On Thermoelectric Currents in Strained Wires. 339 



should be identical ; likewise the order of succession of the 

 liquids. 



Neither is the case ; and so far the theory is not in harmony 

 with experience. 



It must, indeed, be remembered that the values of the edge- 

 angle 6 were only determined approximately with flat bubbles 

 and drops, and can lay no claim to great accuracy — that the 

 magnitude <x l of the free surface of the glass may have had 

 different values in the various researches in consequence of 

 impurities (see § 12, hereafter) — and, finally, that merely the 

 presence of a fluid may alter the molecular nature and therefore 

 also the surface-tension of another, so that the density of a 

 surface bounded by air may be quite different from that of one. 

 bounded by another fluid (compare § 11). 

 [To be continued.] 



XLVII. The Production of Thermoelectric Currents in Wires 

 subjected to Mechanical Strain. By Gr. W. VON Tunzel- 

 MANN, Holder of the Clothivorkers'* Exhibition in Chemistry 

 and Physics at University College, London* . 



THE following inquiry was suggested by some observa- 

 tions recorded in a paper of Sir William Thomson's on 

 the Electrodynamic Qualities of Metals, in the i Philosophical 

 Transactions ' for 1856 ; and the object in view was to investi- 

 gate the conditions under which thermoelectric currents are 

 produced in a circuit composed of a single metal when one 

 portion of the metallic conductor is subjected to a strain and 

 the junctions of the strained and unstrained portions are main- 

 tained at different temperatures. 



The experiments were made upon wires of iron, steel, and 

 copper, the copper wire employed having been obtained from 

 Messrs. Johnson, Matthey & Co. as chemically pure. 



Two tin cans were obtained open at the top, and pierced at 

 the bottom by necks into which india-rubber corks were in- 

 serted ; and through slits in these the wires were passed. The 

 wire was fastened by a clamp in the lower can, and was grasped 

 in the upper one by a pair of wire-drawing dogs attached to 

 the shorter arm of a lever, to the longer arm of which was 

 attached the weight by which the strain was produced. In 

 the earlier experiments ordinary weights were used ; but ulti- 

 mately these were rejected, as it was found impossible to apply 

 and remove them in a sufficiently gradual manner to prevent 

 a certain amount of shock, which introduced complications. 



* Communicated by the Physical Society. 

 Z2 



