TWENTIETH CENTURY PHYSICS. 1 



By R. A. Millikan. 



My position to-niglit is somewhat reminiscent of a story which my 

 father used to be fond of telling of a Scotch preacher who thought 

 that all of the italicized words in the Holy Writ were meant to be 

 emphasized, and so he read " And Abraham said unto his servants, 

 saddle me an ass, and they saddled him." When one of his parish- 

 ioners expostulated with him and told him that he didn't think that 

 was really what was meant, being a Scotchman, the preacher kept 

 his own opinion, but being endowed also with a certain amount of 

 worldly wisdom, he said he would change it, and so the next time he 

 read, "And Abraham said unto his servant, saddle ?ne an ass, and 

 they saddled him." 



The point of the story is that it doesn't make any difference where 

 the emphasis is placed, the situation remains entirely unchanged. I 

 am, however, really glad to be saddled tonight, because I 

 should like to do a little bit, if I can, towards bridging the chasm 

 which we have foolishly — I had almost said idiotically — allowed to 

 grow up between the physicist and the applied physicist, who com- 

 monly is called an engineer. The chemists have been very much 

 more sensible; they have not split up into two groups, called chem- 

 ists and applied chemists, and there is absolutely no more reason why 

 we should have done so, for obviously the physicist is merely the 

 vanguard in the army of engineers, the scout, the explorer, who is 

 given the task of trying to open up new paths for human progress, of 

 prospecting for new leads to nature's gold, and it is just as important 

 that the engineer know where the scout is and what he is doing as it 

 is that the scout know where the army is which is behind and which 

 supports him. 



If you have any respect for my subject or any respect for me you 

 will not expect me to outline in the space of one brief hour the work 

 of modern physics. It is utterly impossible to do, and I can say that 

 without affecting an inordinate egotism. I had the good fortune to 



1 A lecture delivered at the Fifth Midwinter Convention of the American Institute of 

 Electrical Engineers, New York, Feb. 15, 1917. Copyright 1917, by A. I. E. E. Reprinted 

 hy permission from the Proceedings of the American Institute of Electrical Engineers, 

 September, 1917. 



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