59 MOLECULAR AND ATOMIC ENERGY 139 



law of dependence of the ratio of the specific heats on the / 

 number of atoms in the molecule. After Boedeker 1 and 

 Buff 2 had recognised the existence of simple relations 

 "between the ratios for different gases, Naumann 3 gave a 

 formula which is based on the assumption that the ratio 

 of e to E that has been found for diatomic gases, viz. 1 : 3, 

 holds in general for all gases. On theoretical grounds 

 Boltzmann 4 put forward the view that the mean energy e 

 of an atom must be equal to the kinetic energy E of the 

 molecule, but he found this assumption not confirmed by 

 observation. Pining 5 obtained a formula that agrees very 

 well with measurement by starting with the hypothesis that 

 the atoms exert on each other forces which vary inversely as 

 the sixth power of the distance between them. Eddy 6 has 

 made the more general assumption that the action is in- 

 versely proportional to some power of the distance ; but 

 Eicharz 7 has proved by general theorems of mechanics 

 ttet"airscBsumption of this kind respecting the law of action 

 between atoms is inadmissible, as it does not satisfy the 

 conditions for the stability of the molecular combination. 

 A new memoir by Staigmuller 8 on the kinetic theory of 

 polyatomic gases must also be mentioned. 



6O. Degrees of Freedom of -the Motion 



In another way Maxwell 9 and ..Watson 10 have at- 

 tempted to answer the question by taking into account the 



1 Die gesetzmass. Beziehungen zw. d. Dicht. d. spec. Warme u. d. Zusam- 

 mensetzung der Gase, Gottingen 1857; GGtt. Nachr.1857, p. 165; Ann. d. 

 Chem. civ. 1857, p. 205. 



2 Ann. d. Chem. cxv. 1860, p. 301. 



3 Ibid, cxlii. 1867, p. 284 ; Grundriss d. Thermochemie, 1869, p. 44. 



4 Wien. Sitzungsber. Ixiii. pt. 2, 1871, pp. 397, 417. 



5 Ueber die Beziehungen d. Warmecapacitdt der Gase zu den zwischen 

 Atomen wirlienden Kraften, Inaug.-Diss., Jena 1876. 



6 Scient. Proc. Ohio Mech. Inst. 1883, p. 26. 



7 Wied. Ann. xlviii. 1893, p. 476. 



8 Ibid. Ixv. 1898, p. 655. 



9 Nature, xi. 1875, p. 357 ; Scientific Papers, ii. 418 ; Nature, xvL 1877, 

 p. 242. 



10 Kinetic Theory of Gases. Oxford 1876, pp. 27, 37 ; 2nd ed. 1893, 

 p. 81. 



