The grays are the natural cold correlatives, or contrasts, of the warm semi-neutral browns, as well as degradations of blue and its allies. Hence blue added to brown throws it into or toward the class of grays, and hence grays are equally abundant in nature and necessary in art: in both they comprehend a widely diffused and beautiful play of retiring colours in skies, distances, carnations, and the shadowings and reflections of pure light, &c. Gray is, indeed, the colour of space, and has therefore the property of diffusing breadth in a picture, while it furnishes at the same time good connecting tints, or media, for harmonizing the general colouring. Consequently the grays are among the most essential hues of the art, though they must not be suffered to predominate where the subject or sentiment does not require it, lest they cast over the painting that gloom or leaden dulness reprobated by Sir Joshua Reynolds; yet in solemn works they are wonderfully effective, and proper ruling colours. Nature supplies these hues from the sky abundantly and effectively throughout landscape, and Rubens has employed them as generally to correct and give value to his colouring, with fine natural perception in this branch of his art: witness his works in the National Gallery, and in that of the Luxembourg. According to the foregoing relations, grays favour the effects and force of warm colours, which in their turn also give value to grays. It is hence that the tender gray distances of a landscape are assisted, enlivened, and kept in place by warm and forcible colouring in the foreground, gradually connected through intermediate objects and middle distances by demi-tints declining into gray; a union which secures full value to the colours and objects, and by reconciling opposites gives repose to the eye. As a general rule, it may be inferred that half of a picture should be of a neutral hue, to ensure the harmony of the colouring; or at least that a balance of colour and neutrality is quite as essential to the best effect of a painting as a like balance of light and shade. 283. MINERAL GRAY, or Mineral Gr_e_y, as it is often improperly spelt, is obtainable from the lapis lazuli, after the blue and ash have been worked out. So derived, it is a refuse article, worthless if the stone has been skilfully exhausted of its ultramarine. As this is now generally the case, the best mineral gray is no longer a waste product, but a lower species of ash, a pale whitish blue with a grey cast. Possessing the permanence of ultramarine, it may be regarded in colour as a very weak variety of that blue, diluted with a large quantity of white slightly tinged by black. A pigment peculiar to oil painting, it is admirably adapted to that gray semi-neutrality, the prevalence of which in nature has been just remarked. For misty mornings, cloudy skies, and the like, this gray will be found useful. 284. MIXED GRAY