286 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 3 



Is it the old story of Eden ? Have we physicists eaten of the for- 

 bidden fruit of the tree of knowledge, and are we now suffering the 

 consequences? However this may be, we will maintain, despite all 

 accusations to the contrary, that our plight is not to be ascribed to 

 original sin or to total depravity, but that the changes in funda- 

 mental concepts that are causing all the stir have been forced upon 

 us as the logical result of approved methods of scientific study. And 

 so compelling have been the reasons for these changes that there 

 seems to be no more turning back possible for us than for our tradi- 

 tional first parents. We are thrust out of Paradise into contact with 

 the bare world of Nature, and whether we like it or not we must 

 somehow adjust ourselves to the new order of things. Concepts as 

 old as human thinking are gone forever. Strange substitutes are 

 replacing them, and until their novelty wears off it is inevitable that 

 science should for the time appear as romance. 



Would that it might ever remain so! But this is too much to 

 expect. The thing that has been is that which shall be. Through 

 familiarity we shall in time adjust ourselves to these new concepts 

 as we have done to the telephone and more lately to the radio, once 

 things of wonder, illumined by the halo of romance, but now mere 

 commonplaces of our daily existence, matters of bargain and sale, 

 at times even degenerating into nuisances and provocations to 

 profanity. 



The roots of the present revolution (or evolution) may be traced 

 back for two centuries. The student of the history of science can 

 discern during this period a certain trend of thought of which our 

 present plight is but the logical outcome. This trend may be de- 

 scribed as a steady drift away from materialism in our physical 

 concepts. 



The natural philosophers of the eighteenth century followed an- 

 cient tradition in explaining everything in terms of matter, which was 

 regarded as a sine qua non, a basic concept without which physical 

 thought would be impossible. Heat, in the eighteenth century, Avas 

 a form of matter called caloric, which differed from ordinary matter 

 in being unweighable and which could be soaked up by ordinary 

 matter like water in a sponge. Light was another imponderable in 

 the form of very minute corpuscles. Electricity and magnetism 

 were held to be manifestations respectively of the electric and mag- 

 netic fluids. Added to these was another imponderable called 

 " phlogiston ", which was supposed to account for the phenomena of 

 combustion. These five imponderables, together with ordinary 

 matter, formed the stock in trade of eighteenth-century physics. 



The physical science of that period was a rather loose and dis- 

 jointed affair, consisting mainly of uncorrelated facts about these six 



