A.— MATHEMATICAL AND PHYSICAL SCIENCES. 49 



present to fathom them. What would really be most helpful would be a 

 theory of atomic structure in sufficiently definite agreement with experi- 

 ment as regards known elements to enable us to proceed to investigate 

 the properties of elements of higher number than 92 with confidence. On 

 the general question of whether the evolution of elements has proceeded 

 from the simple to the complex, or from the complex to the simple, it does 

 not seem to me very much to the purpose to appeal to evolutionary 

 doctrine and the analogy of organic evolution, in favour of the former 

 alternative. Is it not more to the point that the only cases we can 

 observe (radioactive changes and those induced by radioactive bombard- 

 ment) are of the latter class ? At present this is a question of scientific 

 taste. Perhaps it is not irrelevant to remark that even in organic 

 evolution degeneration of organisms sometimes occurs, and I do not 

 know whether our biological colleagues are in a position to assert that 

 the whole course of organic evolution may not at some future time 

 be reversed by a change of conditions. At all events it is something 

 to have formulated the more restricted question of whether uranium now 

 comes into being on the sun by a synthetic or an analytic process. It 

 would seem that this is a well-framed question, and that the answer can 

 hardly be either both or neither. 



Conclusion. 



The great success of theoretical investigations in recent times naturally 

 leads enterprising spirits to use them not only in interpreting what we know 

 or can verify by observation, but to lead us into regions where experiment 

 is not available as a check. I believe that this does nothing but good in 

 times like ours, when there is no danger of the doctrines even of a master 

 being unduly pressed, if the evidence of observed fact turns against them. 

 At the same time, we must not expect too much of pure intellect unchecked 

 by observation. Theories that do not stand the test of time pass for the most 

 part into complete oblivion, and we are apt to forget how appallingly • 

 large a mass of wreckage the total of them represents. The next generation 

 remembers chiefly those that survive, and does not take full advantage of 

 the lesson of how easy it is for an apparently inevitable conclusion to be 

 wrong. Unless the argument carries its own verification by some accurate 

 and previously unforeseen numerical coincidence, it is hard indeed to tell 

 if we are on the right track. 



Though some of the problems we have been discussing have been only 

 partially or not at all resolved, yet many possible points of approach are 

 opening to our view. 



The attack on Nature's secrets is now conducted along a long line of 

 battle. No sooner does the defence show signs of crumbling at any point 

 than an eager crowd of combatants, not restrained by any undue respect 

 for the traditional modes of scientific thinking, are ready to throw them- 

 selves into the breach. The great array of trained workers in pure science 

 existing in the modern community is powerfully reinforced by workers in 

 applied science, who are backed by the resources of the industrial and 

 financial world and hand back to the physical laboratory the devices 

 which had their birth there in a form infinitely strengthened in power and 

 convenience of application. Thus rearmed with weapons of greater power 

 1929 p 



