Even were it not to be inferred from other evidence, there could be little doubt that the people amongst whom the above conception arose must have been already familiar with tree-worship. The mighty stem, in which the great gods dwelt, was but a poetical amplification of the sacred, spirit-inhabited tree, and arose out of the same idealising process as that which gave birth to the nearly related tree of knowledge and tree of life. Side by side with that of a world-tree the conception of a world-mountain is also met with in the primitive cosmogony of the Chaldaeans, but while the former tradition belonged to Sumir or Southern Babylonia, the latter seems to have prevailed in the Northern Accad, whose inhabitants had once been mountain-dwellers.[261] This “mountain of the world,” “whose head rivalled the heaven,” which had the pure deep for its foundation and was the home of the gods, was placed in the north, and its worship survived in that of the “illustrious mounds” of the Babylonian plain, which were equally regarded as the visible habitation of divine spirits. Isaiah represents the king of Babylon as boasting, “I will ascend into heaven, I will exalt my throne above the stars of God; and I will sit upon the mount of congregation, in the uttermost parts of the north.”[262] It seems clear that the prophet is alluding to the myth of a Chaldaean Olympus, where the gods held their assemblies. In one of the Babylonian hymns this mountain is addressed as, “O thou who givest shade, Lord who castest thy shadow over the land, great mount,”[263] from which it might appear that the idea of the world-mountain was not very strictly dissociated from that of a world-tree.