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[From “The Reader,” December 3, 1864.]
ENGLISH VERSUS ALPINE GEOLOGY

Denmark Hill, 29th Nov.

I SCARCELY know what reply to make, or whether it is necessary to reply at all, to the letter of Mr. Jukes in your last number. There is no antagonism between his views and mine, though he seems heartily to desire that there should be, and with no conceivable motive but to obtain some appearance of it suppresses the latter half of the sentence he quotes from my letter.¹⁶⁶ It is true that he writes in willing ignorance of the Alps, and I in unwilling ignorance of the Wicklow hills; but the only consequent discrepancy of thought or of impression between us is, that Mr. Jukes, examining (by his own account) very old hills, which have been all but washed away to nothing, naturally, and rightly, attributes their present form, or want of form, to their prolonged ablutions, while I, examining new and lofty hills, of which, though much has been carried away, much is still left, as naturally and rightly ascribe a great part of their aspect to the modes of their elevation. The Alp-bred geologist has, however, this advantage, that (especially if he happen at spare times to have been interested in manual arts) he can hardly overlook the effects of denudation on a mountain-chain which sustains Venice on the delta of one of its torrents, and Antwerp on that of another; but the English geologist, however practised in the detection and measurement of faults filled in by cubes of fluor, may be pardoned for dimly appreciating the structure of a district in which a people strong enough to lay the foundation of the liberties of Europe in a single battle,¹⁶⁷ was educated in a fissure of the Lower Chalk.

I think, however, that, if Mr. Jukes can succeed in allaying his feverish thirst for battle, he will wish to withdraw the fourth paragraph of his letter,¹⁶⁸ and, as a general formula, even the scheme which it introduces. That scheme, sufficiently accurate as an expression of one cycle of geological action, contains little more than was known to all leading geologists five-and-twenty years ago, when I was working hard under Dr. Buckland at Oxford;¹⁶⁹ and it is so curiously unworthy of the present state of geological science, that I believe its author, in his calmer moments, will not wish to attach his name to an attempt at generalization at once so narrow, and so audacious. My experience of mountain-form is probably as much more extended than his, as my disposition to generalize respecting; it is less;¹⁷⁰ and, although indeed the apparent limitation of the statement which he half quotes (probably owing to his general love of denudation) from my last letter, to the chain of the Alps, was intended only to attach to the words “quite visibly,” yet, had I myself expanded that statement, I should not have assumed the existence of a sea, to relieve me from the difficulty of accounting for the existence of a lake; I should not have assumed that all mountain-formations of investiture were marine; nor claimed the possession of a great series of stratified rocks without inquiring where they were to come from. I should not have thought “even more than one” an adequate expression for the possible number of elevations and depressions which may have taken place since the beginning of time on the mountain-chains of the world; nor thought myself capable of compressing into Ten Articles, or even into Thirty-nine, my conceptions of the working of the Power which led forth the little hills like lambs, while it rent or established the foundations of the earth; and set their birth-seal on the forehead of each in the infinitudes of aspect and of function which range between the violet-dyed banks of Thames and Seine, and the vexed Fury-Tower of Cotopaxi.

Not but that large generalizations are, indeed, possible with respect to the diluvial phenomena, among which my antagonist has pursued his—(scarcely amphibious?)—investigations. The effects of denudation and deposition are unvarying everywhere, and have been watched with terror and gratitude in all ages. In physical mythology they gave tusk to the Grææ, claw to the Gorgons, bull’s frontlet to the floods of Aufidus and Po. They gave weapons to the wars of Titans against Gods, and lifeless seed of life into the hand of Deucalion. Herodotus “rightly spelled” of them, where the lotus rose from the dust of Nile and leaned upon its dew; Plato rightly dreamed of them in his great vision of the disrobing of the Acropolis to its naked marble; the keen eye of Horace, half poet’s, half farmer’s (albeit unaided by theodolite), recognized them alike where the risen brooks of Vallombrosa, amidst the mountain-clamors, tossed their champed shingle to the Etrurian sea, and in the uncoveted wealth of the pastures,

