K e slide rule dating
This rule had four scales, two on the body (the fixed part) and two on the central slide.
The top three of these are two-cycle logarithmic scales (running from 1-100) and the bottom one is one cycle (1-10).
He took this design to the Tavernier-Gravet firm the successor to Gravet-Lenoir and had them produce it as a standard item in their product line. The Mannheim slide rule was extremely effective, and became a standard configuration produced by numerous makers well into the following century.
The cursor was of the Chisel type, with two fingers jutting to the left of the sliding rectangle; the thin tips of these fingers would point at the scales.
With Robertsons cursor you can move between the various scales at will (and keep track which is which, given the legend on the cursor itself).
That such a useful idea was left out of the Soho design that came years later is probably due to the fact that before the industrial revolution each inventor would devise his own instrument, and the dissemination of new ideas was limited. The cursor came of age in 1851, thanks to a French artillery officer, engineer, and later professor of mathematics called Amde Mannheim.
The first logarithmic calculating rules did not slide at all... Complete with black card case and English printed instruction booklet. Hemmi Jirou & Co was founded in 1895 as the first Japanese slide rule manufacturer. They are particularly renowned for their bamboo and celluloid slide rules.The iconic slide rule, long identified with the science and engineering professions before the advent of the electronic calculator, had two sliding components that set it apart from an ordinary rule: the slide running down the center of its body, and the transparent hairline cursor (also called runner) that moved over both body and slide.The variety of calculations required ran into a problem: to calculate (multiply or divide) or convert between different quantities one needs to move from a number on one scale to the number at the equivalent point on another scale.
This required the two scales to touch each other, so the equivalent points could be pinpointed accurately.
they used fixed scales on a wooden rule that allowed distances to be measured and added using a pair of dividers.