CHAPTER III.

SECTION I.

PRINCIPLES OF COLOURING OBJECTS.

Proceeding to consider Colouring independently of Character or Expression, to which it should be subservient in the higher walks of Art, the attention of the reader must be directed to a circumstance connected with truth of representation.

It has commonly been the practice, under the almost universal sanction of great authorities, to place the student who may be desirous of acquiring the Art of Painting, before some object, and to direct him to copy _what he sees_. But what does he see?

We need not go into the question of _how_ impressions are produced upon the mind, through the medium of the eye; whether a species of picture of the object be, during the inspection, as it were painted upon the retina; and whether that be inverted or anywise different from the real object; or whether, and to what extent, association rectifies the imperfections of our sight. These, and other investigations into the philosophical and physical nature of vision, may be left to the consideration of those who desire to account for particular facts; we have to do with the facts themselves.

In whatever manner the effect may be produced, it is indisputable, that a certain and distinct impression is produced upon the mind, through the medium of the eye, by every object which may be before it, and that impression has a strict relation to the real character of the object; for instance, a marble statue, it appears, or an impression is conveyed of, an object of one unvaried tint. How this impression is conveyed, is of no consequence; it is conveyed; and a series of tints may be artificially arranged upon paper (or any other convenient material), so as also, if not equally, to convey to the mind the impression of a marble statue of uniform whiteness. But upon examination of the drawing or painting, it would be seen, that scarcely any two parts of the _representation_ of the statue were of exactly the same tint. Some parts would be delicately graduated from a point of light, through a series of darker tints, to give the appearance of roundness; while others would be made nearly black by shadow, to give the appearance of projection. The present enquiry has reference solely to Colours, but the same difficulties occur with regard to forms.

Here there is a discrepancy, occasioned by Association, which we shall scarcely find language to explain, but which will in most cases prove of serious perplexity to the student; for there are some other persons like Queen Elizabeth, who have no idea of shadow, unless it be the shadow of a parasol or tree, under which they may escape the intensity of a noon-day sun. The statue will appear, or an impression will be conveyed to the mind, of uniform whiteness. But pictorially speaking, one spot only, that which reflects the greatest light, will appear quite white. All the other parts will _appear_, that is, to convey the impression, they must be made, of an infinite variety of tints, from the brightest light to the deepest shadow. The statue _is_ actually uniformly white, and it appears uniformly white, yet the _appearance_ or representation which must be put upon paper, to convey an impression of that _appearance_ by drawing or painting, is totally opposite, being an infinite variety of tints.

But in a statue, by reason of its convexity, the second species of _appearance_, the Pictorial, is much more readily appreciated, from the strong opposition of light and shadow, than in a flat surface,--a ceiling, a pavement, or meadow, in which the perception of the modifications of colour, arising from what is termed aerial perspective, is considerably influenced, by the Association above mentioned, until the eye has become educated to observe these minute and delicate gradations of tint. Thus, in looking at a meadow, we know the grass to be generally of the same colour throughout, and to an uneducated eye it _appears_ equally green from one end to the other: or the ceiling of a well lighted room, we know it to be of one colour throughout, and it _appears_ of one even tint from the nearest to the most distant extremity; yet pictorially speaking, it _appears_ of an infinite variety of tints, for the effect of the atmosphere is such as to rob the grass of its colour, and to make the white ceiling grey, as they recede from the eye.

It will scarcely be necessary to guard against misconception as to the use of the terms describing the effect of the atmosphere, by explaining that it is not intended to assert that an _actual change_ takes place, or that there is any _actual_ difference in the colour of those parts of objects which are at a distance from the eye; or, that the colour in the distance does not appear to be, as we know it is, the same with that nearest the eye; but that the effect of distance is the _pictorial appearance_ of a modification of tint, by the interposition of the atmosphere, perceptible only to an educated eye.

We know the grass to be equally green throughout, and it appears of the tints which convey that impression; while Association conceals the modification occasioned by the interposition of the atmosphere (which the generality of observers consider as only "air," and of no consequence), and excites the notion that the meadow appears of one equal flat tint. But the distant extremity of the meadow is seen through more or less atmosphere, which is more or less dense; and in proportion to its density will the colour of the grass be _apparently_ altered or changed thereby; and in some instances, as in case of a fog, entirely concealed.

