That this was the original idea of Jupiter, not only in Rome, but among all Italian peoples, admits of no doubt. The earliest form of his name was _Diovis pater_, or _Diespiter_, and his special priest was the flamen dialis; all these words point to a root _div_, shining, and the connexion with _dies_, day, is obvious (cf. JUNO). One of his most ancient epithets is _Lucetius_, the light-bringer; and later literature has preserved the same idea in such phrases as _sub Jove_, under the open sky. All days of the full moon (_idus_) were sacred to him; all emanations from the sky were due to him and in the oldest form of religious thought were probably believed to be manifestations of the god himself. As Jupiter _Elicius_ he was propitiated, with a peculiar ritual, to send rain in time of drought; as Jupiter _Fulgur_ he had an altar in the Campus Martius, and all places struck by lightning were made his property and guarded from the profane by a circular wall. The vintage, which needs especially the light and heat of the sun, was under his particular care, and in the festivals connected with it (_Vinalia urbana_) and _Meditrinalia_, he was the deity invoked, and his flamen the priest employed. Throughout Italy we find him worshipped on the summits of hills, where nothing intervened between earth and heaven, and where all the phenomena of the sky could be conveniently observed. Thus on the Alban hill south of Rome was an ancient seat of his worship as Jupiter _Latiaris_, which was the centre of the league of thirty Latin cities of which Rome was originally an ordinary member. At Rome itself it is on the Capitoline hill that we find his oldest temple, described by Livy (i. 10); here we have a tradition of his sacred tree, the oak, common to the worship both of Zeus and Jupiter, and here too was kept the _lapis silex_, perhaps a celt, believed to have been a thunderbolt, which was used symbolically by the fetiales when officially declaring war and making treaties on behalf of the Roman state. Hence the curious form of oath, _Jovem lapident jurare_, used both in public and private life at Rome.