182 



C. Bar us — Effect of Magnetization on the 



A final datum of interest is the obliquity, w, of the external 

 fibre, or the angle in radians between the axis of the wire and 

 any tangent of the helix into which a straight surface fiber, or 



This is approximately 



generatrix has been twisted 



7tp 

 180 



t being the rate of twist in degrees. This variable w is in- 

 tended to have no more than geometrical significance. It is 

 known that on twisting and again untwisting an iron wire 

 beyond the elastic limits, the fibers do not return upon them- 

 selves to their original forms and positions, but that they 

 become irregularly sinuous lines. 



Table 5. 

 Showing the effect of magnetization on the rigidity of soft iron. Z=30 cm . 





Nos. 1,2. 



Nos. 3, 4. 



Nos. 5, 6. 



Nos. 7, 8. 



Nos. 9, 10. 



Nos.11,12. 



Nos.13,14. 





2p=0-234 



2p = 0-136 



2/3=0-090 



2p=0-110 



2p=0-070 



2/3=0-048 



2/3=0-022 





co 



.- 



CO 



CO 



>o 



to 



« 



.„ 



CO 



CO 



f> 



Eg 



CO 



CO 



CO 



CO 



.- 



CO 



CO 



o 



CO 





© 



— 



© 



_ 



© 





© 



© 





© 



~ 



© 





© 



© 



© 



© 



© 



© 



© 



© 





X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 





3 



-s- 



a. 



3 



-©- 



=1. 



3 



■©- 



=s_ 



3 



•©- 



a. 



3 



■&. 



=i. 



3 



■©- 



y 



3 



-©- 



=*- 



— 0-43 



0-8 



12 



3'2 







































— 0-75|l-5 18 



2-7 



0-9 



24 



3-7 



0-6 



42 



6-4 



0-7 



34 



5-2 



0-5 



37 



5-6 



0-3 



60 



9-2 









— 1-12 23 23 



2-3 







































— 1-503-1 



30 



2-3 



1-8 



43 



3-3 



1-2 



68 



5-2 



1-4 



54 



4-1 



0-9 



82 



6-3 



0-6 



107 



8-2 









— 2-25 









2-7 



49 



2-5 



1-8 



75 



3-8 



2-2 



62 



3-2 









0-9 



116 



5-9 



.. 







— 3-00 









3-6 



51 



2-0 



2-3 



78 



3-0 



29 



65 



2-5 



1-8 



95 



3-6 



1-2 



131 



5-0 



0-6 



86 



3-3 



— 3-75 





















3-2 



66 



2-0 





















-4-50 















3-5 



77 



2-0 









2-7 



104 



2-7 



1-9 



148 



3-8 









— 5-25 



























3-2 



103 



2-3 















-6-00 

































2-5 



156 



3-0 



1-2 



166 



3-2 



— 7-50 

































3-1 



148 



2-3 









— 9-00 







































1-7 



205 



2-6 



— 12-50; 





































2-4 



220 



2-0 



— 15-00 







































2-9 



237 



1-8 



In table 5, I have given values for these variables as obtained 

 with soft iron wires of different thicknesses. The intensity of 

 magnetic field has been stated above (p. 111). Commencing at 

 low values, the rate of twist (r) is successively increased to the 

 maximum value, which can be imparted, i. e., until, with the 

 occurrence of marked permanent set, the limits of resilience of 

 soft iron are fully reached. After this it was usual to twist 

 the wires further, imparting several thousand degrees of per- 

 manent set, whereupon r was decreased from the maximum to 

 zero. In the table, w, <p, ju, are means of the values obtained 

 by thus successively increasing and decreasing r. As before 

 p is the radius and I the length of the wires, of which Nos. 1, 

 2, 3, 4, 5, 6 were drawn down from a single piece of wire, Nos. 



