4.1 Years 1800-1899

Number of slide rules: 12.

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. By the mid-1800s military calculations for artillery applications saw the development of a standard set of scales by Lt. A. Mannheim of France. His labeling of the four scales on his slide rule as A, B, C, and D became standard labels for those 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 decides to develop their own process for manufacturing slide rules, the first of which became available on the American market late in the decade.

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
c.1820	noID	Gunter Rule
c.1840	Davies	Routledge Engineer
1843	Palmer	Palmer’s Computing Scale
1845	Palmer	Palmer’s Pocket Scale
c.1880	Sikes	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