As you might expect from its name, the "Difference Engine" is a strangely difficult object to describe. You might start by imagining the side of a large crib with uprights ringed by small metal wheels ...
v. 1. Mathematical papers -- v. 2. The difference engine and table making -- v. 3. The analytical engine and mechanical notation -- v. 4-5. Scientific and miscellaneous papers -- v. 6. A comparative ...