 
“Quæ Liris quietâ;
Mordet aquâ, taciturnus amnis.”¹⁷¹
 

But the inner structure of the mountain-chains is as varied as their substance; and to this day, in some of its mightier developments, so little understood, that my Neptunian opponent himself, in his address delivered at Cambridge in 1862, speaks of an arrangement of strata which it is difficult to traverse ten miles of Alpine limestone without finding an example of, as beyond the limits of theoretical imagination.¹⁷²

I feel tempted to say more; but I have at present little time even for useful, and none for wanton, controversy. Whatever information Mr. Jukes can afford me on these subjects (and I do not doubt he can afford me much), I am ready to receive, not only without need of his entreaty, but with sincere thanks. If he likes to try his powers of sight, “as corrected by the laborious use of the protractor,” against mine, I will in humility abide the issue. But at present the question before the house is, as I understand it, simply whether glaciers excavate lake-basins or not. That, in spite of measurement and survey, here or elsewhere, seems to remain a question. May we answer the first, if answerable? That determined, I think I might furnish some other grounds of debate in this notable cause of Peebles against Plainstanes, provided that Mr. Jukes will not in future think his seniority gives him the right to answer me with disparagement instead of instruction, and will bear with the English “student’s” weakness, which induces me, usually, to wish rather to begin by shooting my elephant than end by describing it out of my moral consciousness.¹⁷³

J. Ruskin.

[From “The Reader,” December 10, 1864.]
CONCERNING HYDROSTATICS

Norwich, 5th December.

Your pages are not, I presume, intended for the dissemination of the elements of physical science. Your correspondent “M. A. C.” has a good wit, and, by purchasing any common treatise on the barometer, may discover the propriety of exercising it on subjects with which he is acquainted. “G. M.” deserves more attention, the confusion in his mind between increase of pressure and increase of density being a very common one.¹⁷⁴ It may be enough to note for him, and for those of your readers whom his letter may have embarrassed, that in any incompressible liquid a body of greater specific gravity than the liquid will sink to any depth, because the column which it forms, together with the vertical column of the liquid above it, always exceeds in total weight the column formed by the equal bulk of the liquid at its side, and the vertical column of liquid above that. Deep-sea soundings would be otherwise impossible. “G. M.” may find the explanation of the other phenomena to which he alludes in any elementary work on hydrostatics, and will discover on a little reflection that the statement in my last letter¹⁷⁵ is simply true. Expanded, it is merely that, when we throw a stone into water, we substitute pressure of stone-surface for pressure of water-surface throughout the area of horizontal contact of the stone with the ground, and add the excess of the stone’s weight over that of an equal bulk of water.

It is, however, very difficult for me to understand how any person so totally ignorant of every circumstance of glacial locality and action, as “G. M.” shows himself to be in the paragraph beginning “It is very evident,” could have had the courage to write a syllable on the subject. I will waste no time in reply, but will only assure him (with reference to his assertion that I “get rid of the rocks,” etc.), that I never desire to get rid of anything but error, and that I should be the last person to desire to get rid of the glacial agency by friction, as I was, I believe, the first to reduce to a diagram the probable stages of its operation on the bases of the higher Alpine aiguilles.¹⁷⁶

Permit me to add, in conclusion, that in future I can take no notice of any letters to which the writers do not think fit to attach their names. There can be no need of initials in scientific discussion, except to shield incompetence or license discourtesy.

J. Ruskin.

[From “Rendu’s Theory of the Glaciers of Savoy,” Macmillan, 1874.]
JAMES DAVID FORBES: HIS REAL GREATNESS. ¹⁷⁷

The incidental passage in “Fors,” hastily written, on a contemptible issue, does not in the least indicate my sense of the real position of James Forbes among the men of his day. I have asked his son’s¹⁷⁸ permission to add a few words expressive of my deeper feelings.

