"What I meant to say," Clem went on, "was that other people before Watt had found out the power of steam, and had used it too. There was one Hero of Alexandria, who lived about two thousand years ago, who used steam for many interesting purposes, notably for animating various figures that took part in the idolatrous worship of his time, and thus in deceiving the common people. But his contrivances, though engines which went by steam, would hardly be called steam-engines. Between Hero of Alexandria, of 160 B. C., and the Marquis of Worcester, of 1650 A. D., there does not seem to have been much doing in the way of inventing the steam-engine. But the Marquis of Worcester in Charles II.'s time was a great philosopher, and did nobody knows exactly what with steam. But though he did great things, he did not produce a particularly capable engine, though he seems to have known more about steam than anybody else did at his time. After the Marquis of Worcester and before Watt, there were three men who did much towards inventing and improving the steam-engine. Their names were Savery, Papin, and Newcomen. I don't propose to tell you about the inventions of each one; but it's well enough to remember that each one did important service in getting the steam-engine to the point where Watt took hold of it. As it was on Newcomen's engine that Watt made his first serious experiments, I think we should all like to know something about it." THE NEWCOMEN ENGINE. Newcomen's engine may be thus briefly described: The steam was generated in a separate boiler, as in Savery's engine, from which it was conveyed into a vertical cylinder underneath a piston fitting it closely, but movable upwards and downwards through its whole length. The piston was fixed to a rod, which was attached by a joint or chain to the end of a lever vibrating upon an axis, the other end being attached to a rod working a pump. When the piston in the cylinder was raised, steam was let into the vacated space through a tube fitted into the top of the boiler, and mounted with a stopcock. The pump-rod at the further end of the lever being thus depressed, cold water was applied to the sides of the cylinder, on which the steam within it was condensed, a vacuum was produced, and the external air, pressing upon the top of the piston, forced it down into the empty cylinder. The pump-rod was thereby raised; and, the operation of depressing it being repeated, a power was thus produced which kept the pump continuously at work. Such, in a few words, was the construction and action of Newcomen's first engine.[8]