Inventions are often preceded by prototypes that introduce new concepts, serving as models in which development will occur. Sometimes these prototypical ideas arise before they can be carried out in any practical way. Such is the case of the Analytical Engine, which may be considered the great-grandfather of the modern computer. The Analytical Engine is widely recognized as the first conceptual device that incorporated principles found in contemporary computing.

Charles Babbage's first machine was actually the Difference Engine (pictured here), which was begun in 1823. It was designed to calculate differences. Work on this precursor to the Analytical Engine continued over a period of years, but Babbage eventually abandoned it in 1842, when the British government stopped funding it. The Difference Engine was later kept in a museum in South Kensington, England.

What makes the Analytical Engine so truly extraordinary is that it was conceptualized well before electricity...