282 Profs. Dewar and Fleming on the Electrical 



and let p* = volume-specific resistance of the metal at tempera- 

 ture t° C, in O.Gr.S. units ; 

 then logio/o<=logi R* + log ]0 & or pt= Kt k. 



In the following Tables t stands for a Centigrade tempera- 

 ture and pt for the equivalent platinum temperature. 



The reduced observations taken with this thick platinum 

 wire were as follows : — 



Re. 



t°. 



pt- 



pt. 





Corrected 



Corrected 









resistance 



Centigrade 



Volume- 



Platinum 



Eemarks on nature of 



of wire in 



tempera- 



specific 



tempera- 



Bath. 



ohms. 



ture. 



resistance. 



ture. 





5-2171 



195-2 



18388 



192-2 "1 

 139-8 r 



Taken in melted paraffin 



4-6345 



141-0 



16334 



wax. 



4-1876 



98-5 l 



14759 



98-55 \ 





4-1813 



98-05 



14737 



98-10 | 





3-9982 



80-90 



14092 



81-20 "> 



Taken in paraffin oil. 



3-7695 



60-0 



13286 



60-55 | 





3-5440 



39-60 



12491 



40-15 J 





3-3108 



18-45 k 



11669 



18-85 





33043 



17-90? 



11646 



18-25 





3-2991 



17-20 



11628 



17-55 





3-2739 



14-90' : 



11539 



15-20 





3-2487 



12*80'' 



11450 



13-10 





3-2450 



12-60 



11437 



12-85 





3-1136 



0-60 



10974 



0'60 



Taken in melting ice. 



2-8034 

 2-6222 

 2-4225 





9881 

 9242 

 8538 



- 27-8 } 



- 44-0 I 



- 62-7 J 



Taken in paraffin and solid 

 carbonic acid. 



2-2085 





7784 



- 81-9 [ 



Taken in solid carbonic 

 acid and ether. 



2-0138 

 1-9446 





7098 

 6854 



- 99-8 1 

 -106-1 J 



Taken in liquid ethylene. 



0-9473 





3339 



-197 { 



Taken in liquid oxygen 

 boiling at 760 niilliru. 



0-6951 

 0-6921 





2450 

 2439 



-219-7 J 

 -219-9 1 



Taken in liquid oxygen 

 boiling under reduced 

 pressure. 



Volume specific-resistance at 100° C. 



Ditto ditto at 0° C. 



Mean temperature-coefficient between 



0° and 100° C 



= 14814 C.G.S. units. 

 = 10950 „ 



= •003529= a. 

 1 



Reciprocal of temperature- coefficient = — 283 # 4 = 



In order to determine the platinum temperatures the first 

 step was to draw a curve from the observations made between 

 Oe 60 C. and 98°* 55 C, of which the ordinates were specific 

 resistance and the abscissas corrected Centigrade temperatures. 

 This curve enabled us by extrapolation to determine the 

 true volume-specific resistance at 0° C. and 100° C. exactly. 

 Through the summits of the ordinates drawn up at 0° 0. and 



