ELECTEICAL RESISTANCE OP NICKEL AT HIGH TEMPERATURES. 195 



to 230 by successive additions of 10. From the reduced observations in the 

 several experiments, the resistance of any metal corresponding to each one of 

 the chosen platinum resistances can be readily calculated. Thus the number 

 401 in the fourth column means that a piece of thick nickel, whose resistance 

 at 0° C. is 100, has a resistance of 401 at that temperature at which 190 is the 

 resistance of a piece of platinum whose resistance at 0° C. is also 100. In 

 short, the platinum column serves the purpose of a provisional temperature 

 scale, in terms of which the resistances of the other metals are expressed. 

 Under each column a row of differences is added. These bring out strongly 

 the peculiarities which are disclosed by a glance at the curves of Plate XII. 

 (II.). On the left of the platinum column a few numbers are given to indicate 

 the temperature in degrees centigrade. Above the value 320° C, the estima- 

 tion is only approximate, and is based on the assumption that platinum 

 wire changes in resistance according to a parabolic function of the tempera- 

 ture. 700° C. may be regarded as a fair approximation to the highest tem- 

 perature. Besides the nickels and palladium used in the former series of 

 experiments, two specimens of iron were investigated, and are given for pur- 

 poses of comparison. 



Table E.- 



—Comparison < 



if the Resistances of various Metals at different Temperatures. 



Temp. 

 in°C. 



Platinum. 



Palladium. 



Thin Nickel. 



Thick Nickel. 



Iron 



(1). 



Iron 



(2). 





Resist. 



Diff. 



Resist. 



Diff. 



Resist. 



Diff. 



Resist. 



Diff. 



Resist. 



Diff. 



Resist. 



Diff. 





230 



10 



303 



14 



350 



12 



476 



19 



713 



80 



718 



75 



580° 



220 

 210 

 200 



10 

 10 



10 



289 

 275 

 263 



14 

 12 

 14 



338 



(325) 



311 



13 

 13 

 14 



457 

 440 

 418 



17 



22 

 17 



633 

 550 



485 



83 

 65 

 60 



643 



568 

 514 



75 

 54 

 51 



420° 



190 

 180 



10 

 10 



(249) 

 234 



15 

 16 



297 

 282 



15 

 16 



401 

 378 



23 

 43 



425 

 371 



54 

 45 



463 



405 



58 

 50 



320° 



170 



10 



218 



17 



266 



31 



335 



52 



326 



42 



355 



50 



270° 



160 



10 



201 



17 



235 



29 



283 



43 



284 



42 



305 



44 



220° 



150 



10 



184 



17 



206 



30 



240 



34 



242 



28 



261 



42 



180° 



140 



10 



(167) 



17 



176 



24 



206 



36 



214 



34 



219 



32 



130° 



130 



10 



150 



17 



152 



19 



170 



29 



180 



32 



187 



32 



84° 



120 



10 



133 



17 



133 



15 



141 



21 



148 



27 



155 



28 



40° 



110 



10 



(116) 



16 



(118) 



18 



(120) 



20 



121 



21 



127 



27 



0° 



100 





100 





100 





100 





100 





100 





VOL. XXXIII. PART I. 



2D 



