Goethe's Theory of Colours · Johann Wolfgang von Goethe
CONDITIONS OF THE INCREASE OF COLOUR.
323 (209). Here too an increased displacement of the object produces a greater appearance of colour. 324 (210). This increased displacement occurs, 1. By a more oblique direction of the impinging luminous object through mediums with parallel surfaces. 2. By changing the parallel form for one more or less acute angled. 3. By increased proportion of the medium, whether parallel or acute angled; partly because the object is by this means more powerfully displaced, partly because an effect depending on the mere mass co-operates. 4. By the distance of the recipient surface from the refracting medium so that the coloured spectrum emerging from the prism may be said to have a longer way to travel. 5. When a chemical property produces its effects under all these circumstances: this we have already entered into more fully under the head of achromatism and hyperchromatism. 325 (211). The objective experiments have this advantage that the progressive states of the phenomenon may be arrested and clearly represented by diagrams, which is not the case with the subjective experiments.
Text from Project Gutenberg, public domain in the United States.