1826. Similar phenomena have been also investigated with great labour

and success by Purkinje. For a collection of extraordinary facts of the kind recorded by these writers, the reader may consult Scott's Letters on Demonology and Witchcraft.[1] The instances adduced by Müller and others are, however, intended to prove the inherent capacity of the organ of vision to produce light and colours. In some maladies of the eye, the patient, it seems, suffers the constant presence of light without external light. The exciting principle in this case is thus proved to be within, and the conclusion of the physiologists is that external light is only one of the causes which produce luminous and coloured impressions. That this view was anticipated by Newton may be gathered from the concluding "query" in the third book of his Optics. [1] See also a curious passage on the beatific vision of the monks of Mount Athos, in Gibbon, chap. 63. NOTE K.--Par. 140. "Catoptrical colours. The colours included under this head are principally those of fibres and grooved surfaces; they can be produced artificially by cutting parallel grooves on a surface of metal from 2000 to 10,000 in the inch. See 'Brewster's Optics,' p. 120. The colours called by Goethe _paroptical_, correspond with those produced by the diffraction or inflection of light in the received theory.--See Brewster, p. 95. The phenomena included under the title 'Epoptical Colours,' are generally known as the colours of thin plates. They vary with the thickness of the film, and the colour seen by reflection always differs from that seen by transmission. The laws of these phenomena have been thoroughly investigated. See Nobili, and Brewster, p. 100."--S. F. 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."[1] 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."[2] The same writer has some observations to the same effect on the colour of the Rhone at Geneva. A circumstance of an amusing nature which he relates in confirmation of Goethe's theory, deserves to be inserted. "Here (at Strasburg), passing by a shop, I saw a little glass bust of Napoleon, which, relieved as it was against the dark interior of the room, exhibited every gradation of blue, from milky light blue to deep violet. I foresaw that the bust seen from within the shop with the light behind it, would present every degree of yellow, and I could not resist walking in and addressing the owner, though perfectly unknown to me. My first glance was directed to the bust, in which, to my great joy, I saw at once the most brilliant colours of the warmer kind, from the palest yellow to dark ruby red. I eagerly asked if I might be allowed to purchase the bust; the owner replied that he had only lately brought it with him from Paris, from a similar attachment to the emperor to that which I appeared to feel, but, as my ardour seemed far to surpass his, I deserved to possess it. So invaluable did this treasure seem in my eyes, that I could not help looking at the good man with wonder as he put the bust into my hands for a few franks. I sent it, together with a curious medal which I had bought in Milan, as a present to Goethe, and when at Frankfort received the following letter from him." The letter, which Dr. Eckermann gives entire, thus concludes--"When you return to Weimar you shall see the bust in bright sunshine, and while the transparent countenance exhibits a quiet blue,[3] the thick mass of the breast and epaulettes glows with every gradation of warmth, from the most powerful ruby-red downwards; and as the granite statue of Memnon uttered harmonious sounds, so the dim glass image displays itself in the pomp of colours. The hero is victorious still in supporting the Farbenlehre."[4] One effect of Goethe's theory has been to invite the attention of scientific men to facts and appearances which had before been unnoticed or unexplained. To the above cases may be added the very common, but very important, fact in painting, that a light warm colour, passed in a semi-transparent state over a dark one, produces a cold, bluish hue, while the operation reversed, produces extreme warmth. On the judicious application of both these effects, but especially of the latter, the richness and brilliancy of the best-coloured pictures greatly depends. The principle is to be recognised in the productions of schools apparently opposite in their methods. Thus the practice of leaving the ground, through which a light colour is apparent, as a means of ensuring warmth and depth, is very common among the Dutch and Flemish painters. The Italians, again, who preferred a solid under-painting, speak of internal light as the most fascinating quality in colour. When the ground is entirely covered by solid painting, as in the works of some colourists, the warmest tints in shadows and reflections have been found necessary to represent it. This was the practice of Rembrandt frequently, and of Reynolds universally, but the glow of their general colour is still owing to its being repeatedly or ultimately enriched on the above principle. Lastly, the works of those masters who were accustomed to paint on dark grounds are often heavy