Gibbon, Lessing, Newton, Leibnitz, Berkeley, Mill, and other great names, are examples of such a lengthy process of development. Indeed, there is much to support Mr. Galton's view that eminent men surpass ordinary men not only in superiority from the first, but also in a more prolonged development.7 Such a conclusion, it may be observed, would seem to accord with what we know of the general laws of mental evolution. For if we compare the different races of man, or the different species of animals, we find that, in general, the higher the cerebral organisation attained, the longer the process of development. Men of great original power, having the most highly organised type of brain, may be expected to illustrate the most prolonged movement of mental growth. From this point of view we are able, I think, to see the difference between the course of development of a truly great intellect and that of a precocious but stunted intelligence. That there are many clever children that never come to anything,' or at least do not fulfil their early promise, is a fact which nobody, probably, will deny. Some of these would perhaps have distinguished themselves if they had had better opportunities, or at least more ambition and energy of character. But allowing for this, one finds a good remainder of youths who appear to have had a rapid but early arrested mental development. Such an early display of quickness followed by a lengthy period of ordinary mediocrity, or even dulness, looks like a too great forwardness of ordinary human ability. In other words, the clever child is in this case not an exceptional being, but a quite average one, whose cerebral development has somehow outrun the common attainment of his years. He is like a tree that bears fruit too soon. On the other hand, the man of superb ability is precocious just because, having a finer brain to start with, he is raised above the average mental stature of his years. He rather resembles a tree which shoots at once above the surrounding trees, though it may mature and bring forth fruit later than they. JAMES SULLY. See Hereditary Genius, p. 44. Mr. Galton has kindly sent me a fuller statement of his view on this point. LIGHT AND WATER-COLOURS. 'ESTO perpetua!' is the motto prefixed to one of Bewick's charming little cuts, representing village boys building up a snow man; and Michel Angelo himself once modelled a colossus of snow by command of his patron Piero de' Medici. Doubtless the statue was a masterpiece; but to have been enduring it should have been executed in some frozen Malebolge' or the Arctic regions, not in Florence. Scarcely less inimical to some creations of human genius, as admirable in their way as the sculptures of Michel Angelo, are the mere rays of the sun, wasting and waning masterworks of man the more they gladden and vivify the world in which he moves. Scarcely less instant and fatal indeed is the bleaching action of the sun's light on artists' pigments-to many of them at all events, and those usually the most brilliant and beautiful-than is its genial heat on ice and snow. There has been an animated correspondence in the Times on the action of light on water-colours, incidentally raised by a communication of mine, not intended to provoke controversy. I imagined, indeed, that the fading of water-colour pictures and drawings was so obvious and notorious as to be beyond dispute, and my intention was to suggest the best means of counteracting the evil. I was, however, greatly mistaken. I found indeed, to my infinite surprise, that darkness reigned where the fullest enlightenment might have been looked for, and where, literally speaking, darkness was a palliative, light was indirectly recommended. The unqualified assertion, utterly erroneous as it is, that watercolour drawings not only do not fade, but that they actually deepen in tone by age, was advanced by the highest authorities and masters of the art in question. This dictum is indeed astonishing; it is the very reverse of the truth and wofully mischievous in its tendency. Its dogmatic promulgation at this time has alone led me to return to the subject. The question ought indeed to be settled once for all, for on its right understanding literally depends nothing less than the preservation, for indefinite periods, of the admirable masterpieces of a truly national art, or their ultimate extinction and loss to the world. Artists' pigments, whether they are embodied as water' or 'oil' colours or in any other vehicles (generally speaking the substances employed are the same), are of the most varied and diverse nature and origin-mineral, vegetable, and animal. Natural metallic oxides and earths, complex chemical compounds, gums, extracts and the inspissated sap of trees and plants, juices and secretions from insects and the higher animals, are alike pressed into the service of the painter. Modern science and commercial enterprise have in our own time vastly augmented the number and variety of these colouring substances. Unquestionably thereby the artist's palette has been greatly enriched and the physical means of art extended; but whether at the same time those means have been strengthened and improved in the sense of durability is another question. Painters in the old times, when their pigments were comparatively few and simple in their nature, were usually in the habit of preparing, purifying, and refining their own colours. They were alive and attentive to the physical properties of the substances they employed, discarding, as far as they were able, such as were notoriously fugacious in their nature or uncertain in their action upon other colours. Now, on the other hand, artists, as a rule, simply ignore all this, accepting with blind faith whatever the colour merchant offers them; ever craving for some newer and more vivid tint, be it as fixed and eternal as the sapphire's blue or the ruby's red or as shortlived and fleeting as a dream. The colour merchant, however, if he be unscrupulous or even only ignorant and careless, may work infinite mischief to art and artists; as it is, the artist is absolutely at his mercy. The old and salutary motto Caveat emptor' scarcely applies in this case, for there are seldom any instant available means of testing or verifying the representations of the eager tradesman. Certain it is that every day some fresh pigment, guaranteed as absolutely stable and permanent, but of the properties of which the vendor himself may have had no adequate experience, is foisted on the helpless, unsuspecting painter. But this is nothing less than the most cruel and insufferable