When reading non-fiction, I don’t follow up enough on weird references. When I do, it tends to lead to cool stuff. Case in point: William Stanley Jevons’s Logic Piano, a proto-computer built in 1870. Jevons (1832-1885) was instrumental in bringing mathematical modeling to economics and did much to popularize Boolean logic—the same binary model that powers all computers today. The logical piano was the first Boolean machine, the first ancestor to whatever device you are now reading this post on. (Babbage & Lovelace’s famous Analytical & Differential Engines came first, but they used a different, more complicated programming language and were never actually built.)
(I’m basing most of this off a Rutherford Journal article that seems to have been poorly scanned and has some regrettable typos.)
The logic piano is basically a device that automatically produces truth tables for up to four terms. You can see the A, B, C, and D in the picture below. Between each term, the user inputs a relation between them: if you tell is that all As are B and all Bs are C, the machine will examine every possible output, winnow the ones that are logically impossible, and dutifully inform you that every A is also a C. Jevons got a clockmaker to put together the machine, about the size of a dresser, based on his designs.
Four-term logical problems are not especially hard to work out on paper, especially for a logician like Jevons, but he dreamed of eventually scaling up the machine to solve 16-term problems. This was was perfectly viable in theory, though it would have required many more obliging clockmakers. Babbage, too, couldn’t get his Engines built with current metal-casting techniques. I wonder what material constraints are holding back our computers today that might seem trivial in a century. Maybe our great-grandchildren will chortle over our supercomputers, too. I hope they do.