What is Newton's Eighteenth Law

Theory of Color .org

Eighteenth Century, Second Epoch: From Dollond to Our Time

Achromatism

The history of this important discovery is generally well known, being repeated, partly in special writings, partly in textbooks and history books. It is therefore proper for us to say only the essentials; But it is excellent to show how this important elucidation of an unpunished natural property can have a great influence on the practical and not at all on the theoretical.

From ancient times it was known and beyond question that refraction could take place in various ways without the appearance of color. For a long time, therefore, it was viewed as coincidental, which was sometimes added to it. But after Newton sought its cause in the refraction itself and demonstrated the persistence of the phenomenon, the two were considered inseparable.

In spite of this, one could not deny that our eyes see through refraction, that is, since we do not see color fringes or any other apparent coloration of the species with the naked eye, refraction and color appearance can be thought of independently of one another on this occasion.

Rizzetti had already brought this up; but because in some cases his time was still behind, because he missed the next path and had to miss it in his situation, this relationship was not considered any further. It was, however, anatomically and physiologically known that our eyes consist of various means. The conclusion that compensation was possible by various means was obvious, but no one found it.

Be that as it may, Newton himself carried out the so often discussed experiment, the eighth of his second part, by various means and wanted to have found that if in this case the outgoing beam would only be brought to be parallel with the incoming, the color appearance would then be canceled.

At first it may be noticeable that Newton, since he was left with refraction in parallel so-called rays and the color appearance was canceled, did not go any further, but rather that he liked to set up strange theorems which should flow from this experience.

One of Newton's defenders subsequently expressed the kind of conjecture that lead sugar was dissolved in the water Newton uses, which he also uses in other cases. This makes the phenomenon possible, but at the same time a striking observation, that something can come very clearly to the most excellent person without being noticed and understood by him. Enough, Newton persisted in his theoretical convictions as well as in the practical assertion that the dioptric telescope could not be improved. The matter therefore came to a standstill, which could only be lifted by another extraordinary person.

Euler, one of those men who are destined to start all over again, even if they get into the richest harvest of their predecessors, left looking at the human eye, which sees no apparent colors for itself, regardless of whether the objects come through sees and becomes aware of significant refraction, not out of his senses and came up with the connection of menisci filled with various degrees of moisture, and through experiments and calculations he came to the point that he dared to assert that the color phenomenon can be canceled out in such cases and that it there is still refraction left.

The Newtonian School heard this, how cheap, with horror and disgust; In secret, however, we do not know whether it was because of this Eulerian assertion or of our own initiative that Chester-Morehall had secretly and mysteriously assembled achromatic telescope in England, so that such a thing already existed in 1754, although it was not publicly known.

Dollond, a famous optical artist, also contradicted Eulern on Newtonian principles and at the same time began practically to operate against him; but to his own astonishment he discovers the opposite of what he claims; the properties of the flint and crown glass are found, and the achromatism is irrefutable.

In spite of all of this, the school is reluctant for a while; but an excellent man, Klingenstjerna, does a great job of carrying out the theoretical work.

No one could now remain hidden that the doctrine had suffered a fatal wound. But just as she actually only lived in words, so she could also be cured by a word. The cause of the color appearance had been sought in the refraction itself; It was she who developed these primal parts from light, to which, for this purpose, a different degree of breakability was ascribed. But now, with the same refraction, this breakability was very different, and now one took up a word, the expression dispersion, and placed behind this refraction and breakability another dispersion and dispersion that was independent of it, which had to wait in ambush for the opportunity to manifest itself ; and as far as I know, such a patchwork has been accepted without contradiction in the scientific world.

The word diversion occurs already in the most ancient times when one speaks of light. It can be seen as a trival expression to take that which should be considered a force materially and what is a hindered, moderate force as one dismembered, crushed, splintered.

When dazzling sunlight falls against a white wall, it works back from there to all opposite ends and corners, with a more or less weakened force. If, however, a mass of water is directed against this wall with a violent fire engine, this mass also acts back, but disperses and disperses in millions of parts. The expression diffusion of light arose from such a way of thinking.

The more one looked at light as matter, as body, the more appropriate one considered this parable speech. Grimaldi cannot even manage to diffuse, break and tear the light. With Rizzetti, the dispersion of the rays with which he operates also takes place against her will and to her greatest annoyance. Newton, in whom the rays are also broken apart, used this and similar expressions, but only discursively, as explanatory, sensuous; and in this way that word is carried forward until it is finally picked up in the new unexpected emergency that arises and stamped as a made-up word.

I did not have access to all the documents from this important event, so I cannot say who first expressed himself in this way. Suffice it, this made-up word was soon used without hesitation and is still being used without anyone thinking of how that great discovery completely changed and abolished the old. This plaster was used to cover up the damage; And if you want to see briefly an eminent case of how to mend a new rag on an old dress with the greatest calmness and comfort, read Johann Tobias Mayer's brief description of the theory of colors in the beginnings of the theory of nature, especially compare the 630th and 635th paragraphs. If this were an old author, the critics would look around with the greatest care for other Codicibus, in order to emend those passages which have absolutely no meaning with care and caution.

The doctrine, however, may be as it will, life goes on. Achromatic telescopes are made, individual men and whole nations are made aware of the properties of the various types of glass. Clairault in France uses the so-called Pierres de Stras instead of flint glass, and the discovery was quite obvious that the lead lime could impart to the glass the property of disproportionately broadening the color fringes against the refraction. Zeiher in Petersburg did a great job. What Boscovich and Steiner did to advance this matter theoretically and practically will not be forgotten.

Le Baude received the price in France in 1773 for a type of glass that came close to flint. At our time, Dufougerais made a glass in his factory in Mont-Cenis, of which a prism of ten degrees combined with a prism of crown glass of eighteen degrees, which cancel out the appearance of color.

A great deal of this type of glass is still in stock, and it is to be hoped that some of it will be used by the French opticians as prisms from all angles and, for the sake of science, converted into a general article of commerce.

Further and more details about this important epoch can be looked up in Priestley's History of Optics, with Klügel's additions being of great importance. Incidentally, Priestley is to be read with caution, as is the case here. He can experience, he cannot deny the great results against Newton arising from it, but quite unscrupulously gives to understand: Euler was inspired by a wave of Newton, as if someone could wave at something that he stubbornly denies, yes what is even worse, of the possibility of which he has no trace! Our, in this case as well as in others straightforward Klügel does not let him get away with it, but draws attention to this dishonesty in a note.

Joseph Priestley

The history and present state of discoveries relating to vision, light and colors, London 1772 in Quart.

Without wanting to atrophy the merit of this work or deny it the benefit that we ourselves have drawn from it, we are nevertheless compelled to say that in this way especially the fragile Newtonian doctrine has been restored. The author needs the introduced phrases again calmly. Everything that happened in ancient times and in the middle ages is not considered for anything. Newton's experiments and theories are dug up with great bombast. The achromatic discovery is presented as if that teaching had been modified only a little. Everything comes back to being the same, and the theoretical meandering drags on again.

Since one has to look at this work more closely as a material than as a real storytelling, we like to refer our readers to it, because we have only hinted at some of what has been dealt with in detail there in passing.

