328 Profs. Dewar and Fleming on Electrical Resistance 



platinum-silver, iridiuin-platmum, rhodium-platinum, palla- 

 dium-silver, as well as wires of palladium, and of nickel. 



Fig. 1, 



a 



j 



! 

 j 1 



'if 



l 



III 

 1 1 



u 



1 

 1 



1 ^-^ 



II 



9 



Resistance-Coil used in taking resistance of Wires in Liquid Gases. 



(a) Mica rectangle wound round with the wire to be measured. 



(b) Stout insulated Copper-rod Connexions. 



From the London Electric Wire Company was procured some 

 electrolytic copper wire of the highest conductivity obtainable, 

 and also from Messrs. Griffin & Co. some pure annealed iron 

 wire. Other wires of commercial materials, e. g., German- 

 silver, platinoid, tinned copper, tinned iron wire, and com- 

 mercial tin, were also mounted. 



The mean diameter of all these wires was measured with 

 the microscope-micrometer to the nearest ten-thousandth of 

 an inch, and the length also carefully ascertained. The elec- 

 trical resistance of each of these small resistance-coils was then 

 taken at six or seven fixed temperatures, as follows : — 



(1) At about 100° C. when immersed in a paraffin-oil or 

 glycerine bath heated with boiling water. 



