113 
1921-22.] On Models of Ferromagnetic Induction. 
and melted in vacuo^ though such iron shows all the characteristics of 
hysteresis. Compare these values with the calculated field for a row of 
atomic magnets in the form of rods with point poles. Let h be the side of 
the unit cube in the iron crystal. Since the space-lattice is the centred cube 
(see § 24), each unit cube contains two atoms. The volume per atom is 
o 50° 100° 150° ego'" 
Fig. 10. — CCC, group of three equal magnets. BBB, single pair of the same magnets 
with the same pitch. 
accordingly and n, the number of atoms per unit of volume, is ^ 3 . 
Assume that each atom contains a Weber element of moment M, and that 
when the iron is saturated all these elements have turned into complete 
alignment with the field. Then the magnetisation of saturation = 
and M = 
2 
If we treat the atoms as spheres in contact, their diameter is one-half the 
Yensen, “Magnetic and other Properties of Electrolytic Iron melted in vacuoi'^ 
Bullelins of the Engineering Station of the University of Illinois, Nos. 72, 83, 95. 
VOL. XLII. 
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