Slide-rule, 12-inch, boxwood, engraved: "Isaac Carver fecit 1713", with two sliders, in leather case (case badly worn)

The Excise was set up in 1643 to support military expenditure. It rapidly became the largest government department and was known as ‘the monster with 10,000 eyes’. By 1690 a thousand excise men were striding the country armed with seven instruments, including a slide rule similar to this. The principal problem was to find the volume of a barrel, or cask. The end and central measurements, together with the length, could produce a result quite quickly. Gauging rods were used when barrels were not full, which led to more complex calculations. Excise men were the largest group of mathematically literate men in the kingdom.