454 Prof. Beetz on the Influence of Magnetization 



an extreme position could only be due to the circumstance that 

 the bar could not move parallel to itself, but always made an 

 increasing angle with the axis. 



The measurements made with iron bars and with thick iron 

 wires gave the following values, in which L indicates the length 

 of the bar, d its thickness, both in millimetres, and A its expan- 

 sion when the maximum magnetization was attained : — 











L 



No. 



L. 



d. 



Displacement. 



A* 



1 



966 



1-3 



0-8 



138C0000 



2 



922 



4 



0-5 



21200000 



3 



1250 



6 



6-5 



2310000 



4 



1242 



12 



110 



1230000 



5 



1175 



28 



6-4 



2110000 



6 



1010 



12 



00 



42440000 



Accordin 



g to Joule 





720000 



Buff 

 Wert 







420000 

 500000 



tieim 









In all these measurements the stretching was effected by a 

 weight of 1 kilog. No. 6 was a four-edged steel bar, which indi- 

 cates considerably smaller extensions than the iron bars. The 



reason why in these also, the values -r-, were greater than those 



found by Joule, Wertheim, and Buff consists doubtless in the fact 

 that my iron bars were not specially heated and slowly cooled. As 

 the object of these experiments was only to test the applicability of 

 my method, and not to determine the absolute values of the angles 

 of rotation with greater accuracy than had been done previously, I 

 have made no further measurements in this direction ; but I tried, 

 by various positions of the magnetizing spirals, to decide which 

 of the above processes are most favourable for stretching. For 

 this purpose the stretchings were observed when the four spirals 

 were spread, as above, over the whole bar, when, two being stuck 

 in each other, all four were placed in the middle, all four on the 

 fixed end, and all four on the free end, each two on each end of 

 the bar, and, lastly, two on the middle and two on one end. 

 Besides this, the temporary magnetism of the bar was determined 

 while the spirals occupied the above position. The bar was in 

 an east-to-west direction, at a distance of 4 metres from the mag- 

 netometer. In the numbers given for the temporary magnetism, 

 the displacements due to the spirals alone, and those due to re- 

 manent magnetism, have been already deducted. During the 

 whole range of the experiments the current was kept at a con- 

 stant strength. 



