On two occasions I have been asked, 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.

However after the obituary appeared a nephew wrote to say that Charles Babbage was born one year earlier in 1791. The book is a work of natural theology and incorporates extracts from correspondence he had been having with John Herschel on the subject. The main difference between the two engines is that the Analytical Engine could be programmed using punched cards.

Nine years later the Science Museum completed the printer Babbage had designed for the difference engine. In 1991 a perfectly functioning difference engine was constructed from Babbage's original plans.