The colours produced by the transmission of polarised light through chrystalised mediums, were described by Goethe, in his mode, subsequently to the publication of his general theory, under the name of Entoptic Colours. See note to Par. 485.
NOTE L.—Par. 150.
We have in this and the next paragraph the outline of Goethe's system. The examples that follow seem to establish the doctrine here laid down, but there are many cases which it appears cannot be explained on such principles: hence, philosophers generally prefer the theory of absorption, according to which it appears that certain mediums "have the property of absorbing some of the component rays of white light, while they allow the passage of others."97
Whether all the facts adduced by Goethe—for instance, that recorded in Par. 172, are to be explained by this doctrine, we leave to the investigators of nature to determine. Dr. Eckermann, in conversing with Goethe, thus described the two leading phenomena (156, 158) as seen by him in the Alps. "At a distance of eighteen or twenty miles at mid-day in bright sunshine, the snow appeared yellow or even reddish, while the dark parts of the mountain, free from snow, were of the most decided blue. The appearances did not surprise me, for I could have predicted that the mass of the interposed medium would give a deep yellow tone to the white snow, but I was pleased to witness the effect, since it so entirely contradicted the erroneous views of some philosophers, who assert that the air has a blue-tinging quality. The observation, said Goethe, is of importance, and contradicts the error you allude to completely."98