and opaque; and even where this influence of the ground was overcome, the effects of time must be constantly diminishing the warmth of their colouring as the surface becomes rubbed and the dark ground more apparent through it. The practice of painting on dark grounds was intended by the Carracci to compel the students of their school to aim at the direct imitation of the model, and to acquire the use of the brush; for the dark ground could only be overcome by very solid painting. The result answered their expectations as far as dexterity of pencil was concerned, but the method was fatal to brilliancy of colour. An intelligent writer of the seventeenth century[5] relates that Guido adopted his extremely light style from seeing the rapid change in some works of the Carracci soon after they were done. It is important, however, to remark, that Guido's remedy was external rather than internal brilliancy; and it is evident that so powerless a brightness as white paint can only acquire the splendour of light by great contrast, and, above all, by being seen through external darkness. The secret of Van Eyck and his contemporaries is always assumed to consist in the vehicle (varnish or oils) he employed; but a far more important condition of the splendour of colour in the works of those masters was the careful preservation of internal light by painting thinly, but ultimately with great force, on white grounds. In some of the early Flemish pictures in the Royal Gallery at Munich, it may be observed, that wherever an alteration was made by the painter, so that a light colour is painted over a dark one, the colour is as opaque as in any of the more modern pictures which are generally contrasted with such works. No quality in the vehicle could prevent this opacity under such circumstances; and on the other hand, provided the internal splendour is by any means preserved, the vehicle is comparatively unimportant. It matters not (say the authorities on these points) whether the effect in question is attained by painting thinly over the ground, in the manner of the early Flemish painters and sometimes of Rubens, or by painting a solid light preparation to be afterwards toned to richness in the manner of the Venetians. Among the mechanical causes of the clearness of colours superposed on a light preparation may be mentioned that of careful grinding. All writers on art who have descended to practical details have insisted on this. From the appearance of some Venetian pictures it may be conjectured that the colours of the solid under-painting were sometimes less perfectly ground than the scumbling colours (the light having to pass through the one and to be reflected from the other). The Flemish painters appear to have used carefully-ground pigments universally. This is very evident in Flemish copies from Raphael, which, though equally impasted with the originals, are to be detected, among other indications, by the finely-ground colours employed. [1] See "Müller's Elements of Physiology," translated from the German by William Baly, M.D. "The laws of absorption," it has been observed, "have not been studied with so much success as those of other phenomena of physical optics, but some excellent observations on the subject will be found in Herschell's Treatise on Light in the Encyclopædia Metropolitana, § III." [2] "Eckermann's Gespräche mit Goethe," vol. ii. p. 280. Leonardo da Vinci had made precisely the same observation. "A distant mountain will appear of a more beautiful blue in proportion as it is dark in colour. The illumined air, interposed between the eye and the dark mass, being thinner towards the summit of the mountain, will exhibit the darkness as a deeper blue and _vice versâ_."--_Trattato della Pittura_, p. 143. Elsewhere--"The air which intervenes between the eye and dark mountains becomes blue; but it does not become blue in (before) the light part, and much less in (before) the portion that is covered with snow."--p. 244. [3] This supposes either that the mass was considerably thicker, or that there was a dark ground behind the head, and a light ground behind the rest of the figure. [4] "Eckermann's Gespräche mit Goethe," vol. ii. p. 242. [5] Scanelli, "Microcosmo della Pittura," Cesena, 1657, p. 114. NOTE M.--Par. 177. Without entering further into the scientific merits or demerits of this chapter on the "First Class of Dioptrical Colours," it is to be observed that several of the examples correspond with the observations of Leonardo da Vinci, and again with those of a much older authority, namely, Aristotle. Goethe himself admits, and it has been remarked by others, that his theory, in many respects, closely resembles that of Aristotle: indeed he confesses[1] that at one time he had an intention of merely paraphrasing that philosopher's Treatise on Colours.