A. M. Mayer — Physical Properties of Vulcanite. 59 



point in this direction ; probably this thermal after action, like 

 the elastic occurs in an eminent degree in organic substances." 



The specific heat of vulcanite was determined by the method 

 of mixtures. Small fragments of vulcanite were heated to 

 near the temperature of boiling water in Regnault's apparatus 

 and dropped into a water calorimeter. After corrections for 

 equivalents in water of calorimeter and thermometer and for 

 radiation and evaporation, three experiments gave these results : 

 1) -33124 2) -33077 3) -33225 Mean = -33125 



On the diathermancy of vulcanite numerous careful experi- 

 ments were made. The results of these and of experiments 

 on other substances are given in the accompanying diagram of 





A 



0- 













i 



! 





















\B 



































\ C 





( 



p"-~»'^. 



o 























V 

























! 







d1 





\F 































< 



\ 



\ 































\G 



\ 



























E< 











-*•——. 







~- 



















curves. In this diagram the figures on the axis of ordinates 

 give percentages of heat effect on thermopile transmitted by 

 plates of various substances whose thickness in millimeters is 

 given by the figures on axis of abscissae. 



Curve A gives the heat effect of sun's rays transmitted by 

 St. Gobain glass. The solar rays in these experiments and in 

 those of F, G and E were reflected from a speculum -metal 

 mirror of a heliostat. 



Curve B shows the heat effect of rays from a Locatelli lamp 

 transmitted by St. Gobain glass. 



Curve C, the same as B as given by Melloni. 



Curve F, the heat effect transmitted by sun's rays through 

 vulcanite. 



Curve G, the heat effect transmitted by sun's rays through 

 vulcanite. 



