[ 15 ] 



II. On the Thermal Conductivity of Vulcanite. 

 By B. Osgood Peirce*. 



LAST year Dr. R W. Willson and 1 published in tlie 

 ' Proceedings of the American Academy of Arts and 

 Sciences ' an account of some determinations of the thermal 

 conductivities of different kinds of marble, made by the so- 

 called " Wall Method "f. The horizontal bases of a rectangular 

 prism, of height small compared with the area of a horizontal 

 cross section, were kept for a long time at constant tempe- 

 ratures, the final temperatures at two or more points in the 

 vertical axis were determined, and the flux of heat through a 

 definite central portion of the colder base was measured. 



In each experiment of one of our sets a rectangular 

 prism GO centim. square and not more than 6 centim. high 

 was built up of a slab of the material to be tested, enclosed 

 between two other slabs of the same material. Between each 

 two consecutive slabs of the prism was placed a thin metal 

 sheet. This consisted of two rectangular leaves of tinfoil, 

 about 60 centim. long and a little less than 30 centim. wide, 

 placed side by side and separated by a narrow ribbon thermal 

 element made by butt-jointing, end to end, with the help of 

 silver solder, a strip of ger man-silver and a strip of copper of 

 the same thickness as the tinfoil. After the edges of the 

 ribbon had been varnished so as to prevent electrical contact, 

 the ribbon and the tinfoil could be placed close together so as to 

 form a continuous sheet of metal 60 centim. square and about 

 -j'q of a millimetre thick. 



* Communicated by the Author. 



t Despietz, Ami. de Chimie et de Physique, 1827. Peclet, Ann.de 

 Chimie et de Physique, 1841. Tyndall, Phil. Mag-. 1853. Hopkins, Phil. 

 Trans. 1857. Pfaff, Pogg. Ann. cxiii. 1861. J. D. Forbes, Proc. Edin. 



o 



Soc. iv« Angstrom, Pogg. Ann. cxiv. 1861. Neumann, Ann. de Chimie 

 et de Physique, 1862. G. Forbes, Proc. Edin. Soc. viii. J 873. Herschel, 

 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, Yierteljahrschrift d. Ziiricher Naturf. 

 Ges. 1879. Thoulet, Comptes Rendus, 1882. L^garde, Comptes Rendus, 

 1882. v. Littrow, Wien. Ber. lxxi. Stefan, Carl's Rep. xiii. Jannettaz, 

 Vomfites liendus, 1884. Tuchschmid, Beibldtter z. Wied. Ann. 1884. 

 M. Ballo, Diugler's Journ. 1886. H. Meyer, Wied. Ann. 1888. K. Ja- 

 magawa, Beibldtter z. Wied. Ann. 1889. Gr. Stadler, Inaug. Diss., Berne, 

 1889. Yenske, G bit inger Nachrichten, 1891. Grassi, Atti 1st. Kapoli, 

 ]892. Lees, Phil. Trans. 1892. R. Weber, Bull. Soc. Science Nat. 

 Neuch. 1895. Lord Kelvin and Mr. Murray, Proc. Royal Soc. 1895. 

 Peirce and Willson, American Journal of Science, 1895. Lees and 

 Chorlton, Phil. Mag. 1896. Oddone, Rend. R. Accad. d. Lincei, 1897. 

 W r . Yoigt, Wied. Ann. 1898. Lees, Proc. Royal Society, 1898. 



