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. He spent his early career in Japan. He later became a Fellow of the Royal Society, Secretary of the Royal Society of Edinburgh, and President of the Scottish Meteorological Society.
Biography
Knott was born in Penicuik, Midlothian, the son of Pelham Knott, an agent for a paper manufacturer and his wife Ellen. His paternal uncle was the artist Tavernor Knott.
He was educated at Arbroath High School in Angus, and attended the University of Edinburgh, where he studied alongside James Alfred Ewing. He worked on various aspects of electricity and magnetism, obtaining his doctorate in 1879.
He was appointed as an assistant in Natural Philosophy at the University of Edinburgh in 1879, and held this post until 1883, when he left to take up a post at Tokyo Imperial University. He was elected as a Fellow of the Royal Society of Edinburgh in 1880 after being proposed by Peter Guthrie Tait, Alexander Crum Brown, John Gray McKendrick, and Alexander Buchan. He won the Society's Keith Prize for the period 1893-95. He served as Secretary 1905-1912 and General Secretary 1912-1922. He was also a founder of the Edinburgh Mathematical Society, taking the chair for its first meeting on Friday 2 February 1883.
Career in Japan
Japan's Public Works was found in October 1871 with 11 departments, one of which was the engineering institution. Yamao Yozo, head of the institution asked William Rankine and Lord Kelvin to send proper teaching staffs to the technical school through Hugh Mateson, and hired 6 instructors lead by Henry Dyer as a principal, John Milne a Professor of Geology and Mining, and James Alfred Ewing Professor of Physics and Engineering at Tokyo Imperial University from 1878.
When Ewing returned to Scotland in 1883, the rector of Tokyo Imperial University wrote to Lord Kelvin, asking for his recommendation for a successor, Lord Kelvin recommended Knott, and the recommendation was supported by Ewing. Thus, Knott replaced Ewing as Professor of Physics and Engineering at Tokyo Imperial University. For the next nine years, he worked closely with Milne, Gray and the Japanese seismologist Fusakichi Omori in establishing a network of recording seismometers across the Japanese Empire. Knott also taught courses in mathematics, acoustics, and electromagnetism at the Tokyo Imperial University.
Knott also undertook the first geomagnetic survey of Japan, assisted by Japanese geophysicist Tanakadate Aikitsu, from which was developed the first earthquake hazard map of Japan. Knott's key contribution was his background in mathematics and data analysis. One of his innovations was to apply the technique of Fourier analysis to the occurrence of earthquakes. Two chapters in his 1908 book The Physics of Earthquake Phenomena were devoted to this subject, which Knott hoped would enable him to deduce the probability of when future earthquakes would occur.
Cargil Knott married Mary Dixon in 1885, becoming the brother-in-law of the literary scholar James Main Dixon.
On the conclusion of his stay in Japan in 1891, he was awarded the Order of the Rising Sun by Emperor Meiji.
Return to Edinburgh
On his return to Edinburgh, Knott took up the position of a Reader in Applied Mathematics at the University of Edinburgh, holding the post until his death in 1922.
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's equations, derived in terms of potentials, were the first to describe the amplitudes of reflected and refracted waves at non-normal incidence and together with the Zoeppritz equations are now the basis for modern reflection seismology – an important technique in hydrocarbon exploration.