Logarithmic scale
A logarithmic scale is also a graphical scale on one or both sides of a graph where a number x is printed at a distance c·log(x)  from the point marked with the number 1. A slide rule has logarithmic scales, and nomograms often employ logarithmic scales. On a logarithmic scale an equal difference in order of magnitude is represented by an equal distance. The geometric mean of two numbers is midway between the numbers.