ON THE RELATION BETWEEN HEAT CONDUCTIVITY 

 AND DENSITY IN SOME OF THE COMMON WOODS. 



LOUIS W. AUSTIN AND C. W. EASTMAN. 



In 182 8 De la Rive and De Candolle/ after examining the 

 conductivities of five varieties of woods, announced tlie inter- 

 esting fact that along the fibers the thermal conductivities of the 

 different woods were approximately proportional to their den- 

 sities. Some observations made by C. G. StangeP in 1899 in 

 connection with his work on the effect of moisture on the heat 

 conductivities of woods and rocks called attention again to the 

 relations between the conductivities and densities of woods. As 

 far as has been ascertained no other work has been done on the 

 subject since that of De La Hive and De Candolle, the extensive 

 work of TvndalP on woods being confined to the rapidity of 

 propagation of the heat wave, or, diffusivity. 



In our own experimental work a method was made use of 

 which v/as presented in outline by Yoigt* in 1898, the general 

 plan of which is as follows : The specimens whose heat con- 

 ductivities are to be compared are cut in the form of right 

 angled triangles and joined along the hypotenuse, as shown in 

 the figure. If one of the edges AB be heated until a steady 

 flow of heat is established so that the temperature at each point 

 becomes constant, the isothermal lines in the lower specimen 

 will be parallel to the base AB, while in the upper specimen 

 they will be bent upward or downward depending on whether 

 the conductivity is greater or less than in the lower. Accord- 



iDe la Rive and De Candolle, Pogg. Ann., vol. 14, 1828, p. 590. 

 2C. G. Stangel, University of Wisconsin Thesis, 1899. 

 sTyndall, Phil. Trans. Roy. Soc, vol. 143, 1853, p. 217. 

 4Voigt, Wied. Ann., vol. 64, 1898, p. 95. 



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