It has been said that black substances reflect a small quantity of white light, which receives the complementary of the colour contiguous to the black. If this colour is deep, it gives rise to a luminous complementary, such as orange, or yellow, and enfeebles the black; while the other complementaries, such as violet or green, strengthen and purify it. In colours associated with black, if green is juxtaposed therewith, its complementary red, added to the black, makes it seem rusty. Those colours which best associate with black are orange, yellow, blue, and violet. It would be well to remember that black, being always deeper than the juxtaposed colour, entails contrast of tone, and tends to lower the tone of that colour. Most of the black pigments in use are obtained by charring, and owe their colour to the carbon they contain. As the objects of vegetal and animal nature may be blackened through every degree of impurity by the action of fire, black substances more or less fitted for pigments abound. The following are the chief native and artificial black pigments, or colours available as such:-- 289. BLACK LEAD, _Plumbago_, or _Graphite_, contains in spite of its name no lead, being simply a species of carbon or charcoal. In most specimens iron is present, varying in quantity from a mere trace up to five per cent, together with silica and alumina. Sometimes manganese and titanic acid are likewise found. It is curious that carbon should occur in two distinct and very dissimilar forms--as diamond, and as graphite; one, white, hard, and transparent; the other, black, soft, and opaque: the artist, therefore, who uses a pigment of plumbago, paints with nothing more or less than a black diamond. The best graphite, the finest and most valuable for pencils, is yielded by the mine of Borrowdale, at the west end of Derwent Lake, in Cumberland, where it was first wrought during the reign of Elizabeth. A kind of irregular vein traverses the ancient slate-beds of that district, furnishing the carbon of an iron-grey colour, metallic lustre, and soft and greasy to the touch. Universally employed in the form of crayons, &c. in sketching, designing, and drawing, until of late years it was not acknowledged as a pigment: yet its powers in this respect claim a place for it. As a water-colour, levigated in gum in the usual manner, it may be effectively used with rapidity and freedom in the shading and finishing of pencil drawings, or as a substitute therein for Indian ink. Even in oil it may be employed occasionally, as it possesses remarkably the property of covering, forms very pure grey, dries quickly, injures no colour chemically, and endures for ever. These qualities render it the most eligible black for adding to white in minute quantity to preserve the neutrality of its tint.