Description

SOLD – A very good example of Thacher’s calculator.

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 small Keuffel & Esser plaque fitted on a corner of the base.

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). 

Edwin Thacher patented the idea in 1881. K & E bought the rights to sell and manufacture it. Stanley initially produced them for  K & E and production was moved to the U.S.A. near the turn of the century. The inventors name is Thacher, but it was mispelled ‘Thatcher’ on almost all versions.

Contained in original box which has a crack across the lid and some dis-lodging to the corners. The instrument itself is in very nice condition.