Soho Slide Rule by Lenoir

France, 1825-1830, simplex, 25 cm "Soho" scales, boxwood.
By 1790 James Boulton and James Watt modified Coggeshall slide rules to improve their accuracy and usefulness.
By 1799 their Soho slide rule helped to usher in the Industrial Revolution.
It facilitated the design and manufacture of their seminal machine, the steam engine.