April 20th, 1809
James David Forbes FRS FRSE FGS (1809–1868) was a Scottish physicist and glaciologist who worked extensively on the conduction of heat and seismology. Forbes was a resident of Edinburgh for most of his life, educated at its University and a professor there from 1833 until he became principal of the United College of St Andrews in 1859.
Forbes was born on 20 April 1809 at 86 George Street in Edinburgh, the fourth son of Sir William Forbes, 7th Baronet, of Monymusk and Pitsligo (1773–1828) and Williamina Belches of Invermay.
In response to a series of earthquakes near Comrie in Scotland in 1839, a committee was formed in the United Kingdom in order to produce better detection methods for earthquakes. The outcome of this was the production of one of the first modern seismometers by Forbes, first presented in a report by David Milne-Home in 1842.
The most significant instrument resulting from the committee’s work was an inverted-pendulum “seismometer”, designed by James Forbes in 1844. It consisted of a vertical metal rod having a mass C moveable upon it. The rod was supported on a vertical cylindrical steel wire.