For indeed it seems to me that all these questions as to priority of ideas or observations are beneath debate among noble persons. What a man like Forbes first noticed, or demonstrated, is of no real moment to his memory. What he was, and how he taught, is of consummate moment. The actuality of his personal power, the sincerity and wisdom of his constant teaching, need no applause from the love they justly gained, and can sustain no diminution from hostility; for their proper honor is in their usefulness. To a man of no essential power, the accident of a discovery is apotheosis; to him, the former knowledge of all the sages of earth is as though it were not; he calls the ants of his own generation round him, to observe how he flourishes in his tiny forceps the grain of sand he has imposed upon Pelion. But from all such vindication of the claims of Forbes to mere discovery, I, his friend, would, for my own part, proudly abstain. I do not in the slightest degree care whether he was the first to see this, or the first to say that, or how many common persons had seen or said as much before. What I rejoice in knowing of him is that he had clear eyes and open heart for all things and deeds appertaining to his life; that whatever he discerned, was discerned impartially; what he said, was said securely; and that in all functions of thought, experiment, or communication, he was sure to be eventually right, and serviceable to mankind, whether out of the treasury of eternal knowledge he brought forth things new or old.

This is the essential difference between the work of men of true genius and the agitation of temporary and popular power. The first root of their usefulness is in subjection of their vanity to their purpose. It is not in calibre or range of intellect that men vitally differ; every phase of mental character has honorable office; but the vital difference between the strong and the weak—or let me say rather, between the availing and valueless intelligence—is in the relation of the love of self to the love of the subject or occupation. Many an Alpine traveller, many a busy man of science, volubly represent to us their pleasure in the Alps; but I scarcely recognize one who would not willingly see them all ground down into gravel, on condition of his being the first to exhibit a pebble of it at the Royal Institution. Whereas it may be felt in any single page of Forbes’ writing, or De Saussure’s, that they love crag and glacier for their own sake’s sake; that they question their secrets in reverent and solemn thirst: not at all that they may communicate them at breakfast to the readers of the Daily News—and that, although there were no news, no institutions, no leading articles, no medals, no money, and no mob, in the world, these men would still labor, and be glad, though all their knowledge was to rest with them at last in the silence of the snows, or only to be taught to peasant children sitting in the shade of pines.

And whatever Forbes did or spoke during his noble life was in this manner patiently and permanently true. The passage of his lectures in which he shows the folly of Macaulay’s assertion that “The giants of one generation are the pigmies of the next,”¹⁷⁹ beautiful in itself, is more interesting yet in the indication it gives of the general grasp and melodious tone of Forbes’ reverent intellect, as opposed to the discordant insolence of modernism. His mind grew and took color like an Alpine flower, rooted on rock, and perennial in flower; while Macaulay’s swelled like a puff-ball in an unwholesome pasture, and projected itself far round in deleterious dust.

I had intended saying a few words more touching the difference in temper, and probity of heart, between Forbes and Agassiz, as manifested in the documents now¹⁸⁰ laid before the public. And as far as my own feelings are concerned, the death of Agassiz¹⁸¹ would not have caused my withholding a word. For in all utterance of blame or praise, I have striven always to be kind to the living—just to the dead. But in deference to the wish of the son of Forbes, I keep silence: I willingly leave sentence to be pronounced by time, above their two graves.

John Ruskin.

The following letters,¹⁸² one from Forbes to myself, written ten years ago, and the other from one of his pupils, received by me a few weeks since, must, however, take their due place among the other evidence on which such judgment is to be given.

J. R.

II.
MISCELLANEOUS

[From “The Artist and Amateur’s Magazine” (edited by E. V. Rippingille), February 1844, pp. 314-319.]
REFLECTIONS IN WATER. ¹⁸³

To the Editor of “The Artist and Amateur’s Magazine.”

Sir: The phenomena of light and shade, rendered to the eye by the surface or substance of water, are so intricate and so multitudinous, that had I wished fully to investigate, or even fully to state them, a volume instead of a page would have been required for the task. In the paragraphs¹⁸⁴ which I devoted to the subject I expressed, as briefly as possible, the laws which are of most general application—with which artists are indeed so universally familiar, that I conceived it altogether unnecessary to prove or support them: but since I have expressed them in as few words as possible, I cannot afford to have any of those words missed or disregarded; and therefore when I say that on clear water, near the eye, there is no shadow, I must not be understood to mean that on muddy water, far from the eye, there is no shadow. As, however, your correspondent appears to deny my position in toto, and as many persons, on their first glance at the subject, might be inclined to do the same, you will perhaps excuse me for occupying a page or two with a more explicit statement, both of facts and principles, than my limits admitted in the “Modern Painters.”

