636 SCIENCE PROGRESS 



(October 1920). This apparatus was an improvement on that used by Sir 

 J. J. Thomson in his positive-ray work. In Thomson's arrangement a 

 narrow circular beam of positive rays was so deflected by electric and magnetic 

 fields that particles having the same value for the ratio of charge to 

 mass produced a parabolic line on a photographic plate ; in the improved 

 method a very narrow ribbon of rays was deflected so that all such par- 

 ticles are brought together to form a short narrow line on the plate — a mix- 

 ture of particles of different masses giving a mass spectrum. With this 

 apparatus differences of atomic mass of the order of i part in 1,000 could 

 be detected, and the result, as far as neon is concerned, was to show that 

 there is no element of atomic weight 20-2, but only a mixture of two of 

 atomic weights 20 and 22. Further investigation has shown that the 

 majority of the chemical elements are mixtures of isotopes whose atomic 

 weights are all whole numbers on the oxygen scale, and has also demonstrated 

 the existence of isobares, i.e. elements of the same atomic weight but with 

 different nuclear charges and therefore with entirely different properties. 



When Dr. Aston wrote for Science Progress he had dealt at least 

 provisionally with eighteen elements ; his book Isotopes (published by Arnold 

 in 1922) contains an account of his investigation of many others. In this 

 brief note it only remains to pay a small tribute to the extraordinary skill 

 and patience which his work has involved. 



Professor Soddy (A. S. Russell, D.Se.)* 



Although Englishmen have been not ungenerously helped to Nobel 

 prizes in physics, the late Sir William Ramsay and Sir Ernest Rutherford 

 are the only British-born men who have preceded Prof. Soddy in gaining 

 the Nobel prize in chemistry. Indeed, as the first of these was a Scot and 

 the second is a New Zealander, Prof. Soddy has the distinction of being 

 the first English-born chemist to receive this prize. He is also the first 

 Oxford professor to receive a Nobel prize in any subject. 



Prof. Soddy passed from Eastbourne College via University College, 

 Aberystwyth, to Merton, Oxford, becoming a Postmaster there in 1895, 

 and taking a first in chemistry in 1898. In 1899 he was appointed a 

 demonstrator at McGill University, Montreal, where Sir Ernest Rutherford 

 had been appointed professor of physics in the preceding year. His first 

 published research was of importance. He gave the correct interpretation 

 of Crookes' work on the separation of the body uranium X from a solution 

 of uranium by showing that it was the radio-activity of uranium itself which 

 led to the production of uranium X. Later he joined hands with Prof. 

 Rutherford, and the physical measurements of the latter and the chemical 

 work of the former and the ideas of both led to a series of most important 

 discoveries. Their chiefest contribution to science was their explanation 

 of radio-activity, which has not only stood the test of twenty years' subse- 

 quent work, but has in fact inspired every single later experiment and been 

 at the base of every subsequent hypothesis. This is too well known to 

 require description here. They showed that the transformation of one 

 element into another, which the alchemists dreamt about but never 

 achieved, was actually taking place in nature, but with this difference, that 

 it was spontaneous and could not be influenced in any way by man, and 

 with this addition, that the energy unlocked by the atom in transmuting 

 itself, and not the element resulting from the transmutation, was the matter 

 of importance. 



The suggestion of Rutherford and Soddy that the gaseous element 

 helium might be one of the transformation products of a radio-element 

 received brilliant confirmation by the latter in Sir William Ramsay's labora- 

 tory in London in 1903. Soddy and Ramsay examined the gases given off 

 when first an old quantity and second a freshly prepared quantity of radium 



