286 Profs. Dewar and Fleming on the Electrical 



Bt. 



t°. 



pt. 



pt. 



07631 



192-1 



2608-4 



189-2 



0-6652 



137-2 



2273-7 



136-1 



0-6033 



98-15 



2062-2 



98-2 



0-5372 



60-0 



1836-2 



60-55 



0-4646 



18-30 



1588-1 



18-70 



0-4601 



18-20 



1572-7 



18-60 



0-4639 



17-25 



1585-7 



17-60 



0-4355 



0-65 



1488-6 



0-65 



0-3630 





1240-8 



- 42-3 



0-2988 





1021-3 



- 81-9 



0-1140 



... 



389-7 



-197-1 



Volume-specific resistance at 0° C. . = 1468 C.G.S. units*. 

 Mean temperature-coefficient between 



0° and 100° ='00400. 



§11- 



V. Copper. 



A large number of samples of copper have been examined 

 by us at one time or another. The purest copper we have 

 been able to obtain is that sent to us by Mr. J. W. Swan, 

 prepared by him from the electrolysis of pure copper nitrate 

 by his special process. The metal was exceedingly soft and 

 ductile, and was drawn into a very uniform wire without 

 melting or heating, and annealed by heating in hydrogen. 

 We call this particular specimen (May 19th) from the date 

 when it came to us. 



Two coils were prepared from this wire — one, a short coil of 

 300 centim. in length, and one very much longer, of about 

 2100 centim. The reason for this being that at the very low 

 temperatures tne copper loses so much of its resistance and 

 is so good a conductor that unless a considerable length 

 of wire is taken the resistance measurements cannot be made 

 accurately at the very lowest temperatures. For the shorter 

 coil the dimensions were: — ■ 



Length = 300 centim. Mean diameter = 0*025 789 centim. 

 Mean sectional area = 0*00052236 sq. centim. 



L °g4n5ir] = 3-2408464 = log 10 i. 



* This is the most probable value deduced from the whole curve, 



