Perhaps what is offered above as a key to the peculiar expression of Titian’s heads may also serve to explain the difference between painting or copying a portrait. As the perfection of his faces consists in the entire unity and coincidence of all the parts, so the difficulty of ordinary portrait-painting is to bring them to bear at all, or to piece one feature, or one day’s labour on to another. In copying, this difficulty does not occur at all. The human face is not one thing, as the vulgar suppose, nor does it remain always the same. It has infinite varieties, which the artist is obliged to notice and to reconcile, or he will make strange work. Not only the light and shade upon it do not continue for two minutes the same: the position of the head constantly varies (or if you are strict with a sitter, he grows sullen and stupid), each feature is in motion every moment, even while the artist is working at it, and in the course of a day the whole expression of the countenance undergoes a change, so that the expression which you gave to the forehead or eyes yesterday is totally incompatible with that which you have to give to the mouth to-day. You can only bring it back again to the same point or give it a consistent construction by an effort of imagination, or a strong feeling of character; and you must connect the features together less by the eye than by the mind. The mere setting down what you see in this medley of successive, teazing, contradictory impressions, would never do; either you must continually efface what you have done the instant before, or if you retain it, you will produce a piece of patchwork, worse than any caricature. There must be a comprehension of the whole, and in truth a _moral sense_ (as well as a literal one) to unravel the confusion, and guide you through the labyrinth of shifting muscles and features. You must feel what _this_ means, and dive into the hidden soul, in order to know whether _that_ is as it ought to be; for you cannot be sure that it remains as it was. Portrait-painting is, then, painting from recollection and from a conception of character, with the object before us to assist the memory and understanding. In copying, on the contrary, one part does not run away and leave you in the lurch, while you are intent upon another. You have only to attend to what is before you, and finish it carefully a bit at a time, and you are sure that the whole will come right. One might parcel it out into squares, as in engraving, and copy one at a time, without seeing or thinking of the rest. I do not say that a conception of the whole, and a feeling of the art will not abridge the labour of copying, or produce a truer likeness; but it is the changeableness or identity of the object that chiefly constitutes the difficulty or facility of imitating it, and, in the latter case, reduces it nearly to a mechanical operation. It is the same in the imitation of _still-life_,