HALL. — THERMO-ELECTRIC HETEROGENEITY IN ALLOYS. 573 



down without further annealing to a diameter of 0.051 cm. It was then 

 tested, by touching with ice, as the german-silver wire had been tested, first 

 in the hard-drawn condition, then in the annealed condition, then after 

 rubbing bright, then after stretching. The results, in general character 

 and in magnitude of the local electromotive forces developed, were simi- 

 lar to those found with german-silver, though no eccentricity so great 

 as that indicated by certain parts of the curve C 5 in Figure 8 was devel- 

 oped. Annealing increased the local eccentricities. Stretching affected 

 them but little. The maxima and minima appeared to be somewhat less 

 numerous than in the german-silver wires. The curve obtained after 

 brightening differed considerably from that found before brightening, but 

 as six days intervened between the two tests, which gave these curves, 

 it is doubtful whether the change is to be attributed to the scouring 

 alone. 



A piece of constantin wire was drawn cold from a diameter of 0.051 cm. 

 to a diameter of 0.036 cm., approximately. It was then tested, by 

 touching with ice, in the hard-drawn condition, and later in the annealed 

 condition, the annealing being done, as in the case of german-silver and 

 of manganin, by heating to incandescence for a few seconds by means of 

 an electric current. The local electromotive forces found were very 

 small, perhaps one fifth as large as those in german-silver and in man- 

 ganin, and indeed the difficulty of determining their size was so great 

 that the wire was tested in two conditions only. The maxima and 

 minima appeared to be about as frequent as in german-silver. Anneal- 

 ing changed the character of the representative curve, but did not increase 

 its eccentricities. 



It might be suspected that the constantin wire, being nearly twice as 

 large in diameter as the german-silver wire, might not be so much 

 affected locally in temperature by contact with the edge of the ice. 

 Experiments made December 26 showed this idea to be without founda- 

 tion. The edge of ice cooled a copper-constantin junction as effectually as 

 it would cool the smaller (copper) -(german-silver) junction; when placed 

 1 cm. distant from the junction along the constantin it produced about 

 one eighth part as great an effect as when applied at the junction; at 

 1.5 cm. from the junction along the constantin the effect was about 3 per 

 cent of that at the junction. On the other hand, when the edge of ice 

 was applied at a distance of 25 cm. from the junction along the copper 

 wire, 0.036 cm. in diameter, its effect was still perceptible, being appar- 

 ently more than 1 per cent as great as the effect produced by applying the 



