Before electronic computers existed, engineers built mechanical analog devices called differential analysers [1] to compute derivatives and integrals, invented

Before electronic computers existed, engineers built mechanical analog devices called differential analysers [1] to compute derivatives and integrals, invented in 1876 by brothers James Thomson and Lord Kelvin. Famously, cheap differential analysers were built out of Meccano starting in 1934 [2]. After scientists gained access to electronic computers, these old analysers were repeatedly handed down through lower-budget institutions, schools and eventually museums. [1] https://en.wikipedia.org/wiki/Differential_analyser https://en.wikipedia.org/wiki/Differential_analyser [2] http://amg.nzfmm.co.nz/differential_analyser_explained.html http://amg.nzfmm.co.nz/differential_analyser_explained.html