340 



BRIDGMAN. 



reversal in direction of curvature that the annealed iron does. The 

 numerical values are also verv different. At 100° and 12000 ke;. the 

 thermal e.m.f. of soft ingot iron is 7.68 X 10"^ of hard drawn ingot 

 iron 12.80, and of annealed commercial iron 9.56. The mechanical 

 treatment apparently makes more difference than slight differences 

 in chemical composition. 



It is not worth while to give the Peltier and Thomson heats of these 

 two other specimens; if any one is especially interested they may be 



0° 10° 20° 30° 40° 50° 60° 70° 80° 90° 00° 



Temperature 

 Pure Iron Hard Drawn 



Figure 29. American Ingot Iron, Hard Drawn. Thermal E.M.F. of a 

 couple composed of one branch of uncompressed metal, the other compressed 

 to the pressure in kg. /cm.- indicated on the curves, the junctions being at 

 0°C and the temperature plotted as abscissae. 



obtained l:>y calculation from the curAcs, or I will be glad personally 

 to send him the figures. The general character of the effects is quite 

 different from that of the annealed pure iron, due to the reversal in 

 curvature of pure iron between 75° and 100° already mentioned. 

 The Peltier heat of both of these specimens rises from initial negative 

 values to high positive values. The general course of the Thomson 

 heat is from low to high positive \alues with rising pressure and 

 temperature, but both specimens show minima near 40°. 



