This other liquid, finally, is purple because it destroys the green
and the yellow, and allows the terminal colours of the spectrum to
pass unimpeded. From the blending of the blue and the red this
gorgeous purple is produced.

One step further for the sake of exactness. The light which falls upon
a body is divided into two portions, one of which is reflected from
the surface of the body; and this is of the same colour as the
incident light. If the incident light be white, the superficially
reflected light will also be white. Solar light, for example,
reflected from the surface of even a black body, is white. The
blackest camphine smoke in a dark room, through which a sunbeam passes
from an aperture in the window-shutter, renders the track of the beam
white, by the light scattered from the surfaces of the soot particles.
The moon appears to us as if

'Clothed in white samite, mystic, wonderful;'

but were it covered with the blackest velvet it would still hang as a
white orb in the heavens, shining upon our world substantially as it
does now.


§ 8. _Colours of Pigments as distinguished from Colours of Light_.

The second portion of the incident light enters the body, and upon its
treatment there the colour of the body depends. And here a moment may
properly be given to the analysis of the action of pigments upon
light. They are composed of fine particles mixed with a vehicle; but
how intimately soever the particles may be blended, they still remain