I have analyzed, too, the blue colour of the sky
Fig. 1. [left] Shewing the Composition of the Green of the First Order
Fig 2. [right] Shewing the Spectrum produced by the green juices of plants.
for each of these two pairs, the image at left is NYPL copy, that at right is Austrian National Library copy.
illustrating David Brewster (1781-1868 *). “On the Colours of Natural Bodies.” (Read 22nd December 1833.) Transactions of the Royal Society of Edinburgh XII (1834): 538-545
In making a strong beam of the sun’s light pass through the green fluid, I was surprised to observe that its colour was a brilliant red, complementary to the green. By making the ray pass through greater thicknesses in succession, it became first orange and then yellow and yellowish-green, and it would undoubtedly have become blue, if it had been transmitted through a greater thickness of fluid...
I have submitted to the same mode of examination nearly one hundred and fifty coloured media, consisting of fluids extracted from the petals, the leaves, the seeds, and the rhind of plants, — the different substances used in dyeing, — coloured glasses and minerals, — coloured artificial salts, — and different coloured gases; and in all these cases I have obtained results which lead to the same conclusion. I have analyzed, too, the blue colour of the sky...
blue, if; color; spectra; grays
David Brewster, “On the Colours of Natural Bodies” (1833)