In looking at any object through a perfectly transparent medium, such as plate glass, we do not perceive any alteration in the real colours. But when the medium is not perfectly transparent, which is the case with the atmosphere, the colours of all objects seen through it are modified or tinged in proportion to its density, until they are sometimes lost or absorbed in the tint of the medium.

The slightest possible colourless opacity gives a medium approaching to a whitish film, which is very evident when there is light behind it; as in the case of the beams of the moon. This is the clearest state of the atmosphere. As it increases in density, it becomes more and more white, until it becomes a white mist, fog or cloud. The atmosphere is sometimes coloured, as will hereafter be mentioned; at present we have to do with its colourless state.

The opacity of the atmosphere, as a white film over the darkness of space, occasions the blue appearance of the sky; and in proportion to the rarity or density of the medium, is the intensity of colour, or rather depth of tone. If the atmosphere be extremely rare, as in the Polar regions, or at the height of Mont Blanc, the sky appears almost black. And if the atmosphere be thick with vapour, the sky assumes a milky colour, and the blue tint is lost in that of the medium. When the atmosphere is just so rare as to be scarcely perceptible in its influence upon terrestrial objects,--as in Italy, or the eastern climes, where the most distant buildings appear diminished in size, but almost as distinct as those close to the spectator,--yet sufficiently dense to become a veil to the expanse of space, the colour of the sky appears the most intense blue. As near as we can superficially ascertain it,--in the exact medium between such rarity of atmosphere as would afford blackness, and such opacity as would afford whiteness,--we may expect to find the most intensely blue colour in the sky.

As the effect of this colourless opacity of the atmosphere is, to render the appearance of the _darkness of space_ a blue colour, so all dark terrestrial objects are similarly affected by the intervening of this medium, and, in a corresponding degree, become more or less blue. The dark mountains in Wales and Scotland appear of a deep blue, sometimes verging upon purple; and a slight comparison between the colour of the trees close to the spectator and those in the distance, will show how much more blue the latter become, from the influence of the medium through which they are viewed.

And as objects, in proportion to their distance, are more or less affected by the interposition of the atmosphere, so, also, do the parts of the individual objects themselves, become more or less grey as they recede. The boundaries of a white object are less white, and of a black object less black, than the parts nearest the eye. A tree is most green at the prominent parts, and greyer at the top and sides.

This truth is so decidedly felt by the public in general--though perhaps insensibly appreciated and but tacitly acknowledged,--that, as the atmosphere reduces the colours of all objects to a blue tint, so all blue colours convey an impression of distance, and all tints approaching to blue are accordingly designated _retiring colours_.

But the atmosphere is not always colourless. The rays of the sun tinge it with yellow. The rays from a fire or candle tinge it with a colour approaching to red. The combination of smoke tinges it with black or brown; and fogs infuse various degrees of dingy yellow. All these variations affect the colours of the objects seen through the atmosphere, and modify the degree of blue, or quality of grey, tint communicated thereby.

When the atmosphere is coloured by the light of the sun, the blue is modified, more or less, into a warm grey. But owing to the brilliancy resulting from the blaze of light, the tints remain of the utmost purity. All tendency to green is kept in subordination by the pearly tints of those parts which are in shadow. The atmosphere is rendered more dense at the same time that it is coloured by the light of the sun; but the light parts of the objects seen through it are rendered, by the same cause, so much more brilliant, that the density of the medium is partially compensated; while its full effect is apparent upon the shadows seen through it, over which a bright haze diffuses a beautiful blue tint, slightly warmed by the golden colour of the illuminating power. The contrast of the yellow tinge in the lights makes these shadows appear to incline to purple; and at sunset and sunrise, when by the greater quantity of the medium, rendered more dense by the aqueous vapours close to the earth, the colour of the sun's light is enriched to a deep golden hue approaching orange and red, the shadows assume a decidedly purple tint, of which the blue is supplied by the density, and the red by the colour, of the medium. As the light of the sun decreases, the colour of the atmosphere is more evidently tinged with red, until the sun has sunk so far below the horizon, that the shadows of night incorporating with the colour of the vapours, render them a dull grey, sometimes approaching a brown.

In proportion as the atmosphere is illumined does it also become opaque. The sky close to the sun appears much less blue than on the opposite side of the heavens. The beams of the sun, or moon, or even the rays of a candle, become so opaque, as absolutely to conceal all objects behind them.

