ON THE THERMAL CONDUCTIVITIES OF CERTAIN 

 POOR CONDUCTORS. — L 



By B. O. Peikck and R. W. Willson. 



Presented April 13, 1898. 



We have been engaged for several years in an attempt to measnre, by 

 the aid of the so called " Wall Method," the thermal conductivities of 

 certain relatively poor conductors,* and the variations of these conduc- 

 tivities witii the temperature. We have at length succeeded in over- 

 coming some' of the difficulties which we have encountered, and are now 

 ready to describe our apparatus and to give the results of a number of 

 observations made with it. 



When one end of a regular right prism of 2 n sides made of homoge- 

 neous material is kept at a constant temperature, ]^„ and the other end at 

 a constant temperature, V^, while its other faces are kept as nearly as 

 possible at some constant temperature between F^ and FJ, the tempera- 

 tures on the axis of the prism in its final state depend very largely on the 

 ratio of the length of the axis of the prism to that of a diagonal of a cross 



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 Pfaff, Pogg. Ann., CXIII., 1801. J. D. Forbes, Proo. Edin. Soc, IV. AngstWlni, 

 Pogg. Ann., CXIV., 1801. Neumann, Ann. de Chimie et de Piiysique, 1862. G. 

 Forbes, Proc. Edin. Soc, VIII., 1873. Herschell, Lebour, and Dunn, Rep. Brit. 

 Assoc, 1873. V. Beetz, Pogg. Ann. Jubelband, 1874. Smith and Knott, Proc 

 Edin. Soc, 1875. Lodge, Phil. Mag. 1878. Less, Journ. de Phys., VII., 1878. 

 Ayrton and Perry, Phil. Mag., 1878. H. F. Weber, Vierteljahrschrift d. Ziiriclier 

 Naturf. Ges., 1879. Thoulet, Comptes Rendus, 1882. Lagarde, Comptes Rendus, 

 1882. V. Littrow, Wien. Per., LXXI. Stefan, Carl's Rep., XIII. Jannettaz, 

 Comptes Rendus, 1884. Tuchschmid, Beibliitter z. Wied. Ann., 1884. M. Ballo, 

 Dingler's Journ., 1886. H. Meyer, Wied. Ann., 1888. K. Jamagawa, Beibliitter 

 z. Wied. Ann., 1889. G. Stadler, Inaug. Diss., Berne, 1889. Venske, Gilttinger 

 Nachrichten, 1891. Grassi, Atti 1st. Napoli, 1892. Lees, Phil. Trans., 1892. R. 

 Weber, Bull. Soc. Science Nat. Ncuch., 1895. Lord Kelvin and Mr. Murray, Proc 

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