1879.] on the Logic of Architectural Design. 93 



to keep the rain off the walls, is on the same principle strongly marked 

 with horizontal lines and mouldings (for, as it has no weight to carry, 

 we can play with it as wc please), in order to emphasize horizontality, 

 and also to form a decisive stop and finish to the vertical lines of the 

 structure, just as the annulets of the column form a stop to the vertical 

 lines of the fluting. The small flat blocks under the cornice (mutules) 

 have probably a very distant reference to the wooden roof of a timber 

 building and the ends of its rafters, almost the only point which gives 

 any ground for the idea of the wooden origin of the style, which is in 

 general very doubtful, or more than doubtful : the part which these 

 features play in the complete Doric is to break the long line of the 

 cornice and its shadow, and connect it with the repetition of parts 

 which forms an essential element in the substructure. The slope of 

 the pediment expresses, of course, the slope of the roof, and would 

 have no meaning otherwise. The triangular space beneath the pedi- 

 ment is structurally unimportant ; in a small building (or in a timber 

 one) it might bo oj^en ; in a larger one its masonry is required to 

 carry the blocks of the cornice, but it is structurally a secondary 

 portion, and therefore is not unfittingly made a receptacle for sculp- 

 ture, which is also suitably applied in the spaces formed by the 

 metopes ; spaces which are interstructural, and might be left empty, 

 and in which the sculpture is, in fact, executed on the face of com- 

 paratively thin slabs of stone not calculated to carry any great weight, 

 and having only empty space behind them.* 



So far we have been dealing with a method of building in which 

 all the pressures exerted by the materials are vertical, and, as we have 

 seen, the design precisely expresses this constructive system. Greek 

 architecture is, constructively, the placing of a horizontal beam on 

 vertical supports ; and no construction is so simple in its problems 

 and so enduring in its stability as this : it is however a construction 

 wasteful in material, necessitating also the use of large blocks, and 

 limited in tlie size of its openings by the incapability of the material 

 to carry over more than a small distance without breiking even under 

 its own weight alone. The principle of the arch, first employed on a 

 large scale and in a systematic manner by the Eomans, relieves the 

 architect from these restrictions ; it enables him to bridge over large 

 spaces with comparatively small stones, and it employs the material 

 in the way in which it is strongest, in a state of simple compression, 

 and without the disadvantageous effect of cross-strain. But the pres- 

 sures which an arched building exercises differ entirely from those of 

 a lintel building. An arch is exercising upon its points of support 

 an outward or expanding pressure, the angle of which varies with the 

 shape of the arch and the weight and position upon it of the super- 



* In Mr. Tadema's picture, " The Love Missile," a sculptured metope slab is 

 shown as movable on a pivot, and turned round on its centre at right angles to 

 the wall, so as to leave tlie space open at either side : an arrangement which very 

 likely was at times made in Koman imitations of Greek building. 