[2] We have already remarked (Note on par. 150) that Goethe's notion with regard to the production of warm colours, by the interposition of dark transparent mediums before a light ground, agrees with the practice of the best schools in colouring; and it is not impossible that the same reasons which may make this part of the doctrine generally acceptable to artists now, may have recommended the very similar theory of Aristotle to the painters of the fifteenth and sixteenth centuries: at all events, it appears that the ancient theory was known to those painters. It is unnecessary to dwell on the fact that the doctrines of Aristotle were enthusiastically embraced and generally inculcated at the period in question;[3] but it has not been observed that the Italian writers who translated, paraphrased, and commented on Aristotle's Treatise on Colours in particular, were in several instances the personal friends of distinguished painters. Celio Calcagnini[4] had the highest admiration for Raphael; Lodovico Dolce[5] was the eulogist of Titian; Portius,[6] whose amicable relations with the Florentine painters may be inferred from various circumstances, lectured at Florence on the Aristotelian doctrines early in the sixteenth century. The Italian translations were later, but still prove that these studies were undertaken with reference to the arts, for one of them is dedicated to the painter Cigoli.[7] The writers on art, from Leon Battista Alberti to Borghini, without mentioning later authorities, either tacitly coincide with the Aristotelian doctrine, or openly profess to explain it. It is true this is not always done in the clearest manner, and some of these writers might say with Lodovico Dolce, "I speak of colours, not as a painter, for that would be the province of the divine Titian." Leonardo da Vinci in his writings, as in everything else, appears as an original genius. He now and then alludes generally to opinions of "philosophers," but he quotes no authority ancient or modern. Nevertheless, a passage on the nature of colours, particularly where he speaks of the colours of the elements, appears to be copied from Leon Battista Alberti,[8] and from the mode in which some of Leonardo's propositions are stated, it has been supposed[9] that he had been accustomed at Florence to the form of the Aristotelian philosophy. At all events, some of the most important of his observations respecting light and colours, have a great analogy with those contained in the treatise in question. The following examples will be sufficient to prove this coincidence; the corresponding passages in Goethe are indicated, as usual, by the numbers of the paragraphs; the references to Leonardo's treatise are given at the bottom of the page. Aristotle. "A vivid and brilliant red appears when the weak rays of the sun are tempered by subdued and shadowy white,"--154. Leonardo "The air which is between the sun and the earth at sun-rise or sun-set, always invests what is beyond it more than any other (higher) portion of the air: this is because it is whiter."[10] A bright object loses its whiteness in proportion to its distance from the eye much more when it is illuminated by the sun, for it partakes of the colour of the sun mingled with the colour (tempered by the mass) of the air interposed between the eye and the brightness.[11] Aristotle. "If light is overspread with much obscurity, a red colour appears; if the light is brilliant and vivid, this red changes to a flame-colour."[12]--150, 160. Leonardo. "This (the effect of transparent colours on various grounds) is evident in smoke, which is blue when seen against black, but when it is opposed to the (light) blue sky, it appears brownish and reddening."[13] Aristotle. "White surfaces as a ground for colours, have the effect of making the pigments[14] appear in greater splendour."--594, 902. Leonardo. "To exhibit colours in their beauty, the whitest ground should be prepared. I speak of colours that are (more or less) transparent."[15] Aristotle. "The air near us appears colourless; but when seen in depth, owing to its thinness it appears blue;[16] for where the light is deficient (beyond it), the air is affected by the darkness and appears blue: in a very accumulated state, however, it appears, as is the case with water, quite white."--155, 158. Leonardo. "The blue of the atmosphere is owing to the mass of illuminated air interposed between the darkness above and the earth. The air in itself has no colour, but assumes qualities according to the nature of the objects which are beyond it. The blue of the atmosphere will be the more intense in proportion to the degree of darkness beyond it:" elsewhere--"if the air had not darkness beyond it, it would be white."[17] Aristotle. "We see no colour in its pure state, but every hue is variously intermingled with others: even when it is uninfluenced by other colours, the effect of light and shade modifies it in various ways, so that it undergoes alterations and appears unlike itself. Thus, bodies seen in shade or in light, in more pronounced or softer sun-shine, with their surfaces inclined this way or that, with every change exhibit a different colour." Leonardo. "No substance will ever exhibit its own hue unless the light which illumines it is entirely similar in colour. It very rarely happens that the shadows of opaque bodies are really similar (in colour) to the illumined parts. The surface of every substance partakes of as many hues as are reflected from surrounding objects."