MAGNETISATION OF IRON AND OTHER MAGNETIC METAJ.S. 
243 
21,360 ill wrought iron, 15,580 in cast iron, 5030 and 6470 in nickel, and 16,300 in 
cobalt. 
The experiments give a definite meaning to the term “ saturation,” as a})plied to 
magnetic state. When magnetisation is measured by the induction ^■13, the term 
saturation is inapplicable ; there is apparently no limit to the value to which the 
induction may be raised. But, when we measure magnetisation by the intensity of 
magnetism 3, we are confronted with a definite limit—a true saturation value, which 
is reached or closely approached by the application of a comparatively moderate 
magnetic force. There is nothing to show that the approach to tins limit is not 
asymptotic ; but in wrought iron it is practically reached before the magnetic force 
rises to 2000 c.g.s., and after that a ten-fold increase in the force produces no material 
change in the intensity of magnetism. 
Eig. 20. 
§ 39. — The results are further summarised in fig. 20, in which Howland’s curve, 
showing the relation of the permeability p, to the induction is drawn from the data 
supplied by the experiments on^— 
2 I 2 
