Researches on Electro-magnetism. 



203 



Iron core No. 2. 43 windings on 10 millims. length. 



Distance of the forward end of the core from the needle = 780 



millims. 



Iron core No. 4. 43 windings on 10 millims. length. 



Distance of the forward end of the core from the needle = 600 

 millims. 



* The magnetizing force wa.s calciiliited accoriling to the formula 



K=4.3..31-(i2.tan<^. 

 t In takin? the mean of the quotients, the two first are exchulecl. 

 X In taking; the mean licre, tht; lir.st (iiioticnt is excluded, as there is evi- 

 dently some error connected with the experiment. 



