To begin with, there were the feasts of the Sun. The _Bruma_ (_brevissima_) or _Brumalia_ was held on November 24, as the day which ushered in the period of the year during which the sun’s light is diminished. This seems to have been a beginning of winter feast, adopted by Rome from Thrace[816]. The term _bruma_ was also sometimes applied to the whole period between November 24 and the solstice, and ultimately even to the solstitial day itself, fixed somewhat incorrectly by the Julian calendar on December 25[817]. On this day also came a festival, which probably owed its origin to the Emperor Aurelian (270-75), whose mother was a semi-Oriental priestess of the Sun, in one of his Syrian forms as Baal or Belus[818], and who instituted an official cult of this divinity at Rome with a temple on the Quirinal, a _collegium_ of _pontifices_, and _ludi circenses_ held every fourth year[819]. These fell on the day of the solstice, which from the lengthening of the sun’s course was known as the ‘birthday’ of _Sol Novus_ or _Sol Invictus_[820]. This cult was practised by Diocletian and by Constantine before his conversion, and was the rallying-point of Julian in his reaction against Christianity[821]. Moreover, the _Sol Invictus_ was identified with the central figure of that curious half-Oriental, half-philosophical worship of Mithra, which at one time threatened to become a serious rival to Christianity as the religion of the thinking portion of the Roman world[822]. That an important Mithraic feast also fell on December 25 can hardly be doubted, although there is no direct evidence of the fact[823]. The cult of the _Sol Invictus_ was not a part of the ancient Roman religion, and, like the _Brumalia_, the solstitial festival in his honour, however important to the educated and official classes of the empire, was not a folk-festival. It lay, however, exactly between two such festivals. The _Saturnalia_ immediately preceded it; a few days later followed the January _Kalends_.