[1] This was objected to Goethe when his "Beyträge sur Optik" first appeared; he answered the objection by a coloured diagram in the plates to the "Farbenlehre:" in this he undertakes to show that the assumed gradual "correction" of the colours would produce results different from the actual appearance in nature. NOTE O.--Par. 252. These experiments with grey objects, which exhibit different colours as they are on dark or light grounds, were suggested, Goethe tells us, by an observation of Antonius Lucas, of Lüttich, one of Newton's opponents, and, in the opinion of the author, one of the few who made any well-founded objections. Lucas remarks, that the sun acts merely as a circumscribed image in the prismatic experiments, and that if the same sun had a lighter background than itself, the colours of the prism would be reversed. Thus in Goethe's experiments, when the grey disk is on a dark ground, it is edged with blue on being magnified; when on a light ground it is edged with yellow. Goethe acknowledges that Lucas had in some measure anticipated his own theory.--Vol. ii. p. 440. NOTE P.--Par. 284. The earnestness and pertinacity with which Goethe insisted that the different colours are not subject to different degrees of refrangibility are at least calculated to prove that he was himself convinced on the subject, and, however extraordinary it may seem, his conviction appears to have been the result of infinite experiments and the fullest ocular evidence. He returns to the question in the controversial division of his work, in the historical part, and again in the description of the plates. In the first he endeavours to show that Newton's experiment with the blue and red paper depends entirely on the colours being so contrived as to appear elongated or curtailed by the prismatic borders. "If," he says, "we take a light-blue instead of a dark one, the illusion (in the latter case) is at once evident. According to the Newtonian theory the yellow-red (red) is the least refrangible colour, the violet the most refrangible. Why, then, does Newton place a blue paper instead of a violet next the red? If the fact were as he states it, the difference in the refrangibility of the yellow-red and violet would be greater than in the case of the yellow-red and blue. But here comes in the circumstance that a violet paper conceals the prismatic borders less than a dark-blue paper, as every observer may now easily convince himself," &c.--Polemischer Theil, par. 45. Desaguliers, in repeating the experiment, confessed that if the ground of the colours was not black, the effect did not take place so well. Goethe adds, "not only not so well, but not at all."--Historischer Theil, p. 459. Lucas of Lüttich, one of Newton's first opponents, denied that two differently-coloured silks are different in distinctness when seen in the microscope. Another experiment proposed by him, to show the unsoundness of the doctrine of