Then we crossed swiftly east to the tower. It was daylight when we left the braves, prostrate before the tower as it melted into a phantom and vanished. We were safe--all but Nanette. Of what use to me, this safety? Nanette, to me of all the world most dear, was gone. And this time I had a premonition that she was lost to me forever. CHAPTER XVI WHICH THE READER MAY SKIP IF HE CHOOSES I think it advantageous to my narrative now to set down a few scientific facts. The laws, for instance, under which our Time-traveling tower operated. The Indians of 1664 thought the tower was magic. But it was based upon solid science. The laws of Time and Space--the true aspect of the Material Universe--all this is, in our age of 1945, imperfectly understood. So I set down here a few succinct truths. Those of you who care to ponder them may do so. You will find that the scientific aspect of my narrative is much clearer. Those of a different turn of mind may pass over this brief chapter. The basis of the Material Universe is Energy. Energy we can also call by another name--Change. Everything exists because it is changing. The living cell feeds itself and grows; multiplies itself; dies and decays; turns to other forms, liquid and gas--and is not lost, but reconverted. The rocks were gas, then liquid, then solid. The wind and water erodes them--they break, they powder, they blow away, or wash away as dust, and come again in other forms of other things. The atoms, the very electrons of all matter in the universe, are breaking down or building up. All changing. All are nothing but manifestations of Energy. And Matter itself? Take a fragment of solid gold--we find it built of loosely massed molecules, all in movement; and each molecule a group of agitated atoms; and each atom, whirling electrons and a nucleus--infinitely tiny things to which we give these arbitrary names--things which in themselves in their essence are nothing at all save Energy! There is no mass. Nothing of solidity! Whirlpools--vortexes of nothingness! Of such unsolid stuff you who read this are built. And your home, and your city, and the Earth under you, and all the stars of the Heavens! At the basis of all this, also, is unceasing change of position. Every tiny fragment of everything is restless--and every thing, in its entirety, is in motion. We move in space about our tiny Earth. Our Earth whirls us all along; and the Sun sweeps onward, dragging the Earth, itself following some distant Star, which with other Stars is going somewhere. We know all this, now in 1945. We know, too, that nothing has a continuous existence. Your body, as you now sit reading what you may feel are idle theories, at one instant is existing and at the next is blotted out. And lives again another instant. A changed body, just a little different in every tiny essence of your being from what it was before.