but we know from Porphyry that the initiate into the rites of Mithras underwent a baptism by total immersion which was said to expiate his sins[937]. Among the worshippers of Mithras, on the same authority, were also virgins and others vowed to continence[938], and we hear that the Mithraists used, like the Christians, to call each other “Brother” and address their priests as “Father[939].” St Augustine tells us that in his time the priests of Mithras were in the habit of saying, “That One in the Cap [_i.e._ Mithras] is a Christian too!” and it is not unlikely that the claim was seriously made[940]. During the reigns of the Second Flavian Emperors and before Constantine’s pact with the Church, we hear of hymns sung by the legionaries which could be chanted in common by Christians, Mithraists, and the worshippers of that Sun-God the adoration of whom was hereditary or traditional in the Flavian House[941]. The Mithraists also observed Sunday and kept sacred the 25th of December as the birthday of the sun[942]. Of the other rites and ceremonies used in the worship of Mithras we know next to nothing. As appears from the authors last quoted, the whole of the worship was conducted in “mysteries” or secret ceremonies like the Eleusinian and the rites of the Alexandrian divinities, although on a more extended scale. The Mithraic mysteries always took place in a subterranean vault or “cave,” lighted only by artificial light. The ruins of many of these have been found, and are generally so small as to be able to accommodate only a few worshippers[943], whence perhaps it followed that there were often several Mithraea in the same town or city[944]. The chief feature seems to have been always the scene of the Tauroctony or Bull-slaying which was displayed on the apse or further end of the chapel, and was generally carved in bas-relief although occasionally rendered in the round. The effect of this was sought to be heightened by brilliant colouring, perhaps made necessary by the dim light, and there were certainly altars of the square or triangular pedestal type, and a well or other source from which water could be obtained. The benches for the worshippers were of stone and ran at right angles to and on either side of the Tauroctony, so as to resemble the choir stalls in the chancel of a modern church[945]. We have seen that the lion-headed figure was concealed from the eyes of the worshippers, and we know that they used to kneel during at least part of the service, which was not in accord with the practice of either the Greeks or Romans, who were accustomed to stand with upturned palms when praying to the gods[946]. Sacrifices of animals which, if we may judge from the débris left in some of the chapels, were generally birds[947], seem to have been made; but there is no reason to believe the accusation sometimes brought against the Mithraists that they also slaughtered human victims in honour of their god. Lampridius tells us, on the other