72 



SCIENCE 



[N. S. Vol. XXXVII. No. 941 



ing and administration costs. All of the so- 

 cieties maintain some sort of public activity. 

 The Historical Association, and (since the 

 date of this report), the Political Association, 

 have moved in the same direction. 



The net expenditure varies from $30,000 

 for the Academy to $4,000 for the Political 

 Science Association. The measure of the ef- 

 fectiveness of these societies is however not 

 the sums spent but the value of the v^ork done. 

 The Academy, with $30,000 a year to spend, 

 ought certainly to be lending a far greater aid 

 to the problems of the general subject of his- 

 tory, government and economics than the three 

 other societies with their combined income of 

 $27,000. How far that is the case must be left 

 to the decision of those cognizant of the work 

 of the four societies. One thing is certain, 

 that none of the four societies furnishes a 

 sufficiently detailed account; and that the re- 

 port of the American Academy of Political 

 and Social Science shows over $20,000 a year 

 expended for publications as against $18,000 

 for the publications of the other three so- 

 cieties. The published accounts do not fur- 

 nish a basis from which it is possible to find 

 out why its cost per unit for carrying on and 

 printing the publication should be twice as 

 great as those of all the three sister societies 

 doing the same kind of work. Here is an op- 

 portunity for a reform in corporate accounts. 



Albert Bushnell Hart 

 Hakvakd University 



SPECIAL ARTICLES 

 evidence that sodium belongs to a radio- 

 active SERIES OF ELEMENTS 

 By the usual test for radioactivity, i. e., the 

 continued ionization of a gas independent of 

 other physical conditions, sodium as an ele- 

 ment does not display any activity that is 

 definitely greater than that found in all mat- 

 ter. And the ionizing activity of ordinary 

 matter is so slight that it can not be stated 

 with definiteness whether or not it is of itself 

 radioactive. But radioactivity implies a more 

 fundamental change than that of emitting 

 matter and energy continuously. It implies 



an atomic disintegration. If a particles are 

 emitted the atoms go by leaps and bounds to 

 new atoms of other properties, while if j3 and 

 y radiations are emitted the wearing away of 

 the atoms must be just as certain, though no 

 one has been able to conjecture by what steps 

 the change might take place. 



Campbell and Wood' examined the sodium 

 compounds for ionizing radiations. Their 

 apparatus would have detected an activity 

 much less than that of potassium, which is 

 only one thousandth that of uranium. No 

 radiations could be measured. The fact that 

 a given element does not give out a meas- 

 urable ionizing radiation is not necessarily 

 evidence that it is not radioactive. For ex- 

 ample, we may note the case of radium D, 

 which gives no measurable radiations. Tet it 

 disintegrates to half value in about forty 

 years. It is therefore known as a radioactive 

 element. Further, helium as an element may 

 be classed as a radioactive element, providing 

 all helium is of radioactive origin, although 

 of itself no ionizing radiations are emitted. 

 It is sufficient that an element be of radio- 

 active parentage. Thus sodium is a radio- 

 active element if it can be shown that it dis- 

 integrates into other forms of matter or if it 

 is the result of the disintegration of other 

 forms of matter. 



If sodium is a radioactive element we may 

 at present look for other evidence than direct 

 radiations. We shall inquire if in past geo- 

 logic time sodium has accumulated radioac- 

 tivity from other matter, or, on the other hand, 

 if sodium has disappeared or disintegrated 

 into other forms of matter. 



THE EVIDENCE FROM GEOLOGY 



Geophysics furnishes two distinct lines of 

 evidence which favor the hypothesis that so- 

 dium belongs to a series of radioactive ele- 

 ments. The first is based on the age of the 

 earth as determined by radioactive data and 

 by the accumulation of sodium in the ocean. 

 The second is based on the relative accumula- 

 tion in the ocean of sodium compared to 

 chlorine, taken in connection with the relative 



'^ Proa. Camb. Phil. Soc, 14, p. 15. 