Paolo Frisi

We mention this man here, even though he did not publish an eulogy on Newton until later, in 1778, only to remark with little that the older doctrine, as it was presented by Newton, still defends it as it was accepted into the schools , finds its unconditional eulogy, even in the modern epoch, which should have decisively brought about its downfall, if people, living under the pressure of a limited habit, could decisively lift their eyes and minds happily for a new aperçu.

Incidentally, if a sample is required, how a real Newtonian thinks and speaks and imagines the matter, then this very well-written and enthusiastically presented praise can be picked up and taken to heart.

Georg Simon Klügel

The doctrine of achromatism was scattered over the field of science like a fertile and indestructible seed. Some of it fell under the guilty thorns to suffocate there, some of it was pecked and swallowed by the always busy theoretical-critical birds, some of it had the fate of being trampled on the flat path of meanness: so could it is not lacking that in good and sustainable soil a part was faithfully taken up and, where it did not bear fruit immediately, at least germinated in silence.

So we have often enough admired and praised our honest compatriot Klügel when we calmly observed his method of translating and supplementing Priestley's optics. There are faint warnings everywhere, perhaps too faint for them to be heard. Klügel humbly and often repeats that all theoretical enunciations are only parables. It indicates that we only see the reflection and not the essence of things. He remarks that Newton's theory might even have been abolished by the achromatic invention.

If it is not fitting for us to speak of his chief merit, which lies outside our field of vision, we would all the more gladly give him the testimony of an perhaps even rarer merit, that a man like him, of so much mathematical dexterity, science and experience were available to such an extent that the latter allowed an unprejudiced, intelligent overview to prevail in such a way that his scientific treatments, safely, without being dogmatic, warning, without being skeptical, familiarize us with the past, impress the present without looking for to close the future.

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The Newtonian School, however, was free to act as it wished. It was now said so often by many eminent men, in so many writings, which, as it were, were effective every day (for the matter was being pursued lively) that Newton had made a mistake on one main point, and spoke more than any words this is what the dioptric telescope on observatories and mast trees, in the hands of researchers and private individuals, makes louder and more indisputable.

Man, as we have appealed to earlier, is just as happy to submit to authority as he withdraws from it; all that matters is the epochs which lead him to one or the other. In the current epoch of color theory, younger, more ingenious, serious and loyal-minded people were given a certain semi-freedom, which, because they saw no point of union in front of them, turned everyone back on themselves, evoked everyone's own views, favorite opinions, crickets, and so it was conducive to some good, but on the other hand also prophesied and prepared for a kind of anarchy, which in our days has fully appeared.

What individuals have done to fathom and explain the nature of color more in one way or another, without paying particular attention to Newtonian teaching, is now the main task of our further lecture. We take with us whatever else we find on our way, but leave some individual items lying in between, which are not pious or encouraging.

C. F. G. Westfeld

The creation of colors, a hypothesis. Goettingen 1767.

This single sheet certainly deserved to be printed with a number of small, dissolving writings relating to the theory of colors and to avoid oblivion.

The author's lecture is not luminos, and because it immediately becomes involved in controversy, it is by no means pleasant; but his conviction is good. First he expresses it generally as follows: "The difference in colors is only a difference in movement in the annoying fibers of the retina"; but then he comes closer to the matter and ascribes the color effect on the eye to a more or less excited warmth on the retina.

It is with a joyful satisfaction that we see that which was punished and prepared, which was later discovered by Herscheln and carried out further in our time. We want to hear it for ourselves:

“Light is an expansive fire that one can only squeeze into a narrow space in order to convince oneself of the violence of its effects. The retina of the eye has the body's natural warmth. The rays of light that fall on them must increase their natural warmth and expand their fibers the more the denser they are. This difference in the extension of the nervous fibers must produce a different sensation in the soul, and we call these different sensations colors. When the sensations are too intense, there is sometimes a certain feeling associated with them, which we call pain. When the rays of light excite such sensations, they have produced too violent a degree of expansion. The sensations which we call colors must result from a lesser degree of expansion, and of these the most violent sensations are yellow, and less violent are red, green, and blue. "

“A single ray of light expands the part of the retina on which it falls so that it creates the sensation in the soul that we call the yellow color. By dividing this beam of light through the prism into seven parts, one of which is always denser than the other, these seven parts will, depending on their density, produce different expansions, each of which we give its own name. Black bodies suck in most of the rays of light; consequently they produce the slightest extension on the retina; violet a little more, and this rises to the yellow and white bodies, which, because they are the densest, reflect most of the light rays and thereby excite the most violent expansion on the retina. "

“You should notice what we said earlier that the natural warmth of the retina must be increased if we are to see colors, or at all if we are to see. So we can be in a warm, dark room for a long time, in which we cannot see through the warmth. In this case the whole body senses, and therefore the sensations in individual parts cannot be distinguished. In winter, when it is extremely cold, we see colored and uncolored bodies because they throw rays of light into our eyes and thereby arouse greater warmth or greater expansion. "

“The density of the rays of light that the yellow or white color produces in us can be very different without producing any other color. The light that burns yellow nearby also burns that way at a great distance. Chalk looks white near and far. The situation is completely different with the colors that arise from a much reduced density of the light rays: these become black even at a small distance. "

“I don't see how a Newtonian can justify that bodies of faint colors appear black at a distance. If, for example, they only reflect the blue particles of light, why do they not stay just as much blue light particles on the distant retina as on the nearer one? It's not like the taste of a salt that has been diluted with too much water. Even at a distance, the blue light particles are not mixed with anything that could change their effects. They go through the atmosphere, which is full of foreign bodies and other particles of color, but they do not suffer any change as a result. "

“The apparent colors can be explained more easily from this hypothesis than from the others. If the retina, while the eye looked into the light for a long time, or looked at another colored body for some time, was warmed up in proportion to the density of the light rays received, this warmth could only be lost gradually. A warm metal does not suddenly become cold. As the warmth continued, the expansion continued, and consequently the colors, which gradually, as the warmth was lost, passed into other colors. "

“I do not want to go into this hypothesis any further, and for that reason I only want to emphasize the truth of it, separated from the probable. It is true: ›that the rays of light, however simple they may be, must produce warmth and expansion on the retina,‹ that the soul must feel this expansion. Because if you explain the colors as you like, you always have to admit to me that what produces the blue color, for example, cannot have a more violent effect than the warmth of such a blue light particle. "

If, instead of more and less, which always only expresses a gradation, of which one does not know where to begin and where to end, Westfeld would have expressed his opinion as a contradiction and assumed the color effects as warming and cold, so that that of If, on the one hand, increase the natural warmth of the retina, which on the other hand it diminishes, then, according to him, this view could not have been much extended. It belongs in the chapter on the effect of colored lighting, where we have partly already indicated what is necessary, partly we will add what may be necessary in the future.

Guyot

Nouvelles Récréations physiques et mathématiques, à Paris, 1769–70. 4 volumes in 8.

It cannot be repeated enough that a theory does not work better than when it facilitates the practitioner's judgment and promotes his application. The opposite is true of Newtonian; it stands in the way of everyone who wants to start something with colors; and this is also the case here, with a man who, among other physical appearances and powers, wants to use colors for various tricks and amusements.

