It is not mere unrelated variety which charms us, for a forest of all manner of trees is poor in its effect, while a mass of one species of trees is sublime;--the swan, with its purity of unbroken whiteness, is one of the most beautiful of creatures. It is, indeed, only harmonious and chordal variety, that variety which is necessary to secure and extend unity (for the greater the number of objects which by their differences become members of one another, the more extended and sublime is their unity), which is essentially beautiful. _Variety_ is never so conspicuous as when united with some intimation of _unity_. For example, the perpetual change of clouds is monotonous in its very dissimilarity, nor is difference ever striking where no connection is implied; but if through a range of barred clouds crossing half the heavens, all governed by the same forces, and falling into one general form, there be yet a marked and evident dissimilarity between each member of the great mass--one more finely drawn, the next more delicately moulded, the next more gracefully bent--each broken into differently modelled and variously numbered groups,--the _variety_ is doubly striking because contrasted with the perfect _unity_ and _symmetry_ of which it forms a part. Now, of that which is thus necessary to the perfection of things, all types and suggestions must be beautiful in whatever way they may suggest or manifest it. To the perfection of beauty in lines, colors, forms, masses, or multitudes, the appearance of unity is absolutely essential. Let the artist look to it, that our pictures may gain expression; our music cease to weary us through the unceasing dissimilarity of its parts, highly adorned arabesques running into each other, graceful, but without significance, without any perceptible principle of unity in the jarring '_motifs_;' and our poems have some certain theme, that their highly wrought details may not confuse and bewilder the spirit always in search of some central unity. Like the burning sands which, clinging not together in any sweet union of fellowship, blind and confuse us with their drifting masses, are all such essays in art; for an idea capable of quickening an artistic creation must be vitally One, and every great work, notwithstanding its variety and the manifold complexity of its parts, must form a Whole.