794 PROFESSOR PIAZZI SMYTH ON COLOUR, 
turf, but with scarlet cloth. Couleur de rose, do you suggest? No: it was 
couleur de soldier’s coat ; so excessively pronounced in red was the aspect at 
that moment of what I knew to be merely green grass: and yet the daisies in 
it, here and there, remained all of them exquisitely white. 
Still again I looked through the black-green bottle at a plant of flourishing 
Palmetto in an earthenware pot on the table at my elbow. I scanned it very 
closely, while the sun shone upon it, over all its lights and shades, over all its 
leaves, stalks and stem almost microscopically, and made myself as sure as I 
could be by clear, strong eye-sight of anything whatever even of things nearest 
at hand,—that, though the earth in the pot was black, yet both plant and pot 
were absolutely of one and the same colour; and that colour was a signal 
species of red, of a more beautiful kind and even sublime degree of redness of 
red than I had ever met with in any sort or kind of gardening before ! 
The instant the dark bottle was removed, the plant was green, and the pot 
a dull brown-red. But how had their recent simultaneous and most super- 
lative redness been brought about, through means too of an almost pitch-dark 
blue-green medium ? 
The reason thereof is duplex ; but not very far to seek with the aid of 
spectroscopy. Judson’s green, the medium concerned, is intensely di-chroic, 
and when very dark will transmit little, if any, part of the spectrum except the 
extreme red. Wherefore, if it meets with another di-chroic either green or 
brown, it allows none of that green or brown, however bright, to pass ; and only 
such portions of their red spectral bands as correspond with its own red band. 
But that band, as shown already in our Table of Reds, page 787, is far 
further up towards Nature’s mysterious beginning and fountain-head of both 
the spectrum and red, than is any of the red of the, for railway signal-lamps 
most approved, ruby-red glass. Wherefore by so much, expressible too in 
spectrum number, is the red ray of di-chroic green vegetation, when seen 
through Judson’s dark green-black dye, more magnificently, purely and _per- 
fectly red, than any red colour that human eye has yet seen without the 
discriminating assistance of the spectroscope. 
But over and above the redness of any reds thus made manifest, there was 
such brilliance! Whence therefore came the light for that almost sun-shiny 
illumination, whose vigour lent such a positiveness to the transformation scene ? 
It comes in a manner out of the very darkness of the dark bottle itself ; and 
by means of an interesting interference of the waves of light. In fact it re- 
minds one closely, though with a variation, of the terrestrial circumstances 
under which the incandescent sodium vapour of the sun may be seen dark, in 
place of bright ; viz., it must be looked at through another supply of also 
incandescent sodium vapour, but not so bright or hot as the first. 
Similarly then, though vice versd, the essence of success in making our 