He soon finds that in order to produce all the colors he only needs three main colors, which he may call primordial and primary colors. He brings these in lighter, gradually darkening rows on translucent paper stretched over a square frame, first uses them individually, but then connects them in such a way that the lighter and darker stripes are crossed; and so all shades of color really arise, both with the intention of mixing and of lightening and darkening, for which latter purpose, however, he still makes a special device.

To use this frame, he made a box in which they fit, one side of which was completely open and directed towards the sun, but the other was provided with a sufficient opening so that one could see the colored surfaces.

In these operations, which are so simple, and precisely because they are so simple, Newtonian theory stands in his way, about which he expresses himself as follows, although with previously sent protestations that he does not dare to contradict the astute and curious system:

“The effect produced by these colored translucent papers does not seem to agree with the present system of the formation of colors. Because the paper on which you have applied the blue paint, for example, throws the blue rays back when you look at it through the large opening of the box while the other is closed. But if you look through the smaller one, while the larger one is turned towards the sun, you see the same blue rays through the paper. According to the system, however, this would be a contradiction, because the same paper reflects the same rays and lets them through. Nor can one say that the paper only throws back a part and lets the other pass through: for with this assumption, the paper, by allowing only part of the blue rays to pass through, would have the power to devour all the rest, since if you put the yellow frame behind the blue one, nothing can be seen but green rays, which the blue frame should rather devour. Yes, one shouldn't see any color at all: for the only blue rays that are able to pass through the blue frame would have to be swallowed up by the second frame, which only lets the yellow ones through. The same observation can be made with all other colors which are produced by the different positions of these colored frames. "

And so this intelligent, small-scale man, in his own way and in his own way, saw and expressed the absurdity of the Newtonian system: again a Frenchman who also attests to the prudent cleverness and dexterity of his nation.

Mauclerc

Traité des Couleurs et Vernis, à Paris 1773.

The color bodies do not have the same content in relation to one another, and the yellow is more extensive than the blue, so that if one wants to balance their effects with one another to form a green, one must take three parts of blue against two parts of yellow. The high red is also stronger than the blue, and you have to take five parts of blue against four parts of red if the mixture is to fall straight into the middle of the two.

Marat

Découvertes sur le Feu, l'électricité et la lumière, à Paris 1779. 8vo.

Découvertes sur la Lumière, à Londres et à Paris 1780. 8vo.

Notions élémentaires d'Optique, à Paris 1784. 8vo.

Without going into the large number of experiments on which Marat bases his convictions, it can only be our intention here to indicate the course he has taken.

The first one provides laborious research into what he calls fiery fluid, fluide igné. He brings burning, glowing, heated bodies into the sunlight and observes the shadows of their outflows and what else becomes visible on this occasion.

Since he now wants to make the preceding even clearer, he uses the lens of a solar microscope in a dark chamber and thereby notices more precisely the shadows of the bodies, the fumes, the various movements and gradations.

We immediately become aware of the transition to what actually interests us, and since he also observes cold, even cold bodies in this way, he finds that something of his own is also going on around them. He notices shadows and streaks of light, lighter and darker lines that accompany the silhouette of the body.

If the fiery liquid had become visible penetrating out of the body during those first attempts, then a property of light now becomes visible to him, which is supposed to consist in the fact that it lets itself be attracted to the bodies by passing them. He observes the phenomena closely and wants to find that this attraction, from which Grimaldi's earlier so-called diffraction arises, differs according to the different nature of the body. He observes and measures the strength of these forces of attraction and how far the atmosphere of this attraction would like to extend.

On this occasion he notices those color fringes that are already known to us. He only finds two colors, the blue and the yellow, to which the third, the red, can only be seen afterwards.

The light is now attracted, it is diverted from its path; this also indicates to him the property of a fluid. He persists in the old concept of the decomposition of light into colored parts of light; but for him these are neither five nor seven, nor innumerable, but only two, at most three.

Since he now uses the objective glass of a solar microscope in these experiments, which we called the paroptic, as with those concerning the fiery liquid, the dioptric experiences of the second class, the refraction cases, are immediately associated with the paroptic, their relationship Of course, it cannot be denied, and from this point of view he contradicts Newton's teaching by listing roughly those experiments which we and others have also submitted. He stated emphatically that the appearance of color arises only at the edges, that it arises only in a simple opposition, that one can break the light back and forth as much as one likes without there being any appearance of color. And even if he admits that light is decomposed, he maintains stiffly and firmly: it is only decomposed on the paroptic path through so-called diffraction, and refraction does nothing more than make the appearance eminent.

He now operates with attempts and arguments against the diverse refangibility in order to give his diverse inflexibility the desired reputation; Then he adds something about the colored shadows, which also betrays his attention and sagacity, and promises to work through these and related matters further.

Anyone who has followed our outline of the theory of colors and the historical thread of our endeavors will themselves overlook the relationship we have with this researcher. According to our own conviction, paroptic colors are closely related to those appearing during refraction (E. 415). However, whether one can, as we believed, derive these phenomena from the double shadow alone, or whether one must resort to the more mysterious effects of light and the body in order to explain these phenomena, we like to leave it undecided because for us and others there is still much to be done in this area.

We only notice that we consider the paroptic cases related to the refraction cases, but not identical. Marat, on the other hand, who wants to identify it completely, finds his way in the objective experiments when the image of the sun passes through the prism; but in subjective experiments, where it cannot be thought that the light is approaching the borderline of a picture drawn on a flat board, it must of course behave strangely in order to force a diffraction here too. It is strange enough that the Newtonians likewise get in the way of subjective experiments in their process.

How little favor the Maratian endeavors found with the naturalists, especially with the academy, can be imagined, since he admitted the traditional doctrine, although he immediately admitted its final result, the decomposition of light, on the way it took attacked so decisively. The report of the commissioners is to be seen as a model of how grimacing an evil will behaves in order to at least eliminate something that cannot be completely denied.

As far as we are concerned, we believe that Marat, with a great deal of acumen and the gift of observation, brought the theory of colors, which arise from refraction and so-called inflexion, to a very delicate point, which is worth further investigation, and from whose elucidation we can unite hope for true growth in color theory.

Finally we note that the last two writings named above, which actually interest us, are to a certain extent identical, in that the second can only be regarded as an editing and epitome of the first, which is by Christ. Ehrenfried Weigel translated into German and accompanied by notes, Leipzig was published in 1733.

H. F. T.

Observations sur les ombres colorées, à Paris 1782.

This author, who has remained unknown as far as we know, makes his own and well-behaved appearance in the history of science. Without being familiar with the theory of nature at all, or even with this particular chapter of light and colors, he notices the colored shadows which, once he has noticed them, he becomes aware of everywhere. With a calm and patient interest he observes the various cases in which they appear, and finally arranges ninety-two experiences in this book, through which he thinks he will come closer to the nature of these phenomena. But all these experiences and so-called experiences are only ever observed cases, through the accumulation of which the answer to the question is played out more and more. The author by no means has the gift of learning what several cases have in common, of narrowing them down, and of combining them in convenient experiments. Since this last is done by us (E. 62-80), it is now easier to overlook what the author actually saw with his eyes and how he interpreted the appearances.

