JF Ptak Science Books Quick Post
Just a quick post here on patented mathematical tools using long wooden planks in a sliding frenzy to find displayable answers for 19th century schoolchildren and their addition problems. I know a good set of Napier's bone could come in very handy (appearing much earlier on than these instruments), but I'm just not sure what kids could learn from using these tools–like any other calculating device, early or late, they have a questionable quidity so far as appreciating the essence of numbers is concerned. That said, the drawing for the Meyers' machine is beautiful, and could no doubt lead to a number of short, noir-y stories.
Source: Google Patents, here.