# Dictionary of National Biography, 1927 supplement/Moseley, Henry Gwyn Jeffreys

​MOSELEY, HENRY GWYN JEFFREYS (1887–1915), experimental physicist, the only son of Henry Nottidge Moseley [q.v.], Linacre professor of anatomy in the university of Oxford, was born at Weymouth 23 November 1887, and educated at Eton and at Trinity College, Oxford, of which he was a Millard scholar, graduating with honours in natural science in 1910. On both sides he was descended from families of great scientific ability, and he early showed marked originality of mind and interest in science. As an undergraduate he pursued his studies with great determination, with a preference for his own methods; he also rowed every year in one or other of the college boats. Immediately after graduation, he was appointed lecturer in physics in the university of Manchester and began research under the direction of Professor (Sir) E. Rutherford. He soon developed into a rapid and skilful experimenter with unusual powers of continuous work, and showed to a marked degree that combination of practical ability and philosophic insight so necessary for attacking new and difficult problems. Following a number of important investigations in the subject of radio-activity, Moseley began that work on the X-ray spectra of the elements with which his name is inseparably connected. (Sir) W. H. Bragg and W. L. Bragg had already shown that the wave-length of X-rays could be determined by the crystal method, and had found evidence of bright lines superimposed on the continuous spectrum. Moseley proceeded to examine systematically the relation between the bright-line spectra given by different elements; and found that all the elements gave similar types of spectra, and that the frequency of vibration of corresponding lines was proportional to the square of a number which varied by unity in passing from one element to the next. From these observations, he was able to draw conclusions of far-reaching importance in connexion with the constitution of atoms. He deduced that the nuclear charge of an element, in fundamental units, was equal to its atomic or ordinal number, and varied from 1 in hydrogen to 92 in uranium; he further showed that only three elements were missing between aluminium and gold, and predicted their spectra. His results brought out clearly that the main properties of an element are determined not by its atomic weight but by a whole number defining its nuclear charge. This law of Moseley ranks in importance with the discoveries of the periodic law of the elements and of spectrum analysis, and is in many respects more fundamental than either.
In 1914 Moseley travelled with his mother to Australia to attend the meeting of the British Association. He returned to England in order to enlist at once in the new army, and he obtained his commission as lieutenant in the Royal Engineers. He took part in the Gallipoli ​campaign, and was killed in action on 10 August 1915 at the age of twenty-seven. He was unmarried. The premature death of a young man of such brilliant promise and achievement was everywhere recognized as an irreparable loss to science. His friends and scientific admirers in many countries united to erect a memorial tablet in the physical laboratory of the university of Manchester. He bequeathed his property to the Royal Society to aid scientific research, and a studentship bearing his name has been instituted.
[Personal knowledge.]
E. R.