Given the rarity of the book, we think it would be a good idea to give a short extract from it, according to the rubrics of the chapters.

Introduction. Historical news of what Leonardo da Vinci, Buffon, Millot and Nollet leave behind about the colored shadows.

First part. What it takes to produce colored shadows. Namely two lights, or light from two sides; then a decided proportion of the brightness on both sides.

Second part. About the various means of producing colored shadows and the diversity of their colors.

  1. Of colored shadows created by the direct light of the sun. Here both the shadows when the sun goes down and during the day in moderate light are observed.

  2. Colored shadows, brought about by the reflection of the sunlight. Here mirrors, walls and other objects that reflect light are drawn into the experience.

  3. Colored shadows created by the light of the atmosphere and illuminated by the sun. These are seen less often because the sunlight has to be very weak in order not to completely cancel out the shadow created by the atmosphere. They therefore usually only occur when the sun has partly sunk below the horizon.

  4. Colored shadows, produced by the light of the atmosphere alone. If not from two sides, it must at least fall across the board. These experiments are actually only to be made in rooms.

  5. Colored shadows created by artificial lights. Here the author uses two or more candles, which he then relates to the fireplace.

  6. Colored shadows, brought about by the atmospheric light and an artificial one. These are the best-known experiments with the candle and daylight, made under the most varied of empirical conditions.

  7. Colored shadows, brought about by the moonlight and an artificial light. This is without question the most beautiful and eminent of all experiences.

Third part. From the cause of the different colors of the shadows. Since in the foregoing he believes that the above requirement of a double light and a certain ratio of the two-sided brightness has now been completely beyond doubt, as he progresses it seems to him particularly questionable why the same back light does not always color the shadows the same.

  1. About the light and the colors. Above all, he adheres to the Newtonian teaching, but cannot connect his colored shadows with refraction. He has to look for it in reflection, but is not quite sure how to act.

  2. He comes to Gauthier's system, which seems to favor him more, because here the colors are composed of light and shadow. He also gives a rather cumbersome excerpt; but this doctrine, too, is no more sufficient than Newton's to explain the colored shadows.

  3. Of different kinds of colored shadows. He observes that these phenomena are not alike in that one can ascribe a certain reality to some and only a certain apparence to others. But because he lacks the word of the riddle, he cannot find his way out of the matter. It is striking that the red shadows come from the setting sun and the clouds accompanying it; but why does the opposite shadow change from blue to green on this occasion? He laboriously shows that these colors, when the shadows are thrown on a really colored ground, are modified and mixed according to the same.

  4. About the color of the air. Contains the confused and obscure opinions of naturalists about such an easily explained phenomenon (E. 151).

  5. Comments on the creation of the colored shadows. The doubts and difficulties in explaining the colored shadows in this way only increase. The author approaches the right thing, however, by concluding that the colors of these shadows are owed both to the light which causes the shadow and to that which illuminates it.

    The author observes so closely and turns the matter around so often that he always immediately encounters contradictions as soon as he has stipulated something. He clearly sees that the requirement that he had previously set up a certain proportion of the lights in relation to one another is not sufficient; He looks for it in certain properties of the luminous bodies, especially of the flames, and also touches on the fact that different lights do not spread the same colors in the same way.

  6. Observations on the causes of the different shade colors. He again diversified the experiments, especially in order to recognize the path by which one shade color merges into the other, and whether this transition occurs according to a certain order. In doing so, he always insists on the concept of the different intensities of light and tries to help himself through, whether it only succeeds poorly. And because he goes to work honestly, he continually encounters new contradictions that he admits and then tries to reunite with what he has already established. His latest results are as follows:

    Colored shadows arise:

    1. by the stronger or weaker light that the shadows receive.

    2. by the greater or lesser clarity of the light that produces the shadows.

    3. by the greater or lesser distance between the lights and the shadows.

    4. of the greater or lesser distance of the shadow-casting bodies from the ground that receives them.

    5. of the greater or lesser incidence of both the shadow and the light that illuminates them against the ground that receives them.

    6. One could also say of the color of the ground which receives the shadows.

In this way the author concludes his work, which I can judge all the better because, without knowing his efforts, I have previously been on the same path; from which time I still have a small treatise written in this sense.

This calmly participating observer is not lacking in conscientiousness and accuracy. It shows the slightest circumstances: the year, the season, the day, the hour; the heights of the heavenly ones, the position of the artificial lights; the greater or lesser clarity of the atmosphere; Distance and all kinds of reference: but the main thing remains hidden from him, namely that the one light must to some extent color the white ground on which it falls and projects the shadow. So he escapes the fact that the sinking sun turns the paper yellow and then red, whereby in the first case the blue and then the green shadow emerges. He escapes the fact that when a light shines back from walls a yellowish glow is thrown on a white background and a violet shadow is produced there; that the candle opposite the daylight also gives the paper a yellowish red glow, which demands the blue shadow. He overlooks the fact that if he lets an atmospheric light fall into his room from two sides, a yellowish glow from a neighboring house can mix in again. Even if you operate with two candles at night, one can only stand closer than the other to a yellowish wall. So a fire in the open fire is not both stronger and more powerful than a candle, but it even brings out a red glow, especially when there are many glowing coals around it; therefore, like when the sun goes down, light green shadows appear. The moonlight colors every white surface with a decidedly yellow glow; and so all the contradictions which the author encounters arise merely from the fact that he observes the secondary circumstances very precisely, without the main condition becoming clear to him.

We have already indicated that lights with a weak effect are to be regarded as colored and coloring (E. 81 ff.). We do not want to be denied that, in a certain sense, the greater or lesser intensity of the light follows the appearance of the colored shadows; only it does not work as such, but as colored and coloring. How one is asked again to heed the shadowy and shadowy relationship of color, under whatever conditions it may appear.

Diego de Carvalho e Sampayo

Tratado das Cores. Malta, 1787.

Dissertação sobre as cores primitivas. 1788. To this is attached:

Breve Tratado sobre a composição artificial das cores.

Elementos de agricultura. Madrid, 1790.1791.

Memoria sobre a formação natural das Cores. Madrid, 1791.

The author, a Knight of Malta, happens to be led to the observation of colored shadows. After a few observations he immediately hurries to a kind of theory and tries to convince himself of it through several attempts. His experiences and attitudes are recorded in the first four writings mentioned above and epitomized in the last. We tighten them even more to give our readers an idea of ​​these honest but strange and inadequate endeavors.

Theoretical principles

»The colors manifest and form themselves through the light. The light that emanates from luminous bodies or that radiates back from dark bodies contains the same colors and produces the same phenomena. The vividness of the light is just as destructive to the colors as the depth of the shadow. With a middle light, the colors appear and form. "

“There are two primitive colors: red and green. Blue and yellow are not primitive colors. Black is a positive color, it comes from red and green. White is a positive color and arises from the extreme separation of the primitive colors, red and green. "

Experiences which guided the author to his theory

“The reason to accept and see red and green as primitive colors came about by chance in December 1788, at Lamego. I came into a room and saw green and red reflections on the wall. When I looked for the light which they brought out, I found that it came from the sun, which came through the window and shone on the opposite wall and the green cloth with which a table was covered. In between stood a chair, with the shadow of which the colored reflections of red and green met. "

“I pulled the chair away so that no body would stand in between, and immediately the colors disappeared. I put my Spanish pipe, which I had in hand, between them, and the same colors formed immediately, and I noticed that the red color corresponded with the reflection of the green cloth and the green with the part of the wall on which the sun was falling fell."

