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 Engineis a saga of ingenuity and will-and the dawning of a new age.