The ratio of the residual magnetization to its previous maximum value measures the retentiveness, or retentivity, of the metal.'
A metal which has great retentiveness may at the same time have small coercive force, and it is the latter quality which is of chief importance in permanent magnets.
On the other hand, the form of the third curve, with its large intercepts on the axes of H and B, denotes that the specimen to which it relates possesses both retentiveness and coercive force in a high degree; such a metal would be chosen for making good permanent magnets.
Ewing has also examined the effects produced by longitudinal compression upon the susceptibility and retentiveness of nickel, and found, as was to be expected, that both were greatly increased by pressure.
The distances between drains he showed must be regulated by the greater or less retentiveness of the ground operated upon, and gave io to 40 ft.