In a glowing sunshine, the particles of the atmosphere loaded with light, produce that soft haze or _caligine_, "as the Italian hath it," by which the colours of every object seen through it, are assimilated in one broad, warm, grey tone, however varied the tints of the objects in reality may be.

Another singular appearance takes place in remote objects, of which no one has so fully availed himself as Turner, for the production of pictorial beauties, and the brilliancy of sunshine. The atmosphere, which becomes most visible when before shadows, is frequently so much illuminated by the sun's rays, as to make the shadows appear nearly equally light with the illuminated parts of the objects; and the only distinction between the lights and shadows is to be found in the difference of tint--the shadows being blue or purple, and the lights a warm yellow, or fleshy colour.

The practice in art, both in Oil and in Water colours, has been an imitation of the process of nature, and with similar results. It is usual in Oil to paint the distance stronger in colour than it is intended to remain, and when dry, to pass some very thin opaque colour (technically to scumble) over the whole. Thus the most perfectly aerial tints are produced. In Water Colours, owing to the different quality of the materials employed, another method is adopted. White, or any opaque pigment (except when used in conjunction with Oil painting), has a disagreeable effect; so it is considered advisable partially to wash out the too highly coloured distance, and aerial tints similar to those produced by the scumble are obtained.

However requisite it may be philosophically to account for these appearances, it is unnecessary to perplex the reader of the present work with a questionable statement of the greater impetus of rays of certain colours enabling them to penetrate through the dense atmosphere, while others are more feeble, and are swallowed up and absorbed by the medium through which they in vain essay to pass. This may be a very pretty story to amuse children with, and such philosophers as are verging on their second childhood; but while so simple a method can be discovered of accounting for the blueness of the sky and distant objects, and one that can be so easily exemplified as that given in the previous pages, we shall not be the parties to contribute to that amusement, by writing "the history of some blue rays that were lost in a fog." Nor is this the place to point out the absurdity of such theories; it will be sufficient to remark that _if_ they are correct, all distant objects must appear _red_; and the blueness of the sky can only be accounted for by the hypothesis, that the atmosphere is a sort of trap for the blue rays of all the light that has passed and is passing through it!

Such being the effect of the atmosphere, and such being the antagonizing influence of Association in looking at Nature, it has been found necessary for the purposes of Art, in representation, to exaggerate the former, to overstep the modesty of Nature, and thus to produce what may be termed conventional imitations or translations of Nature.

For, in looking at a picture, Association again affects us; and as we know what is before us to be a flat surface, this can only be overcome by increasing the effects produced by atmospheric influence, reflections, refractions, &c. Hence the colour of all distant objects are reduced to some tone of grey, oscillating between the extremes of bright blue or even purple, and the medium between black and white as the subject, may be in sunshine cold daylight; or, as the taste of the artist may lead him to prefer one scale of colouring to another. Those who delight in the sunny skies of Italy, or tropical climates, represent the distance by the purest blue that Ultramarine affords. Others, who delineate the village church or cathedral tower, represent them of a dark grey. Mountain scenery is represented of a deep Indigo blue, sometimes inclining to a decided purple, as all must remember in the drawings of the late Mr. Robson.

If this exaggeration or pictorial license be objected to, as an unnecessary departure from truth or the beauty of Nature, let the most inveterate worshipper of verisimilitude place himself before a landscape under bright sunshine, on a clear day, and make an exact representation, if he be able, of what he sees; and he will be convinced that in such an instance, something more and very different is required, to make a finely coloured picture. It cannot be that the colours of the original are deficient in beauty, but that an essential quality of the beauty of Nature cannot be preserved by Imitative Art. He will find that it will not be possible to preserve even slightly the gradation of tints before him, without descending almost to blackness in the shadows, which will be destructive of brilliancy of sunshine, and at the same time, of that quality which is indispensable in a work of Art, _breadth_. He will find that in comparison with the brightness of the sky, the trees will look as dark as they are represented by Ruysdael and Hobbima, but who incontestibly do not give the idea of sunshine. As in translating from one language to another, he will find that a literal version may give the bones, but not the spirit of the text; and that something more is required to transfer the full force and character of the original. Herein consists a great part of the art of colouring objects. It may be that the scene being unbounded in Nature, is acted upon by extraneous circumstances which cannot be called to the aid of a picture.

