There has been much study of these sculptures, and many scholars have written about them. There is still a difference of opinion as to which gods are here represented, but I shall give you the most generally accepted opinion, which calls _a_, Hermes, or Mercury, the messenger of the gods; _b_, Apollo; _c_, Artemis, or Diana; _d_, Ares, or Mars; _e_, Iris, who is attending upon _f_, Hera, or Juno; _g_, Zeus, or Jupiter; h__, Athena, Minerva, or Pallas; _i_, Hephaestus, or Vulcan; _j_, Poseidon, or Neptune; _k_, Dionysus, or Bacchus; _l_, _m_, _n_ are more doubtful, but are probably Aphrodite, or Venus, Demeter, or Ceres, and Triptolemus, the boy who was a favorite with Ceres, who invented the plough and first sowed corn. Now, these two groups of divinities were divided by a very singular group containing five figures (Fig. 28). There has been much controversy as to these figures and what they are doing. They seem to be unconscious of the great gods who are near to them on either side. The greater number of critics consider that the two maidens, _e_ and _d_, are of the number who have embroidered the peplos; the central figure, _c_, a priestess of Athena; _a_, the Archon Basileus; and _b_, a consecrated servant-boy, who is delivering up the peplos. Other critics believe, however, that these figures are all preparing for the sacred ceremonies about to begin, and that the priest is giving the boy-servant a garment which he has taken off. Other theories may arise, and we can only listen to them all, and yet not know the truth; but the more we study the more we shall admire these exquisite figures. [Illustration: FIG. 28.--THE FIVE CENTRAL FIGURES.] Just here I will call your attention to one feature of these antique bas-reliefs which is called _Isocephalism_, and means that all the heads are at an equal height. You will see that all figures, whether standing or sitting, walking, in chariots, or on horseback, have the heads on the same level. These three groups, the five central figures and the two groups of gods, are approached on each side by long, continuous processions, and these processions each start out from the south-west corner of the Parthenon, so that one branch goes along the south and a part of the east side, and the other and longer division marches on the whole of the west and north, and a portion of the east side. I shall give here a series of pictures which are all explained by their titles, and will give you an excellent idea of this magnificent frieze, and doubtless many of my readers have studied or will study and admire it in the British Museum (Figs. 29, 30, 31, 32, 33, 34, 35). [Illustration: FIG. 29--YOUTHS PREPARING TO JOIN THE CAVALCADE.]