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'Catholic Organon'

The proliferation of specialist slide rules in the eighteenth century inspired schoolmaster John Suxspeach to create a universal one. This was designed to be used in different disciplines and types of inquiry, and represents an early attempt to enforce universal standards through instrumentation.

Bringing order to the sciences?

As with many mathematical instruments, John Suxspeach's 'Catholic-Organon, or Universal Sliding Foot-Rule' (above) originated as a personal device. Working as a schoolmaster in Stepney, London, he was implored to make the device available to the public, securing the first Royal Patent for a slide rule in 1753.

The device itself was complex. It had a number of scales and carried two sliders, each with brass inserts, which allowed it to be used as a protractor or level. The hollow slider between the two main pieces was probably meant to hold some kind of telescope.

Suxspeach's rule was manufactured by Benjamin Parker and came with an extensive manual. Evidence suggests, however, that it was unsuccessful. Because it was not particularly suited to one purpose, uneducated professionals were not interested in mastering its use. Application-specific rules had scales that were more legible, and their purposes were more readily understood.

Standardising the slide rule

Mannheim slide rule
Mannheim slide rule (Wh.6515)

It was not until the 19th century that a true 'standard' slide rule was produced.  Victor Mayer Amédée Mannheim was a student at the École d'Application in Metz, France in 1859, when he came up with his idea for a standardized slide rule for arithmetic calculations. His design was ten inches long and had only four scales, along with a cursor that allowed the user to clearly align numbers.

By the 20th century, precision manufacturing equipment greatly improved the accuracy and consistency of rules produced to this design. Such rules came into wide use as modern engineering and other physical sciences became further established as professions. Whether the increased standardisation of measurement caused or was caused by this broader economic shift is still an open question.

Mikey McGovern

Mikey McGovern, 'A 'universal' slide rule? John Suxspeach's 'Catholic organon'', Explore Whipple Collections, Whipple Museum of the History of Science, University of Cambridge.

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