254 



A. W. Davison 



(3) Fusing in an electric arc. By using a carbon block for 

 cathode, and twisting the wires, then using the junction for 

 anode, a current will melt the metals, and make an excellent 

 junction. This scheme was finally resorted to for all the junc- 

 tions except the Ph-M ones. 



(4) For Ph-M junctions, a very satisfactory union was 

 effected by melting the lead in a Bunsen flame, and joining the 

 other metal in this way. 



(5) In the case of the lead-mercury element, the Hg was con- 

 tained in a tube of the form shown in fig. 8. The lead was 

 cleaned, and inserted into the mercury in one end, and the copper 

 line was inserted in the other end. Considerable caution had 

 to be exercised to keep the lead from amalgamating, but by pre- 

 paring a fresh specimen each time, this greatest difficulty was 

 overcome. 



Results of measurements of an advance lead thermo-couple (fig. 

 10). Current goes from Advance to lead in the hot junction. 

 Junctions (e) and (g) at 0°; >S = 5000 ohms, so (d) = .00004864 

 volts per mm. 



