148 THE SCIENTIFIC PAPERS OF 



absolute zero, and which I call y. The total resistance of a 

 conductor at any temperature, T, would, therefore, be expressed 

 by the formula 



The law of increase expressed by this formula is graphically 

 represented by diagram No. 3, Plate 16, the spaces between the 

 abscissal axis and the parabola expressing the resistances due to 

 the absolute motion of the particles ; the arithmetically increasing 

 field of resistance above the parabolic curve expressing the increase 

 due to increase of distance between adjoining particles ; and the 

 field below the X axis, the constant resistance of the material 

 under all conditions. It remained to be seen whether, in giving 

 suitable values to the co-efficients a, /3, and y, this law of increase 

 could be made to coincide with the observed results. 



In deciding the abscissal axis according to temperature, and 

 fixing the zero Centigrade at the point where the ordinate equals 

 a unit of resistance in the first diagram, or an amount equal to 

 the specific resistance at that temperature in the second, it will be 

 observed that the portion of the curve where the absolute zero (or 

 any other point of the thermal scale) falls, is completely fixed ; 

 and it was important to see whether, in starting from that point, 

 the curvatures as represented by the above formula would agree 

 with those of the experimental lines of the different metals. 



Three points of each of the experimental curves, including the 

 zero Centigrade, were taken, and the experimental values for T and 

 r at these points being put into the above formula, the numerical 

 values for a, ft, and y were obtained for each metal. If written 

 down with these numerical co-efficients, the formula is as follows : 



For platinum r = -0021448T* + '0024187T + '30425 

 r = -039869T* + '00216407T - "24127 

 r= -092183T* + -00007781T - "50196 

 For copper r = -026577T* + -0031443T - -29751 



For iron r=-072545T* + -0038133T- 1-23971 

 For aluminium r = -05951436T* + -00284603T - '76492 

 For silver r = -0060907T* + -0035538T - -07456 



Curves constructed in accordance with these expressions are 

 shown^in the portions below C. and above 350 C., of diagram 1, 



