140. But it did not then occur to me to ask, much as I always disliked the English Perpendicular, what would have been the effect on the spectator's mind, had the buildings been striped vertically instead of horizontally; nor did I then know, or in the least imagine, how much _practical_ need there was for reference from the structure of the edifice to that of the cliff; and how much the permanence, as well as propriety, of structure depended on the stones being _couchant_ in the wall, as they had been in the quarry: to which subject I wish to-day to direct your attention. 141. You will find stated with as much clearness as I am able, in the first and fifth lectures in "Aratra Pentelíci," the principles of architectural design to which, in all my future teaching, I shall have constantly to appeal; namely, that architecture consists distinctively in the adaptation of form to resist force;--that, practically, it may be always thought of as doing this by the ingenious adjustment of various pieces of solid material; that the perception of this ingenious adjustment, or structure, is to be always joined with our admiration of the superadded ornament; and that all delightful ornament is the honouring of such useful structures; but that the beauty of the ornament itself is independent of the structure, and arrived at by powers of mind of a very different class from those which are necessary to give skill in architecture proper. 142. During the course of this last summer I have been myself very directly interested in some of the quite elementary processes of true architecture. I have been building a little pier into Coniston Lake, and various walls and terraces in a steeply sloping garden, all which had to be constructed of such rough stones as lay nearest. Under the dextrous hands of a neighbour farmer's son, the pier projected, and the walls rose, as if enchanted; every stone taking its proper place, and the loose dyke holding itself as firmly upright as if the gripping cement of the Florentine towers had fastened it. My own better acquaintance with the laws of gravity and of statics did not enable me, myself, to build six inches of dyke that would stand; and all the decoration possible under the circumstances consisted in turning the lichened sides of the stones outwards. And yet the noblest conditions of building in the world are nothing more than the gradual adornment, by play of the imagination, of materials first arranged by this natural instinct of adjustment. You must not lose sight of the instinct of building, but you must not think the play of the imagination depends upon it. Intelligent laying of stones is always delightful; but the fancy must not be limited to its contemplation. [Illustration: PLATE V.--DOOR OF THE BAPTISTERY. PISA.]