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 1698, Thomas Savery of London
applied for a patent for a pumping engine. At the same time, a
Hollander, Christian Huygens, was trying to perfect an engine in which
gun-powder was used to cause regular explosions in much the same way as
we use gasoline in our motors.

All over Europe, people were busy with the idea. Denis Papin, a
Frenchman, friend and assistant of Huygens, was making experiments with
steam engines in several countries. He invented a little wagon that was
driven by steam, and a paddle-wheel boat. But when he tried to take a
trip in his vessel, it was confiscated by the authorities on a complaint
of the boatmen's union, who feared that such a craft would deprive them
of their livelihood. Papin finally died in London in great poverty,
having wasted all his money on his inventions. But at the time of his
death, another mechanical enthusiast, Thomas Newcomen, was working
on the problem of a new steam-pump. Fifty y