A second correction is intended to overcome the apparent tendency of a building to spread outwards towards the top. This is met by inclining the columns slightly inwards. So slight, however, is the inclination, that were the axes of two columns on opposite sides of the Parthenon continued upwards till they met, the meeting-point would be 1952 yards, or, in other words, more than one mile from the ground. Another optical correction is applied to the horizontal lines. In order to overcome a tendency which exists in all long lines to seem as though they droop in the middle, the lines of the architrave, of the top step, and of other horizontal features of the building, are all slightly curved. The difference between the outline of the top step of the Parthenon and a straight line joining its two ends is at the greatest only just over 2 inches. The last correction which it is necessary to name here was applied to the vertical proportions of the building. The principles upon which this correction rests have been demonstrated by Mr. John Pennethorne;[14] and it would hardly come within the scope of this volume to attempt to state them here: suffice it to say, that small additions, amounting in the entire height of the order to less than 5 inches, were made to the heights of the various members of the order, with a view to secure that from one definite point of view the effect of foreshortening should be exactly compensated, and so the building should appear to the spectator to be perfectly proportioned. The Parthenon, like many, if not all Greek buildings, was profusely decorated with coloured ornaments, of which nearly every trace has now disappeared, but which must have contributed largely to the splendid beauty of the building as a whole, and must have emphasised and set off its parts. The ornaments known as Doric frets were largely employed. They consist of patterns made entirely of straight lines interlacing, and, while preserving the severity which is characteristic of the style, they permit of the introduction of considerable richness. The principal remaining examples or fragments of Greek Doric may be enumerated as follows:-- IN GREECE. Temple of (?) Athena, at Corinth, ab. 650 B.C. Temple of (?) Zeus, in the island of Ægina, ab. 550 B.C. Temple of Theseus (Theseum), at Athens, 465 B.C. Temple of Athena (Parthenon), on the Acropolis at Athens, fin. 438 B.C. The Propylæa, on the Acropolis at Athens, 436-431 B.C. Temple of Zeus at Olympia. Temple of Apollo Epicurius, at Bassæ,[15] in Arcadia (designed by Ictinus). Temple of Apollo Epicurius, at Phigaleia, in Arcadia (built by Ictinus). Temple of Athena, on the rock of Sunium, in Attica. Temple of Nemesis, at Rhamnus, in Attica. Temple of Demeter (Ceres), at Eleusis, in Attica. IN SICILY AND SOUTH ITALY.