First, for the experimental proof of my assertion that “on clear water, near the eye, there is no shadow.” Your correspondent’s trial with the tub is somewhat cumbrous and inconvenient;¹⁸⁵ a far more simple experiment will settle the matter. Fill a tumbler with water; throw into it a narrow strip of white paper; put the tumbler into sunshine; dip your finger into the water between the paper and the sun, so as to throw a shadow across the paper and on the water. The shadow will of course be distinct on the paper, but on the water absolutely and totally invisible.

This simple trial of the fact, and your explanation of the principle given in your ninth number,¹⁸⁶ are sufficient proof and explanation of my assertion; and if your correspondent requires authority as well as ocular demonstration, he has only to ask Stanfield or Copley Fielding, or any other good painter of sea; the latter, indeed, was the person who first pointed out the fact to me when a boy. What then, it remains to be determined, are those lights and shades on the sea, which, for the sake of clearness, and because they appear such to the ordinary observer, I have spoken of as “horizontal lines,” and which have every appearance of being cast by the clouds like real shadows? I imagined that I had been sufficiently explicit on this subject both at pages 330 and 363:¹⁸⁷ but your correspondent appears to have confused himself by inaccurately receiving the term shadow as if it meant darkness of any kind; whereas my second sentence—“every darkness on water is reflection, not shadow”—might have shown him that I used it in its particular sense, as meaning the absence of positive light on a visible surface. Thus, in endeavoring to support his assertion that the shadows on the sea are as distinct as on a grass field, he says that they are so by contrast with the “light reflected from its polished surface;” thus showing at once that he has been speaking and thinking all along, not of shadow, but of the absence of reflected light—an absence which is no more shadow than the absence of the image of a piece of white paper in a mirror is shadow on the mirror.

The question, therefore, is one of terms rather than of things; and before proceeding it will be necessary for me to make your correspondent understand thoroughly what is meant by the term shadow as opposed to that of reflection.

Let us stand on the sea-shore on a cloudless night, with a full moon over the sea, and a swell on the water. Of course a long line of splendor will be seen on the waves under the moon, reaching from the horizon to our very feet. But are those waves between the moon and us actually more illuminated than any other part of the sea? Not one whit. The whole surface of the sea is under the same full light, but the waves between the moon and us are the only ones which are in a position to reflect that light to our eyes. The sea on both sides of that path of light is in perfect darkness—almost black. But is it so from shadow? Not so, for there is nothing to intercept the moonlight from it: it is so from position, because it cannot reflect any of the rays which fall on it to our eyes, but reflects instead the dark vault of the night sky. Both the darkness and the light on it, therefore—and they are as violently contrasted as may well be—are nothing but reflections, the whole surface of the water being under one blaze of moonlight, entirely unshaded by any intervening object whatsoever.

Now, then, we can understand the cause of the chiaro-scuro of the sea by daylight with lateral sun. Where the sunlight reaches the water, every ripple, wave, or swell reflects to the eye from some of its planes either the image of the sun or some portion of the neighboring bright sky. Where the cloud interposes between the sun and sea, all these luminous reflections are prevented, and the raised planes of the waves reflect only the dark under-surface of the cloud; and hence, by the multiplication of the images, spaces of light and shade are produced, which lie on the sea precisely in the position of real or positive light and shadows—corresponding to the outlines of the clouds—laterally cast, and therefore seen in addition to, and at the same time with, the ordinary or direct reflection, vigorously contrasted, the lights being often a blaze of gold, and the shadows a dark leaden gray; and yet, I repeat, they are no more real lights, or real shadows, on the sea, than the image of a black coat is a shadow on a mirror, or the image of white paper a light upon it.¹⁸⁸

Are there, then, no shadows whatsoever upon the sea? Not so. My assertion is simply that there are none on clear water near the eye. I shall briefly state a few of the circumstances which give rise to real shadow in distant effect.

