A nice website devoted Babbage's Difference Engine #2. The Difference Engine was Babbage's design for a machine that could calculate polynomials, a forerunner of the modern-day computer. Definitely something to look into for those interested in machines and gadgetry. Another great source, in some ways even better, is John Walker's Analytical Engine page; it has original texts relevant to Babbage's designs by Babbage himself and by Lady Ada Augusta. (The Analytical Engine was a generalized Difference Engine; i.e., the idea behind it was to do more than could be done with a Difference Engine. Of course, even the Difference Engine was not built at the time, although a working version was recently made by the Science Museum in London. They had to correct a few minor errors in the design, but as everything they did could have been done by the Victorians they proved conclusively that the problem with the building the machine was not, as some had thought, the limits of Victorian engineering.) Fascinating stuff.
Incidentally, Babbage was probably the first to try to apply what we would today call computer science to major philosophical questions; the interesting, sometimes insightful and sometimes very odd, result is his Ninth Bridgewater Treatise, which (as Babbage notes right away) is not a Bridgewater Treatise at all, but some notes and remarks gesturing at how he would write such a work. He also responds to the greatest and philosophically most important Bridgewater Treatise, the third (first in order of publication), by none other than William Whewell, the great philosopher and historian of science. The Calculating Engine, as Babbage calls it here, makes an appearance in a number of arguments about providence and miracles -- Babbage thinks of providence in terms of what we would call algorithms.
