Professor C G Barkla, Edinburgh

by E T Whittaker

DEATH OF PIONEER IN PHYSICS

The death yesterday of Charles Glover Barkla, F.R.S., Nobel Laureate, Professor of Natural Philosophy in Edinburgh University, has removed the most distinguished representative of the experimental sciences in the Scottish professoriate. Barkla was a Lancashire man, and studied physics first in Liverpool under Oliver Lodge for whom he retained throughout his life an affectionate veneration. Like most brilliant men from the English provincial universities, after taking his degree he migrated to Cambridge to work with J J Thomson, who after his discovery of the electron in 1897 had created at the Cavendish Laboratory a school of physical research which has never been equalled.

Among the younger men about the time when Barkla went there in 1899 were (Lord) Rutherford, the present Lord Rayleigh, (Sir) J C M'Lennan, (Sir) O W Richardson, (Sir) J S Townsend, and Professors C T R Wilson, H A Wilson, H S Allen, and J A M'Clelland, all of whom attained great distinction . Here, at Thomson's suggestion, Barkla began his first important piece of research, on the secondary radiation from gases exposed to X-rays. His results led him to conclude that the scattered radiation could not be produced by massive particles such as atomic ions, and to infer that it must be produced by electrons in the atoms; and this led Thomson to the further deduction that the number of electrons in the atom was of the order of the atomic weight. The further development of Barkla's scientific work and his great discoveries are described in Professor Born's contribution below.

TWO GREAT HONOURS

The success of the Cambridge research led to the offer that he should return to Liverpool as a lecturer, and in 1909 to his appointment as Professor of Physics in King's College, London. This was followed four years later by his election to the Chair of Natural Philosophy in Edinburgh University. In 1917 he received the two greatest honours of his life, the Nobel Prize for Physics and the Hughes Medal of the Royal Society.

The Professor of Natural Philosophy governs the largest department in Edinburgh University, and it is essential that he should be an excellent lecturer, capable of interesting large classes. Barkla, who combined a magnificent voice and commanding presence with a lucid style and complete mastery of his subject, was eminently successful. Many of his former pupils occupy distinguished positions in the world of physics.

One of his chief interests outside his professional subject was music. At Cambridge he had been a member of the choir of King's College Chapel, and he was a frequent and much appreciated singer at University concerts in Edinburgh. He was a deeply religious man, and a faithful member of the Methodist Church.

Barkla married Miss Mary Cowell, daughter of J T Cowell, J.P., Receiver-General of the Isle of Man. They had three sons and one daughter, who all became graduates - two in medicine, one in physics, and one in music. The loss of his youngest son, a surgeon of most brilliant promise, the Ettles Scholar of his year, who was killed in Africa fifteen months ago, was a terrible blow, and may have aggravated his breakdown in health. The other sons are both on active service abroad.

Charles Glover Barkla's obituary, written by E T Whittaker, appeared in The Scotsman on Tuesday, 24 October 1944.

The article below by Born appeared at the same time.


IMPORTANT X-RAY DISCOVERY

By Professor MAX BORN, F.R.S.

When eight years ago I first came to Edinburgh, it was a strange experience to become a colleague of a man who, although not much older, had already become celebrated in the scientific world when I was graduating, and whose discoveries have marked an epoch in physics. He received me with utmost kindness, and our two departments have ever since worked in harmony under the same roof. It is only a few weeks ago that we cycled together in the Spey valley and sat on the shore of the lovely Loch An Eileen. Now a sudden illness has ended his life. His death is a great personal loss to me.

An adequate account of Barkla's scientific work cannot be given! in a few lines. I shall only mention the most important of his discoveries, all concerned with X-rays. Röntgen had done his work, so thoroughly that, after the discovery of the new radiation in 1895, more than ten years went by before an essentially new fact was found, and it was Barkla who did it. He discovered that X-rays show the phenomenon of polarisation in a similar way to light, and this was the first indication that they were waves of the same kind as light (which was proved later by others.)

An even more important result was obtained by Barkla from an investigation of the scattering of X-rays by different substances. By measuring the absorption of the diffuse radiation scattered in all directions he showed that it contained, beside the deflected incident radiation, another part which changed its properties with the substance of the scatterer, but depended only on the type of chemical elements present, not on their chemical combination or the physical state of the substance. This discovery of this characteristic radiation of the atoms has proved to be one of the most important steps in the investigation of atomic structure. When a few years later X-ray spectroscopy was developed, all his results were confirmed and supplemented by many details. It is mainly this work for which the Nobel Prize was awarded to him. Barkla continued through all his life to investigate the properties of X-rays, and numerous papers by him and his pupils have been published. By his death physics has lost one of the great pioneers of a great period of discovery.