on the Physical Properties of Gases. 417 



Table I. that, at a temperature of about 70° C, 



1+ £=1-671, !J- =-00048, 0=350; 

 whence it follows that 



-=1-609. 

 c 



If Q is large and about 5000° or 4727° C, Table II. gives 

 us for a temperature of 70° 



1+ ? = 1-0028, j| =-00004, 



whence 



-=1-423. 



In the above we have confessedly taken I too large, as we 

 showed that 2\0 O was its superior limit ; if we were to take 

 I = 2X# x "4, we should get 



- =1-403. 



G 



c' 

 The value of— for the permanent gases is about 1*408. 



Not only does this result confirm our former conclusion 

 that 6 is very large, but it adds largely to the probability of 

 the general theory here set forth, since the great difficulty of 

 the kinetic theory of gases hitherto has been to explain the 



d 



value of — for the permanent gases whose molecules are 



diatomic. Mercury vapour which has simple molecules, or is 

 monatomic, and which therefore has no dissociation, has the 

 value given by the ordinary theory, as has been shown re- 

 cently by Messrs. Kundt and Warburg. 



21. To satisfy experience, it is further necessary to show that 

 c does not vary much within the ordinary range of temperature. 

 We have 



„^{ <2 x,-x,)(»§ + ?) + *,-I§} 



-¥{^-«.S}> 



where tc is a fraction. Hence 

 dc _ AT/1 d 2 ^ 



Phil. Mac,. S. 5. Vol. 3. No. 20. June 1877. 2 E 



