Dr. C. Fromme on the Magnetism of Steel Bars. 189 



tions, by subjecting unhardened steel bars to magnetizing 

 forces acting always in the same direction. 



§ 2. Having regard to the reasons above touched upon, I 

 selected only two sorts of steel, differing in specific gravity 

 and possessing great homogeneity. Of each sort five pieces 

 were cut ; and since the theory developed by Neumann and 

 Kirchhoff, of the magnetization of an ellipsoid of rotation, had 

 been verified for soft iron, they were brought into the form of 

 an elongated ellipsoid of rotation. 



In Table I. are collected : — the semi- major and minor axes 

 a and b of the ellipsoids ; the constants 0, determined by the 

 equation 



C = 47ro-(c7 2 - 1) | \ log nat. ^±| - ^ j , 



the specific gravities s ; the volumes v ; and the absolute 

 weights m, — first, as the bars came fresh from the workshop of 



Table I. 





a. 



b. 



C. 





millim. 



millim. 



millim. 



millim. 







I. 1. 



40025 



40015 



12-685 



12-739 



1-28361 



1-29081 



2 



55-355 



55-305 



12-505 



12-500 



0-82805 



0-82876 



3. 



70165 



70107 



12-840 



12-865 



0-61995 



0-62239 



4. 



89-990 



89-863 



12-645 



12-650 



0-42521 



0-42565 



5. 



100-403 



100-395 



10187 



10-188 



0-26063 



0-26069 



II. 1. 



40-595 



40-600 



12-449 



12-441 



1-23199 



1-23081 



2. 



55 423 



55-412 



12-599 



12-592 



0-83506 



0-83462 



3. 



70-353 



70-295 



12-410 



12-395 



0-58875 



0-58842 



4. 



90-245 



90-270 



12-628 



12-597 



0-42189 



0-42025 



5. 



99-895 



99-940 



10-248 



10178 



0-26506 



0-26221 









cub. 



centim. 



cub. 

 centim. 



milligr. 



milligr. 



I. 1. 



7-82366 



7-82059 



26780 



26756 



209519 



209258 



2. 



7-82737 



7-82123 



35666 



35634 



279169 



278700 



3. 



7-81957 



782195 



48176 



48106 



376712 



376283 



4. 



7-82397 



7-82274 



62661 



62598 



490258 



489689 



5. 



7-82184 



7-82148 



47438 



47374 



371052 



370532 



II. 1. 



7'83577 



7-83384 



25865 



25817 



202674 



202248 



2. 



7-83514 



7-83221 



36961 



36901 



289596 



289019 



3. 



7-83353 



7-83240 



47007 



46786 



368235 



366449 



4. 



783534 



7-83366 



62842 



62567 



492385 



490125 



5. 



7-83426 



783116 



47363 



47144 



371050 



369195 



