colours are due tc the mechanical state of the surface is to be found in the fact, established by Brewster, that by stamping the shell carefully upon black sealing-wax we transfer the grooves, and produce upon the wax the colours of mother-of-pearl.