These works exhibit three well-defined stages of development. In the earliest and rudest structures the stones are gigantic in size and untouched by the chisel; in the next oldest the stones are worked into irregular polygonal blocks; while in the latest the blocks are cut into rectangular shapes and laid in regular courses. The walls of the old citadels or castles of several Grecian cities exhibit specimens of this primitive architecture (see p. 90). ORDERS OF ARCHITECTURE.--There are three styles, or orders, of Grecian architecture--the Doric, the Ionic, and the Corinthian. They are distinguished from one another chiefly by differences in the proportions and ornamentation of the column. [Illustration: DORIC CAPITAL.] [Illustration: IONIC CAPITAL.] The Doric column is without a base, and has a simple and massive capital. At first the Doric temples of the Greeks were almost as massive as the Egyptian temples, but later they became more refined. The Ionic column is characterized by the spiral volutes of the capital. This form was borrowed from the Assyrians, and was principally employed by the Greeks of Ionia, whence its name. The Corinthian order is distinguished by its rich capital, formed of acanthus leaves. This type is made up of Egyptian, Assyrian, and Grecian elements. The addition of the acanthus leaves is said to have been suggested to the artist Callimachus by the pretty effect of a basket surrounded by the leaves of an acanthus plant, upon which it had accidentally fallen. The entire structure was made to harmonize with its supporting columns. The general characteristics of the several orders are well portrayed by the terms we use when we speak of the "stern" Doric, the "graceful" Ionic, and the "ornate" Corinthian. [Illustration: CORINTHIAN CAPITAL.] TEMPLE OF DIANA AT EPHESUS.--The temple of Diana at Ephesus was regarded as one of the wonders of the world. The original structure was commenced about the beginning of the sixth century B.C., and, according to Pliny, was one hundred and twenty years in process of building. Croesus gave liberally of his wealth to ornament the shrine. In the year 356 B.C., on the same night, it is said, that Alexander was born, an ambitious youth, named Herostratus, fired the building, simply to immortalize his name. Alexander offered to rebuild the temple, provided that he be allowed to inscribe his name upon it. The Ephesians gracefully declined the proposal by replying that it was not right for one deity to erect a temple to another. Alexander was obliged to content himself with placing within the shrine his own portrait by Apelles--a piece of work which cost $30,000. The value of the gifts to the temple was beyond all calculation: kings and states vied with one another in splendid donations. Painters and sculptors were eager to have their masterpieces assigned a place within its walls, so that it became a great national gallery of paintings and statuary.