First, and perhaps foremost, in the ritual of the lower stratum, of the dead and of chthonic powers, three was, for some reason that escapes us, a sacred number[752]. The dead were thrice invoked; sacrifice was offered to them on the third day; the mourning in some parts of Greece lasted three days; the court of the Areopagus, watched over by deities of the underworld, sat, as has been seen (p. 242), on three days; at the three ways the threefold Hecate of the underworld was worshipped. It was easy and natural that threefold divinities should arise to keep ward over a ritual so constituted. When the powers of the underworld came to preside over agriculture, the transition from two to three seasons would tend in the same direction. For two seasons a duality was enough—the Mother for the fertile summer, the Maid for the sterile winter—but, when the seasons became three, a trinity was needed, or at least would be welcomed. Last, the influence of art must not be forgotten. A central figure of the mother, with her one daughter, composes ill. Archaic art loved heraldic groupings, and for these two daughters were essential. Such compositions as that on the Boeotian amphora in fig. 60 might easily suggest a trinity[753]. * * * * * Once the triple form established, it is noticeable that in Greek mythology the three figures are always regarded as _maiden_ goddesses, not as mothers. They may have taken their rise in the Mother and the Maid, but the Mother falls utterly away. The Charites, the Moirae, the Horae, are all essentially maidens. The reverse is the case in Roman religion; trinities of women goddesses of fertility occur frequently in very late Roman art, but they are Matres, Mothers[754]. Three Mothers are rather heavy, and do not dance well. [Illustration: FIG. 73.] In the archaic votive relief[755] in fig. 73 we have the earliest sculptured representation of the maiden trinity extant. Had the relief been uninscribed, we should have been at a loss how to name the three austere figures. Two carry fruits, and one a wreath. They might be Charites or Eumenides, or merely nymphs. Most happily the sculptor has left no doubt. He has written against them Κορας Σοτιας, ‘Sotias (dedicated) the Korai’ the Maidens.’ Sotias has massed the three stately figures very closely together; he is reverently conscious that though they are three persons, yet they are but one goddess. He is half monotheist.