92 



question was first put to mechanics. If a positive answer was indicated 

 the question was put to nature and the research went on. If the equations 

 indicated a negative result the question was dropped and the research 

 abandoned. 



Physics was an exact science. Other sciences were not exact sciences 

 because their theories and hypotheses could not be mathematically ex- 

 pressed — the relation between cause and effect was not expressible in 

 algebraical symbols. Physics was an exact science whose fundamental 

 principles had been discovered and its laws expressed by equations. All 

 that remained to be done was to make more accurate measurements of 

 physical quantities for use as coefficients and exponents. 



Let me quote from the 1894 catalogue and later catalogues of one of 

 the largest universities in the United States. 



"While it is never safe to affirm that the future of physical science 

 has no marvels in store. * * * it seems probable that most of the grand 

 underlying principles have been firmly established and that further ad- 

 vances are to be sought chiefly in the rigorous application of these princi- 

 ples to all the phenomena which come under our notice. * * * An 

 eminent scientist has remarked that the future truths of physical science 

 are to be looked for in the sixth place of decimals." The foregoing is a 

 verbatim quotation from the introductory statement preceding the list 

 of courses in physics offered at one of our great universities, written, I 

 think, in 1894. "Underlying principles firmly established," "Future truths 

 in sixth decimal place," 1894. Then came the discovery of Roentgen rays. 

 1895; Becquerel rays, 1S96; Zeeman effect, 1S9G: radium, 1898; atomic 

 disintegration, the transformation of matter, the thermal effect of radio- 

 activity, and intra atomic energy. 1903. I am unable to locate the sixth 

 decimal idea in recent catalogues. 



J. J. Thomson likens the discovery of Roentgen rays to the discovery 

 of gold in a sparsely populated country. Workers come in large numbers 

 to seek the gold, many of them finding that "the country has other products, 

 other charms, perhaps even more valuable than the gold itself." 



The chief value of Roentgen's discovery was not that it furnished us 

 a new kind of light for the investigation of dark places, but in the fact 

 that it led a host of workers to study vacuum tube discharges — the dis- 

 charge of electricity in gases and the effects of such discharges on matter 

 itself. The old dusty Crookes* tube was taken down from the far corner 