As it is impossible with pigments to rival the brightness of light, it has been found necessary to adopt some method of forcing the effect of colours, so as to conceal or to supply a compensation for this deficiency, and _apparently_ to produce the vigour of truth.

This has led to a division, which rivals in fierceness as in name, the feud of the Bianchi and the Neri of Italy, into two great schisms or factions of colourists, of whom, it is to be regretted, too many are apt to consider those of the opposite party as lost in the depths of absurdity. The hostility and contempt are quite mutual, and equally ungrounded.

A writer in Blackwood's Magazine of the Neri faction says, "We have received a prescriptive right to make war upon the rising heresy of light pictures, and we will wage it to the knife," or some such expressions.

Certain tones of colour have been found to be almost universally recognized as agreeables; and by the above mentioned class of artists and critics, the Neri, it is held to be "fine colouring," to reduce every representation, without consideration of propriety, to these conventionally agreeable tones. Plate. Sir Joshua Reynolds commends a picture of a moonlight scene by Rubens, which is so rich in colour, that if you hide the moon it appears like a sunset.

The background of the far-famed Mercury, Venus and Cupid, by Corregio, in the National Gallery, and the sky of the Bacchus and Ariadne, by Titian, in the same collection, are instances of this practice, the use of conventionally agreeable tones, which may be seen by every one. It would be difficult to say what the former was meant for, except _background_ to the figures; and no one ever saw a sky such a blue as the latter. It irresistibly brings to mind the counter-criticism of a sceptic to the admiration of a landscape by Poussin, in which Sir ----, a worshipper of the old masters, was indulging:--"What I like so much is, it looks so _like_ an _old picture_."--"Yes," said the sceptic, "and the _sky_ looks as _old_ as the _rest_ of the _picture_, for you never see such a sky now-a-days."

The Neri apparently give up all hope of rivalling the brightness of nature; but by forcing the shadows and general tone of the whole picture, endeavour to produce the same _gradation_ of light and shadow as in nature, but on a lower scale.

The Bianchi party, on the other hand, endeavour to compensate for the want of positive brilliancy, by refining or increasing the delicacy and beauty of the tints.

Light is the origin, or immediate cause of _colour_, and the brighter the light, the greater variety of tints will be found or displayed. As we cannot rival the cause, the Bianchi contend that we must increase the effect by introducing _colour_ in lieu of those _tints_ which in nature appear neutral; and thus conceal the weakness of our imitation of the cause, by making it apparently produce greater effects. Thus all greys are rendered by pure Ultramarine blue tints, or delicate pearly purple, and the greatest possible variety of beautiful and delicate colours are introduced in the light; while the shadows are generally of a neutral colour, the most decidedly contrasting with the tints in the light. But sometimes the colour is also carried through the shadows as well as the lights; positive crimson being introduced into those of leaves or grass; while those of flesh are rendered by a dull red; and those of a sandy bank by pure blue. Plate.

The Neri complain that the Bianchi want tone, and the Bianchi that the Neri want purity and light.

Each of these factions contends, that all the difficulty of fine colouring is to be found only in their own aim; while they hold in perfect contempt the productions of their opponents, as being of such facile achievement as to the sarcasm of Michael Angelo,--to be "fit only for children," and beneath the attention of those who profess to study the Fine Arts.

The main difference between the principles of these two parties or factions, will be found to lie in the treatment of the atmospheric influence and association, previously alluded to. The Bianchi availing themselves of the former circumstance, as a reason for introducing a great variety of pearly greys, on the purity and beauty of which they contend fine colouring is dependent; and the Neri availing themselves of the latter, as an excuse for the introduction of breadth of warm tones, and the omission of as much as possible of the cool tints, which are deemed so indispensable by their rivals; they limit the representation of atmospheric influence to the least possible degree. Titian's Venuses are masses of the local colour of flesh, broken with so little half-tint, that they are scarcely round, and satisfy few but critics sufficiently learned in the Art, to be contented with the beauties of _Art_, as a substitute for the imitation of _Nature_.