I. Any admixture of opaque coloring matter, as of mud, chalk, or powdered granite renders water capable of distinct shadow, which is cast on the earthy and solid particles suspended in the liquid. None of the seas on our south-eastern coast are so clear as to be absolutely incapable of shade; and the faint tint, though scarcely perceptible to a near observer,¹⁸⁹ is sufficiently manifest when seen in large extent from a distance, especially when contrasted, as your correspondent says, with reflected lights. This was one reason for my introducing the words—“near the eye.”

There is, however, a peculiarity in the appearances of such shadows which requires especial notice. It is not merely the transparency of water, but its polished surface, and consequent reflective power, which render it incapable of shadow. A perfectly opaque body, if its power of reflection be perfect, receives no shadow (this I shall presently prove); and therefore, in any lustrous body, the incapability of shadow is in proportion to the power of reflection. Now the power of reflection in water varies with the angle of the impinging ray, being of course greatest when that angle is least: and thus, when we look along the water at a low angle, its power of reflection maintains its incapability of shadow to a considerable extent, in spite of its containing suspended opaque matter; whereas, when we look down upon water from a height, as we then receive from it only rays which have fallen on it at a large angle, a great number of those rays are unreflected from the surface, but penetrate beneath the surface, and are then reflected¹⁹⁰ from the suspended opaque matter: thus rendering shadows clearly visible which, at a small angle, would have been altogether unperceived.

II. But it is not merely the presence of opaque matter which renders shadows visible on the sea seen from a height. The eye, when elevated above the water, receives rays reflected from the bottom, of which, when near the water, it is insensible. I have seen the bottom at seven fathoms, so that I could count its pebbles, from the cliffs of the Cornish coast; and the broad effect of the light and shade of the bottom is discernible at enormous depths. In fact, it is difficult to say at what depth the rays returned from the bottom become absolutely ineffective—perhaps not until we get fairly out into blue water. Hence, with a white or sandy shore, shadows forcible enough to afford conspicuous variety of color may be seen from a height of two or three hundred feet.

III. The actual color of the sea itself is an important cause of shadow in distant effect. Of the ultimate causes of local color in water I am not ashamed to confess my total ignorance, for I believe Sir David Brewster himself has not elucidated them. Every river in Switzerland has a different hue. The lake of Geneva, commonly blue, appears, under a fresh breeze, striped with blue and bright red; and the hues of coast-sea are as various as those of a dolphin; but, whatever be the cause of their variety, their intensity is, of course, dependent on the presence of sun-light. The sea under shade is commonly of a cold gray hue; in sun-light it is susceptible of vivid and exquisite coloring: and thus the forms of clouds are traced on its surface, not by light and shade, but by variation of color by grays opposed to greens, blues to rose-tints, etc. All such phenomena are chiefly visible from a height and a distance; and thus furnished me with additional reasons for introducing the words—“near the eye.”

IV. Local color is, however, the cause of one beautiful kind of chiaro-scuro, visible when we are close to the water—shadows cast, not on the waves, but through them, as through misty air. When a wave is raised so as to let the sun-light through a portion of its body, the contrast of the transparent chrysoprase green of the illuminated parts with the darkness of the shadowed is exquisitely beautiful.

Hitherto, however, I have been speaking chiefly of the transparency of water as the source of its incapability of shadow. I have still to demonstrate the effect of its polished surface.

Let your correspondent pour an ounce or two of quicksilver into a flat white saucer, and, throwing a strip of white paper into the middle of the mercury, as before into the water, interpose an upright bit of stick between it and the sun: he will then have the pleasure of seeing the shadow of the stick sharply defined on the paper and the edge of the saucer, while on the intermediate portion of mercury it will be totally invisible¹⁹¹. Mercury is a perfectly opaque body, and its incapability of shadow is entirely owing to the perfection of its polished surface. Thus, then, whether water be considered as transparent or reflective (and according to its position it is one or the other, or partially both—for in the exact degree that it is the one, it is not the other), it is equally incapable of shadow. But as on distant water, so also on near water, when broken, pseudo shadows take place, which are in reality nothing more than the aggregates of reflections. In the illuminated space of the wave, from every plane turned towards the sun there flashes an image of the sun; in the un-illuminated space there is seen on every such plane only the dark image of the interposed body. Every wreath of the foam, every jet of the spray, reflects in the sunlight a thousand diminished suns, and refracts their rays into a thousand colors; while in the shadowed parts the same broken parts of the wave appear only in dead, cold white; and thus pseudo shadows are caused, occupying the position of real shadows, defined in portions of their edge with equal sharpness: and yet, I repeat, they are no more real shadows than the image of a piece of black cloth is a shadow on a mirror.

