Ur-Gur of the second dynasty of Ur, in invoking Nannar, calls the latter 'the powerful bull of Anu.' The reference is interesting, for it shows that already in these early days the position of Anu, as the god of the heavenly expanse, was fixed.

The moon appearing in the heavens, and the resemblance of its crescent to a bull's horn,[74] are the two factors that account for the expressive epithet used by Ur-Bau.

That the worship of the god of heaven _par excellence_ should not have enjoyed great popularity in the early days of the Babylonian religion might seem strange at first sight.

A little reflection, however, will make this clear.

A god of the heavens is an abstract conception, and while it is possible that even in an early age, such a conception may have arisen in some minds, it is not of a character calculated to take a popular hold.
As we proceed in our attempt to trace the development of the Babylonian religion, we will find the line of demarcation separating the theological system, as evolved by the schoolmen, from the popular phases of the religion, becoming more marked.