“I took the cloth off the table so that the sun just fell on the wall, and there too the colors disappeared, leaving only a dark shadow from the bodies in between. I made the sun just fall on the cloth without falling on the wall, and the colors also disappeared, and the dark shadow that the light reflecting off the wall produced resulted from the bodies in between. "

In doing these experiments I observed that the colors appear more vivid when the room is dark and the reflections stronger than the natural light, and that they even finally disappeared when the natural light which you let in through the window or door that exceeded reflexes in strength. "

“When repeating the experiments, I positioned myself so that part of the sun fell on the white wall and another on part of my scarlet Maltese uniform, and watching the reflections on the wall saw them red and green again, so that the green color with the red reflex and the red with the light on the wall corresponded. "

“As often as I made these observations, the same results were obtained. The result is that the light of the sun is an achromatic liquid, with the property like water of being able to be colored with all colors and that in this liquid some colored and very fine particles float, which, differently coloring the light, float through Refraction, reflection and inflection all form those colors which we see on natural bodies and in colored light. "

»The light, seen as an element, is not a simple body, but composed of different principles. An achromatic, extremely fine, transparent liquid forms its basis, and a colored, heterogeneous, dark matter constantly swims in this liquid. "

If there was not an achromatic liquid in the light, the intensity of the colors of the light in each of its kinds would always be the same; for example the red would always keep the same strength without being able to dilute to lighten or concentrate to darken. But now experience shows that the colors of light concentrate and dilute without changing their nature; so it follows that in the same light there must exist an achromatic matter capable of producing such modifications. "

“The colored matter of light does not have to be homogeneous either: if it were only of one nature, for example red, one would see nothing more in all bodies than this color, light or dark, according to the degree of intensity or dilution of light. But now one sees in the bodies an astonishing variety of different colors, not only in terms of intensity but also in terms of quality; consequently the colored matter which swims in the achromatic liquid is not homogeneous, but of different properties. "

“A series of new and decisive experiments that I have made on light have sufficiently proven that there is a colored matter of two kinds: one capable of making us feel the red color, and another that can bring out a feeling of green color. All the other colors which one sees in the light are composed of these two and are to be regarded as the mere results of their mutual connection with the achromatic matter to a state of greater or lesser density. For the light has the power to concentrate, so that it acquires a shine and an unbearable strength for the organ of sight; and at the same time the ability to thin oneself so much that it is no longer noticeable to the same organ and no longer makes the objects visible. "

"Finally, the colored matter of light is naturally dark because, by combining by means of appropriate devices, it either prevents the achromatic rays from passing freely or obscures the surface of the objects over which this colored matter spreads."

tries

His device is not inept at producing colored shadows. He prepares hollow tubes, one end covered with light silk witnesses, some of them white, some of different colors. He places these in the shutter of a camera obscura in such a way that he can bring either his achromatic lights or his differently colored lights onto an opposing board. In between he places any body in order to produce a single or double shadow. Since he calls his silk coatings lenses, we want to keep this term for the sake of brevity.

A white lens gives colorless light and black shadows.

Two white lenses give colorless light and colorless penumbra.

A red and a white lens give a bright light and a red glow, which he calls reflex, then red and green penumbra.

A green and a white lens give a weak green light and then green and red penumbra.

A red and a green lens give a darkened light without any color, then red and green penumbra.

So far everything is fine. But now he combines a white lens with the red and green lens and claims to have received blue, yellow, as well as orange and violet in many ways.

Now he goes on to put an orange lens and a white lens together. It receives a faint orange light, then orange and blue shadows. A white and blue lens give it a faint blue light and blue and yellow shadows. (Should be called red and yellow.) A yellow and white lens give it a bright yellow light and yellow and purple shadows. A purple and white lens together now give it purple and greenish shadows.

As you can see, this violet had the effect of pure red; but the author believes that he is back to the beginning where he started. However, instead of observing and following up on the correct experiences that nature offered him of the contrast between colors, he considered the required shimmering colors to be real, really colors drawn out of the light, and deluded by that mean experiment in which one did not A secondary circumstance which we had not yet had the opportunity to develop, he insisted on his first whimsical aperçu in Lamego, red and green, perhaps in honor of his Maltese uniform and the carpet, as the only original colors to be addressed.

His efforts are sincere, his attention precise and sustained. He becomes aware of the dark quality of color, the necessity of a colorless light for the appearance of color, and carries out all the pairs of demanding colors quite correctly; only he rushes to judge and does so little as H. F. T. on the aperçu that the second color is physiological.

The last of the above-named works, beautifully printed on 32 pages in small quarters, deserves to be translated in its entirety and accompanied by the copper plate accompanying it, since only two hundred copies exist, and all sincere attempts to arrive at the truth are valued and even the mistakes are instructive.

Robert Waring Darwin

On the Ocular Spectra of Light and Colors. Printed in the Philosophical Transactions, Volum. 76. p. 313, dated November 1785. Reprinted in Erasmus Darwin's Zoonomy.

This essay on the ghosts of the eyes is without a doubt the most detailed of all that has appeared, although the above mentioned writing by Father Scherffer should be placed alongside it. After the content display, there is a short introduction, which contains a classification of these ghosts and some literary notes. The headings and summaries of its chapters are as follows:

  1. Activity of the retina in seeing.

  2. From ghosts for want of sensitivity.

    The retina is not so easily activated by less irritation if it has recently suffered a stronger one.

  3. Of ghosts from excess of sensitivity.

    The retina is more easily aroused to activity by a greater stimulus if it has recently experienced a lesser one.

  4. Of direct ghosts in the eyes.

    An irritation beyond the natural level excites the retina to a convulsive activity, which ceases in a few seconds.

  5. A stimulus stronger than the last mentioned excites the retina to convulsive activity, which alternately disappears and returns.

  6. Reverse ghosts of the eyes.

    The retina, after being excited to activity by a stimulus which is again somewhat greater than the last-mentioned, falls into an opposite convulsive activity.

  7. The retina, after being excited to activity by a stimulus which is again greater than the last-mentioned, falls into several successive convulsive activities.

  8. The retina, after being excited to activity by a stimulus somewhat greater than the last mentioned, falls into a fixed, convulsive activity which lasts for several days.

  9. A stimulus greater than the previous one produces a temporary paralysis in the organ of the face.

  10. Mixed comments. Here the author makes observations which, for a quite natural reason, do not fit with the preceding ones.

    1. Of direct and reverse ghosts that exist at the same time. Of mutual direct ghosts.Of a connection between direct and reverse ghosts. From a ghostly court. Rules for predicting the colors of the ghosts.

