Digesting the main sections of Volume IV of Dr. Needham's magnum opus, this book is concerned with the immense advances made in early and medieval China in mechanical engineering. It discusses in simple but eminently readable terms the status of engineers, their tools and materials, then basic mechanical principles, followed by machinery powered by animals, man and even by steam, vehicles for land transport, six centuries of hidden clockwork, windmills and aeronautics. Since China was far ahead of the West in ancient and medieval times, this volume helps make clear the immense debt owed by Western civilization to the Chinese. Such debts included the important mechanical principles of transforming rotary motion to a to-and-fro motion of a crank and vice-versa. They invented the first efficient harness for horses and the first mechanical clocks.