772 



MK J. D. HAMILTON DICKSON ON 



Palladium. 



The curve connecting E.M.F. and temperature for this metal, though extending 

 beyond its vertex, nevertheless afforded so small opportunity for an exhaustive test 

 that it was thought more conclusive to treat it by shearing. The co-ordinates of the 

 sheared curve were taken to be 



T = t + 200, and H = E/200 + 2T - 100, 



and the observations gave the A-sh eared curve on Plate XL The mid-points of twelve 

 chords parallel to the axis of T were observed ; their values are given in the annexed 

 Table XII., and they are shown on the A-curve above the short line a to which the 

 chords are parallel. A second series of parallel chords gave the set of mid-points shown 

 above the short line b to which this set of chords is parallel ; these chords make with 

 the axis of T an acute angle whose tangent is 2/5, and therefore easily obtained on the 

 diagram. The b set of points again lie very closely on a straight line, which is, as 

 nearly as it is possible to observe, parallel to the line of the a-points. 



Table XII. 



H: 



T. 



H. 



T. 



130 



1421 



250 



136 



150 



1411 



270 



135 



170 



140| 



290 



133-| 



190 



139 



310 



1321 



210 



138 



330 



131 



230 



137 



350 



1291 



From these twelve a-points the equation of the nearest straight line to them was 

 found, by least squares, to be 



T + l7Wl7 = 150 ' 127185 (68) 



Hence the axis of the parabola makes a small angle with the axis of H whose cotangent 



is 17'3728 17. Adopting this value, the equation of the curve was calculated by least 



squares from twenty of the thirty-six observations recorded. The vertex of the curve 



was found to be at 



T = 127-1909, H = 363-620, 



and the latus rectum was 73*001867. These values lead to this equation connecting T 

 and H, 



( T ^7^817- U8 - 121322 ) 2 = 73 - 12271 Kl7^7- H + 356 - 2987 • • (69) 



or, in a form more suited for calculation, 



E= -938656-42 -3874-56340+ 124045-1428^/0 

 where 



(70) 



= / + 389-347142. 



