We must be on our guard, however, lest we exaggerate this pantheistic or universalistic influence. We have a sufficient corrective in the development of Dyaus, an ancient god of the sky, who became, in one of his later forms, the Greek Zeus--that is to say, a king of gods as well as of men--the ruler of Olympus--the supreme member of a polytheistic community. And this development is but representative of a large class which have proceeded on similar lines--the class which come to their own in the concept of a Heaven-Father. For example, Tylor shows that, in the religion of the North American Indians, "the Heaven-god displays perfectly the gradual blending of the material sky itself with its personal deity"; and that the Chinese Tien, Heaven, the highest deity of the state religion, underwent a like theologic development. The mystic influence remains in Christianity, as witness Keble: "The glorious sky embracing all Is like the Maker's love." It may be affirmed, then, without fear of contradiction, that the elemental phenomena of the sky, overarching all with its unlimited span, has provided men with the idea of an all-embracing deity--this idea, among others, is immanent there and awaits still further development. Awaits further development--for the mystic influences persist and suggest deeper interpretations. Browning, though not an avowed nature-mystic, felt the thrill and the emotion of the sky. "The morn has enterprise, deep quiet droops With evening, triumph takes the sunset hour." As for the emotional value of the universal span of the sky, its power to tranquillise by a sense of vast harmony and unity, Christina Rossetti knew it: "Heaven o'erarches you and me, And all earth's gardens and her graves. Look up with me, until we see The day break and the shadows flee. What though to-night wrecks you and me If so to-morrow saves?" Here, as is almost inevitable, the thought of the expanse is associated with the alternate coming on of darkness and the breaking of the dawn; but the change and alternation gains its unity and ultimate significance from the all-inclusiveness of the sky as the abiding element. Walt Whitman brings out another aspect of this subtle but powerful influence. He addresses the sky: "Hast Thou, pellucid, in Thy azure depths, medicine for case like mine? (Ah, the physical shatter and troubled spirit of me the last three years.) And dost Thou subtly, mystically now drip it through the air invisibly upon me?" In similar mood Jefferies writes: "I turned to the blue heaven over, gazing into its depth, inhaling its exquisite colour and sweetness. The rich blue of the unattainable flower of the sky drew my soul towards it, and there it rested, for pure colour is rest of heart."