fraud, the consequences of which it seems scarcely necessary to dwell upon. To this subject, however, the attention of eminent scientific authorities is now being directed; the field as yet has been but little tilled, and there is both honour and profit to be gleaned by the qualified and earnest labourer in it. This matter lies, indeed, at the root of the question before us; it is for chemists and other scientists to deal with it effectually. The general subject of the preservation of the admirable works of past times in water-colours, however, is a manysided one, and there is so great a wealth of illustration to be brought to bear upon it that I shall probably find it impossible to entirely avoid trenching on the province of the scientist, or to steer quite clear of topics not strictly relevant to the speciality under consideration. Thus, for instance, the two processes of oil and water-colour painting, whilst they have in their nature much in common, are also in many respects radically different, and the incidental elucidation of some of the main points of difference will be essential to my argument and necessary in disabusing the public mind of more than one fallacy. There are two especial agencies inimical to the permanence of painters' pigments '-chemical action and reaction in colours when included within some common medium or vehicle ('locked up,' as it is technically called, by gums, size, oils, or varnishes) and the bleaching or fading action of the sun's light. Of these agencies the former is of little moment in water-colour painting, but the latter, on the contrary, is the active and especial enemy of that art. 6 I am not a scientist, so I shall try to confine myself to the practical illustration of facts, avoiding as far as possible any endeavour to explain the theory of the action of light on colouring substances. Of course if it can be shown that some pigments, heretofore habitually made use of by water-colour painters, are more or less fugacious, while others are stable and permanent, and if the two classes of colours have been made use of in the same picture, it stands to reason that any work so executed must, if freely exposed to the light of day, suffer gradual alteration and deterioration in an unequal manner. That is to say, portions of the work will retain their original force and purity of tint, while others will change in varying measure, or even vanish altogether. Obviously for any picture or drawing to be perennial—that is, unfading—if exposed to daylight, it would need to be entirely executed throughout with unalterable colours. Such a selection of tints is doubtless quite possible, but as water-colour chromatography stands at present this would entail the abandonment of a great number of the most beautiful and serviceable pigments in current use. There is, however, hope for the future; if modern science were once seriously brought to bear on the question of the replacement of fugacious or uncertain pigments by permanent and unchanging ones, it cannot be but that adequate and abundant substitutes should be soon forthcoming. The resources of nature are infinite; in this case doubtless it rests with man only to force the secrets from her reluctant breast. Of the pigments in present use, as might have been expected, the most stable are those of the mineral kingdom; many such colours are in fact perhaps absolutely unalterable in so far as the influence of light is concerned. On the other hand, the great majority of colours of vegetable and animal origin are more or less unstable and fleeting. I cannot indeed call to mind a single pigment in these categories which can be deemed absolutely permanent, while many of them have an existence scarcely less brief than that of the gaily coloured flowers whose tints they rival or surpass. The essentially non-permanent pigments of course are of every degree of mutability, some reasonably resistant and comparatively long-lived, others, so to speak, whose existence is to be measured by days and months rather than years or generations. For this mutability, in whatever measure nevertheless, there is a sovereign remedy: as the active enemy is light so is the saviour darkness. It is probable even that the most evanescent pigments would be unchanged if kept entirely secluded from the light. It is needless to say, however, that drawings are not meant to be hidden under a bushel. The bushel, however, will serve our turn for the moment. Some people are very hard to convince, and it will be well to thoroughly clinch the nail we are driving. Water-colour drawings, as the President of the Royal Water Colour Institute says, do not fade. He is speaking, be it noted, of antecedent works of English painters. Now let anyone take one of these drawings, something of little value (for it is question of an experiment in corpore vili), framed and glazed as usual. Let one half of the drawing be covered with several sheets of stout paper pasted outside the glass, so as to form a perfectly opaque dark envelope, the other half remaining visible, as before. Let the drawing be then hung up and exposed to the light, say for a year. To suspend it face outwards in a window casement is the best method. At the end of the period let the paper covering of the darkened half be removed; the result will, I apprehend, be convincing to the most incredulous person. The drawing will have become a dual work, one half (the darkened one) remaining just as it was at first, whilst the other will have faded and become a pale, disjointed muddle, the two halves being as distinctly and sharply bounded as if a wet sponge had been passed over a moiety of the surface. More striking still is another demonstration. Both experiments, by the way, have been frequently carried out, and the most careful notes taken of the results by more than one enquirer. It is this: Let a series of even flat tints of water-colours be laid in parallel strips or bands side by side on a sheet of paper, the colours chosen being such as are currently furnished by the colour merchant, and to which varying repute as to durability attaches. Take, on the one hand, the carbon blacks, Indian ink and lampblack, simple oxides and ochres, such as Indian red, light red, burnt sienna, and yellow ochre, mineral and chemically prepared colours, such as ultramarine, cobalt, and aureolin; and on the other hand carmine, crimson lake, madder brown, sepia, bistre, indigo, sap green, gamboge, gallstone, and brown pink. Cut the sheet of paper in two across the series of parallel bands, so as to have two equal sets of tints. Keep one of |