ELECTRICAL RESISTANCE OE NICKEL AT HIGH TEMPERATURES. 189 



these wires ; tables C and D give the corresponding results for platinum and 

 palladium. They are added simply for the sake of comparison. 



The first column contains the corrected temperatures ; the second the 

 resistances corrected for the connections ; and the third these resistances 

 reduced so as to make the resistance at 0° C. equal to 100. The value of the 

 resistance of the wire at 0° C. was in all cases calculated — in the case of 

 platinum and palladium from the empirical parabolic formula which was found 

 to agree well with the observations, and in the case of nickel by the method of 

 successive differences from the first five or six numbers. This latter method 

 was used because, for the nickel measurements, it was found quite impossible 

 to obtain a suitable formula of ascending powers of temperature up even to the 

 fourth. The reduced resistances of the third column for each wire are repre- 

 sented graphically in their relation to temperatures on Plate XII. (I.). The 

 diameters and specific resistances of each wire are given at the head of each 

 list of numbers. 



The resistances throughout are measured with greater accuracy than the 

 temperatures. In some cases, the temperature being steady, the resistance 

 was adjusted by means of a large shunt set in an arc along with the units of the 

 resistance box. In other cases — and this was latterly found the more con- 

 venient method — the resistance was fixed as near as the coils would allow, and 

 the temperature of the wire slowly raised till the current through the galvano- 

 meter just vanished. Hence, although the resistances in table A appear only 

 to the third significant figure, they are really certain to the fourth. 



Table A. — Thick Nickel. 



Diameter = 



= •05 cm. Specific resistance = 9697 ( 



C.G.S.). 





Resistance of 



Resistance reduced 



Temperature. 



Wire used. 



for comparison. 



0°C. 



■724 ohms 



100 



10° 



•757 



104-6 



20° 



•79 



1091 



29° 



•82 



113-3 



66°-4 



■ 95 



131-2 



88° 



1-03 



142-3 



98°-6 



1-07 



147-8 



114°-6 



1-14 



157-5 



122°-6 



1-17 



1616 



131°-6 



1-21 



167-1 



142°-3 



1-26 



174-0 



167° 



1-37 



189-2 



187° 



1-47 



203-0 



198°-5 



1-53 



211-3 



215° 



1-62 



223-8 



220°.3 



1-65 



227-9 



233° 



1-72 



237-6 



251° 



1-83 



252-8 



255° 



1-85 



255-5 



264°-8 



1-91 



263-8 



267°-5 



1-93 



266-6 



