THE FIELD OF EXPERIMENTAL RESEARCH. 



By Elihu Thompson. 



Physical research by experimental methods is both a broadening and 

 a narrowing field. There are many gaps yet to be filled, data to be 

 accumulated, measurements to be made with great precision, but the 

 limits within which we must work are becoming, at the same time, 

 more and more defined. 



The upper ranges of velocities, temperatures, and pressures which 

 manifest themselves in the studv of the stellar universe are forever 

 beyond the range of experiment. But while the astronomer must wait 

 for opportunities to observe, the experimenter can control his condi- 

 tions and employ his methods and his apparatus at once to the question 

 in hand. Still this work must be done within a certain range or must 

 be limited to conditions more or less easy to recognize. In spite of 

 this fact, however, the progress made during the past century is not 

 likely to cease or abate in the next, and the ever-increasing number of 

 workers bodes well for the future enrichment of our science. 



Whatever may be our ideas of fundamental entities, as expressed in 

 various theories, whether, as an example, we regard the ether as like 

 an infinitely mobile fluid, or as an incompressible solid, or as a jelly, 

 or whether we incline to think that being an electro-magnetic medium 

 it may be without mechanical properties, which properties depend in 

 some way upon the electro-magnetic nature of the ether, we can not 

 reach sure ground without the experimental test. 



The development in the field of research by experiment is like the 

 opening of a mine, which as it deepens and widens continualh^ yields 

 new treasure, but with increased difficulty, except when a rich vein is 

 struck and worked for a time. In general, however, as the work 

 progresses there will be needed closer application and more refined 

 methods. We ma}' , indeed, find our limit of depth in the mine of 

 experiment in inordinate cost, in temperatures too high, oi- in pressures 

 beyond the limits of our skill to control. 



^Address of the vice-president and chairman of section B, physics, before the 

 American Association for the Advancement of Science at the Columbus meeting, 

 August, 1899. Printed in Science, August 25, 1899. 



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