396 Royal Society, 



annealing on zinc wire, making it brittle and crystalline, which might 

 give a different condition, as the "annealed" in Magnus's experi- 

 ment, and the "unhammered" in the experiment now adduced. 

 Setting aside this case, the author concludes that generally the effect 

 of permanent lateral compression is the same as that of permanent 

 longitudinal extension, or of hardening by wire-drawing, upon the 

 thermo-electric quality of a wire placed longitudinally in an electric 

 circuit; that in iron it is a deviation from the constrained metal 

 towards bismuth, and that in all the other metals mentioned it is a 

 deviation towards antimony ; and that in copper and iron it is the 

 reverse of the effect experienced by the same metal while under the 

 stress that caused the strain. Since no kind of strain, except uni- 

 form condensation or dilatation in all directions, is free from the 

 directional attribute, it appeared probable to the author that the 

 thermo-electric effects remaining in a metal left with a longitudinal 

 strain, retained after the stress that caused it is removed, must be 

 different in different directions. He therefore experimented on iron 

 hardened by longitudinal compression, and found that it deviates 

 from soft iron towards antimony, or in the contrary way to iron 

 hardened by longitudinal traction. From this, and from the results 

 quoted above, it follows that in iron hardened by compression in one 

 direction, the thermo-electric qualities in this direction differ from 

 those in lines perpendicular to it, as antimony differs from bismuth ; 

 that the reverse statement applies to iron hardened by traction in one 

 direction ; and that these differing thermo-electric qualities have in' 

 each case the thermo-electric quality of soft iron intermediate between 

 them. 



These various results show that the character of the effect in each 

 case is decided by distorting stress or by distortioriy and leave entirely 

 open, and only to be answered by further experiments, the questions : 

 what is the thermo-electric effect of pressure or traction, applied 

 uniformly in all directions to a metal? and what is the thermo- 

 electric effect of a permanent condensation or dilatation remaining in 

 the metal, when freed from the force by which that condensation or 

 dilatation was produced ? 



Experiments are also described, by which the author found that 

 in soft iron under magnetic force, and in that retaining magnetism, 

 when removed from the magnetizing force, directions along the lines 

 of magnetization deviate thermo-electrically towards antimony ; and 

 that directions perpendicularly across the lines of magnetization in 

 soft iron, deviate towards bismuth, from the unmagnetized metal. 

 He illustrates this conclusion by an experiment on a riband of iron, 

 magnetized nearly at an angle of 45° to its length, and heated along 

 one edge while the other is kept cool. When the two ends, kept 

 at the same temperature, are put in communication with the elec- 

 trodes of a galvanometer, a powerful current is indicated, in such 

 a direction, that if pursued along a rectangular zigzag from edge to 

 edge through the band, the course is always /row across to along the 

 lines of magnetization through the hot edge, and from along to acros9 

 the lines (^magnetization through the cold edge. 



