Even Mark Twain, who scoffed at superstition all his life, often said that, as he came into the world with Halley's Comet, in the year 1835, so he expected to die in 1910, the year of the comet's next appearance. Strangely enough, his half-jesting prophecy was fulfilled, for he really did die in that year. Astronomers to-day can figure out in advance what is to happen in the heavens with an exactness which would have seemed magical in olden times, and is hardly less astonishing even now. Their power is largely due to improved scientific instruments, proficiency in mathematics and greater accuracy in the measurement of time. Not only is the date of an eclipse of the sun now known in advance, but so also is the exact path of the shadow across the world, and the instant of its appearance in any given place. We now have glanced briefly at a few of the features of early humanity's dependence upon the clocks of nature and the way in which they influenced its manner of life. We still depend upon these great primeval timepieces and we do it for the most part unconsciously, for our master clocks must still be set by the motion of the heavenly bodies. That motion, which now we know to be really the revolution of our earth, is still the legislator and supreme court of time. But we have learned to make and carry everywhere a wonderful machine, whose revolving wheels and pointing hands keep tryst with the stars in the heavens and move to the rhythm of wheeling worlds. And so familiar is this talisman of man's making, that we forget to look beyond it or think of time at all save as the position of the hands upon the dial. We carry with us carelessly a toy which tells tales upon the solar system—our watch is a pocket universe. CHAPTER THREE _How Man Began to Model After Nature_ We now have reached a point far ahead of our story and must take a backward step. We have been seeing man as a mere observer of nature; but man doesn't stop with nature as he finds it—his man-brain drives him forward; he must make improvements of his own. Animals may live and die and leave no trace save their bones, which for the most part soon disappear, but man always leaves traces behind him. He has always interfered with nature, or rather has modeled after nature, seeing in her work the revelations of principles and laws that he might utilize in varying ways for his own benefit and progress. Our material civilization is built up from the accumulated results of all this study and control of nature by hundreds of millions of busy brains and hands, through tens of thousands of years.