Goethe's Theory of Colours · Johann Wolfgang von Goethe
431.
First condition.--The contact of two smooth surfaces of hard transparent bodies. First case: if masses or plates of glass, or if lenses are pressed against each other. Second case: if a crack takes place in a solid mass of glass, chrystal, or ice. Third case: if lamellæ of transparent stones become separated. Second condition.--If a surface of glass or a polished stone is breathed upon. Third condition.--The combination of the two last; first, breathing on the glass, then placing another plate of glass upon it, thus exciting the colours by pressure; then removing the upper glass, upon which the colours begin to fade and vanish with the breath. Fourth condition.--Bubbles of various liquids, soap, chocolate, beer, wine, fine glass bubbles. Fifth condition.--Very fine pellicles and lamellæ, produced by the decomposition of minerals and metals. The pellicles of lime, the surface of stagnant water, especially if impregnated with iron, and again pellicles of oil on water, especially of varnish on aqua fortis. Sixth condition.--If metals are heated; the operation of imparting tints to steel and other metals. Seventh condition.--If the surface of glass is beginning to decompose. First condition, first case. If two convex glasses, or a convex and plane glass, or, best of all, a convex and concave glass come in contact, concentric coloured circles appear. The phenomenon exhibits itself immediately on the slightest pressure, and may then be gradually carried through various successive states. We will describe the complete appearance at once, as we shall then be better enabled to follow the different states through which it passes.
The centre is colourless; where the glasses are, so to speak, united in one by the strongest pressure, a dark grey point appears with a silver white space round it: then follow, in decreasing distances, various insulated rings, all consisting of three colours, which are in immediate contact with each other. Each of these rings, of which perhaps three or four might be counted, is yellow on the inner side, blue on the outer, and red in the centre. Between two rings there appears a silver white interval. The rings which are farthest from the centre are always nearer together: they are composed of red and green without a perceptible white space between them. We will now observe the appearances in their gradual formation, beginning from the slightest pressure. On the slightest pressure the centre itself appears of a green colour. Then follow as far as the concentric circles extend, red and green rings. They are wide, accordingly, and no trace of a silver white space is to be seen between them. The green is produced by the blue of an imperfectly developed circle, mixing with the yellow of the first circle. All the remaining circles are, in this slight contact, broad; their yellow and blue edges mix together, thus producing a beautiful green. The red, however, of each circle, remains pure and untouched; hence the whole series is composed of these two colours.
A somewhat stronger pressure separates the first circle by a slight interval from the imperfectly developed one: it is thus detached, and may be said to appear in a complete state. The centre is now a blue point; for the yellow of the first circle is now separated from this central point by a silver white space. From the centre of the blue a red appears, which is thus, in all cases, bounded on the outside by its blue edge. The second and third rings from the centre are quite detached. Where deviations from this order present themselves, the observer will be enabled to account for them, from what has been or remains to be stated. On a stronger pressure the centre becomes yellow; this yellow is surrounded by a red and blue edge: at last, the yellow also retires from the centre; the innermost circle is formed and is bounded with yellow. The whole centre itself now appears silver white, till at last, on the strongest pressure, the dark point appears, and the phenomenon, as described at first, is complete. The relative size of the concentric circles and their intervals depends on the form of the glasses which are pressed together. We remarked above, that the coloured centre is, in fact, an undeveloped circle. It is, however, often found, on the slightest pressure, that several undeveloped circles exist there, as it were, in the germ; these can be successively developed before the eye of the observer.
Ideas discussed in this chapter
Text from Project Gutenberg, public domain in the United States.