A photo of some of my ”slide rules”. On the left is a Stanley Fuller cylindrical slide rule from 1884. In the centre is a Thacher from early 1920’s and on the right is a home made complex number calculator. They all operate on the same principle as the traditional linear slide rule. The Stanley has an effective length of nearly 13m and the Thacher of almost 22m, giving them an accuracy of up to 5 significant figures. So much more tactile and impressive than a pocket calculator.