[18] Aristotle. "So, again, with regard to the light of fire, of the moon, or of lamps, each has a different colour, which is variously combined with differently coloured objects." Leonardo. "We can scarcely ever say that the surface of illumined bodies exhibits the real colour of those bodies. Take a white band and place it in the dark, and let it receive light by means of three apertures from the sun, from fire, and from the sky: the white band will be tricoloured."[19] Aristotle. "When the light falls on any object and assumes (for example) a red or green tint, it is again reflected on other substances, thus undergoing a new change. But this effect, though it really takes place, is not appreciable by the eye: though the light thus reflected to the eye is composed of a variety of colours, the principal of these only are distinguishable." Leonardo. "No colour reflected on the surface of another colour, tinges that surface with its own colour (merely), but will be mixed with various other reflections impinging on the same surface:" but such effects, he observes elsewhere, "are scarcely, if at all, distinguishable in a very diffused light."[20] Aristotle. "Thus, all combinations of colours are owing to three causes: the light, the medium through which the light appears, such as water or air, and lastly the local colour from which the light happens to be reflected." Leonardo. "All illumined objects partake of the colour of the light they receive. "Every opaque surface partakes of the colour of the intervening transparent medium, according to the density of such medium and the distance between the eye and the object. "The medium is of two kinds; either it has a surface, like water, &c., or it is without a common surface, like the air."[21] In the observations on trees and plants more points of resemblance might be quoted; the passages corresponding with Goethe's views are much more numerous. It is remarkable that Leonardo, in opposition, it seems to some authorities,[22] agrees with Aristotle in reckoning black and white as colours, placing them at the beginning and end of the scale.[23] Like Aristotle, again, he frequently makes use of the term black, for obscurity; he even goes further, for he seems to consider that blue may be produced by the actual mixture of black and white, provided they are pure.[24] The ancient author, however, explains himself on this point as follows--"We must not attempt to make our observations on these effects by mixing colours as painters mix them, but by remarking the appearances as produced by the rays of light mingling with each other."[25] When we consider that Leonardo's Treatise professes to embrace the subject of imitation in painting, and that Aristotle's briefly examines the physical nature and appearance of colours, it must be admitted that the latter sustains the above comparison with advantage; and it is somewhat extraordinary that observations indicating so refined a knowledge of nature, as regards the picturesque, should not have been taken into the account, for such appears to be the fact, in the various opinions and conjectures that have been expressed from time to time on the painting of the Greeks. The treatise in question must have been written when Apelles painted, or immediately before; and as a proof that Aristotle's remarks on the effect of semi-transparent mediums were not lost on the artists of his time, the following passage from Pliny is subjoined, for, though it is well known, it acquires additional interest from the foregoing extracts. "He (Apelles) passed a dark colour over his pictures when finished, so thin that it increased the splendour of the tints, while it protected the surface from dust and dirt: it could only be seen on looking into the picture. The effect of this operation, judiciously managed, was to prevent the colours from being too glaring, and to give the spectator the impression of looking through a transparent crystal. At the same time it seemed almost imperceptibly to add a certain dignity of tone to colours that were too florid." "This," says Reynolds, "is a true and artist-like description of glazing or scumbling, such as was practised by Titian and the rest of the Venetian painters." The account of Pliny has, in this instance, internal evidence of truth, but it is fully confirmed by the following passage in Aristotle:--"Another mode in which the effect of colours is exhibited is when they appear through each other, as painters employ them when they glaze (ἐπαλειφοντες)[26] a (dark) colour over a lighter one; just as the sun, which is in itself white, assumes a red colour when seen through darkness and smoke. This operation also ensures a variety of colours, for there will be a certain ratio between those which are on the surface and those which are in depth."