    2. Variability and liveliness of the ghosts, caused by strange light.

    3. Variability of the ghosts in terms of number, shape and relaxation.

    4. Variability of ghosts with the intention of shine. The visibility of the blood circulation in the eye.

    5. Mutability of the ghosts with the intention of clarity and size, with a new way of enlarging objects.

    6. Enough.

Anyone who looks carefully at these summaries and rubrics will notice what is to blame in the author's presentation. Waring Darwin, like his blood or namesake, Erasmus Darwin, make the mistake, with all the merit of cheerful and careful observation, that, as doctors, they take all phenomena more pathological than physiological. Waring recognizes in his first article that all seeing would depend on the activity of the retina, and now he does not take the natural path of determining and designating the laws according to which such a healthy organ works and counteracts, but he subordinates them the artificial medical form on how they react to weaker and stronger stimuli; which in this case is of little importance, indeed, in experience, as one can see from its rubrics, cannot be determined at all.

We have repeatedly examined the content of this treatise, as well as the others that have become known to us, separately and on the basis of nature itself, to the detriment of our own eyes, and tried to draw the general outlines in our section of physiological, no less the appendix of pathological colors , in which everything is included, sought to find the best order according to which the phenomena can be represented and viewed.

So instead of going through the Darwinian Essay article by article, instead of expressing applause and displeasure in detail, we ask our readers, who might be particularly interested, to hold this essay together with our first notified section of the draft and to see for themselves what has been achieved there .

When reviewing the Darwinian essay, we carefully selected and retained the expression eye specter, partly because that which appears without physicality is called a ghost according to common usage, partly because this word, by designating the prismatic appearance, is called civil rights brought and acquired in color theory. We wished that the word "eye illusions", which the otherwise deserving translator of Darwinian Zoonomy used for it, should be banned once and for all. The eye is not mistaken; it acts legally and thereby makes reality what one is entitled to call a ghost in terms of words but not in essence.

We add the literary notes reported above, which we owe partly to the author and partly to the translator.

Doctor Jurin in Smith's optics, over. Aepinus in the Petersburg New Commentaries Vol. X. Béguelin in the Berlin Memoirs Vol. II. 1771. D'Arcy, History of the Academy of Sciences 1765. De la Hire, Buffon, Memoirs of the French. Academy 1743. Christ. Ernst Wünsch, Visus phaenomena quaedam. Lips. 1776. 4. Joh. Eichel, Experimenta circa sensum videndi, in Collectaneis societatis medicae Havniensis. Vol. I. 1774. 8.

Anton Raphael Mengs

Lezioni pratiche di pittura, in his works, published at Parma in 1780 in Quart.

Mengs put the reason for the harmony we feel in a painting in the chiaroscuro, just as he ascribed the most excellent effect to the general tone. The colors, on the other hand, were only individual tones for him, with which one specified the surfaces of the bodies, which were to subordinate themselves to the chiaroscuro and the general tone, without making any claim to conformity and wholeness precisely for themselves and among themselves.

He noted, however, that when one color is used in its utter vivacity, another must in some way be outweighed by another in order to be tolerable. And so his open mind and good taste found the simple laws of color harmony without, however, seeing their physiological basis.

“In using colors, it is necessary to observe their balance if we are to find the way to use them with grace and to accompany them well. There are actually only three colors, yellow, red and blue. One must never use this in and of itself in a work; but if one wanted to use one of them, and in fact pure, then one should look for the way to put another, mixed of two, aside: as an example, accompany the pure yellow with violet, because this is made up of red and Blue exists. If a pure red has been used, then for the same reason add the green, which is a mixture of blue and yellow. In particular, the union of yellow and red, which gives rise to the third mixture, is difficult to use to advantage, because this color is too vivid, so one must add the blue to accompany it.

See what we have said about this in the natural context in the appropriate place (E. 803 ff.).

Jeremias Friedrich Gülich

Complete coloring and bleaching book etc. etc. Six volumes. Ulm, 1779 to 1793.

This man, who resided in Sindelfingen near Stuttgart and was last employed in Baden, whose life deserved to be better known, was at home in his craft, in his semi-art, as you can call it, as far as we can judge him. All the requirements in dyeing, insofar as they are thought of as preparatory as well as executing and completing, were at hand, as well as the most diverse applications which one has gradually devised of colors for all kinds of materials and fabrics.

Given the great breadth and the precise detail of his knowledge, he looked around for a guide by which he could wiggle his way through the labyrinth of natural and artistic phenomena. But since he had neither a scholarly nor a philosophical nor a literary education, it was very difficult, if not impossible, for his capable character to find his way around everywhere.

He saw that all the dyer's procedures were based on very simple maxims, which, however, were hidden under a jumble of individual recipes and accidental treatments and could hardly be grasped.

It became clear to him that with a clever use of acids and alkalis much, almost everything, could be done, and with the urge for generality which he felt in himself, he wanted the material of his business and its application not only, but also the whole at the same time To put nature in an equally simple contrast to the foundation. Therefore fire and water became the two main elements for him. He added the acids to the one and the alkalis to the latter. He wanted to find the crimson color in the former and the blue in the latter, and this concluded his theory; the rest should develop and result from this.

Since the most eminent and permanent colors were to be produced from metals, he also paid them excellent attention and special reverence. Gold and iron shall answer fire, acids, and crimson; copper shall answer especially well to water, alkalis, and blue, and shall be appropriate; and wherever these colors are found, something should be found that is not exactly metallic, but closely related and analogous to the metallic.

It is easy to see that this type of conception is very limited and must often enough become inconvenient to use. However, because his experience is very sure and steady, and his artistic treatment is masterful, this strange terminology brings up relationships that would otherwise not have been thought of, and he has to make the phenomena quite clear himself so that they become multifaceted and he gets through them can gain something from his strange theory. At least it seemed to us that a revision of this book, according to a freer theoretical view, would have many uses.

Since, as the title of his book shows, the dyer’s first concern, the colorlessness and purity of the fabrics on which he wants to work, never out of sight; Since he carefully specifies the means of removing all color and impurity from such substances: he must of course be highly repugnant of Newtonian seven-colored dirt, as in his simpler view of the sevenfold society of primary colors; therefore he behaved very annoyingly and unfriendly to the Newtonian doctrine.

He got along more or less with the chemists of his time, Meyer, Justi and others. The acidum pingue of the first is not entirely repugnant to him; with the second he stands in various ways. So he is not unknown in what was written about the art of dyeing in his time and what was otherwise said about the theory of colors.

So much is enough to refresh the memory of a man who led a laborious and serious life and who was not only concerned with working and creating for himself and his people, but also what he experienced and how he did put things in order, eagerly wanted to communicate to others about utility and convenience.

Eduard Hussey Delaval

Trial and remarks on the cause of permanent colors of opaque bodies. Translated and edited by Crell. Berlin and Stettin 1788. 8 °.

The actual content of this writing, although it is of great importance in the theory of colors, can be expressed in a few words. The author's main focus is on the σκιερον, on the dark property of color, which we have repeatedly pointed to.

He deals particularly well with coloring substances from the mineral kingdom, then also from the vegetable and animal kingdom; it shows that these substances, in their finest and most concentrated state, do not show any color in striking light, but rather appear black.

Even pure dyes dissolved in moisture and colored glasses show no color when there is a dark background behind them, but only when there is a lighter background behind them. But then they let their colored property be seen just as well as with light falling through.

Whatever may be objected to against the author's method of approach in his experiments, the result remains unchanged for those who know how to imitate and manipulate them, in which the whole foundation of dyeing and painting is expressed.

