Dr. Balfour Stewart, meteorologist and geophysicist, died on the 19th of December, 1887.
Balfour Stewart may or may not have been a radiant individual with a magnetic personality, but according to biographies, his scientific “industry” on the topic of heat and terrestrial magnetism was “indefatigable”. He devoted the greater part of his life to physics and research into those subjects in addition to meteorology. And, as stated in his obituary in the ‘Times’ of December, 1887, Stewart’s life “was an active and highly useful one” and his work spanned the disciplines of “original investigation”, “accurate and laborious observation” and “practical teaching”. He is especially famous for his seminal research on radiant heat, which contributed to the foundation of spectrum analysis and a few burnt fingers. Stewart was a pioneer in studying the upper atmosphere and, in particular, his study of the Earth’s magnetic field and the electric currents above it led to the discovery of the ionosphere. Of course, he didn’t know it as the ionosphere as that phrase was coined later by another Scot, Watson-Watt, the inventor of radar.
Radiant heat first claimed Stewart’s attention whilst he was at Edinburgh and by 1858, he had completed his first investigations into the subject. Those yielded a remarkable extension of Pierre Prévost’s ‘Law of Exchanges’, which enabled Stewart to establish the important fact that radiation is not a surface phenomenon, but takes place, like absorption, throughout the interior of the radiating body. He made the discovery that the radiative and absorptive powers of a substance are equal, objects radiate and absorb energy of the same wavelength, not only for the radiation as a whole, but also for its every constituent.
Stewart won a distinguished reputation by his discoveries and writings in physics and meteorology and honours from widely distant places were conferred upon him. He became President of the Physical Society of London, President of the Literary and Philosophical Society of Manchester, and a Fellow of the Royal Society. He was the author of several successful textbooks on theoretical and practical physics; well known to every student of science for generations and he also wrote the excellent article on ‘Terrestrial Magnetism’ for the 9th edition of the ‘Encyclopædia Britannica’. Stewart was a mathematician and a physicist and was quoted by R. H. Kargon in ‘Science in Victorian Manchester’ as caustically stating, “I do not think the division of the subject into two parts – into applied mathematics and experimental physics a good one, for natural philosophy without experiment is merely mathematical exercise, while experiment without mathematics will neither sufficiently discipline the mind or sufficiently extend our knowledge in a subject like physics”.
Amongst the notable works published by Stewart himself was his ‘Treatise on Heat’, which is an excellent introduction to the subject of temperature, but the work he wrote in conjunction with another physicist and fellow Scot, Professor Peter Guthrie Tait, also deserves special mention. That was called ‘The Unseen Universe’ and at first, it was published anonymously. Stewart was a devoted churchman and, strangely enough, prominently identified with the Society for Psychical Research, but his collaborative work was intended to argue that science was not incompatible with religious doctrines. That, of course, was a common misconception at the time amongst the unenlightened as it remains. When Tait wrote Stewart’s obituary in the ‘Times’, he made mention of their joint treatise, writing that it “has experienced every variety of reception, from hearty welcome and approval …to the extremes of fierce denunciation, or of lofty scorn”. Both Tait and Stewart believed what they called “a simple fact”, which was that “human science has its limits; and that there are realities with which it is altogether incompetent to deal”.
Balfour Stewart was born in Edinburgh on the 1st of November, 1828. He was educated in Dundee, at the University of St Andrews and at the University of Edinburgh. Under his tutor at Edinburgh, Professor Kelland, Stewart displayed excellent ability and could have become a mathematician, but in hindsight, it’s better that he later confined himself almost exclusively to experimental physics. Initially, Stewart pursued a mercantile career for about ten years; in Leith and afterwards in Australia, before he returned to Scotland to resume his studies. From 1856, he worked in Edinburgh University as an assistant to Professor J. D. Forbes, one of the “ablest of experimenters”. Stewart had previously been a distinguished member of Forbes’ class and under the latter’s guidance, Stewart developed his interest in natural philosophy (what we now call physics).
In 1858, whilst he was still working with his former Professor, Stewart completed the first set of his investigations on radiant heat and arrived at his remarkable conclusions. His paper, which was published in the ‘Transactions of the Royal Society of Edinburgh’, documented the greatest leap in knowledge of the subject since the early days of his mentor, Forbes, and an Italian geezer called Melloni, who also got a bit hot around the collar about heat. From 1859 until 1870, Stewart was the Director of Kew Observatory, where he quite naturally became interested in problems of meteorology and terrestrial magnetism. He was awarded the Royal Society’s Rumford Medal in 1868 and left Kew to take up the post of Professor of Natural Philosophy at Owen’s College in Manchester.
That year of 1870, Stewart was very seriously injured in a bad railway accident and he never fully recovered. Sadly, in just a few short months, he passed from vigorous activity in the prime of life to grey headed old age. Balfour Stewart died on the 19th of December, 1887, as a result of a stroke he suffered the day previously, at his estate of Ballymagarvey in Balrath, in County Meath, Ireland. At the time of his death he was President of the Physical Society of London and a member of the committee appointed to advise the Government on solar physics.