50 Mr. H. Tomlinsou on the Thermoelectrical Properties 



through 10 divisions, showing that the condenser was being 

 charged. Almost immediately after B had touched A, it "was 

 removed, and after allowing sufficient time for the wires to 

 cool B "was again placed on A, when a deflection through 10 

 divisions of the scale in the opposite direction indicated the 

 discharge of the condenser. This experiment was repeated 

 several times with fairly uniform results: and by comparing 

 the deflection thus obtained with that produced by a Daniell's 

 cell, it was ascertained that the E.M.F. produced by putting 

 iron at a bright red temperature on iron at about 15° C. was 

 one twentieth of a volt, i. e. considerably more than twice a- 

 much as would be developed in a single element of bismuth 

 and antimony with one junction at 100° C. and the other at 

 0°C. 



It has long been known that hot iron is negative to cold 

 iron, and this seems to be so at all temperatures, but it has 

 not, the author believes, been noticed before* how very 

 suddenly the negativeness is increased when the temperature 

 reaches a bright red. If the wire B be heated to a tempera- 

 ture between dull red and bright red before being placed on 

 A, there is a current from A to B which can be readily 

 detected if the condenser be cut out and the galvanometer 

 connected directly with A and B, but no effect whatever could 

 be detected when the condenser was used as in the experiment. 



Experiment IV. 

 A piece of the same iron wire was connected direct! v with 

 the two terminals A, B of a reflecting galvanometer of 7 B.A. 

 units resistance (fig. 3). A portion C D of the wire was 

 Fipr. 3. 



heated above a bright red by a burner, and as soon as the 



required temperature had been reached the burner was 



* Unless we except Prof. P. G. Tait's observations, which will be 

 referred to presently. 



