In 1821 an inventor and mathematician named Charles Babbage was reviewing a set of mathematical tables. After finding an excess of errors in the results, he exclaimed, I wish to God these calculations had been executed by steam. Thus began Babbage's lifelong enterprise to design and build a mechanical calculating engine-the world's first computer. Drawing on Babbage's original notes and designs, Doron Swade recounts both Babbage's nineteenth-century quest to build a calculating machine-the Difference Engine-and Swade's own successful attempt to build a replica for the bicentennial of Babbage's birth. Set against the tantalizing background of Victorian science and politics with a colorful cast of characters, The Difference Engine is a saga of ingenuity and will-and the dawning of a new age.