132 RESPONSE IN THE LIVING AND NON-LIViVG 
individual magnet. The bar as a whole, nevertheless, ex- 
hibits no external magnetisation. This is held to be due 
the fact that the molecular magnets are turned either 
in haphazard directions or in closed chains, and there is 
therefore no resultant polarity. But when the bar is 
subjected to a magnetising force by means, say, of a sole- 
noid carrying electrical current, the individual molecules 
are elastically deflected, so that all the molecular magnets 
tend to place themselves along the lines of magnetising 
force. All the north poles thus pomt more or less one 
way, and the south poles the other. The stronger the 
magnetising force, the nearer do the molecules approach 
to a perfect alignment, and the greater is the induced 
magnetisation of the bar. 
The intensity of this duced magnetisation may be 
measured by noting the deflection it produces on a 
freely suspended magnet in a magnetometer. 
The force which produces that molecular deflection, 
to which the magnetisation of the bar is immediately due, 
is the magnetising current 
flowing round the solenoid. 
The magnetisation, or the 
molecular effect, is measured 
produced 
Magnetisation 
by the deflection of the mag- 
ae netometer. We may express 
Fie, 82.—Curve or Macnetisatron the relation between Gatse 
and effect by a curve in which 
the abscissa represents the magnetising current, and 
the ordinate the magnetisation produced (fig. 82). 
In such a curve we may roughly distinguish three 
parts. In the first, where the force is feeble, the mole- 
