Thermal Conductivity of Vulcanite. 



23 



a piece of solid drawn brass tube 12*3 centim. in outside dia- 

 meter and 13*5 centim. nigh, with carefully squared ends, was 

 held centrally in Z by means of a wooden disk turned to fit 

 it, and a central pin inserted in H, and was then soldered 

 firmly to Z. This was accomplished, after many trials of 

 other materials, by the use of white pitch as a flux ; and the 

 result left nothing to be desired. The walls of the pot thus 

 formed were jacketed on the outside, except for a height of 



Fie-. 2. 





Fig-. 3. 



inch-thick casting of 



about 2 millim. at the bottom, by an 



hard rubber made for the purpose in the form of a cylindrical 



shell. This casting, which was cut off square at the top of 





