es? BarRRETT— On some novel Tnermo-LElectric Phenomena. 
a copper-steel couple at different temperatures is not the same for a rising as for a 
falling temperature. This I have found to be the case with couples formed of 
several other metals, provided one element of the couple is iron or steel or other alloy 
of iron. When the other metal is platinum, the difference in the two curves is 
well seen, though with a platinum-iron couple, the difference of E. M. F. in heating 
and cooling is less marked than with a platinum-steel couplé. In the latter case, a 
considerable area is enclosed by the curves (representing the relation between 
thermo-electric foree and temperature) during heating and during cooling. 
Hence, at a given temperature, say 500° C., of the hot junction, the E. M. F. of a 
platinum-steel couple is considerably higher during heating than during cooling. 
The reverse is the case with a couple formed of Hadfield’s nickel-manganese- 
steel and copper, or a couple formed of the same alloy with platinum; in both 
these cases at any given temperature, the EK. M. FE. is dower during heating than 
during cooling. With a couple formed of the same alloy and iron, as described in 
the earlier part of this paper, there is also a slightly lower E. M. F. at corresponding 
temperatures during heating than during cooling, but the difference only exists at 
certain parts of the scale, and is so small that it could not be shown on the curve 
as reduced in the Plate. With the nickel-manganese-steel alloy mentioned on the 
top of p. 115 (containing 19 instead of 25 per cent. of nickel) coupled with iron, the 
EK. M. F’. is slightly Aigher at corresponding temperatures in heating than in cooling 
up to the level part of the curve, ¢.e. about 400° C., where the E. M. i. becomes 
almost the same in heating as in cooling—vyery slightly lower, however—and 
remains so until the curve rises, when the E. M. F. again becomes higher at cor- 
responding temperatures in heating than in cooling up to the highest temperature 
reached : in this case, therefore, the curves showing the E. M.F. during heating 
and cooling cross each other twice, first at about 400° and next about 800°C. 
Thope, in a subsequent paper, to give the results of further investigation which 
I am pursuing on this interesting phenomenon, together with the curves for the 
K.M.F. of various couples during heating and cooling—thermo-electric hysteresis 
curves as they may be called.* It is very probable that the peculiar thermo- 
electric deportment of iron, and some of the alloys of iron described in this 
paper, is intimately associated with the phenomenon of recalescence, or rather 
of the series of recalescent points which exist in iron and steel. 
*As was pointed out by Professor G. F. Fitz Gerald, F.T.C.D., F.R.S., at the meeting of the Society 
when this paper was read, the thermo-electric hysteresis here referred to is, no doubt, the cause of the 
thermo-current which is produced in an iron wire steadily moyed through a flame, a phenomenon first 
noticed and inyestigated by Dr. F. T. Trouton, F.R.S. See Proc. Royal Dublin Society, March, 1886. I 
am also greatly indebted to Professor FitzGerald for other suggestions he has made in reading the proof 
of this paper. 
