Cargill Gilston Knott FRS, FRSE LLD (30 June 1856 – 26 October 1922) was a Scottish physicist and mathematician who was a pioneer in seismological research.

[1] He was educated at Arbroath High School in Angus, and attended the University of Edinburgh, where he studied alongside James Alfred Ewing.

Six came, including geologist John Milne and physicist James Alfred Ewing, who became professors at the college, which became part of Tokyo Imperial University.

Ewing returned to Scotland in 1883 and the University rector asked Lord Kelvin to recommend a successor.

While in Japan, Knott began to develop mathematical equations describing how seismic vibrations are reflected and transmitted across the boundary between seawater and seabed.

After returning to the University of Edinburgh in 1892, he expanded upon this research to describe the behaviour of earthquake waves at the interface between two different types of rock.

Knott continued his work as a mathematician, including quaternion methods of his professor and mentor Peter Guthrie Tait.

As Michael J. Crowe describes,[9] this paper set straight wayward theorists that expected to find associativity in systems like hyperbolic quaternions.

In Knott's introduction to his textbook edition he says "Analytically the quaternion is now known to take its place in the general theory of complex numbers and continuous groups,...".