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V. 



ON SOME NOVEL THERMO-ELECTEIC PHENOMENA. 

 By W. F. BARRETT, P.R.S., 



Professor of Experimental Physics in the Royal College of Science for Ireland. 



(Plate IXa.) 

 [Read Februaet 22, 1899.] 



In the course of a determination of some of the physical properties possessed by 

 various new alloys of iron, which had been prepared by Mr. R. A. Hadfield, of 

 Sheffield, I found the thermo-electric behaviour of a particular nickel steel, to 

 which five per cent, of manganese had been added, to be so remarkable that it 

 seemed worthy of a separate note. 



The analysis of this alloy (kindly supplied to me by Mr. Hadfield) was as 

 follows : — 



Iron, . . . . 68"8 per cent. 



Nickel, . . . 25-0 ,, 



Manganese, . . 5*0 ,, 



Carbon, . . . 1'2 ,, 



The specific electrical resistance of this alloy was found by Mr. Brown and 

 myself to be higher than any other alloy we had hitherto examined.* It amounted 

 to no less than 97-52 microhms per cubic cent, (at 15° C). At the same time its 

 variation of resistance with change of temperature was comparatively small, the 

 temperature coefficient being 0-08 per cent, per degree C. (between 0° and 250° C). 



The thermo-electric behaviour of the various alloys of iron which Mr. Hadfield 

 had kindly placed in my possession was in course of investigation, and the 

 enormous electrical resistance of this specimen, and of another similar alloy with 

 somewhat less nickel, led me to try earlier than I should otherwise have done some 

 of its other physical properties. 



A preliminary experiment was made by coupling a wire of this new alloy 

 successively with different metals and testing the thermo-electric power of the 

 various junctions up to a red heat. When an iron wire was used as the second 

 metal the thermo-electric force quickly rose till a certain temperature much below 

 redness was reached, and then remained almost stationary, notwithstanding the 



* See Trans. R.D.S., Vol. vn., Part 4. 



TEANS. EOT. DUB. SOC, N.S. VOL. Til., PAET V. U 



