168 



Dr. M. Maclean. On the Effects of 



allowed to cool slowly for about an hour and a half in the ashes below 

 the fire. It was previously found that heating the wire to red heat 

 by an electric current and allowing it to cool slowly did not anneal it. 



§ 5. The resistances of all the undrawn wires, and the specific 

 gravities of both the undrawn and drawn wires, were carefully deter- 

 mined by the usual laboratory methods. The results obtained are 

 given in Table II. 



Table II. 



Conductor. 



Steel, annealed 



Aluminium 



Nickel 



Lead, commercial . . 

 Lead, pure 



Cross section 

 of undrawn 

 and drawn 

 wires in sq. cm. 



-007504 



7 



78 



0-004141 



7 



762 



-04594 



2 



-8 



-01697 



2 



-796 



-01179 



8 



-9 



-002475 



8 



•85 



-01145 



11 



-36 



-00256 



11 



•36 



-01150 



11 



35 



-00236 



11 



-357 



Specific 

 gravity of 

 undrawn 

 and drawn 

 wires. 



Eesistance of the undrawn 

 wires in C.G-.S. units 

 at 14° C. 



Per c.c. 



1 13,900 



108,100 



1 3,546 



9,931 



1 9,430 



83,920 



1 20,560 



233,100 



j 20,300 



230,200 



Per cm. 



long, 

 weighing 

 a gramme. 



§ 6. By multiplying the current per division given in Table I, by 

 the total resistance in the circuit, calculated from the results in Table 

 II, the thermo-electric difference per degree betv/een drawn and un- 

 drawn wires is found. The numbers are given in Table III. 



Table III. 













Thermo- 





Eesistance in ohms 







electric 





of 60 cms. of wire. 



Total 





difference 









resistance 



Total 



in mikro- 



Conductor. 







external 



resistance 



volt per 









to galvano- 



in circuit. 



degree C. 









meter. 





diff'erence 





Undrawn. 



Drawn. 







of tem- 



1 











perature. 



Steel, annealed. . . . 



0-1111 



-2015 



0-3126 



1-813 



-1028 





-0047 



-0125 



0172 



1-517 



-0099 



Nickel 



-0480 



-2287 



-2767 



1-777 ' 



-3784 



Lead, commercial . 



0-1077 



-4820 



-5897 



2-09 



026 





0-1059 



0-5162 



0-6221 



2-12 



-0076 



