Page:Van Loon--The Story of Mankind.djvu/468

404, Gottfried Leibnitz of Leipzig had perfected the system of infinitesimal calculus. Eight years before the peace of Westphalia, Newton, the great English natural philosopher, was born, and in that same year Galileo, the Italian astronomer, died. Meanwhile the Thirty Years War had destroyed the prosperity of central Europe and there was a sudden but very general interest in "alchemy," the strange pseudo-science of the middle-ages by which people hoped to turn base metals into gold. This proved to be impossible but the alchemists in their laboratories stumbled upon many new ideas and greatly helped the work of the chemists who were their successors.

The work of all these men provided the world with a solid scientific foundation upon which it was possible to build even the most complicated of engines, and a number of practical men made good use of it. The Middle-Ages had used wood for the few bits of necessary machinery. But wood wore out easily. Iron was a much better material, but iron was scarce except in England. In England therefore most of the smelting was done. To smelt iron, huge fires were needed. In the beginning, these fires had been made of wood, but gradually the forests had been used up. Then "stone coal" (the petrified trees of prehistoric times) was used. But coal as you know has to be dug out of the ground and it has to be transported to the smelting ovens and the mines have to be kept dry from the ever invading waters.

These were two problems which had to be solved at once. For the time being, horses could still be used to haul the coal-wagons, but the pumping question demanded the application of special machinery. Several inventors were busy trying to solve the difficulty. They all knew that steam would have to be used in their new engine. The idea of the steam engine was very old. Hero of Alexandria, who lived in the first century before Christ, has described to us several bits of machinery which were driven by steam. The people of the Renaissance had played with the notion of steam-driven war chariots. The Marquis of Worcester, a contemporary of Newton, in his book of inventions, tells of a steam engine. A little later, in the year