170. I cannot arrest you to-day by the statement of any of the laws of sight and distance which determine the proper depth of bas-relief. Suppose that depth fixed; then observe what a pretty problem, or, rather, continually varying cluster of problems, will be offered to us. You might, at first, imagine that, given what we may call our scale of solidity, or scale of depth, the diminution from nature would be in regular proportion, as, for instance, if the real depth of your subject be, suppose, a foot, and the depth of your bas-relief an inch, then the parts of the real subject which were six inches round the side of it would be carved, you might imagine, at the depth of half an inch, and so the whole thing mechanically reduced to scale. But not a bit of it. Here is a Greek bas-relief of a chariot with two horses (upper figure, Plate XXI.) Your whole subject has therefore the depth of two horses side by side, say six or eight feet. Your bas-relief has, on this scale,[34] say the depth of a third of an inch. Now, if you gave only the sixth of an inch for the depth of the off horse, and, dividing him again, only the twelfth of an inch for that of each foreleg, you would make him look a mile away from the other, and his own forelegs a mile apart. Actually, the Greek has made the _near leg of the off horse project much beyond the off leg of the near horse_; and has put nearly the whole depth and power of his relief into the breast of the off horse, while for the whole distance from the head of the nearest to the neck of the other, he has allowed himself only a shallow line; knowing that, if he deepened that, he would give the nearest horse the look of having a thick nose; whereas, by keeping that line down, he has not only made the head itself more delicate, but detached it from the other by giving no cast shadow, and left the shadow below to serve for thickness of breast, cutting it as sharp down as he possibly can, to make it bolder. 171. Here is a fine piece of business we have got into!--even supposing that all this selection and adaptation were to be contrived under constant laws, and related only to the expression of given forms. But the Greek sculptor, all this while, is not only debating and deciding how to show what he wants, but, much more, debating and deciding what, as he can't show everything, he will choose to show at all. Thus, being himself interested, and supposing that you will be, in the manner of the driving, he takes great pains to carve the reins, to show you where they are knotted, and how they are fastened round the driver's waist, (you recollect how Hippolytus was lost by doing that); but he does not care the least bit about the chariot, and having rather more geometry than he likes in the cross and circle of one wheel of it, entirely omits the other!