The architects of Rome marvellously extended the range of their art, and gave it a flexibility by which it accommodated itself to the widest variety of materials and conditions. They made the arch and vault the basis of their system of design, employing them on a scale previously undreamed of, and in combinations of surpassing richness and majesty. They systematized their methods of construction so that soldiers and barbarians could execute the rough mass of their buildings, and formulated the designing of the decorative details so that artisans of moderate skill could execute them with good effect. They carried the principle of repetition of motives to its utmost limit, and sought to counteract any resulting monotony by the scale and splendor of the design. Above all they developed planning into a fine art, displaying their genius in a wonderful variety of combinations and in an unfailing sense of the demands of constructive propriety, practical convenience, and artistic effect. Where Egyptian or Greek architecture shows one type of plan, the Roman shows a score. +GREEK INFLUENCE.+ Previous to the closing years of the Republic the Romans had no art but the Etruscan. The few buildings of importance they possessed were of Etruscan design and workmanship, excepting a small number built by Greek hands. It was not until the Empire that Roman architecture took on a truly national form. True Roman architecture is essentially imperial. The change from the primitive Etruscan style to the splendors of the imperial age was due to the conquest of the Greek states. Not only did the Greek campaigns enrich Rome with an unprecedented wealth of artistic spoils; they also brought into Italy hosts of Greek artists, and filled the minds of the campaigners with the ambition to realize in their own dominions the marble colonnades, the temples, theatres, and propylæa of the Greek cities they had pillaged. The Greek orders were adopted, altered, and applied to arcaded designs as well as to peristyles and other open colonnades. The marriage of the column and arch gave birth to a system of forms as characteristic of Roman architecture as the Doric or Ionic colonnade is of the Greek.