With this object Watt had invented his original wheel-engine.

But no steps were taken to introduce it into practical use.

At length he prepared a model, in which he made use of a crank connected with the working beam of the engine, so as to produce the necessary rotary motion.
There was no originality in this application.

The crank was one of the most common of mechanical appliances.

It was in daily use in every spinning wheel, and in every turner's and knife-grinder's foot-lathe.
Watt did not take out a patent for the crank, not believing it to be patentable.