James David Forbes lived from 20 April 1809 to 31 December 1868. He was a physicist best known for his work on the conduction of heat, and on glaciology. The wider picture in Scotland at the time is set out in our Historical Timeline.
James David Forbes was born in Edinburgh. He was the fourth son of Sir William Forbes, 7th Baronet. He became a student at the University of Edinburgh in 1825 and was soon having papers published in the Edinburgh Philosophical Journal. At the age of 19 he was elected to be a Fellow of the Royal Society of Edinburgh. In 1832 at the age of 23 he was elected to the Royal Society of London.
In 1833 Forbes was appointed to the post of Professor of Natural Philosophy at the University of Edinburgh following the death of the previous incumbent, Sir John Leslie. He held the post until 1859 and is credited not only as an excellent teacher but for his wider contribution to the development of the university over nearly three decades. In 1859 he became Principal of the United College, part of the University of St Andrews. He held this post until his death on the last day of 1868.
Much of Forbes' scientific career was spent looking at aspects of heat, including the way the conduction of heat through iron varied with temperature, the polarisation of infra-red energy, and the effect of the atmosphere on the sun's rays. He then turned his attention to the measurement of the temperature of the earth at different depths, and to factors determining the flow of glaciers. During a series of visits to Switzerland and Norway he almost incidentally produced the definitive data set on the boiling point of water at different altitudes. He also had an interest in geology, publishing papers on the geology of areas as widely spread as the Pyrenees and the Cuillin on the Isle of Skye.