Last Monday with Gramps Emily covered a pot pourri of maths-tech-sciency-vintage things. For starters, they looked at Napier’s Bones and learned how to use them for multiplication and division. Next (I think; I’m writing this from a summary Emily wrote minutes after her lesson, but it might not make as much sense now as it did then!) they looked at scales to work out reciprocals, which can also be used for parallel resistors. The also looked at a logarithmic scale using the powers of 2 to multiply, divide, and find squares and square roots. If that makes no sense (will have to get Gramps to check!) that would be because I confess to having no idea what a reciprocal is, and I managed to erase anything to do with logarithms from my mind moments after finishing my maths O level some 22 years ago. Ahem. But whatever it was, Emily understood it, which was impressive.
Next they looked at Gramps’ vintage adding machine, which was made approximately 50 years ago in what was then East Germany. They also looked at some more slide rules, one about the same age as the adding machine and one made in 1956; they also examined a circular slide rule and how that worked, and logarithmic paper. Finally, they had a look at some fun kinegrams – there are instructions there for how to make your own using illustration software, which Emily hasn’t had a chance to do yet but intends to have a go at.