been a later invention of the Hellenes originating in more scientific mechanics; as indeed the Greek tradition refers it to the natural philosopher Democritus (294-397).  With this priority of Hellenic over Roman arch-building the hypothesis, which has been often and perhaps justly propounded, is quite compatible, that the vaulted roof of the Roman great -cloaca-, and that which was afterwards thrown over the old Capitoline well-house which originally had a pyramidal roof,(34) are the oldest extant structures in which the principle of the arch is applied; for it is more than probable that these arched buildings belong not to the regal but to the republican period,(35) and that in the regal period the Italians were acquainted only with flat or overlapped roofs.(34) But whatever may be thought as to the invention of the arch itself, the application of a principle on a great scale is everywhere, and particularly in architecture, at least as important as its first exposition; and this application belongs indisputably to the Romans.  With the fifth century began the building of gates, bridges, and aqueducts based mainly on the arch, which is thenceforth inseparably associated with the Roman name.  Akin to this was the development of the form of the round temple with the dome-shaped roof, which was foreign to the Greeks, but was held in much favour with the Romans and was especially applied by them in the case of the cults peculiar to them, particularly the non-Greek worship of Vesta.(37)

Something the same may be affirmed as true of various subordinate, but not on that account unimportant, achievements in this field.  They do not lay claim to originality or artistic accomplishment; but the firmly-jointed stone slabs of the Roman streets, their indestructible highways, the broad hard ringing tiles, the everlasting mortar of their buildings, proclaim the indestructible solidity and the energetic vigour of the Roman character.

Plastic and Delineative Art

Like architectural art, and, if possible, still more completely, the plastic and delineative arts were not so much matured by Grecian stimulus as developed from Greek seeds on Italian soil.  We have already observed(38) that these, although only younger sisters of architecture, began to develop themselves at least in Etruria, even during the Roman regal period; but their principal development in Etruria, and still more in Latium, belongs to the present epoch, as is very evident from the fact that in those districts which the Celts and Samnites wrested from the Etruscans in the course of the fourth century there is scarcely a trace of the practice of Etruscan art.  The plastic art of the Tuscans applied itself first and chiefly to works in terra-cotta, in copper, and in gold-materials which were furnished to the artists by the rich strata of clay, the copper mines, and the commercial intercourse of Etruria.  The vigour with which moulding in clay was prosecuted is attested