118 Thermo-electric Powers of Metals and Alloys. 



No. 24 

 Carbon-Lead Couple. 



One junction at 0° 0. ; the other okpt . 



- E.M.R 



of Couple 

 in C.G-.S. units. 



Temperature pt° 



in degrees of 



StandardPlatinum 



Thermometer. 





EM.F. 



of Couple 

 in C.Gr.S. units. 



Temperature pt° 



in degrees of 



Standard Platinum 



Thermometer. 



+ 127950 

 + 109830 

 + 97840 

 + 74550 

 4- 62110 

 + 46980 

 + 31560 

 + 22690 

 + 10510 



- 3210 



- 14630 



- 23780 



+ 98-2 

 + 85-9 

 + 77-0 

 + 60-1 

 + 50-7 

 + 38*9 

 + 263 

 + 201 

 + 9-0 



- 43 



- 14-7 



- 23-0 



- 34400 



- 46070 



- 59360 



- 77750 



- 89560 

 - 109880 

 -122080 

 -129490 

 -132770 

 -141460 

 -149480 



o 



- 33-3 



- 44-9 



- 58 6 



- 79-7 



- 93-9 

 -121-6 

 -140-6 

 -152-5 

 -1618 

 -179-4 

 -196-2 



We propose to reserve for a future communication a full 

 discussion of the interpretation of these curves and the 

 bearing of the facts they disclose on the usually accepted 

 thermo-electric theory. Meanwhile it may be sufficient to 

 note that none of these thermo-electric curves are true 

 parabolas over their whole extent. Many of the curves 

 as drawn in the chart in Plate IV. are curves of double 

 curvature, and in some cases point to the existence of 

 more than one neutral point with lead. We propose to 

 convert this chart of electromotive forces into a chart of 

 thermo-electric powers, in which last condition it will lend 

 itself better to a discussion of results. A few remarks may, 

 however, be made respecting the thermo-electromotive force 

 curves shown in the chart. The lines of iron and pianoforte- 

 steel, as well as some others, have changes of curvature at 

 certain points which indicate that the thermo-electric lines 

 are broken lines. The line of antimony has two points at 

 which its tangent becomes parallel to the line of lead, indi- 

 cating that the thermo-electric line of antimony cuts that of 

 lead twice. The bismuth lines are very peculiar. The curves 

 marked Bismuth No. 1 and Bismuth No. 2 are specimens of 

 impure or commercial bismuth ; but both these and the curve 

 of pure bismuth have a sudden break or discontinuity in their 

 course at about —80°, which we think is not due to errors 



