342 Von Tunzelmann on the Production of Thermoelectric 



W = tension applied to wire in pounds, = 3 times weight 



actually applied to lever; 

 M = number of measures of shot effective in stretching 



wire, = 3 times number actually applied to lever ; 

 © = temperature of lower can ; 

 D = mean deflection of galvanometer ; 

 C = strength of current in terms of the standard current. 



A considerable number of preliminary experiments were 

 made to verify Thomson's results and to determine the best 

 form of apparatus, the arrangement ultimately adopted being 

 that already described. These experiments (which are not 

 described here) gave a general idea of the phenomena to be 

 looked for. The alteration of resistance from strain is not 

 taken into consideration, as EL Tomlinson's experiments, Proc. 

 Roy. Soc. 1876 (vol. xxv. p. 451), have shown that it is too 

 small to have an appreciable influence upon the results. 



Experiment 1. — An iron wire *46 millim. diameter. % = 

 16°; W = 31'5. The result is given in the accompanying 

 Table, the direction of the current being U.S., the first read- 

 ing being taken immediately after the weight was applied. 

 It will be observed that the current does not reach its full 

 strength immediately upon the application of the weight, but 

 rises rapidly to a maximum, and then gradually falls to a 

 strength at which it remains steady. 



Time j. 



(minutes). 



2-5 



5 6 



10 3 



15 2 



20 2 



25 . . . . , 2 



Experiment 2. — A similar wire. © = 16°. The readings 

 were taken immediately after the application of the weight. 

 The sign # means that there is a deflection, but too small to 

 be measured. 



W. D. Direction. 



6 * U.S. 



9 ..... 5 U.S. 



12 ..... 3-5 U.S. 



15 ..... 3 U.S. 



18 * S.U. 



21 / wire 



\ broke. 



