184 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1924. 



simpler are the conceptions needed for its explanation. The rapid- 

 ity and certitude of the advance in this epoch have largely depended 

 on the fact that it has been possible to devise experiments so that few 

 variables were involved. For example, the study of the structure of 

 the atom has been much facilitated by the possibilitj^ of examining 

 the effects due to a single atom of matter, or, as in radioactivity or 

 X rays, of studying processes going on in the individual atom which 

 were quite uninfluenced by external conditions. 



In watching the rapidity of this tide of advance in physics I have 

 become more and more impressed by the power of the scientific 

 method of extending our knowledge of nature. Experiment, directed 

 by the disciplined imagination either of an individual, or still better, 

 of a group of individuals of varied mental outlook, is able to achieve 

 results which far transcend the imagination alone of the greatest 

 natural philosopher. Experiment without imagination, or imagina- 

 tion without recourse to experiment, can accomplish little, but, for 

 effective progress, a happy blend of these two powers is necessary. 

 The unknown appears as a dense mist before the eyes of men. In 

 penetrating this obscurity we can not invoke the aid of supermen, 

 but must depend on the combined efforts of a number of adequately 

 trained ordinary men of scientific imagination. Each in his own 

 special field of inquiry is enabled ]^y the scientific method to pene- 

 trate a short distance, and his work reacts upon and influences the 

 whole body of other workers. From time to time there arises an 

 illuminating conception, based on accumulated knowledge, which 

 lights up a large region and shows the connection between these in- 

 dividual efforts, so that a general advance follows. The attack 

 begins anew on a wider front, and often with improved technical 

 weapons. The conception which led to this advance often appears 

 simple and obvious when once it has been put forward. This is a 

 common experience, and the scientific man often feels a sense of dis- 

 appointment that he himself had not foreseen a development which 

 ultimately seems so clear and inevitable. 



The intellectual interest due to the rapid growth of science to-day 

 can not fail to act as a stimulus to young men to join in scientific 

 investigation. In every branch of science there are numerous prob- 

 lems of fundamental interest and importance which await solution. 

 We may confidently predict an accelerated rate of progress of scien- 

 tific discovery, beneficial to mankind certainly in a material but pos- 

 sibly even more so in an intellectual sense. In order to obtain the 

 best results certain conditions must, however, be fulfilled. It is 

 necessary that our universities and other specific institutions should 

 be liberally supported, so as not only to be in a position to train ade- 

 quately young investigators of promise, but also to serve themselves 

 as active centers of research. At the same time there must be a 



