The key to the future is — more and more frequently — found in the past. Reflecting, man recalls earlier efforts and ideas; modifies and improves upon them. Primitive rockets were the precursors of travel to the moon. Da Vinci's sketches of an airfoil, which would carry a man, foretold supersonic passenger travel. The list is endless. It may well be that air engines, such as the Stirling cycle engine detailed in this book will put a technology devised in 1817 against the problems of today, especially the petroleum energy crunch. As the reader will learn, this remarkable engine will run on a variety of fuels in automotive applications and is the focal point of on-going development in that area. Perhaps more important, the Stirling is a basically simple engine which will operate on solar energy, and, as a result, it promises to be a most powerful weapon in a yet-to-be-declared war on starvation by providing the power to irrigate food crops on arid soil now barren. It's a story as old as time. By looking back, one may plot a truer course for surging forward.