Conduction of Heat through Rarefied Gases. 1 L 



very important, as even a small temperature change is 

 sufficient to produce quite an appreciable " Sensitive State." 

 Research work in magnetism at temperatures other than 

 ordinary room temperature is somewhat difficult to carry out; 

 low temperature research is moreover very costly; and it 

 seems to the authors of great importance that the special 

 precautions necessary in such work should be widely 

 known. 



II. Some Remarks on Conduction of Heat through Rarefied 

 Gases. By Prof. M. S. Smoluchowski, Ph.D., LL.D* 



IT has been shown, by researches published more than te n 

 years agof, that the apparent decrease of thermic con- 

 ductivity of gases, with progressing rarefaction, is due not 

 to a decrease of the coefficient of conductibility, but to a 

 surface phenomenon, analogous to the sliding of gases 

 discovered by Kundt and Warburg. 



There also the kinetic explication of this phenomenon has 

 been given, which leads us to expect the existence of a very 

 simple law of conduction for extreme rarefactions, the 

 quantity of transmitted heat then being proportional to the 

 gas pressure and independent of the thickness of the layer 

 of £as. 



Experimental evidence of such relations has been given 

 first in some experiments of C. F. Brush}, and recently in a 

 careful investigation by F. Soddy and A. J. Berry §. 



The form of the law for extreme rarefactions being estab- 

 lished, the question arises as to the value of the constant of 

 proportionality, or as these authors put it : the quantity of 

 heat, referred to unit of hot surface, one degree of difference 

 of temperature and 0*01 mm. of mercury pressure, which 

 they designate by Q. 



I had found by a roughly approximative reasoning || 

 (assuming the molecules to be divided in three parts, moving 

 parallel to the axes) that the flux of heat carried for one 

 degree of difference of temperature ought to be of the 



* Part of a paper which will be published in the Bulletin de V Acad., 

 Cracovie, 1910, Communicated by the Author. 



f Smoluchowski, Ann. d. Phys. Ixiv. p. 101 0898) ; Wien. Ahad. 

 Sitzgsber. cvii. p. 304 (1898), cviii. p. 5(1899); Phil. Mag. xhi. p. 199 

 (1898) : Gehrcke, Ann. d. Phys. ii. p. 102 (1900). 



X Phil. Mao-, xlv. p. 31 (1898). 



§ Proc. Roy Soc. lxxxiii. A. p. 254 (1910). 

 jl Wien. Ahad. Sitzg&ber. cvii. p. 328 (1898). 



