Bk. IV. Ch. V. BRIDGES AND AQUEDUCTS. 375 mistake considering their different heights — or have built solidly over the smaller arches to bring up the level, which would have been 251. Bridge of Trajan, at Alcantara, in Spain. a far greater error in construction than the other is in taste. The bridge consists of six arches, the whole length of the roadway being 650 ft. ; the two central arches are about 100 ft. span ; the roadway is 140 ft. above the level of the stream which it crosses. The piers are Avell proportioned and graceful ; and altogether the work is as fine and as tasteful an example of bridge-building as can be found anywhere, even in these days of engineering activity. The bridge Avhich the same Emperor erected over the Danube was a far more difficult work in an engineering point of view but the superstructure being of wood, resting only on stone piers, it would necessarily have possessed much less architectural beauty than this, or indeed many others. These examj^les of tnis class of Roman works must suflice ; they are so typical of the style that it was impossible to omit them altogether, though the subject scarcely belongs in strictness to the objects of this work. The bridges and aqueducts of the Romans richly deserve the attention of the architect, not only because they are in fact the only Avorks which the Romans, either from taste or from social i)Osition, were enabled to carry out without affectation, and with all their originality and power, but also because it was in building these works that the Romans acquired that constructive skill and largeness of 13roportion which enabled them to design and carry out works of such vast dimensions, to vault such spaces, and to give to their buildings generally that size and impress of power which form their chief and frequently their only merit. It Avas this too that enabled them to originate that new style of vaulted buildings which at one period of the Middle Ages promised to reach a degree of perfection to which no architecture of the world had ever attained. The Gothic style, it is true, perished at a time when it was very far from completed ; Ijut it is a point of no small interest to know where and under wliat
