Now in nothing more than in painting is prevention better than cure--indeed cure may be said to be here out of the question: for good or for evil a picture once painted is painted for ever. Without a strong constitution there is no hope for it; no chemistry can strengthen the sickly frame, restore the faded colour, stop the ravages of consumption: Science stands helpless before dying Art. And yet, she sighs to think, it might have been otherwise. If durable pigments had been employed, if her counsel had been sought, this need not have been. In the history of modern art the use and abuse of colours would furnish a sad chapter, telling of gross ignorance, and a grosser indifference. Happily there is promise of a healthier state of things. When this comes, Art will be less shy to consult her sister: in the interests of both there should be closer union. Without waiting till the picture is finished--for then it will be too late--let her, if in doubt, frankly display the contents of her palette and ask advice. Now, not knowing what pigments are chosen or how they are used, never standing by and watching the progress of the work, how can Science lend her aid? She would willingly, for she herself needs help: at present her knowledge is limited, not so much of the chemistry of colours as of the properties of pigments. She seeks to mix her pound of theory with an ounce of practice, and craves a warmer welcome to the studio. For any approximation to the truth to be arrived at, facts must be noted with the conditions under which they occur, not by one sister alone nor by the other alone, but by both. In future, Art and Science should go hand in hand, mutually dependent on each other, mutually trustful of each other, working with and for each other, earnestly and patiently. FOOTNOTES: [C] Light is either direct or diffused--direct, when the sun's rays fall upon any object; diffused, when ordinary daylight illumines objects with white light, causing them to appear of their peculiar colours. ADDENDUM. With the present rapid progress of applied chemistry, an addendum in a work of this kind is quite excusable. Even while the book is being printed some fact may be announced which the author or editor would wish to insert. In our case this has happened. Very recently there has been introduced in France as a pigment 308. TUNGSTEN WHITE,