This class of colouring is founded upon the power of Association, previously alluded to, by which, the local colour overpowers the greys of atmospheric influence; in other words, that to the eyes of the many, _flesh_ looks of a _flesh_ colour, and ought to be so represented. But the _full_ effect of Association is here not allowed for. In looking at flesh, we know it to be flesh colour; and we know it to be round; and it requires some education of the eye to discover the atmospheric influence, as well as the minute gradations in form. But on the other hand, in looking at a picture, we know it to be a flat surface; and however far the _imagination_ may be willing or have a tendency to supply the deficiencies in the representation, _Association_ is an _antagonist_ and not an ally. This will become evident upon making outlines of objects and filling them up with flat tints; imagination will not have power to make them appear to be round, or to recede. The beauties of this class of colouring are solely conventional.

Titian, Giorgione, and Sir Joshua Reynolds lead the van of the Neri; Rubens, Vandyke, and Lawrence are at the head of the Bianchi; unless, indeed, we should consider Turner as general-in-chief of the latter. Claude was probably of the Bianchi faction; but Time, who is the great ally of the Neri, has made him appear in some of his productions an adherent of that party.

It may be added, that most historical painters lean to the Neri faction, on account of the disadvantage arising from too close an approach to the common appearance of every-day nature, of which the effect is described in the proverb, that "familiarity breeds contempt," and consequently is destructive of that grandeur, solemnity, or refinement which is indispensable in high art; and they take refuge in the "cloistered tone" of Ludovico Caracci, so commended by Sir Joshua Reynolds, a conventional beauty which will presently be noticed. The Landscape painters, on the other hand, almost universally belong to the Bianchi party; as truth or _apparent_ truth is so much more indispensable in subjects that only display the scenery of nature, and which depend upon that resemblance for producing an impression, than in subjects which appeal to the passions by the display of some stirring incident. From the nature of the materials employed, the tendency of oil painting is to the side of the Neri; whilst the general inclination induced by Water-colour drawing, is in favour of the Bianchi party. The _alleged_ principle of the colouring of the Neri is deduced from the hypothesis laid down by Sir Isaac Newton, that neither white nor black are _colours_, therefore say the Neri, "neither should appear in a finely coloured picture; the brightest lights should not be white; the deepest shadows should not be black;" nevertheless, those productions which are cited by this party as the finest specimens of colour in existence, _do_ contain both _white_ and _black_. In the celebrated picture by Giorgione, copied recently by Mr. Ward, R.A., to the eye of the uninitiated are presented both white lights, and black shadows. The former, it is true, are reduced by _Time_ or glazing; and the latter are excused as having lost their original colour.

But this principle can scarcely be said to be carried out, except in such pictures as possess the "cloistered tone" of Ludovico Caracci alluded to. Here the lights are warm and golden, as if transmitted through stained glass. The atmospheric greys are introduced to no greater extent than is indispensable to prevent the picture appearing rusty. The shadows are deep rich browns, into which are thrown still warmer reflections; and the whole picture is subdued to a soft-mysterious effect, which is admirably adapted to produce what is technically termed _repose_, and to excite gentle, reverential, solemn, and even affectionate feelings. It is a style of colouring peculiarly suited to religious subjects; and in representations of interiors, may be said to be like nature, because Nature _may_ be made to appear like it. (_See Plate._)

This principle of colouring may be carried out on a higher scale than is generally found among the productions of its advocates, and abstractedly, is undoubtedly calculated to lead to very beautiful results; though it may be questioned, whether it is sufficient to entitle the party exclusively to arrogate to themselves the designation of _colourists_, as they are in the habit of doing. For the principle of the Bianchi is likewise adapted to produce exceedingly beautiful colouring; and without some rational or scientific standard by which the comparative beauty of individual colours may be determined, so as to distinguish between fine colours and fine colouring, the admirers of this class of colours may, with the greatest justice, contend that it is equally beautiful with that of the opposite party; while it has this superiority, that it will enable the Artist to produce much more resemblance in the representation of _external_ nature, and will be much less artificial in the effects produced as imitation of interiors.

And they derive a strong argument in favour of their mode of proceeding being correct, and most likely to stand, from the circumstance, that the pictures of Vandyke, many of which are _now_ claimed by the Neri as painted on their principle, when first done were frequently censured as being too _raw_ or _white_.

Further, it should be observed that, by too many of the Neri party, their great object of worship, _Tone_, is limited to the rich warm brownish yellow which is legitimately superinduced in oil pictures by the action of Time, or glazing; and surreptitiously obtained by washing with tobacco-water. But an inspection of the works of the Dutch school, who belong to a third party which considers both the Bianchi and Neri to be in the wrong, as too artificial, will show that _tone_ may be cool as well as warm, and that there is a silvery _tone_ which has as devoted admirers as those of the Golden Image--(_see Plates of Ruysdael and of Ostade_).

