The plan of almost any Greek temple will be found to be referable to one or other of the types just described, although there are great differences in the proportions of the several parts.  It remains only to add that in almost every case the principal front was toward the east or nearly so.  When Greek temples were converted into Christian churches, as often happened, it was necessary, in order to conform to the Christian ritual, to reverse this arrangement and to place the principal entrance at the western end.

The next thing is to study the principal elements of a Greek temple as seen in elevation.  This brings us to the subject of the Greek “orders.”  There are two principal orders in Greek architecture, the Doric and the Ionic.  Figs. 51 and 61 show a characteristic specimen of each.  The term “order,” it should be said, is commonly restricted in architectural parlance to the column and entablature.  Our illustrations, however, show all the features of a Doric and an Ionic facade.  There are several points of agreement between the two:  in each the columns rest on a stepped base, called the crepidoma, the uppermost step of which is the stylobate; in each the shaft of the column tapers from the lower to the upper end, is channeled or fluted vertically, and is surmounted by a projecting member called a capital; in each the entablature consists of three members—­architrave, frieze, and cornice.  There the important points of agreement end.  The differences will best be fixed in mind by a detailed examination of each order separately.

Our typical example of the Doric order (Fig. 51) is taken from the Temple of Aphaia on the island of Aegina—­a temple probably erected about 480 B.C. (cf.  Fig. 52.) The column consists of two parts, shaft and capital.  It is of sturdy proportions, its height being about five and one half times the lower diameter of the shaft.  If the shaft tapered upward at a uniform rate, it would have the form of a truncated cone.  Instead of that, the shaft has an entasis or swelling.  Imagine a vertical section to be made through the middle of the column.  If, then, the diminution of the shaft were uniform, the sides of this section would be straight lines.  In reality, however, they are slightly curved lines, convex outward.  This addition to the form of a truncated cone is the entasis.  It is greatest at about one third or one half the height of the shaft, and there amounts, in cases that have been measured, to from 1/80 to 1/140 of the lower diameter of the shaft.[Footnote:  Observe that the entasis is so slight that the lowest diameter of the shaft is always the greatest diameter.  The illustration is unfortunately not quite correct, since it gives the shaft a uniform diameter for about one third of its height.] In some early Doric temples, as the one at Assos in Asia Minor, there is no entasis.  The channels or flutes in our typical column are twenty in number.  More rarely we find sixteen; much more