CONSTITUTED OF SPHERICALLY SYMM1.TIMCAL M< 'LKCULES. 463 



experimental evidence we can adduce in favour of the value f = \ will confirm that 

 theorem. 



As both theories treat of monatomic gases, we must seek for evidence with regard 

 to them. When tins paper was written the only monatomic ga-s, <>f which I was 

 aware, for which i> is known was mercury vapour, referred to by MEYER.* While 

 a number of polyatomic gases obeyed his law fairly closely, this monatomic gas 

 alone tunned a striking exception. Koc.nf lias determine' 1 fl tor mercury vapour at 

 273 C. and 380 C., and also at the much lower temperature 203 C. ; SCHLEIER- 

 MAOHERf has determined ^ at 203 C. ; these data, together with the theoretically 

 calculated value of C t ,, lead to :5 - 15 as the value of./! MKYKK raises some weighty 

 objections against the accuracy of the data, viz., (i) that KOCH'S three values of /z 

 show an unlikely amount of variation with the temperature ; (ii) that the conden- 

 sation of saturated mercury in the capillary tub;- probably affected the determination 

 of n ; and (iii) that it is uncertain whether the vapour is completely monatomic at. 

 203 C. While the resulting value of f is certainly unreliable, it is hard to conceive 

 of the experimental errors being so great as to explain the difference between 

 T6027 and 3' 15. So far as it goes, it tends rather to the support of the present 

 theory. 



Quite recently, however, I have found that SCHWARZE had disproved MEYEK'S 

 theory nine years ago, by showing that / = 2' 5 for the true monatomic gases 

 argon and helium. As these determinations are important in this connection, a 

 few details of them will be given. SCHLEIERMACHER'S method, now generally 

 accepted as the best, was used to determine ^, heat l>eing conducted by the gas from 

 a heated platinum wire. The gases were very carefully prepared and purified, || and 

 in the reduction of the observations (which were made at two temperatures) due 

 corrections were applied for the heat lost by conduction along the wire and for the 

 temperature drop at the walls. The following values of S u were obtained : 



Argon 0-00003894, Helium 0'0003386, Air 0'00005690, 

 the last named being determined as a check on the apparatus, and agreeing well with 



* ' Kinetic Theory,' p. 205. 



t ' WIED. Ann.,' 1889, xxxvi., p. 346. 



J Ibid., 1883, xix., p. 857. 



\V. SCHWARZE, 'Inaugural Dissertation,' Halle, 1902; 'Ann. d. Physik,' 11, p. 303, 1903; ' Pbys. 

 Xi'itschrift,' 4, p. 229, 1903. 



MKHI.ISS (' Halle Diss., 1 1902) made an earlier determination of ^ for argon by the STEFAS-WiNKEl.MAXX 

 method, and found / = 2-44; this result was in such striking disagreement with MEYEK'S theory that 

 SCHWARZE investigated the mutter very thoroughly, both for argon and for helium, by the more accurate 

 method due to ScHLElKUM. \CHF.K. The result was quite unexpected, and neither observer seemed inclined 

 to regard it ;ia a confirmation of MAXWELL'S hypothesis, but rather as being due to a numerical defect in 

 MI.YI.KS theory which view is nearer the truth, according to the present theory. 



|| The helium contained per cent, impurity (probably of neon); the same matetial was used by 

 Seiiri.i/r. C Ann. d. Phys.,' 6, p. 303, 1901) to determine the value of p used above. 