It may not be becoming in the author of the present work to decide between these great disputants; but from the statement respecting Vandyke's pictures, that they were considered _raw_ when fresh painted, as well as from the nature of the materials employed, it is evident, that the productions of Titian, Giorgione, and other celebrated colourists, were not, when first painted, of such deep tones as they exhibit now; and it may be suspected that the reputation, which was derived from the _original_ colouring of their pictures, has, to a certain extent, been attached to the colouring they at present exhibit; and that veneration of talent, and respect for authority, have given sanction to what would be repudiated by the Great men whose names form the slogan of the party, and is not really entitled to commendation.

That the two principles may be combined, and so produce higher qualities than either affords alone, is hardly possible, when their opposite treatment of the effects of atmospheric influence and association are taken into consideration.

But this compromise may be made between them with advantage both to Amateurs and Artists; that the style of the Neri, including that of the Dutch school, may be considered as most applicable to the representation of interiors and quiet or grand subjects; while that of the Bianchi may be considered as most suited to exteriors, and subjects of gaiety and animation.

For the benefit of the Amateur, it will be necessary to say something more upon the style of colouring adopted by the Dutch school, the productions of which among the cognoscenti, are termed pictures of _Tone_; tone being in this instance used in opposition to positive colour, and as implying varieties of the ternary combinations, called neutral tints, or greys, but otherwise possessing the qualities of tone in a general sense, namely, transparency.

This style of colouring is peculiarly adapted to the class of subjects on which the Masters of the Dutch school generally exercised their pencils, homely interiors; but when applied to out-of-door scenes, although undoubtedly possessed of certain conventional beauties, such as harmonious arrangement and balance of tones, it has a tendency to look dull and heavy. The landscapes of Ruysdael and Hobbima do not reckon among their beauties, that of vivacity or cheerfulness. They may be clear and bright and fresh, as their admirers say, but they do not represent Nature under her most bewitching aspect, nor is the style of the school adapted to do so. It leans to the side of the Neri, from its dread of brilliant colours. It is unaffected, sober, and in many instances, such as interiors or close woody scenes under grey daylight, possesses great truth; but from its limited application, and unpretending effect, is scarcely to be put into competition, as a style of Fine Colouring, with the higher aims of the two great parties before mentioned. Plate.

Such is the present state of the theory of Fine Colouring; from which it is evident, that, except in a very limited class of subjects, Truth _cannot_ be made the test--that even in this class of subjects, it is disputed whether it _should_ be made the test; and that it is also disputed, to what extent a departure from truth is admissible; or rather, what quantity of resemblance to Nature is indispensable, and what method may be the best of compensating the want of accurate transcription; in short, what is the true _idiom_ of Fine Colouring in Art, so as fully to translate the beauties of Nature.

The fashion of the day rather leans to the Bianchi party in Water-colour drawings, if not in Oil paintings; but the principles of _none_ of the parties are _fully_ developed in the works of their existing followers. The followers of the Dutch school are sacrificing part of their truth for some, but it may be doubted whether the best, part of the conventional tones of both the other parties. The Bianchi are more regardless of truth than they need be, even to develope their principles to the utmost. And the Neri admit themselves to be wandering in a maze, without any fixed ideas of their own principles, and therefore are less frequently successful than the reverse; and they are equally obnoxious to the charge of departing farther from truth, than is necessary to give their own principles full play. Very recently a heresy of this faction adopted a peculiarity of tone, which is not to be found in the works of any of the great men of their party; and which is obnoxious to two serious objections. It is a greenish tone that unavoidably excites the idea of corruption and decay, which, having a tendency towards the disgusting, is not tolerable in the Fine Arts; and the second objection is, that, in their zeal for transparency, they had lost solidity to such an extent, that a portrait of George IV. by a celebrated artist, had the appearance of a vision, or of having been spun out of green glass bottles.

The beginner and the Amateur have already been warned against the dangers of green in pictures. And it may now be added, that transparency should reside in the _colours_ to conceal the appearance of pigments, but that the substances represented should appear as _solid_ as in nature.