The author's lecture, however, is not one of the happiest. His conviction does not coincide with Newtonian, and yet he cannot break free from it, any more than from the terminology by which it is expressed. Furthermore, through his deduction one sees through the thread to which he is clinging, but he devours it himself and thereby confuses the reader.

Since he works excellently in the chemical field, the way he imagined his time and the terminology of that time, in which the phlogiston was supposed to have such wonderfully contradicting effects, of course contradict him. Knowledge of the various types of air is on the way; but the author still lacks the great advantages of modern French chemistry and its linguistic usage, which of course means that we are now going much further. It therefore takes a conviction of his main principles and a good will to undress and recognize what is genuine and meritorious in his work.

We have valued him for many years and therefore already (E. 572 ff.) Listed his convictions, combined with ours.

He works best with the plants. It removes the color from them and a white structure remains. This drawn out color becomes darker and darker when it is condensed, manifests its shadowy nature, approaches the black, indistinguishable, and can again be communicated to another white surface and represented in its previous specification and glory. It's more difficult in the animal kingdom. In the mineral kingdom there are more obstacles to carrying out the principle. However, he firmly insists on it, and uses it happily wherever it is empirically applicable.

In the preface two short essays, which are not particularly favorable to the author, are included by the editor, one by Klügel, the other by Lichtenberg. In the first we find a comfortable and honest skepticism, in the second a witty and skillful skepticism. We should like to make a remark here, which deserves to be printed with a block: namely, that in such a way, as happened by both men here, all empirical science can be destroyed: because nothing that appears to us in experience is absolutely addressed and can be pronounced, but still carries a limiting condition with it, so that we should not call black black, white not white, insofar as it is before us in experience: so every attempt has to be as it will, and show what he wants, as it were a secret enemy with him who limits what the attempt utters a potiori and makes insecure. This is the reason why one does not get very far in teaching, even in teaching; only the doer, the artist who decides, who grasps what is right and knows how to make it fruitful.

The Delavali conviction that we know is juxtaposed with the theory of Newton's lamellae, and of course they are very closely related. With Newton the color does not come from the surface either, but the light has to penetrate through a lamella of the body and return decomposed. In Delaval's work, the color of this lamella is specified and is seen no differently than when there is a light, white background behind it, from which the light then returns, likewise specifically colored.

It is particularly noteworthy in Lichtenberg's essay how the Newtonian doctrine was once again supported by chemical auxiliary troops at that time. A latent heat had been averaged out, why shouldn't there also be a latent light? and why shouldn't the colored lights, which according to the theory belong to light, also play hiding one after the other, and if it is the popular yellow to look out, why shouldn't the rest of them be able to listen teasingly in ambushes?

Two strange passages from an intended essay, which we believe are favorable to us, one of which we have already cited earlier (E. 584), may take their place here:

"As I pass by, I notice that perhaps the doctrine of colors has so far had so many difficulties precisely because everything was supposed to be explained in one way, for example refraction."

We have repeated often enough that everything depends on the way in which one arrives at a science. Newton started from a phenomenon of refraction, from a derived complex. As a result, refraction became the main focus, the main artificial word, and what happened in a single case, the basic rule, the basic law for the general. If several, indeed innumerable, basic colors were adopted here, those that came from painting and dyeing only needed three colors; only two more observers and detectors, and so everything changed according to the different views.

Carvalho and the French H. F. T. found the colored shadows extremely important and laid the entire basis of the theory of color aside. But all these phenomena, they may have names as they like, have an equal right to be basic phenomena. The physiological, physical, chemical colors listed by us are all equally empowered to attract the attention of observers and theorists. Nature alone has the true republican sense, since man leans straight towards the aristocracy and monarchy, and lets this his peculiarity take place everywhere, especially also in theorizing.

"Also, for other reasons, it seems to me probable that in order to perceive a color, our organ must receive some of all light (white) at the same time."

What Lichtenberg utters here in passing, is that something different from what Delaval claims? only that the latter brings the light behind the dark and thereby makes the specification of the dark appear, and that the former mixes the light with the dark, which is nothing more than that one appears with and through the other. Whether I glaze a transparent blue over yellow or whether I mix yellow and blue is in a certain sense the same: because a green is produced in both ways. That type of treatment, however, is much higher, as we probably need not go into further.

Incidentally, Delaval's lecture becomes insecure and inconspicuous, especially when he arrives at the murky means. He returns to the Newtonian doctrine without retaining it in all its purity; thereby, as with so many others, there arises an unfortunate eclectic vacillation. For one must either confess to Newton or renounce him entirely.

Johann Leonhard Hoffmann

An attempt at a history of painterly harmony in general and of color harmony in particular, with explanations from the art of music and many practical comments, Halle 1786.

This man, whose memory has almost completely disappeared, lived for about a year in Leipzig as a privatizing scholar, was valued as a good physicist and legal man, but was unable to wriggle out of a poor existence. He took a considerable part in physical, technological, economic journals and other writings with this content. We did not know more about him.

His reported writing shows him to be a man well educated through studies. Knowledge of languages, antiquity, art history and quite faithful participation in art itself is visible everywhere. Without being an artist himself, he seems to have occupied himself with painting, but especially with painting, as a good observer and eye-catcher, in that he sees and penetrates the requirements of art and technology.

However, since he cannot find any real foundation in everything that is required of the painter and what he achieves, he tries to establish a theoretical view by comparison with the art of music and the painterly and musical phenomena, as well as the treatment of both arts to parallelize with each other.

Such a comparison, already suggested by Aristotle, favored by the nature of the phenomena itself, and attempted by several people, can really only entertain us by playing with certain fluctuating similarities, and by dropping one, grasping the other, and always going on like this rocking us back and forth in a witty way.

In the empirical way, as we noted earlier (E. 748 ff.), The two arts can never be compared, just as little as two standards of different lengths and divisions are kept side by side. Even if one incision fits somewhere, the others do not meet; if one moves up to bring those next to one another, the first ones shift again, and so one is necessarily driven to a higher type of calculation.

We cannot make this clearer than if we juxtapose those phenomena and concepts that he parallelizes.

Light loud

Darkness silence

shadow

Light rays sound rays

Color tone

Color body instrument

Whole colors Whole tones

Mixed colors half tones

Broken color deviation of the tone

Bright height

Dark depth

Color row octave

Repeated series of colors several octaves

Chiaroscuro in unison

Heavenly colors. High tones

Earthly (brown) colors contrast tones

Dominant tone solo voice

Light and penumbra prime and second voice

Indig violoncell

Ultramarine Viole and Violin

Green human throat

Yellow clarinet

Crimson Trumpet

Rose red hoboe

Kermestot flute

Purple French Horn

Violet bassoon

Adjustment of the tuning palette of the instruments

Tract application

Colorful wash drawing piano concert

Impasted painting symphony

With this kind of strict juxtaposition, which is partly really expressed in the book, partly only brought about and introduced by context and style, everyone sees the forced, arbitrary and unsuitable of two great self-contained natural phenomena, insofar as they are partly to be compared with one another.

