Description

This instrument consists of a cylinder that revolves in an open framework made by 20 triangular brass bars. Each bar is covered in a paper on two of its visible sides, and each piece of paper has two scales. These bars are held between two metal rings which are mounted to a wood base. There are wooden knobs on either side of the instrument that both rotate the cylinder, and move it from right to left. There are detailed usage instructions pasted to the top of the wooden base that holds the slide rule. The instrument is stored in a mahogany case with a white Keuffel & Esser label nailed to the inside lid. The label notes the model number (4012) and the serial number (4611).

Before the development of digital calculators, slide rules were the instruments of choice for complex mathematical equations, but most slide rules could only calculate to a few decimal places. In 1881, engineer Edwin Thatcher designed a cylindrical slide rule that could perform calculations to five decimal places (to perform similar calculations, a traditional slide rule would have to be 66 feet long). This calculator became an essential tool for scientists, engineers, and anyone else who needed to perform large mathematical calculations.

Serial number 4611.

Additional Information

More information: Model 4012 Catalog Pages