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Глава 4 - оцифровка страниц 114-118
CHAPTER IV
COMPLEMENTARY COLOURS
SOON after the discovery of the Aura, a friend called our attention to the fact, that if a light was gazed at, and the eyes turned first to one side and then to the other of any person, the colours of the spectre were often not the same. After having convinced ourselves that this peculiarity did occur, we thought it might be a help in diagnosis, but for that purpose we knew that the investigation by means of complementary colours must be made methodical. We began by gazing at a gaslight for the employment of its complementary colour, not that we thought that such a crude method would be satisfactory, but to discover its defects, so that they might guide us in our future experiments. We noticed that the resulting phantom was not a single colour, as the main portion had one colour, but was surrounded by another quite different. The inconvenience of having to work with two or more colours simultaneously was immediately apparent, an insurmountable difficulty arising from the constant changing of the colours of the spectre, quickly one after the other, an effect caused by the slight movement of the eyes necessary for seeing the image on the two sides of the subject, consequently no accurate results could be obtained. It was felt that if any benefit was to be derived from this process, a monochromatic spectre was essential. After many experiments we came to the conclusion that pieces of coloured paper answered the purpose better than anything else.
This chapter will be entirely devoted to this problem, viz.: the effect of the Aura upon complementary colours—a more extraordinary property can hardly be conceived. The change observed is as follows: —When a monochromatic spectre is employed the shade of the colour becomes either lighter or darker under certain conditions. As may be expected, it is a very difficult and complicated subject to deal with, but we will give the best explanation we can; yet some of the theories may appear farfetched or even heterodox; nevertheless, they are advanced for the want of better hypotheses. As the subject is entirely dependent upon colour-vision some preliminary remarks are required on that process.
It is a generally accepted fact, that there are three sets of colour-sensitive nerves in the eyes, and that all the colours perceived arise from the stimulation of one, two or all of these sets of nerves, either separately or in conjunction. When more than one set of nerves are excited, they are usually unequally stimulated. The true physiological primary colours are those that can stimulate only one set of colour-sensitive nerves simultaneously. One method of ascertaining a person's own personal primary colours, is to press the closed eye, when there will usually be seen small yellow dots all over the field of vision. Intermingling with these are much larger discs of blue, and lastly red points intermediate in size between the yellow and blue discs. The yellow are the most numerous and the blue next in number.
When all the colour-sensitive nerves are excited equally the object is called white, but when unequally it is coloured. We have for many years considered that each person possesses his own primary colours, and accordingly sees a coloured object differently to any one else, but by means of education every one calls the colour by the same name. For instance let two persons A and B look at a coloured object, usually designated as a shade of yellow. This colour might only stimulate one set of colour-sensitive nerves of A, and would be to him a pure yellow. On the other hand with B, not merely might the yellow-sensitive nerves be excited, but to a slight extent the blue-sensitive nerves; he would see it as a greenish colour. But as A and B have both been taught that the colour is a certain shade of yellow, whenever they see it, they will both call it by the same name. Nevertheless, if A saw it with B's eyes he would immediately say it was a greenish yellow, while B, looking through A's eyes, would give it some other name. Each would be correct. It follows as a corollary, that every one sees nature in hues different from what his neighbour does. It is unnecessary to enter more fully into this theory, but according to it the writer's primary colours are, at the present time, red, yellow and blue. Twenty years ago purple took the place of blue. We do not propose to consider any other theories, since this one will do perfectly well for our purpose.
Putting aside for the time being all theories, it will be found that when one set of colour-sensitive nerves is completely fatigued, the observer is, for the time being, colour-blind. If the red-sensitive nerves be the ones exhausted, he will be red-blind, although he will be able to perceive perfectly all the colours that do not contain red; in addition he will see any colour that has a mixture of red, as the hue would be if all the red colour were removed. Taking a simple example, purple would have the appearance of a shade of blue. This artificial colour blindness causes the eyes to become hyper-sensitive to all colours and shades of colours, that do not contain red, as red in an ordinary way helps to obscure a very faint tint of any colour. The following experiment has been tried by several people and will furnish a proof. When a band of light, tinged very faintly with carmine, is thrown upon a white screen from a magic lantern, it will have a certain visibility; but