86 Mr. J. P. Joule on some Ejects of Magnetism. 



Experiment 7. 



The uniformity of the numbers in the last columns of the 

 preceding tables shows that where the inelal possesses a con- 

 siderable degree of retentive power the anomaUes occasioned 

 by the reaction of the magnetic particles upon one anotlier, 

 which have been already adverted to, do not exist to any con- 

 siderable extent, and presents an additional confirmation of 

 the law I have stated, viz. tJie elongation is proportional, in a 

 given bar, to the square of the magnetic intensity. 



I now made trial of a bar of steel one yard long, half an 

 inch broad, and a (]uarter of an inch thick, weighing 23 oz. It 

 was hardened to a certain extent throughout its whole length, 

 but not to such a degree as entirely to resist the action of the 

 file. " _ 



Experiment 8. 