It is astonishing that the author, who vigorously declares himself against the color piano and considers it impracticable and useless, found such pleasure in creating a labyrinth himself, as it were, from the intertwining of the two arts. This becomes quite confusing in his last chapters, when he describes the motus rectus and contrarius, intervals, consonances and dissonances, the modus major and minor, chord and disharmony, octaves in a row and whatever else is inherent in music, also in color theory and who wants to find the art of painting that applies it.

As a basically astute man, he must, of course, ultimately come up against the fact that painting demands simultaneous harmony and music successive one. Of course, he does not find the intervals of the colors as determinable and measurable as those of the tones. Since he does not close his color scale in itself, but instead presents them in a row instead of in a circle, in order to be able to reconnect them to a lighter octave, he does not know which one to make the first and which the last and how he should bring about this connection most naturally. He opposes the fact that from a certain yellow he can never go straight through red and blue to a lighter yellow, and he must feel that there is an infinite difference between the operation by which one dilutes a color and between that whereby one advances to a higher tone.

It is just as sad to look at it when he believes that one can put any color in the minor by making certain modifications, as one can do with the tones, because the individual tones are much more indifferent to the whole musical range than the individual colors to the periphery in which they are set up: for the colors themselves make the majus and minus in this circle, they themselves make this decided opposition, which is visible and perceptible and which cannot be undone without destroying the whole.

The tones, on the other hand, are, as I said, of an indifferent nature, but they are subject to the secret law of an equally decided opposition, which, however, is not necessarily and invariably perceptible in itself, as is the case with color, but, at the discretion of the artist, in everyone Tone and its sequence flowing from it can be made audible and perceptible.

While we are rushing towards the end, we are pleased to have found an opportunity to explain this important point, which has already been alluded to in more than one way in the course of our lecture.

The little book itself deserves a place in the collection of every nature and art lover, both so that the memory of a good, almost completely forgotten man is preserved, and so that the difficulty, even impossibility of such an undertaking is made clearer to everyone. Ingenious persons will find amusement and amusement in the artificial but honestly meant and, as far as it will go, seriously carried out efforts of the author.

Robert Blair

Experiments and Observations on the unequal Refrangibility of Light, in the Transactions of the Edinburgh Royal Society, Vol. 3, 1794.

The phenomenon of achromatism was now generally known and, especially by the simple prismatic experiments, had been put beyond all doubt; but there were many things that stood in the way of applying this natural law to objective glasses, both from the chemical and the mechanical side, in that it had its difficulties in preparing an internally perfectly pure flint glass and in grinding glasses that fitted exactly together. In particular, however, there were some obstacles when one wanted to increase the width of the lens glasses over a certain amount.

It was known that not only solid, but also all kinds of liquid agents are capable of increasing the appearance of color. Doctor Blair occupied himself with these last ones, all the more because he wanted to have found that in the usual way, by combining flint and crown glass, the achromatism could not be perfect.

He had the Newtonian way of thinking on his side: for if one thinks of the spectrum as a finished series of rays, unequally refracted in all its individual parts, one can hope that an opposing means will cancel out at most part of it, but not all of it could improve. This had been discussed earlier and Dr. Blair's attempts, and the conclusions drawn from them, were received with favor by the Newtonians.

We want to hear it ourselves first and then follow up on what we are about to remember in the case.

Attempts by Dr. Blair on the chromatic power of different liquids and resolutions

»Different resolutions of metals and semi-metals in different shapes were always more chromatic than crown glass. The dissolution of some salts in water, for example the crude ammonia salt, greatly increases the phenomenon. Hydrochloric acid also has this power, and the more concentrated it is, the stronger it works. I found, therefore, that those liquids have the highest chromatic power in which the hydrochloric acid and the metals are combined. The chemical preparation, called Causticum antimoniale or Butyrum Antimonii, possesses in its most concentrated state, when it has drawn enough moisture to be liquid, this power to an astonishing degree, so that three wedges of crown glass are necessary to obtain the color to cancel, which have been brought about by an opposite wedge of the same angle. The large amount of the semi-metal contained in this solution and the concentrated state of the hydrochloric acid seem to produce this hardly believable effect. "

“Corrosive sublimated mercury, with a dissolution of raw ammonia salt in water, is the closest in strength. They can be made so strong that the angle of a prism of crown glass, which is supposed to compensate for their color appearance, has to be twice as large. Here, too, the mercury and the hydrochloric acid are evidently the cause of the phenomenon: for neither the water nor the volatile alkaline salt, as the other parts of the composition, show such an effect when examined individually. "

»The essential oils follow first. Those that are obtained from resinous minerals work the most: than from natural mountain oil, coal and ambergris. Their relationship to the crown glass is roughly two to three. The essential oil of sassafras is not much less effective. Essential lemon oil, very real, behaves like three to four, turpentine oil like six to seven, and essential rosemary oil the potency is even less. "

"Expressed oils do not differ that much from the crown glass, as do rectified spirits, and the ethers of nitre and vitriol."

Lecture by Dr. Blair
  1. “The unequal refangibility of light, as it was discovered by Isaac Newton and discussed at length, is only established without being contradicted in that the refraction takes place at the border of some medium and an empty space. Then the rays of different colors are refracted unequally, the rays that make red are the least, and the rays that make violet the most breakable rays. "

  2. The discovery of what was called the differently dispersing force in the differently refracting media shows that Newtonian theorems are not general when he concludes: that the difference in refraction between the most and least refractive rays is always in a given ratio stand by the refraction of the medium-refrangible. There is no doubt that this proposition is true as to the means by which experiences are made; but there are some exceptions to it. "

  3. "For Mr. Dollond's experience shows that the difference in refraction between the red and violet rays, in relation to the refraction of the entire brush, is greater in certain types of glass than in water, and greater in flint glass than in crown glass."

  4. The first series of the experiments mentioned above shows that the property of scattering the colored rays to a higher degree than crown glass is not limited to a few means, but belongs to a great variety of liquids, and some of them to a very extraordinary degree. Metal dissolutions, essential oils, mineral acids, with the exception of vitriolic acids, are most remarkable in this regard. "

  5. “Some of the inferences which result from the combination of such means, which have different dispersing powers, and which have not yet been sufficiently considered, can be explained in this way. Although the greater refangibility of the violet from the red rays, when the light goes from some means into an empty space, can be regarded as a law of nature, it is certain properties of the means on which it depends which of these rays depends , at the transition of light from one medium to another, which are mostly supposed to be refrangible, or to what extent there is any difference in their breakability. "

  6. "The application of Huyghen's demonstrations to the improvement of the deviation that is written off the spherical shape of the lenses, whether they be solid or liquid, can be seen as the next step in improving the theory of binoculars."

  7. Then in experiments which were made with objective glasses with a very wide aperture, and in which both deviations were improved, insofar as the principles permit, it is found that the color deviation cannot be completely improved by the common combination of two means of different dispersive power. The homogeneous green rays are then the most refreshed ones, first combined in these blue and yellow, then indigo and orange combined, then violet and red combined, which are the least refrangled. "

  8. 'If this color production were constant and the length of the secondary spectrum the same, in all the connections of the means where the whole refraction of the brush is equal, the perfect improvement of that deviation which arises from the difference in refangibility would be impossible and as one an insurmountable obstacle to the improvement of dioptric instruments. "