Of a ruling Principle, or Law, we can only get a notion by observing the effects of certain things in relation to the mind; the uniformity of which leads us to infer something which is unchangeable and permanent. It is in this way that, either directly or indirectly, we learn the existence of certain laws that invariably control us. Thus, indirectly, from our disgust at monotony, we infer the necessity of variety. But variety, when carried to excess, results in weariness. Some limitation, therefore, seems no less needed. It is, however, obvious, that all attempts to fix the limit to Variety, that shall apply as a universal rule, must be nugatory, inasmuch as the _degree_ must depend on the _kind_, and the kind on the subject treated. For instance, if the subject be of a gay and light character, and the emotions intended to be excited of a similar nature, the variety may be carried to a far greater extent than in one of a graver character. In the celebrated Marriage at Cana, by Paul Veronese, we see it carried, perhaps, to its utmost limits; and to such an extent, that an hour's travel will hardly conduct us through all its parts; yet we feel no weariness throughout this journey, nay, we are quite unconscious of the time it has taken. It is no disparagement of this remarkable picture, if we consider the subject, not according to the title it bears, but as what the Artist has actually made it,--that is, as a Venetian entertainment; and also the effect intended, which was to delight by the exhibition of a gorgeous _pageant_. And in this he has succeeded to a degree unexampled; for literally the eye may be said to _dance_ through the picture, scarcely lighting on one part before it is drawn to another, and another, and another, as by a kind of witchery; while the subtile interlocking of each successive novelty leaves it no choice, but, seducing it onward, still keeps it in motion, till the giddy sense seems to call on the imagination to join in the revel; and every poetic temperament answers to the call, bringing visions of its own, that mingle with the painted crowd, exchanging forms, and giving them voice, like the creatures of a dream. To those who have never seen this picture, our account of its effect may perhaps appear incredible when they are told, that it not only has no story, but not a single expression to which you can attach a sentiment. It is nevertheless for this very reason that we here cite it, as a triumphant verification of those immutable laws of the mind to which the principles of Composition are supposed to appeal; where the simple technic exhibition, or illustration of _Principles_, without story, or thought, or a single definite expression, has still the power to possess and to fill us with a thousand delightful emotions.