The fourth and last division of our subject is the Harmony of Parts; or the essential agreement of one part with another, and of each with the whole. In addition to our first general definition, we may further observe, that by a Whole in Painting is signified the complete expression, by means of form, color, light, and shadow, of one thought, or series of thoughts, having for their end some particular truth, or sentiment, or action, or mood of mind. We say _thought_, because no images, however put together, can ever be separated by the mind from other and extraneous images, so as to comprise a positive whole, unless they be limited by some intellectual boundary. A picture wanting this may have fine parts, but is not a Composition, which implies parts united to each other, and also suited to some specific purpose, otherwise they cannot be known as united. Since Harmony, therefore, cannot be conceived of without reference to a whole, so neither can a whole be imagined without fitness of parts. To give this fitness, then, is the ultimate task and test of genius: it is, in fact, calling form and life out of what before was but a chaos of materials, and making them the subject and exponents of the will. As the master-principle, also, it is the disposer, regulator, and modifier of shape, line, and quantity, adding, diminishing, changing, shaping, till it becomes clear and intelligible, and it finally manifests itself in pleasurable identity with the harmony within us. To reduce the operation of this principle to precise rules is, perhaps, without the province of human power: we might else expect to see poets and painters made by recipe. As in many other operations of the mind, we must here be content to note a few of the more tangible facts, if we may be allowed the phrase, which have occasionally been gathered by observation during the process. The first fact presented is, that equal quantities, when coming together, produce monotony, and, if at all admissible, are only so when absolutely needed, at a proper distance, to echo back or recall the theme, which would otherwise be lost in the excess of variety. We speak of quantity here as of a mass, not of the minutiae; for _the essential components_ of a part may often be _equal quantities_, (as in a piece of architecture, of armour, &c.,) which are analogous to poetic feet, for instance, a spondee. The same effect we find from parallel lines and repetition of shapes. Hence we obtain the law of a limited variety. The next is, that the quantities must be so disposed as to balance each other; otherwise, if all or too many of the larger be on one side, they will endanger the imaginary circle, or other figure, by which every composition is supposed to be bounded, making it appear "lop-sided," or to be falling either in upon the smaller quantities, or out of the picture: from which we infer the necessity of balance. If, without others to counteract and restrain them, the parts