The study of motors and motive power is one which calls for the highest engineering qualities. In this, as in every other of the mechanical arts, theory, while it has an important function, occupies second place.
Experimenting.—The great improvements have been made by building and testing; the advance has been step by step. Sometimes a most important invention will loom up as a striking example to show how a valuable feature lies hidden and undeveloped.
An illustration of this may be cited with respect to the valve of the steam engine. For four hundred years there was no striking improvement in the valve. The various types of sliding and rocking valves were modified and refined until it was assumed that they typified perfection. At one stroke the Corliss valve made such an immense improvement that the marvel was as much in its simplicity as in its performance.
The reasons and the explanations will be set forth in the section which analyzes valve motion. In this, as in other matters, it shall be our aim to explain why the different improvements were regarded as epochs in the production of motors.
THE STEAM GENERATOR
The most widely known and utilized source of power is the steam engine. Before its discovery wind and water were the only available means, except the muscular power of man, horses and other animals, which was used with the crudest sort of contrivances.
In primitive days men did not value their time, so they laboriously performed the work which machinery now does for us.