Annealing of Cold Hard Steel. 



401 



given under q and p respectively. In most cases q is indi- 

 vidually determined. 



Table III. — Specific Resistance of the Glass-hard Steel 

 Rods, measured June 4th and 8th, 1885. 



(Effective length 20 centim. to 26 centim.) 



No. 



qx!0 G . \ 2p X10 3 . 



rt- 



t. 



aXlO 3 . 



s . 





centim. 2 centim. 



microhm. 



°C. 





microhm. 



1 



5152 



\ 



9260 



275 



15 



460 



2 



5168 





9250 



27-8 



1-5 



460 



3 



5126 





8870 



28-3 



16 



437 



4 



5173 





8810 



270 



1-6 



43-8 



5 



5139 



► 80-6 



8840 



27-2 



1-6 



43-7 



6 



5165 



9260 



26-8 



1-5 



461 



7 



5164 





9200 



270 



1-5 



45-8 



8 



5143 





9260 



263 



1-5 



460 



9 



5174 





8720 



26-3 



1-5 



436 



10 



5214 



/ 



8950 



251 



1-5 



451 



11 



1520 



^ 



30670 



25-2 



1-5 



45-1 



12 



1520 





30320 



253 



1-6 



44-4 



13 



1520 



}-44 



30620 



24-8 



1-5 



450 



14 



1520 



J 



30080 



255 



1-6 



44-1 



15 



1520 



30990 



26-8 



1-5 



45-4 



16 



12560 



^ 



3400 



26-4 



1-7 



410 



17 



12610 



1 



3382 



26-4 



1-7 



41-0 



18 



12400 



V 126-5 



4144 



26-6 



1-5 



49-5 



19 



12650 



12620 \) 



3643 



26-7 



1-6 



443 



20 



3427 



27-2 



1-7 



415 



Finally, Table IV. contains the electrical constants of these 

 rods made about 37 months after the first measurement. It 

 also contains the variations, Ar t , of the resistance per centi- 

 metre, as well as the variations, As , of the specific resistance. 

 It will be seen that As is negative throughout, whereas the 

 effect of atmospheric influence and the unavoidable abrasion in 

 cleaning the surfaces of the wires before measurement, would 

 produce a positive error. The same bridge and the same stan- 

 dards of German silver are used both in the measurements of 

 Table III. and of Table IV. The fact that the wires differ in 

 diameter, and therefore very largely in resistance, is a guaran- 

 tee against the effect of differences of sectional errors of the 

 bridge-wire. Again, although As () is essentially the difference 

 of secular change between the steel wire and the German- 

 silver standards, the fact that two standards (1*0 ohm and 

 0*1 ohm respectively) were used, at least partially eliminates 



