Wiedemann and Franz on the Conductibility of Metals for Heat. 37 



7. Platinum, 8. German silver, 4b. Brass. 



4-75 millims. thick. 5 millims. thick. 6-2 millims. thick. 



9. Tin, 

 6-3 millims. thick. 



10. Lead, 

 6-2 millims. thick. 



11. Rose's 



fusible metal, 



G millims. thick. 



Taking the bar experimented with in each case as a datum 

 line, marking the points at which the observations were made 

 along it, and erecting at each point a perpendicvilar to express 

 the temperature at that point, we obtain, by uniting the ends 

 of all the perpendiculars, a curve which represents the manner 

 in which the heat is distributed throughout the bar. In Plate I. 

 this process is carried out for each bar, the curves which refer to 

 the thicker bars being distinguished ft'om the others by being 

 drawn in dotted lines. 



Itemembcriug that the steepest curves belong to the substances 

 which conduct heat the most imperfectly, we obtain from the 

 diagram the order of conductivity as follows : — 



I. T%m bars. 



Silver, 



Copper, 



Gold, 



Brass, 



Iron, 



Steel, 



Platinum, 



German silver. 



