Supplement to Nature 



No. 281 1" 



SEPTEMBER 15, 1923 



The Electrical Structure of Matter.^ 



By Prof. Sir Ernest Rutherford^ D.Sc, LL.D., Ph.D., F.R.S., President of the British Association. 



IT was in 1896 that this Association last met in Liver- 

 pool, under the presidency of the late Lord Lister, 

 that great pioneer in antiseptic surgery, whose memory 

 is held in affectionate remembrance by all nations. 

 His address, which dealt mainly with the history of the 

 application of antiseptic methods to surgery and its 

 connexion with the work of Pasteur, that prince of 

 experimenters, whose birth has been so fittingly cele- 

 brated this year, gave us in a sense a completed page 

 of brilliant scientific history. At the same time, in 

 his opening remarks, Lister emphasised the importance 

 of the discovery by Rontgen of a new type of radiation, 

 the X-rays, which we now see marked the beginning 

 of a new and fruitful era in another branch of science. 

 The visit to Liverpool in i8g6 was for me a memorable 

 occasion, for it was here that I first attended a meeting 

 of this Association, and here that I read my first 

 scientific paper. But of much more importance, it 

 was here that I benefited by the opportunity, which 

 these gatherings so amply afford, of meeting for the 

 first time many of the distinguished scientific men of 

 Great Britain and the foreign representatives of science 

 who were the guests of this city on that occasion. The 

 year 1896 has always seemed to me a memorable one 

 tor other reasons, for on looking back with some sense 

 of perspective we cannot fail to recognise that the last 

 Liverpool meeting marked the beginning of what has 

 been aptly termed the heroic age of physical science. 

 Never before in the history of physics has there been 

 witnessed such a period of intense activity when dis- 

 I overies of fundamental importance have followed one 

 mother with such bewildering rapidity. 

 The discovery of X-rays by Rontgen had been pub- 

 lished to the world in 1895, while the discovery of the 

 radioactivity of uranium by Becquerel was announced 

 early in 1896. Even the most imaginative of our 

 scientific men could never have dreamed at that time 

 of the extension of our knowledge of the structure of 

 matter that was to develop from these two fundamental 

 discoveries, but in the records of the Liverpool meeting 

 we see the dawning recognition of the possible conse- 

 cjuences of the discovery of X-rays, not only in their ap- 

 plication to medicine and surgery-, but also as a new and 

 powerful agent for attacking some of the fundamental 

 problems of physics. The address of Sir J. J. Thomson, 

 president of Section A, was devoted mainly to a dis- 

 cussion of the nature of the X-rays, and the remarkable 

 l)ropertics induced in gases by the passage of X-rays 

 through them— the beginning of a new and fruitful 

 branch of study. 



In applied physics, too, this year marked the begin- 

 ning of another advance. In the discussion of a paper 



' Inaugural address delivered to the British Association at Liverpool on 

 September u. 



which I had the honour to read, on a new magnetic 

 detector of electrical waves, the late Sir William Preece 

 told the meeting of the successful transmission of 

 signals for a few hundred yards by electric waves 

 which had been made in England by a young Italian, 

 G. Marconi. The first public demonstration of signal- 

 ling for short distances by electric waves had been given 

 by Sir Oliver Lodge at the Oxford Meeting of this 

 Association in 1894. It is startling to recall the 

 rapidity of the development from such small beginnings 

 of the new method of wireless intercommunication over 

 the greatest terrestrial distances. In the last few years 

 this has been followed by the even more rapid growth 

 of the allied subject of radiotelephony as a practical 

 means of broadcasting speech and music to distances 

 only limited by the power of the transmitting station. 

 The rapidity of these technical advances is an illus- 

 tration of the close interconnexion that must exist 

 between pure and applied science if rapid and sure 

 progress is to be made. The electrical engineer has 

 been able to base his technical developments on the 

 solid foundation of Maxwell's electromagnetic theory 

 and its complete verification by the researches of Hertz, 

 and also by the experiments of Sir Oliver Lodge in the 

 University of Liverpool — a verification completed long 

 before the practical possibilities of this new method of 

 signalling had been generally recognised. The later 

 advances in radiotelegraphy and radiotelephony have 

 largely depended on the application of the results of 

 fundamental researches on the properties of electrons, 

 as illustrated in the use of the thermionic valve or 

 electron tube which has proved such an invaluable 

 agent for both the transmission and reception of 

 electric waves. 



It is of great interest to note that the benefits of this 

 union of pure and applied research have not been 

 one-sided. If the fundamental researches of the 

 workers in pure science supply the foundations on 

 which the applications are surely built, the successful 

 practical application in turn quickens and extends the 

 interest of the investigator in the fundamental problem, 

 while the development of new methods and appliances 

 required for technical purposes often provides the 

 investigator with means of attacking still more difficult 

 questions. This important reaction between pure and 

 applied science can be illustrated in many branches of 

 knowledge. It is particularly manifest in the industrial 

 development of X-ray radiography for therapeutic and 

 industrial purposes, where the development on a large 

 scale of special X-ray tubes and improved methods of 

 excitation has given the physicist much more efficient 

 tools to carry out his researches on the nature of the 

 rays themselves and on the structure of the atom. In 

 this age no one can draw any sharp line of distinction 



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