--_De Sensu et Sensili_. Aristotle's notion respecting the derivation of colours from white and black may perhaps be illustrated by the following opinion on the very similar theory of Goethe. "Goethe and Seebeck regard colour as resulting from the mixture of white and black, and ascribe to the different colours a quality of darkness (σκιερὸν), by the different degrees of which they are distinguished, passing from white to black through the gradations of yellow, orange, red, violet, and blue, while green appears to be intermediate again between yellow and blue. This remark, though it has no influence in weakening the theory of colours proposed by Newton, is certainly correct, having been confirmed experimentally by the researches of Herschell, who ascertained the relative intensity of the different coloured rays by illuminating objects under the microscope by their means, &c. "Another certain proof of the difference in brightness of the different coloured rays is afforded by the phenomena of ocular spectra. If, after gazing at the sun, the eyes are closed so as to exclude the light, the image of the sun appears at first as a luminous or white spectrum upon a dark ground, but it gradually passes through the series of colours to black, that is to say, until it can no longer be distinguished from the dark field of vision; and the colours which it assumes are successively those intermediate between white and black in the order of their illuminating power or brightness, namely, yellow, orange, red, violet, and blue. If, on the other hand, after looking for some time at the sun we turn our eyes towards a white surface, the image of the sun is seen at first as a black spectrum upon the white surface, and gradually passes through the different colours from the darkest to the lightest, and at last becomes white, so that it can no longer be distinguished from the white surface"[27]--See par 40, 44. It is not impossible that Aristotle's enumeration of the colours may have been derived from, or confirmed by, this very experiment. Speaking of the after-image of colours he says, "The impression not only exists in the sensorium in the act of perceiving, but remains when the organ is at rest. Thus if we look long and intently on any object, when we change the direction of the eyes a responding colour follows. If we look at the sun, or any other very bright object, and afterwards shut our eyes, we shall, as if in ordinary vision, first see a colour of the same kind; this will presently be changed to a red colour, then to purple, and so on till it ends in black and disappears."--_De Insomniis_. [1] "Geschichte der Farbenlehre," in the "Nachgelassene Werke." Cotta, 1833. [2] The treatise in question is ascribed by Goethe to Theophrastus, but it is included in most editions of Aristotle, and even attributed to him in those which contain the works of both philosophers; for instance, in the Aldine Princeps edition, 1496. Calcagnini says, the treatise is made up of two separate works on the subject, both by Aristotle. [3] His authority seems to have been equally great on subjects connected with the phenomena of vision; the Italian translator of a Latin treatise, by Portius, on the structure and colours of the eye, thus opens his dedication to the Cardinal Ercole Gonzaga, of Mantua:--"Grande anzi quasi infinito è l'obligo che ha il mondo con quel più divino che umano spirito di Aristotile." [4] In a letter to Ziegler the mathematician, Calcagnini speaks of Raphael as "the first of painters in the theory as well as in the practice of his art." This expression may, however, have had reference to a remarkable circumstance mentioned in the same letter, namely, that Raphael entertained the learned Fabius of Ravenna as a constant guest, and employed him to translate Vitruvius into Italian. This MS. translation, with marginal notes, written by Raphael, is now in the library at Munich. "Passavant, Rafael von Urbino." [5] Lodovico Dolce's Treatise on Colours (1565) is in the form of a dialogue, like his "Aretino." The abridged theory of Aristotle is followed by a translation of the Treatise of Antonius Thylesius on Colours; this is adapted to the same colloquial form, and the author is not acknowledged: the book ends with an absurd catalogue of emblems. The "Somma della Filosofia d'Aristotile," published earlier by the same author, is a very careless performance. [6] A Latin translation of Aristotle's Treatise on Colours, with comments by Simon Portius, was first published, according to Goethe, at Naples in 1537. In a later Florentine edition, 1548, dedicated to Cosmo I., Portius alludes to his having lectured at an earlier period in Florence on the doctrines of Aristotle, at which time he translated the treatise in question. Another Latin translation, with notes, was published later in the same century at Padua--"Emanuele Marguino Interprete:" but by far the clearest view of the Aristotelian theory is to be found in the treatise of Antonio Vidi Scarmiglione of Fuligno ("De Coloribus," Marpurgi, 1591). It is dedicated to the Emperor Rudolph II. Of all the paraphrases of the ancient doctrine this comes nearest to the system of Goethe; but neither this nor any other of the works alluded to throughout this Note are mentioned by the author in his History of the Doctrine of Colours, except that of Portius. [7] An earlier Italian translation appeared in Rome, 1535. See "Argelatus Biblioteca degli Volgarizzatori." [8] "Della Pittura e della Statua," Lib. I, p. 16, Milan edition,