Now just consider the amount of sympathy with human nature, and observance of it, shown in this one bas-relief; the sympathy with disputing monks, with puzzled aldermen, with melancholy recluse, with triumphant prelate, with palsy-stricken poverty, with ecclesiastical magnificence, or miracle-working faith. Consider how much intellect was needed in the architect, and how much observance of nature before he could give the expression to these various figures--cast these multitudinous draperies--design these rich and quaint fragments of tombs and altars--weave with perfect animation the entangled branches of the forest. But you will answer me, all this is not architecture at all--it is sculpture. Will you then tell me precisely where the separation exists between one and the other? We will begin at the very beginning. I will show you a piece of what you will certainly admit to be a piece of pure architecture; [Footnote: See Appendix III., "Classical Architecture."] it is drawn on the back of another photograph, another of these marvellous tympana from Notre Dame, which you call, I suppose, impure. Well, look on this picture, and on this. Don't laugh; you must not laugh, that's very improper of you, this is classical architecture. I have taken it out of the essay on that subject in the "Encyclopædia Britannica." Yet I suppose none of you would think yourselves particularly ingenious architects if you had designed nothing more than this; nay, I will even let you improve it into any grand proportion you choose, and add to it as many windows as you choose; the only thing I insist upon in our specimen of pure architecture is, that there shall be no mouldings nor ornaments upon it. And I suspect you don't quite like your architecture so "pure" as this. We want a few mouldings, you will say--just a few. Those who want mouldings, hold up their hands. We are unanimous, I think. Will, you, then, design the profiles of these mouldings yourselves, or will you copy them? If you wish to copy them, and to copy them always, of course I leave you at once to your authorities, and your imaginations to their repose. But if you wish to design them yourselves, how do you do it? You draw the profile according to your taste, and you order your mason to cut it. Now, will you tell me the logical difference between drawing the profile of a moulding and giving _that_ to be cut, and drawing the folds of the drapery of a statue and giving _those_ to be cut. The last is much more difficult to do than the first; but degrees of difficulty constitute no specific difference, and you will not accept it, surely, as a definition of the difference between architecture and sculpture, that "architecture is doing anything that is easy, and sculpture anything that is difficult."