204 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



The most natural explanation seems to be this theory of the atom 

 as a ver}^ complex world, one shut up entirely to itself. Exterior 

 events have no relation to what passes on within, nor does what 

 happens witliin affect the exterior world. That can not be strictly 

 true or else we would be utterly ignorant that there is anything 

 within and the atoms would appear as simple material points. The 

 truth is that we can see what happens within only as through a very 

 small window, and there is practically no exchange of energy between 

 the interior and wliat is outside; there is consequently no tendency 

 to equipartition of energy between the atomic world and that without. 

 The internal temperature, as I have just stated, does not tend to 

 approach equality with that outside. That is why the specific heats 

 are the same as if no internal complexity existed. Let us now imagine 

 a complex body made up of a hollow sphere whose inner wall is abso- 

 lutely impervious to heat and mthin which is a great number of 

 various bodies. Then the obsei'ved specific heat of such a body 

 would be that of the exterior sphere just as if tlie interior bodies did 

 not exist. 



The door which closes the interior of this atomic world opens, how- 

 ever, from time to time, as when a particle of radium is shot off. 

 The atom becomes degraded in rank in the radioactive hierachy. 

 ^A^iat happened then? How did this decomposition differ from an 

 ordinary chemical decomposition? In what respect does the atom 

 of uranium, formed of helium and something else, have more title to 

 the name atom than the half molecule of cyanogen, for instance, 

 which behaves in so many ways like a simple body though formed of 

 carbon and nitrogen? Doubtless the atomic heat (I do not know 

 that it has been measured) of uranium must obey the law of Dulong 

 and Petit and would con-espond to that of a simple atom. It should 

 then become double at the moment of the emission of the helium 

 particle, when the primordial atom decomposes into two secondary 

 atoms. Through that decomposition the atom acquired further 

 degrees of freedom through which it may act upon the exterior 

 world and the new degrees of freedom should become evident in an 

 increased specific heat. ^Vliat would be the difference between the 

 specific heat of all the components and that of the compound body ? 

 One would expect that the heat set free by the decomposition would 

 vary very rapidly with the temperature so that the formation of the 

 radioactive molecule, which is strongly endothermic at ordinary 

 temperatures, would become exothermic at higher temperatures. We 

 could thus undei-stand better how the radioactive compounds could 

 form, a process which is very mysterious. 



Iloweveij the conception of a little closed world, opened at moments, 

 does not suffice to solve our i)roblem. It would be necessary that tlio 



