Prof. E. Bouty's Studies on Magnetism, 



III. 



Needles of 2 millims. diameter. 

 Needle A. Needle B. 



197 



millim . 



Length 141 



Magnetic moment. 165*4 

 Ratio of the end fourths to 

 the middle ones 



0789 



millim. 



Length 143 



Magnetic moment . 46*15 

 Ratio of the end fourths to ) 0-709 

 the middle ones ...... \ 



IV. 



Needles of 2 millims. diameter. 



Needle A. 



millim. 



Length 122 



Magnetic moment . 135*75 



Ratio of the end fourths to 



the middle ones 



0*687 



Needle B. 



millim. 



Length 120 



Magnetic moment \ rq 



less than . . . . J 

 Ratio of the end fourths to 



the middle ones 



|o. 



662 



B. Needles presenting consequent points. — We have just seen 

 that, in a regular needle, the fragments from the extremities 

 possess a lower magnetic moment than those which come from 

 the centre. 



The consequent points behave like poles of less force than 

 the extreme poles ; the fragments which include them possess, 

 with equal length, a higher magnetic moment than that of the 

 end fragments, but lower than that of the fragments derived from 

 the interval between two consequent points. 



We conclude this section by indicating a means of verifying 

 the perfect regularity of a magnetized needle : — After separating 

 a sufficient length of the extremities, we break the middle piece 

 into fragments of arbitrary, unequal lengths. If the mother 

 needle was regular, the characteristic points obtained by taking 

 for abscissa the length of the fragments, and for ordinate their 

 magnetic moment, will be situated on a regular curve. The 

 slightest irregularities will then be seen by simple inspection of 

 , the figure obtained. 



4. Separation, parallel to the axis, of Prismatic Bundles. — 

 Observations on the Temporary Magnetism of Steel. 



The difficulty of breaking a needle along a plane parallel to 

 its axis induced us to investigate the more practical case of 

 superposed strips composing a bundle. The results furnished by 

 this examination apply only approximately to breaking, since 

 the latter may be regarded as the extreme case of separation — 

 when the parts facing each other on both sides of the plane of 

 separation are at an indefinitely minute distance. 



We form a prismatic bundle with a number of pieces of watch- 