But your correspondent will say, “What does it matter to me, or to the artist, whether they are shadows or not? They are darkness, and they supply the place of shadows, and that it is all I contend for.” Not so. They do not supply the place of shadows; they are divided from them by this broad distinction, that while shadow causes uniform deepening of the ground-tint in the objects which it affects, these pseudo shadows are merely portions of that ground-tint itself undeepened, but cut out and rendered conspicuous by flashes of light irregularly disposed around it. The ground-tint both of shadowed and illumined parts is precisely the same—a pure pale gray, catching as it moves the hues of the sky and clouds; but on this, in the illumined spaces, there fall touches and flashes of intense reflected light, which are absent in the shadow. If, for the sake of illustration, we consider the wave as hung with a certain quantity of lamps, irregularly disposed, the shape and extent of a shadow on that wave will be marked by the lamps being all put out within its influence, while the tint of the water itself is entirely unaffected by it.

The works of Stanfield will supply your correspondent with perfect and admirable illustrations of this principle. His water-tint is equally clear and luminous whether in sunshine or shade; but the whole lustre of the illumined parts is attained by bright isolated touches of reflected light.

The works of Turner will supply us with still more striking examples, especially in cases where slanting sunbeams are cast from a low sun along breakers, when the shadows will be found in a state of perpetual transition, now defined for an instant on a mass of foam, then lost in an interval of smooth water, then coming through the body of a transparent wave, then passing off into the air upon the dust of the spray—supplying, as they do in nature, exhaustless combinations of ethereal beauty. From Turner’s habit of choosing for his subjects sea much broken with foam, the shadows in his works are more conspicuous than in Stanfield’s, and may be studied to greater advantage. To the works of these great painters, those of Vandevelde may be opposed for instances of the impossible. The black shadows of this latter painter’s near waves supply us with innumerable and most illustrative examples of everything which sea shadows are not.

Finally, let me recommend your correspondent, if he wishes to obtain perfect knowledge of the effects of shadow on water, whether calm or agitated, to go through a systematic examination of the works of Turner. He will find every phenomenon of this kind noted in them with the most exquisite fidelity. The Alnwick Castle, with the shadow of the bridge cast on the dull surface of the moat, and mixing with the reflection, is the most finished piece of water-painting with which I am acquainted. Some of the recent Venices have afforded exquisite instances of the change of color in water caused by shadow, the illumined water being transparent and green, while in the shade it loses its own color, and takes the blue of the sky.

But I have already, Sir, occupied far too many of your valuable pages, and I must close the subject, although hundreds of points occur to me which I have not yet illustrated¹⁹². The discussion respecting the Grotto of Capri is somewhat irrelevant, and I will not enter upon it, as thousands of laws respecting light and color are there brought into play, in addition to the water’s incapability of shadow.¹⁹³ But it is somewhat singular that the Newtonian principle, which your correspondent enunciates in conclusion, is the very cause of the incapability of shadow which he disputes. I am not, however, writing a treatise on optics, and therefore can at present do no more than simply explain what the Newtonian law actually signifies, since, by your correspondent’s enunciation of it, “pellucid substances reflect light only from their surfaces,” an inexperienced reader might be led to conclude that opaque bodies reflected light from something else than their surfaces.

The law is, that whatever number of rays escape reflection at the surface of water, pass through its body without further reflection, being therein weakened, but not reflected; but that, where they pass out of the water again, as, for instance, if there be air-bubbles at the bottom, giving an under-surface to the water, there a number of rays are reflected from that under-surface, and do not pass out of the water, but return to the eye; thus causing the bright luminosity of the under bubbles. Thus water reflects from both its surfaces—it reflects it when passing out as well as when entering; but it reflects none whatever from its own interior mass. If it did, it would be capable of shadow.