22 ' SECTIONAL ADDRESSES 



for changing his methods. In the Manchester days the work was all 

 done with astonishingly simple means — old tobacco tins for home-made 

 electroscopes and so on — and it would have been easy for anyone to say, 

 ' We have got many first-rate results out of these tobacco tins, and there 

 are plenty more to get, so why change ? ' There would have been plenty 

 more to get, and he could have occupied a whole laboratory getting them, 

 but all the time the world was going beyond them to costly apparatus 

 on an engineering scale, which were beginning to yield results beyond 

 the capacity of tobacco tins. Rutherford perceived this as early as any- 

 one and was ready to undertake these engineering feats — and to collect 

 the money to pay for them too. But I will say no more of this work, 

 since it is only necessary to apply to him in this place and during our 

 present week of meeting the words written on the tomb of another great 

 man — Si monumentum requiris, ctrcufmpice. 



When we try to assess the qualities, as opposed to the performance, of 

 great men of science, we can make a dichotomy of them into two classes ; 

 the dichotomy is of course not exact, but it divides them as well as such 

 things do. There is the type of genius who seems to have been born 

 with a knowledge of some branch of nature, so that he has only to grow 

 up, learn to read and write, and then be told what the difficulties are in 

 order to understand and explain them. Perhaps Lord Kelvin was the 

 typical instance, for he seemed to know all about thermodynamics 

 spontaneously at the age of 22. Then there is the opposite type of which 

 the late Lord Rayleigh was an example, who seem not to have a natural 

 understanding of things, but to know more precisely than common men 

 what they do not understand and by mastering it to gain a very deep 

 insight into nature. It is a question of whether it is easier to conquer 

 the world by understanding it or by not understanding it. It is a matter 

 of taste which type each of us prefers, whether the inspiration which 

 seems to know what the world is like directly, or the careful induc- 

 tion, picking a cautious way between this difficulty and that objection. 

 Each type may show the demerits of its quality, in the one case a certain 

 inelasticity that follows the inspiration, in the other a sometimes too 

 pedestrian rate of advance. On the principle that I like to see the 

 machinery as well as its products, I confess that it is the second type 

 that attracts me more. A rigid dichotomy of this kind is a misleading 

 over-simplification, and most scientific men have shared the two characters 

 in various proportions, but it is not hard to classify Rutherford. He 

 had that quality of being prepared for anything, of making each discovery 

 fit on to the last and suggest the next, of taking the world as he found it, 

 which is typical of my second class, those whom I have called great by 

 not understanding. But I must turn to my main subject, and will only 

 add that the life and work of Rutherford is the best possible text I could 

 choose for the kind of view which I want to put before you. 



In choosing a theme for my address I was in some difficulty. The 

 main subjects of present interest in physics, the nucleus of the atom, 

 cosmic rays, and the phenomena at deep temperatures, are being dealt 

 with in the discussions of our Section, so that they would be excluded 

 even apart from the fact that I cannot speak on them with authority. It 



