Next in order of invocation to Janus came Jupiter, and his priest, the Flamen Dialis, was likewise the second in rank, according to ancient rule, after the _rex sacrorum_. Unlike Janus, Jupiter (to use the spelling familiar in England) was at all times a great power for the Roman people, and one who could be all the more valued because he was intelligible. No one doubted then, and no one doubts now, that he was the god of the light and of heaven, _Diovis pater_, or rather perhaps the heaven itself[253] with all its manifestations of rain and thunder, of blessing and damage to the works of man; the common inheritance of the Italian peoples, dwelling and worshipped in their woods and on their hills; and, as we know now, also the common inheritance of all Aryan stocks, the "European Sky-god," as Mr. A. B. Cook has traced him with learning and ingenuity from the Euxine to Britain.[254] Jupiter must have had a long and important history in Latium before the era of the Roman City-state; Dr. Frazer has seen this, and set it forth in his lectures on the early history of the kingship, though basing his conclusions on evidence much of which will not bear a close examination.[255] The one substantial proof of it lies in the unique and truly extraordinary character of the taboos placed on his flamen, and to some extent on the flamen's wife, by the Roman _ius divinum_. Even if we suppose that some of these may have been later inventions of an ecclesiastical college like the pontifices (and this is hardly probable), many of them are obviously of remote antiquity, and can only have originated at a time when the magical power of the man responsible for the conduct of Jupiter was so precious that it had to be safeguarded in these many curious ways. I have already suggested that the scene of the early paramount importance of Jupiter and his flamen, in that age perhaps a king of some kind, was Alba Longa, which by universal tradition was the leading city of Latium before Rome rose to importance, and where the sky-god was worshipped on his holy mountain as the religious centre of Latium from the earliest times. I have also suggested that when the new warlike city on the Tiber took the place of Alba, the worship was transferred thither, but lost its strength in the process, and that the flamen was little more than a survival even in the most primitive period of what we may call for the moment Roman history. This can be accounted for by the fact that the traditions of primitive Rome were connected much more closely with Mars than with Jupiter. Not till Etruscan kings founded the great temple on the Capitol, which was to endure throughout all later ages of Roman dominion, did the sky-god become the supreme guardian deity of his people, under the titles of Optimus Maximus, the best and greatest of all her deities.