402 On the Secular Annealing of Cold Hard Steel. 



the error due to variations in the standards. Moreover, the 

 electrical effects of corresponding variations of temper (steel) 

 and of the drawn strain which the German silver may possibly 

 carry are enormously different. For instance, if glass-hard 

 steel is boiled long enough the change of resistance may reach 

 12 per cent, and more. The effect of boiling German silver 

 is of the order of some tenths per cent.* Hence I appre- 

 hend no serious error in ascribing the whole of the observed 

 variation of s in Table IV. to secular annealing of the glass- 

 hard steel rods under experiment. 



Table IV. — Specific Resistance of the Glass-hard Steel Rods, 

 measured July 9th, 1888, and the Secular Variation. 

 (q as in Table III. ; effective length about 23 centim.) 



No. 



2pXl0 6 



r t - 



t. 



Ar t . 



aXlO 3 . 



s . 



As . 





centim. 



microhm. 



°C. 



microhm. 





microhm. 



microhm. 



1 



^ 



8460 



^ 



-790 



) 



417 



- 42 



2 





8430 





-820 



417 



- 43 



3 





8010 





-860 





393 



- 4-4 



4 





7950 





-850 





39-3 



- 4-4 



5 

 6 



► 80-6 



8010 

 8460 



>28 



-830 

 -800 



-1-7 



39-4 

 420 



- 43 



- 41 



7 





8400 





-800 





41-5 



- 4-3 



8 





8510 





-750 





41-9 



- 41 



9 





7920 





-800 





39-2 



- 43 



10 



J 



8170 



) 



-780 



J 



40-8 



- 4-3 



11 



) 



27860 



1 



-2810 



] 



40-5 



- 4-6 



12 





27710 





-2610 



I 



40-3 



- 4-2 



13 



^44 



28000 



}>29 



-2620 



[VI 



407 



- 43 



14 





27490 



i 



-2590 



J 



40-0 



- 41 



15 



; 



28400 



; 



-2590 



413 



- 41 



16 



1 



2807 



] 



- 590 



1 



333 



- 7-7 



17 

 19 



1 126-5 



2807 

 2830 



[29 



- 570 



- 810 



21 



33-4 

 33-8 



- 7-5 

 -10-5 



20 



J 



2808 



) 



- 620 



J 



33-5 



- 8-0 



Summarizing the results of Tables III. and IV., it appears 

 that during the 37 months between the two series of observa- 

 tions the specific resistance of the rods has fallen from 46*5 

 to 42*5 in case of the thin rods (diameter < *08 centim.), and 

 from 43' 7 to 35*4 in the case of the thicker rods (diameter 

 *13 centim.). Hence the variations are a decrement of specific 

 resistance amounting to some ten or even twenty per cent, 

 in the extreme cases. This may be stated succinctly as 

 follows : — mean atmospheric temperature acting on freshly 



* Cf. Bulletin U. S. G. S. No. 14, p. 94. 



