Kinda hard to explain, but on a paper, three scales are printed, looking sort of like slide-rule scales. Numbers. Say the top one is gross pay, the middle one is a percentage, and the bottom one is net pay. You lay a ruler across any two, and read the answer on the third.

There’s a specific name for this kind of computational thingie…and I don’t know what it is.

Relatedly, there are lookup tables with a slidable cardboard window to only show one row at a time. A lot of teachers used to have something called an EZ-Grader, for instance, which you could set for a total number of questions, and see at a glance which number corresponds to what percentage.

There’s a novel (or ongoing serial, I’m not sure which) by one Rob Garitta called “Numbers Running”, excerpts of which can be read on the Twilight Of The GM blog site. It concerns a backward (by interstellar standards; their indigenous production base is roughly equivalent to early-mid Twentieth century Earth) planet called Zaonia. When Zaonia is embargoed by the equivalent of the Trade Federation, the people there rediscover pre-electronic ways of doing things, including log tables, slide rules, analog mechanical computers and nomograms; with which they can do the math necessary to get independent tramp freighters into orbit and back again.

A vernier is used for very precisely measuring the position of one object along another, such as the two pieces of a micrometer. It consists of a pair of scales with slightly different spacings, such that the two will line up only at a single tick mark.

reminds me of college days (many many years ago) when everybody reluctantly converted from Cycles per Second to Hertz. Someone created a handy guide to conversion, including a semi-log graph and a nomogram.

Can we assume this is a whoosh? Lemme check my calculator, but I always converted from CPS to Hz by removing the “CPS” and substituting “Hz”. Too esoteric?

Little-known secret: you can use the CPS-Hz nomogram to implement ROT-26 encryption. It’s twice as secure as the ROT-13 cypher.

I’ve encrypted a message using ROT-26 below. Decryption via nomogram or supercomputer is left as an exercise for the reader. Here’s the encrypted message: