Gunter's Scale

The Gunter’s Scale uses logarithmic and other scales to assist in numerical and trigonometric calculations. Instead of using a sliding scale like the later slide rule to assist in the addition or subtraction of logarithms, the user of a Gunter’s Scale uses dividers to mark sums and differences. The Gunter’s Scale is particularly specialized for nautical use, as some of its scales make direct solution of dead reckoning problems relatively easy. Developed by Edmund Gunter in 1623, Gunter's Scales or Rules continued to be made and used into the 19th century.