4.1 Years 1800-1899

Number of slide rules: 16.

Besides being a tool for the occasional scientist or mathematician of the day, slide rules were used during this period for navigational computations, the calculations of timber measurements and building trades, and the computation of taxes – especially for the taxation of alcohol. So-called “gauging rules” or “excise rules” were used to measure and calculate the volume of liquid within a barrel and determine the tax on the product. The late 1700s and early 1800s also saw slide rules used for calculations in the development of steam engines, called engineer’s rules, or “Soho” rules, as developed by J. Watt and M. Boulton. Their scales were a variant of the earlier carpenter’s rules introduced years earlier by H. Coggeshall in 1677. By the mid-1800s military calculations for artillery applications saw the development of a standard set of scales by Lt. A. Mannheim of France. The four scales on his slide rule were labeled as A, B, C, and D and while such labeling of scales were common on other rules, his became standard labels for those particular scales as found on almost every slide rule since. In 1890, slide rules were only being manufactured in Great Britain, Germany, and France. The Duplex (double-sided) slide rule was invented in 1891 by William Cox of England, and he assigned his patent to Keuffel and Esser in the U.S. That year K&E decided to develop their own process for manufacturing slide rules, the first of which became available on the American market late in the decade. While K&E was the first long-lasting producer of premium slide rules in the U.S., a limited number of slide rules were manufactured by others in this country as early as the early 1840s (Palmer’s Computing Scale) and various carpenter’s rules such as by Belcher Brothers and by Stanley in the 1850s.

Of technical note, the latter part of this century also saw the development of electromagnetism, the telephone, the light bulb, the combustion engine, and aerial flight such as ballooning and airships.

Year	Maker	Model
1809	Jacob and Halse	Sector
1816-1824	Gill	Comparative Rule
1816-1824	Gill	Proof Rule
c.1820	noID	Gunter Rule
c.1840	Davies	Routledge Engineer
1843	Palmer	Palmer’s Computing Scale
1845	Palmer	Palmer’s Pocket Scale
1845-1849	Dring and Fage	Excise Officers Rule
c.1858	Stanley	No. 15
c.1880	noID	Comparative Rule
1883-1902	Dring and Fage	Inland Revenue Rule
1897	Faber	360
c.1898	K&E	American/Favorite
1898-1900	Faber	365
1898-1925	E.S.A. London	Harrow Mark Reducer
1899-1902	Faber	367